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Default Super Capacitor Voltage Protection Circuit

When connecting "super capacitors" in series to increase the working
voltage above the level of the individual capacitors, does anyone have an
active voltage clamp that would not discharge the capacitors when the power
supply is disconnected? Most "super" capacitors have a working voltage of
2.5 or 2.7 VDC... I would like to connect 10 capacitors in series for a 25
VDC capacitor stack. Most suggestions call for connecting equalizing
resistors in parallel with each capacitor, but I would rather have a
circuit that would not discharge the capacitors when the power is off...
anyone have any ideas?

Thanks,

Bill
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Default Super Capacitor Voltage Protection Circuit

On 08 Aug 2014 15:50:31 GMT, EngineeringGuy
wrote:

When connecting "super capacitors" in series to increase the working
voltage above the level of the individual capacitors, does anyone have an
active voltage clamp that would not discharge the capacitors when the power
supply is disconnected? Most "super" capacitors have a working voltage of
2.5 or 2.7 VDC... I would like to connect 10 capacitors in series for a 25
VDC capacitor stack. Most suggestions call for connecting equalizing
resistors in parallel with each capacitor, but I would rather have a
circuit that would not discharge the capacitors when the power is off...
anyone have any ideas?

Thanks,

Bill


Need more details. What does "...when the power supply is
disconnected" mean? Schematically show us the configuration... show
with equalizing resistors.

...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| San Tan Valley, AZ 85142 Skype: skypeanalog | |
| Voice480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.
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Default Super Capacitor Voltage Protection Circuit

EngineeringGuy wrote:

When connecting "super capacitors" in series to increase the working
voltage above the level of the individual capacitors, does anyone have an
active voltage clamp that would not discharge the capacitors when the
power supply is disconnected? Most "super" capacitors have a working
voltage of 2.5 or 2.7 VDC... I would like to connect 10 capacitors in
series for a 25
VDC capacitor stack. Most suggestions call for connecting equalizing
resistors in parallel with each capacitor, but I would rather have a
circuit that would not discharge the capacitors when the power is off...
anyone have any ideas?

Well, a couple diodes across each cap would not leak a whole lot
when forward biased below the forward conduction voltage.
With plain Si diodes, that might be 5 diodes in series. they would
start leaking somewhere below 3 V, and conduct pretty strongly
at 3.5 V.

You could also look a Schottky diodes and see what values of Vf you
see. If they start to conduct at .4 V, then 7 in series would
give you 2.8 V turn-on. You can get surface mount SOT23 dual diodes
wired in series, so that would only take 4 parts.

Jon
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Default Super Capacitor Voltage Protection Circuit - scan0002.png

On 08 Aug 2014 15:50:31 GMT, EngineeringGuy
wrote:

When connecting "super capacitors" in series to increase the working
voltage above the level of the individual capacitors, does anyone have an
active voltage clamp that would not discharge the capacitors when the power
supply is disconnected? Most "super" capacitors have a working voltage of
2.5 or 2.7 VDC... I would like to connect 10 capacitors in series for a 25
VDC capacitor stack. Most suggestions call for connecting equalizing
resistors in parallel with each capacitor, but I would rather have a
circuit that would not discharge the capacitors when the power is off...
anyone have any ideas?


The relays are all Normally Open (Form A) with 24 volt DC coils.

John Fields


Attached Thumbnails
Super Capacitor Voltage Protection Circuit-scan0002-png  
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Default Super Capacitor Voltage Protection Circuit

In article ,
EngineeringGuy wrote:

When connecting "super capacitors" in series to increase the working
voltage above the level of the individual capacitors, does anyone have an
active voltage clamp that would not discharge the capacitors when the power
supply is disconnected? Most "super" capacitors have a working voltage of
2.5 or 2.7 VDC... I would like to connect 10 capacitors in series for a 25
VDC capacitor stack. Most suggestions call for connecting equalizing
resistors in parallel with each capacitor, but I would rather have a
circuit that would not discharge the capacitors when the power is off...
anyone have any ideas?

Thanks,

Bill


You can probably find just the right color of power LED that can shunt
700mA. Just make sure they don't get thermal runaway faster than they
can drain the cap. If you don't like all the glow, shunt voltage
references and trickle charger shunts have current consumption that's
low compared to ultracapacitor leakage.

But there's a catch...

The capacitors will eventually loose equalization through
self-discharge. When you apply power again, shunts on less-leaky caps
could be exposed to the full power supply current. It's not a big deal
from a solar trickle charger but imagine trying to make practical shunts
if your supply is over 10 Amps. That's why resistors are simpler when
you need balancing.


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Default Super Capacitor Voltage Protection Circuit - scan0002.png

On Fri, 08 Aug 2014 18:16:22 -0500, John Fields
wrote:


The relays are all Normally Open (Form A) with 24 volt DC coils.


---
Oops...

The circuit latches when +V is disconnected. :-(

John Fields
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Default Super Capacitor Voltage Protection Circuit

Jon Elson wrote:
EngineeringGuy wrote:

When connecting "super capacitors" in series to increase the working
voltage above the level of the individual capacitors, does anyone have an
active voltage clamp that would not discharge the capacitors when the
power supply is disconnected? Most "super" capacitors have a working
voltage of 2.5 or 2.7 VDC... I would like to connect 10 capacitors in
series for a 25
VDC capacitor stack. Most suggestions call for connecting equalizing
resistors in parallel with each capacitor, but I would rather have a
circuit that would not discharge the capacitors when the power is off...
anyone have any ideas?

Well, a couple diodes across each cap would not leak a whole lot
when forward biased below the forward conduction voltage.
With plain Si diodes, that might be 5 diodes in series. they would
start leaking somewhere below 3 V, and conduct pretty strongly
at 3.5 V.

You could also look a Schottky diodes and see what values of Vf you
see. If they start to conduct at .4 V, then 7 in series would
give you 2.8 V turn-on. You can get surface mount SOT23 dual diodes
wired in series, so that would only take 4 parts.

Jon

Sounds silly to me; why use the diodes in the forward bias mode,when
the reverse bias mode seems far better?
That way, the capacitors are always reverse polarity protected.

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Default Super Capacitor Voltage Protection Circuit - scan0002.png

John Fields wrote:
On 08 Aug 2014 15:50:31 GMT, EngineeringGuy
wrote:

When connecting "super capacitors" in series to increase the working
voltage above the level of the individual capacitors, does anyone have an
active voltage clamp that would not discharge the capacitors when the power
supply is disconnected? Most "super" capacitors have a working voltage of
2.5 or 2.7 VDC... I would like to connect 10 capacitors in series for a 25
VDC capacitor stack. Most suggestions call for connecting equalizing
resistors in parallel with each capacitor, but I would rather have a
circuit that would not discharge the capacitors when the power is off...
anyone have any ideas?


The relays are all Normally Open (Form A) with 24 volt DC coils.

John Fields

OOOh...a completely solid-state solution.
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Default Super Capacitor Voltage Protection Circuit

On 08 Aug 2014 15:50:31 GMT, EngineeringGuy wrote:

When connecting "super capacitors" in series to increase the working
voltage above the level of the individual capacitors, does anyone have an
active voltage clamp that would not discharge the capacitors when the power
supply is disconnected? Most "super" capacitors have a working voltage of
2.5 or 2.7 VDC... I would like to connect 10 capacitors in series for a 25
VDC capacitor stack. Most suggestions call for connecting equalizing
resistors in parallel with each capacitor, but I would rather have a
circuit that would not discharge the capacitors when the power is off...
anyone have any ideas?

Thanks,

Bill


Supercap data sheets are universally terrible. And various "supercaps" are very
different.

You might measure a leakage vs voltage curve and decide whether they might be OK
in series without external equalization.


--

John Larkin Highland Technology Inc
www.highlandtechnology.com jlarkin at highlandtechnology dot com

Precision electronic instrumentation
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Default Super Capacitor Voltage Protection Circuit

On 8/9/2014 6:09 PM, Robert Baer wrote:
Jon Elson wrote:
EngineeringGuy wrote:

When connecting "super capacitors" in series to increase the working
voltage above the level of the individual capacitors, does anyone
have an
active voltage clamp that would not discharge the capacitors when the
power supply is disconnected? Most "super" capacitors have a working
voltage of 2.5 or 2.7 VDC... I would like to connect 10 capacitors in
series for a 25
VDC capacitor stack. Most suggestions call for connecting equalizing
resistors in parallel with each capacitor, but I would rather have a
circuit that would not discharge the capacitors when the power is off...
anyone have any ideas?

Well, a couple diodes across each cap would not leak a whole lot
when forward biased below the forward conduction voltage.
With plain Si diodes, that might be 5 diodes in series. they would
start leaking somewhere below 3 V, and conduct pretty strongly
at 3.5 V.

You could also look a Schottky diodes and see what values of Vf you
see. If they start to conduct at .4 V, then 7 in series would
give you 2.8 V turn-on. You can get surface mount SOT23 dual diodes
wired in series, so that would only take 4 parts.

Jon

Sounds silly to me; why use the diodes in the forward bias mode,when
the reverse bias mode seems far better?
That way, the capacitors are always reverse polarity protected.


Because the reverse breakdown voltage is not well specified. It is
guaranteed to be above some value, but where exactly will that be? How
many diodes do you know of that will protect a 2.7 volt cap when the
diode is reverse biased?

LEDs might be a good choice for forward biased protection. Some of them
work at 2.7 volts or so. Add a single Si diode and you will get a very
small amount of current flow in the cap working voltage range with the
knee in the I/V curve somewhere above 2.7 volts depending on the color
used.

--

Rick


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Default Super Capacitor Voltage Protection Circuit

On Sun, 10 Aug 2014 16:19:02 -0400, rickman wrote:

On 8/9/2014 6:09 PM, Robert Baer wrote:
Jon Elson wrote:
EngineeringGuy wrote:

When connecting "super capacitors" in series to increase the working
voltage above the level of the individual capacitors, does anyone
have an
active voltage clamp that would not discharge the capacitors when the
power supply is disconnected? Most "super" capacitors have a working
voltage of 2.5 or 2.7 VDC... I would like to connect 10 capacitors in
series for a 25
VDC capacitor stack. Most suggestions call for connecting equalizing
resistors in parallel with each capacitor, but I would rather have a
circuit that would not discharge the capacitors when the power is off...
anyone have any ideas?
Well, a couple diodes across each cap would not leak a whole lot
when forward biased below the forward conduction voltage.
With plain Si diodes, that might be 5 diodes in series. they would
start leaking somewhere below 3 V, and conduct pretty strongly
at 3.5 V.

You could also look a Schottky diodes and see what values of Vf you
see. If they start to conduct at .4 V, then 7 in series would
give you 2.8 V turn-on. You can get surface mount SOT23 dual diodes
wired in series, so that would only take 4 parts.

Jon

Sounds silly to me; why use the diodes in the forward bias mode,when
the reverse bias mode seems far better?
That way, the capacitors are always reverse polarity protected.


Because the reverse breakdown voltage is not well specified. It is
guaranteed to be above some value, but where exactly will that be? How
many diodes do you know of that will protect a 2.7 volt cap when the
diode is reverse biased?

LEDs might be a good choice for forward biased protection. Some of them
work at 2.7 volts or so. Add a single Si diode and you will get a very
small amount of current flow in the cap working voltage range with the
knee in the I/V curve somewhere above 2.7 volts depending on the color
used.


You're whistling somewhere inappropriate if you think diodes are going
to match and track well enough.

This is one of those annoying cases where the OP has vanished after
the initial post and is not answering questions. Without more info,
it's a wasted effort.

Something along the lines of Field's relay method post... maybe with
MOSFET's... is most likely to succeed... just needs the right controls
:-}


...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| San Tan Valley, AZ 85142 Skype: skypeanalog | |
| Voice480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.
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Default Super Capacitor Voltage Protection Circuit

In article ,
Jim Thompson
wrote:

On Sun, 10 Aug 2014 16:19:02 -0400, rickman wrote:

On 8/9/2014 6:09 PM, Robert Baer wrote:
Jon Elson wrote:
EngineeringGuy wrote:

When connecting "super capacitors" in series to increase the working
voltage above the level of the individual capacitors, does anyone
have an
active voltage clamp that would not discharge the capacitors when the
power supply is disconnected? Most "super" capacitors have a working
voltage of 2.5 or 2.7 VDC... I would like to connect 10 capacitors in
series for a 25
VDC capacitor stack. Most suggestions call for connecting equalizing
resistors in parallel with each capacitor, but I would rather have a
circuit that would not discharge the capacitors when the power is off...
anyone have any ideas?
Well, a couple diodes across each cap would not leak a whole lot
when forward biased below the forward conduction voltage.
With plain Si diodes, that might be 5 diodes in series. they would
start leaking somewhere below 3 V, and conduct pretty strongly
at 3.5 V.

You could also look a Schottky diodes and see what values of Vf you
see. If they start to conduct at .4 V, then 7 in series would
give you 2.8 V turn-on. You can get surface mount SOT23 dual diodes
wired in series, so that would only take 4 parts.

Jon
Sounds silly to me; why use the diodes in the forward bias mode,when
the reverse bias mode seems far better?
That way, the capacitors are always reverse polarity protected.


Because the reverse breakdown voltage is not well specified. It is
guaranteed to be above some value, but where exactly will that be? How
many diodes do you know of that will protect a 2.7 volt cap when the
diode is reverse biased?

LEDs might be a good choice for forward biased protection. Some of them
work at 2.7 volts or so. Add a single Si diode and you will get a very
small amount of current flow in the cap working voltage range with the
knee in the I/V curve somewhere above 2.7 volts depending on the color
used.


You're whistling somewhere inappropriate if you think diodes are going
to match and track well enough.


Late generation high efficiency LEDs have incredibly sharp conduction
knees, amazing matching between components, and low internal resistance.
LED manufacturers have put lots of black magic into those chips to break
past normal efficiency limitations. Their only imperfection as a shunt
regulator is that the voltage drops with temperature.

The problem of handling full inrush current after the caps have
self-discharged to different voltages remains unresolved. I still think
resistors would balance the best.


This is one of those annoying cases where the OP has vanished after
the initial post and is not answering questions. Without more info,
it's a wasted effort.

Something along the lines of Field's relay method post... maybe with
MOSFET's... is most likely to succeed... just needs the right controls
:-}


...Jim Thompson

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Default Super Capacitor Voltage Protection Circuit

rickman wrote:
On 8/9/2014 6:09 PM, Robert Baer wrote:
Jon Elson wrote:
EngineeringGuy wrote:

When connecting "super capacitors" in series to increase the working
voltage above the level of the individual capacitors, does anyone
have an
active voltage clamp that would not discharge the capacitors when the
power supply is disconnected? Most "super" capacitors have a working
voltage of 2.5 or 2.7 VDC... I would like to connect 10 capacitors in
series for a 25
VDC capacitor stack. Most suggestions call for connecting equalizing
resistors in parallel with each capacitor, but I would rather have a
circuit that would not discharge the capacitors when the power is
off...
anyone have any ideas?
Well, a couple diodes across each cap would not leak a whole lot
when forward biased below the forward conduction voltage.
With plain Si diodes, that might be 5 diodes in series. they would
start leaking somewhere below 3 V, and conduct pretty strongly
at 3.5 V.

You could also look a Schottky diodes and see what values of Vf you
see. If they start to conduct at .4 V, then 7 in series would
give you 2.8 V turn-on. You can get surface mount SOT23 dual diodes
wired in series, so that would only take 4 parts.

Jon

Sounds silly to me; why use the diodes in the forward bias mode,when
the reverse bias mode seems far better?
That way, the capacitors are always reverse polarity protected.


Because the reverse breakdown voltage is not well specified. It is
guaranteed to be above some value, but where exactly will that be? How
many diodes do you know of that will protect a 2.7 volt cap when the
diode is reverse biased?

LEDs might be a good choice for forward biased protection. Some of them
work at 2.7 volts or so. Add a single Si diode and you will get a very
small amount of current flow in the cap working voltage range with the
knee in the I/V curve somewhere above 2.7 volts depending on the color
used.

Err..any (reasonable) silicon diode reverse polarity connected WRT
the cap will conduct in the region of 620mV; one certainly does not need
to have more in series. And the diode reversed biased (capacitor forward
biased) will will have essentially zero current.
Now,if 620mV is a bit much for these soup-er-boop-a-doop capacitors,
then instead of sand power, go for flower power (Ge) at about 320mV.
Unfortunately, they are not exactly the bees' knees and are a bit
leaky of the electronic honey.

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Default Super Capacitor Voltage Protection Circuit

On 8/11/2014 12:44 AM, Robert Baer wrote:
rickman wrote:
On 8/9/2014 6:09 PM, Robert Baer wrote:
Jon Elson wrote:
EngineeringGuy wrote:

When connecting "super capacitors" in series to increase the working
voltage above the level of the individual capacitors, does anyone
have an
active voltage clamp that would not discharge the capacitors when the
power supply is disconnected? Most "super" capacitors have a working
voltage of 2.5 or 2.7 VDC... I would like to connect 10 capacitors in
series for a 25
VDC capacitor stack. Most suggestions call for connecting equalizing
resistors in parallel with each capacitor, but I would rather have a
circuit that would not discharge the capacitors when the power is
off...
anyone have any ideas?
Well, a couple diodes across each cap would not leak a whole lot
when forward biased below the forward conduction voltage.
With plain Si diodes, that might be 5 diodes in series. they would
start leaking somewhere below 3 V, and conduct pretty strongly
at 3.5 V.

You could also look a Schottky diodes and see what values of Vf you
see. If they start to conduct at .4 V, then 7 in series would
give you 2.8 V turn-on. You can get surface mount SOT23 dual diodes
wired in series, so that would only take 4 parts.

Jon
Sounds silly to me; why use the diodes in the forward bias mode,when
the reverse bias mode seems far better?
That way, the capacitors are always reverse polarity protected.


Because the reverse breakdown voltage is not well specified. It is
guaranteed to be above some value, but where exactly will that be? How
many diodes do you know of that will protect a 2.7 volt cap when the
diode is reverse biased?

LEDs might be a good choice for forward biased protection. Some of them
work at 2.7 volts or so. Add a single Si diode and you will get a very
small amount of current flow in the cap working voltage range with the
knee in the I/V curve somewhere above 2.7 volts depending on the color
used.

Err..any (reasonable) silicon diode reverse polarity connected WRT
the cap will conduct in the region of 620mV; one certainly does not need
to have more in series. And the diode reversed biased (capacitor forward
biased) will will have essentially zero current.
Now,if 620mV is a bit much for these soup-er-boop-a-doop capacitors,
then instead of sand power, go for flower power (Ge) at about 320mV.
Unfortunately, they are not exactly the bees' knees and are a bit
leaky of the electronic honey.


I don't follow your reasoning at all. The OP wants to work at increased
voltages by using multiple super caps in series. Why would you think
620 mV would be a high enough voltage?

The way resistors work to equalize the voltage on the caps is to provide
a small leakage current around the cap, higher when the voltage is
higher reducing the charge on that cap relative to the others. The
difference with the diodes is that they conduct much less current when
the cap is in its normal working range. Only when it exceeds the
working range by some margin does the diode start to conduct
significantly bypassing a significant portion of the charging current.

There has to be some headroom between the working voltage and the damage
voltage since the diodes won't have a highly stable knee voltage. But
given enough margin this should work well. If there is not enough
margin then something with a better regulated knee would need to be used
like a voltage regulator.

--

Rick
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Default Super Capacitor Voltage Protection Circuit

rickman wrote:
On 8/11/2014 12:44 AM, Robert Baer wrote:
rickman wrote:
On 8/9/2014 6:09 PM, Robert Baer wrote:
Jon Elson wrote:
EngineeringGuy wrote:

When connecting "super capacitors" in series to increase the working
voltage above the level of the individual capacitors, does anyone
have an
active voltage clamp that would not discharge the capacitors when the
power supply is disconnected? Most "super" capacitors have a working
voltage of 2.5 or 2.7 VDC... I would like to connect 10 capacitors in
series for a 25
VDC capacitor stack. Most suggestions call for connecting equalizing
resistors in parallel with each capacitor, but I would rather have a
circuit that would not discharge the capacitors when the power is
off...
anyone have any ideas?
Well, a couple diodes across each cap would not leak a whole lot
when forward biased below the forward conduction voltage.
With plain Si diodes, that might be 5 diodes in series. they would
start leaking somewhere below 3 V, and conduct pretty strongly
at 3.5 V.

You could also look a Schottky diodes and see what values of Vf you
see. If they start to conduct at .4 V, then 7 in series would
give you 2.8 V turn-on. You can get surface mount SOT23 dual diodes
wired in series, so that would only take 4 parts.

Jon
Sounds silly to me; why use the diodes in the forward bias mode,when
the reverse bias mode seems far better?
That way, the capacitors are always reverse polarity protected.

Because the reverse breakdown voltage is not well specified. It is
guaranteed to be above some value, but where exactly will that be? How
many diodes do you know of that will protect a 2.7 volt cap when the
diode is reverse biased?

LEDs might be a good choice for forward biased protection. Some of them
work at 2.7 volts or so. Add a single Si diode and you will get a very
small amount of current flow in the cap working voltage range with the
knee in the I/V curve somewhere above 2.7 volts depending on the color
used.

Err..any (reasonable) silicon diode reverse polarity connected WRT
the cap will conduct in the region of 620mV; one certainly does not need
to have more in series. And the diode reversed biased (capacitor forward
biased) will will have essentially zero current.
Now,if 620mV is a bit much for these soup-er-boop-a-doop capacitors,
then instead of sand power, go for flower power (Ge) at about 320mV.
Unfortunately, they are not exactly the bees' knees and are a bit
leaky of the electronic honey.


I don't follow your reasoning at all. The OP wants to work at increased
voltages by using multiple super caps in series. Why would you think 620
mV would be a high enough voltage?

The way resistors work to equalize the voltage on the caps is to provide
a small leakage current around the cap, higher when the voltage is
higher reducing the charge on that cap relative to the others. The
difference with the diodes is that they conduct much less current when
the cap is in its normal working range. Only when it exceeds the working
range by some margin does the diode start to conduct significantly
bypassing a significant portion of the charging current.

There has to be some headroom between the working voltage and the damage
voltage since the diodes won't have a highly stable knee voltage. But
given enough margin this should work well. If there is not enough margin
then something with a better regulated knee would need to be used like a
voltage regulator.

I guess that you cannot read hat i said.



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Default Super Capacitor Voltage Protection Circuit

On 8/11/2014 11:20 PM, Robert Baer wrote:
rickman wrote:
On 8/11/2014 12:44 AM, Robert Baer wrote:
rickman wrote:
On 8/9/2014 6:09 PM, Robert Baer wrote:
Jon Elson wrote:
EngineeringGuy wrote:

When connecting "super capacitors" in series to increase the working
voltage above the level of the individual capacitors, does anyone
have an
active voltage clamp that would not discharge the capacitors when
the
power supply is disconnected? Most "super" capacitors have a working
voltage of 2.5 or 2.7 VDC... I would like to connect 10
capacitors in
series for a 25
VDC capacitor stack. Most suggestions call for connecting equalizing
resistors in parallel with each capacitor, but I would rather have a
circuit that would not discharge the capacitors when the power is
off...
anyone have any ideas?
Well, a couple diodes across each cap would not leak a whole lot
when forward biased below the forward conduction voltage.
With plain Si diodes, that might be 5 diodes in series. they would
start leaking somewhere below 3 V, and conduct pretty strongly
at 3.5 V.

You could also look a Schottky diodes and see what values of Vf you
see. If they start to conduct at .4 V, then 7 in series would
give you 2.8 V turn-on. You can get surface mount SOT23 dual diodes
wired in series, so that would only take 4 parts.

Jon
Sounds silly to me; why use the diodes in the forward bias mode,when
the reverse bias mode seems far better?
That way, the capacitors are always reverse polarity protected.

Because the reverse breakdown voltage is not well specified. It is
guaranteed to be above some value, but where exactly will that be? How
many diodes do you know of that will protect a 2.7 volt cap when the
diode is reverse biased?

LEDs might be a good choice for forward biased protection. Some of them
work at 2.7 volts or so. Add a single Si diode and you will get a very
small amount of current flow in the cap working voltage range with the
knee in the I/V curve somewhere above 2.7 volts depending on the color
used.

Err..any (reasonable) silicon diode reverse polarity connected WRT
the cap will conduct in the region of 620mV; one certainly does not need
to have more in series. And the diode reversed biased (capacitor forward
biased) will will have essentially zero current.
Now,if 620mV is a bit much for these soup-er-boop-a-doop capacitors,
then instead of sand power, go for flower power (Ge) at about 320mV.
Unfortunately, they are not exactly the bees' knees and are a bit
leaky of the electronic honey.


I don't follow your reasoning at all. The OP wants to work at increased
voltages by using multiple super caps in series. Why would you think 620
mV would be a high enough voltage?

The way resistors work to equalize the voltage on the caps is to provide
a small leakage current around the cap, higher when the voltage is
higher reducing the charge on that cap relative to the others. The
difference with the diodes is that they conduct much less current when
the cap is in its normal working range. Only when it exceeds the working
range by some margin does the diode start to conduct significantly
bypassing a significant portion of the charging current.

There has to be some headroom between the working voltage and the damage
voltage since the diodes won't have a highly stable knee voltage. But
given enough margin this should work well. If there is not enough margin
then something with a better regulated knee would need to be used like a
voltage regulator.

I guess that you cannot read hat i said.


Ok, I understand now.

--

Rick
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Default Super Capacitor Voltage Protection Circuit

Kevin McMurtrie wrote in
:

In article ,
Jim Thompson
wrote:

On Sun, 10 Aug 2014 16:19:02 -0400, rickman wrote:

On 8/9/2014 6:09 PM, Robert Baer wrote:
Jon Elson wrote:
EngineeringGuy wrote:

When connecting "super capacitors" in series to increase the
working voltage above the level of the individual capacitors,
does anyone have an
active voltage clamp that would not discharge the capacitors
when the power supply is disconnected? Most "super" capacitors
have a working voltage of 2.5 or 2.7 VDC... I would like to
connect 10 capacitors in series for a 25
VDC capacitor stack. Most suggestions call for connecting
equalizing resistors in parallel with each capacitor, but I
would rather have a circuit that would not discharge the
capacitors when the power is off... anyone have any ideas?
Well, a couple diodes across each cap would not leak a whole lot
when forward biased below the forward conduction voltage.
With plain Si diodes, that might be 5 diodes in series. they
would start leaking somewhere below 3 V, and conduct pretty
strongly at 3.5 V.

You could also look a Schottky diodes and see what values of Vf
you see. If they start to conduct at .4 V, then 7 in series
would give you 2.8 V turn-on. You can get surface mount SOT23
dual diodes wired in series, so that would only take 4 parts.

Jon
Sounds silly to me; why use the diodes in the forward bias
mode,when
the reverse bias mode seems far better?
That way, the capacitors are always reverse polarity protected.

Because the reverse breakdown voltage is not well specified. It is
guaranteed to be above some value, but where exactly will that be?
How many diodes do you know of that will protect a 2.7 volt cap when
the diode is reverse biased?

LEDs might be a good choice for forward biased protection. Some of
them work at 2.7 volts or so. Add a single Si diode and you will
get a very small amount of current flow in the cap working voltage
range with the knee in the I/V curve somewhere above 2.7 volts
depending on the color used.


You're whistling somewhere inappropriate if you think diodes are
going to match and track well enough.


Late generation high efficiency LEDs have incredibly sharp conduction
knees, amazing matching between components, and low internal
resistance. LED manufacturers have put lots of black magic into those
chips to break past normal efficiency limitations. Their only
imperfection as a shunt regulator is that the voltage drops with
temperature.

The problem of handling full inrush current after the caps have
self-discharged to different voltages remains unresolved. I still
think resistors would balance the best.


This is one of those annoying cases where the OP has vanished after
the initial post and is not answering questions. Without more info,
it's a wasted effort.

Something along the lines of Field's relay method post... maybe with
MOSFET's... is most likely to succeed... just needs the right
controls
:-}


...Jim Thompson



Jim... I haven't vanished, just out of town. I don't quite understand
what clairification you require... 10 caps in series to give 27VDC total
operating voltage.. each with "something" in parallel to prevent over
voltage... overvoltage will cause "super capacitors" to short and fail..
that "something" must be such that it will not discharge the capacitors
when the 25 volts is removed, turned off, disconnected, not charging,
etc.

Bill
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Default Super Capacitor Voltage Protection Circuit

EngineeringGuy wrote:
Kevin wrote in
:

In ,
Jim
wrote:

On Sun, 10 Aug 2014 16:19:02 -0400, wrote:

On 8/9/2014 6:09 PM, Robert Baer wrote:
Jon Elson wrote:
EngineeringGuy wrote:

When connecting "super capacitors" in series to increase the
working voltage above the level of the individual capacitors,
does anyone have an
active voltage clamp that would not discharge the capacitors
when the power supply is disconnected? Most "super" capacitors
have a working voltage of 2.5 or 2.7 VDC... I would like to
connect 10 capacitors in series for a 25
VDC capacitor stack. Most suggestions call for connecting
equalizing resistors in parallel with each capacitor, but I
would rather have a circuit that would not discharge the
capacitors when the power is off... anyone have any ideas?
Well, a couple diodes across each cap would not leak a whole lot
when forward biased below the forward conduction voltage.
With plain Si diodes, that might be 5 diodes in series. they
would start leaking somewhere below 3 V, and conduct pretty
strongly at 3.5 V.

You could also look a Schottky diodes and see what values of Vf
you see. If they start to conduct at .4 V, then 7 in series
would give you 2.8 V turn-on. You can get surface mount SOT23
dual diodes wired in series, so that would only take 4 parts.

Jon
Sounds silly to me; why use the diodes in the forward bias
mode,when
the reverse bias mode seems far better?
That way, the capacitors are always reverse polarity protected.

Because the reverse breakdown voltage is not well specified. It is
guaranteed to be above some value, but where exactly will that be?
How many diodes do you know of that will protect a 2.7 volt cap when
the diode is reverse biased?

LEDs might be a good choice for forward biased protection. Some of
them work at 2.7 volts or so. Add a single Si diode and you will
get a very small amount of current flow in the cap working voltage
range with the knee in the I/V curve somewhere above 2.7 volts
depending on the color used.

You're whistling somewhere inappropriate if you think diodes are
going to match and track well enough.


Late generation high efficiency LEDs have incredibly sharp conduction
knees, amazing matching between components, and low internal
resistance. LED manufacturers have put lots of black magic into those
chips to break past normal efficiency limitations. Their only
imperfection as a shunt regulator is that the voltage drops with
temperature.

The problem of handling full inrush current after the caps have
self-discharged to different voltages remains unresolved. I still
think resistors would balance the best.


This is one of those annoying cases where the OP has vanished after
the initial post and is not answering questions. Without more info,
it's a wasted effort.

Something along the lines of Field's relay method post... maybe with
MOSFET's... is most likely to succeed... just needs the right
controls
:-}

...Jim Thompson



Jim... I haven't vanished, just out of town. I don't quite understand
what clairification you require... 10 caps in series to give 27VDC total
operating voltage.. each with "something" in parallel to prevent over
voltage... overvoltage will cause "super capacitors" to short and fail..
that "something" must be such that it will not discharge the capacitors
when the 25 volts is removed, turned off, disconnected, not charging,
etc.

Bill

....with NOTHING to protect each one from reverse voltage?

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Default Super Capacitor Voltage Protection Circuit

On Tue, 12 Aug 2014 22:16:35 -0700, Robert Baer wrote:

EngineeringGuy wrote:
Kevin wrote in
:

In ,
Jim
wrote:

On Sun, 10 Aug 2014 16:19:02 -0400, wrote:

On 8/9/2014 6:09 PM, Robert Baer wrote:
Jon Elson wrote:
EngineeringGuy wrote:

When connecting "super capacitors" in series to increase the
working voltage above the level of the individual capacitors,
does anyone have an active voltage clamp that would not discharge
the capacitors when the power supply is disconnected? Most
"super" capacitors have a working voltage of 2.5 or 2.7 VDC... I
would like to connect 10 capacitors in series for a 25 VDC
capacitor stack. Most suggestions call for connecting equalizing
resistors in parallel with each capacitor, but I would rather
have a circuit that would not discharge the capacitors when the
power is off... anyone have any ideas?
Well, a couple diodes across each cap would not leak a whole lot
when forward biased below the forward conduction voltage.
With plain Si diodes, that might be 5 diodes in series. they
would start leaking somewhere below 3 V, and conduct pretty
strongly at 3.5 V.

You could also look a Schottky diodes and see what values of Vf
you see. If they start to conduct at .4 V, then 7 in series would
give you 2.8 V turn-on. You can get surface mount SOT23 dual
diodes wired in series, so that would only take 4 parts.

Jon
Sounds silly to me; why use the diodes in the forward bias
mode,when
the reverse bias mode seems far better?
That way, the capacitors are always reverse polarity protected.

Because the reverse breakdown voltage is not well specified. It is
guaranteed to be above some value, but where exactly will that be?
How many diodes do you know of that will protect a 2.7 volt cap when
the diode is reverse biased?

LEDs might be a good choice for forward biased protection. Some of
them work at 2.7 volts or so. Add a single Si diode and you will
get a very small amount of current flow in the cap working voltage
range with the knee in the I/V curve somewhere above 2.7 volts
depending on the color used.

You're whistling somewhere inappropriate if you think diodes are
going to match and track well enough.

Late generation high efficiency LEDs have incredibly sharp conduction
knees, amazing matching between components, and low internal
resistance. LED manufacturers have put lots of black magic into those
chips to break past normal efficiency limitations. Their only
imperfection as a shunt regulator is that the voltage drops with
temperature.

The problem of handling full inrush current after the caps have
self-discharged to different voltages remains unresolved. I still
think resistors would balance the best.


This is one of those annoying cases where the OP has vanished after
the initial post and is not answering questions. Without more info,
it's a wasted effort.

Something along the lines of Field's relay method post... maybe with
MOSFET's... is most likely to succeed... just needs the right
controls
:-}

...Jim Thompson


Jim... I haven't vanished, just out of town. I don't quite understand
what clairification you require... 10 caps in series to give 27VDC
total operating voltage.. each with "something" in parallel to prevent
over voltage... overvoltage will cause "super capacitors" to short and
fail..
that "something" must be such that it will not discharge the capacitors
when the 25 volts is removed, turned off, disconnected, not charging,
etc.

Bill

...with NOTHING to protect each one from reverse voltage?


Reverse polarity protection is important too, but what he is asking about
is individual cell overvoltage protection, for which he needs a 2.7 volt
shunt regulator across each cell, which will bypass a fully charged cell
while allowing the rest of the string to fully charge. The forward
polarity diode string others have suggested is a crude, high tempco shunt
regulator of sorts when used as suggested, but a much more precise and
stable voltage limit could be set with IC shunt regulators.

By replacing the resistor string with any variety of shunt regulator you
do also need to consider replacing the other feature of a resistor
string: preventing individual cell reverse polarity when the capacitor
string is fully discharged.
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Default Super Capacitor Voltage Protection Circuit

On 13 Aug 2014 04:31:20 GMT, EngineeringGuy
wrote:

[snip]
In article ,
Jim Thompson
wrote:

[snip]

This is one of those annoying cases where the OP has vanished after
the initial post and is not answering questions. Without more info,
it's a wasted effort.

Something along the lines of Field's relay method post... maybe with
MOSFET's... is most likely to succeed... just needs the right
controls
:-}

...Jim Thompson



Jim... I haven't vanished, just out of town. I don't quite understand
what clairification you require... 10 caps in series to give 27VDC total
operating voltage.. each with "something" in parallel to prevent over
voltage... overvoltage will cause "super capacitors" to short and fail..
that "something" must be such that it will not discharge the capacitors
when the 25 volts is removed, turned off, disconnected, not charging,
etc.

Bill


HOW the "25 volts is removed, turned off, disconnected, not charging"
matters.

It seems to me that "over voltage" would be managed across the whole
stack, with equalizing resistors across each cell.

Perhaps making the charging voltage sufficiently large that the OVP is
always active during charging.

When the charging voltage is removed, "something" in the OVP, because
it is inactive, disconnects the equalizing resistors/elements??

What "leakage" current can you tolerate?

...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| San Tan Valley, AZ 85142 Skype: skypeanalog | |
| Voice480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.


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Default Super Capacitor Voltage Protection Circuit

On 13 Aug 2014 04:31:20 GMT, EngineeringGuy wrote:

Kevin McMurtrie wrote in
:

In article ,
Jim Thompson
wrote:

On Sun, 10 Aug 2014 16:19:02 -0400, rickman wrote:

On 8/9/2014 6:09 PM, Robert Baer wrote:
Jon Elson wrote:
EngineeringGuy wrote:

When connecting "super capacitors" in series to increase the
working voltage above the level of the individual capacitors,
does anyone have an
active voltage clamp that would not discharge the capacitors
when the power supply is disconnected? Most "super" capacitors
have a working voltage of 2.5 or 2.7 VDC... I would like to
connect 10 capacitors in series for a 25
VDC capacitor stack. Most suggestions call for connecting
equalizing resistors in parallel with each capacitor, but I
would rather have a circuit that would not discharge the
capacitors when the power is off... anyone have any ideas?
Well, a couple diodes across each cap would not leak a whole lot
when forward biased below the forward conduction voltage.
With plain Si diodes, that might be 5 diodes in series. they
would start leaking somewhere below 3 V, and conduct pretty
strongly at 3.5 V.

You could also look a Schottky diodes and see what values of Vf
you see. If they start to conduct at .4 V, then 7 in series
would give you 2.8 V turn-on. You can get surface mount SOT23
dual diodes wired in series, so that would only take 4 parts.

Jon
Sounds silly to me; why use the diodes in the forward bias
mode,when
the reverse bias mode seems far better?
That way, the capacitors are always reverse polarity protected.

Because the reverse breakdown voltage is not well specified. It is
guaranteed to be above some value, but where exactly will that be?
How many diodes do you know of that will protect a 2.7 volt cap when
the diode is reverse biased?

LEDs might be a good choice for forward biased protection. Some of
them work at 2.7 volts or so. Add a single Si diode and you will
get a very small amount of current flow in the cap working voltage
range with the knee in the I/V curve somewhere above 2.7 volts
depending on the color used.

You're whistling somewhere inappropriate if you think diodes are
going to match and track well enough.


Late generation high efficiency LEDs have incredibly sharp conduction
knees, amazing matching between components, and low internal
resistance. LED manufacturers have put lots of black magic into those
chips to break past normal efficiency limitations. Their only
imperfection as a shunt regulator is that the voltage drops with
temperature.

The problem of handling full inrush current after the caps have
self-discharged to different voltages remains unresolved. I still
think resistors would balance the best.


This is one of those annoying cases where the OP has vanished after
the initial post and is not answering questions. Without more info,
it's a wasted effort.

Something along the lines of Field's relay method post... maybe with
MOSFET's... is most likely to succeed... just needs the right
controls
:-}

...Jim Thompson



Jim... I haven't vanished, just out of town. I don't quite understand
what clairification you require... 10 caps in series to give 27VDC total
operating voltage.. each with "something" in parallel to prevent over
voltage... overvoltage will cause "super capacitors" to short and fail..
that "something" must be such that it will not discharge the capacitors
when the 25 volts is removed, turned off, disconnected, not charging,
etc.

Bill


Do you know how much voltage is safe for those caps? Do you have a
voltage:current curve?


--

John Larkin Highland Technology Inc
www.highlandtechnology.com jlarkin at highlandtechnology dot com

Precision electronic instrumentation
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Default Super Capacitor Voltage Protection Circuit

On Wed, 13 Aug 2014 18:02:27 -0700, John Larkin
wrote:
[snip]


This is one of those annoying cases where the OP has vanished after
the initial post and is not answering questions. Without more info,
it's a wasted effort.

Something along the lines of Field's relay method post... maybe with
MOSFET's... is most likely to succeed... just needs the right
controls
:-}

...Jim Thompson


Jim... I haven't vanished, just out of town. I don't quite understand
what clairification you require... 10 caps in series to give 27VDC total
operating voltage.. each with "something" in parallel to prevent over
voltage... overvoltage will cause "super capacitors" to short and fail..
that "something" must be such that it will not discharge the capacitors
when the 25 volts is removed, turned off, disconnected, not charging,
etc.

Bill


Do you know how much voltage is safe for those caps? Do you have a
voltage:current curve?


Do you have a clue? Not likely :-}

...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| San Tan Valley, AZ 85142 Skype: skypeanalog | |
| Voice480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.
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Default Super Capacitor Voltage Protection Circuit

Glen Walpert wrote:
On Tue, 12 Aug 2014 22:16:35 -0700, Robert Baer wrote:

EngineeringGuy wrote:
Kevin wrote in
:

In ,
Jim
wrote:

On Sun, 10 Aug 2014 16:19:02 -0400, wrote:

On 8/9/2014 6:09 PM, Robert Baer wrote:
Jon Elson wrote:
EngineeringGuy wrote:

When connecting "super capacitors" in series to increase the
working voltage above the level of the individual capacitors,
does anyone have an active voltage clamp that would not discharge
the capacitors when the power supply is disconnected? Most
"super" capacitors have a working voltage of 2.5 or 2.7 VDC... I
would like to connect 10 capacitors in series for a 25 VDC
capacitor stack. Most suggestions call for connecting equalizing
resistors in parallel with each capacitor, but I would rather
have a circuit that would not discharge the capacitors when the
power is off... anyone have any ideas?
Well, a couple diodes across each cap would not leak a whole lot
when forward biased below the forward conduction voltage.
With plain Si diodes, that might be 5 diodes in series. they
would start leaking somewhere below 3 V, and conduct pretty
strongly at 3.5 V.

You could also look a Schottky diodes and see what values of Vf
you see. If they start to conduct at .4 V, then 7 in series would
give you 2.8 V turn-on. You can get surface mount SOT23 dual
diodes wired in series, so that would only take 4 parts.

Jon
Sounds silly to me; why use the diodes in the forward bias
mode,when
the reverse bias mode seems far better?
That way, the capacitors are always reverse polarity protected.

Because the reverse breakdown voltage is not well specified. It is
guaranteed to be above some value, but where exactly will that be?
How many diodes do you know of that will protect a 2.7 volt cap when
the diode is reverse biased?

LEDs might be a good choice for forward biased protection. Some of
them work at 2.7 volts or so. Add a single Si diode and you will
get a very small amount of current flow in the cap working voltage
range with the knee in the I/V curve somewhere above 2.7 volts
depending on the color used.

You're whistling somewhere inappropriate if you think diodes are
going to match and track well enough.

Late generation high efficiency LEDs have incredibly sharp conduction
knees, amazing matching between components, and low internal
resistance. LED manufacturers have put lots of black magic into those
chips to break past normal efficiency limitations. Their only
imperfection as a shunt regulator is that the voltage drops with
temperature.

The problem of handling full inrush current after the caps have
self-discharged to different voltages remains unresolved. I still
think resistors would balance the best.


This is one of those annoying cases where the OP has vanished after
the initial post and is not answering questions. Without more info,
it's a wasted effort.

Something along the lines of Field's relay method post... maybe with
MOSFET's... is most likely to succeed... just needs the right
controls
:-}

...Jim Thompson


Jim... I haven't vanished, just out of town. I don't quite understand
what clairification you require... 10 caps in series to give 27VDC
total operating voltage.. each with "something" in parallel to prevent
over voltage... overvoltage will cause "super capacitors" to short and
fail..
that "something" must be such that it will not discharge the capacitors
when the 25 volts is removed, turned off, disconnected, not charging,
etc.

Bill

...with NOTHING to protect each one from reverse voltage?


Reverse polarity protection is important too, but what he is asking about
is individual cell overvoltage protection, for which he needs a 2.7 volt
shunt regulator across each cell, which will bypass a fully charged cell
while allowing the rest of the string to fully charge. The forward
polarity diode string others have suggested is a crude, high tempco shunt
regulator of sorts when used as suggested, but a much more precise and
stable voltage limit could be set with IC shunt regulators.

By replacing the resistor string with any variety of shunt regulator you
do also need to consider replacing the other feature of a resistor
string: preventing individual cell reverse polarity when the capacitor
string is fully discharged.

A resistor does NOTHING to prevent cell reverse polarity.

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Default Super Capacitor Voltage Protection Circuit

In article ,
Robert Baer wrote:

Glen Walpert wrote:
On Tue, 12 Aug 2014 22:16:35 -0700, Robert Baer wrote:

EngineeringGuy wrote:
Kevin wrote in
:

In ,
Jim
wrote:

On Sun, 10 Aug 2014 16:19:02 -0400, wrote:

On 8/9/2014 6:09 PM, Robert Baer wrote:
Jon Elson wrote:
EngineeringGuy wrote:

When connecting "super capacitors" in series to increase the
working voltage above the level of the individual capacitors,
does anyone have an active voltage clamp that would not discharge
the capacitors when the power supply is disconnected? Most
"super" capacitors have a working voltage of 2.5 or 2.7 VDC... I
would like to connect 10 capacitors in series for a 25 VDC
capacitor stack. Most suggestions call for connecting equalizing
resistors in parallel with each capacitor, but I would rather
have a circuit that would not discharge the capacitors when the
power is off... anyone have any ideas?
Well, a couple diodes across each cap would not leak a whole lot
when forward biased below the forward conduction voltage.
With plain Si diodes, that might be 5 diodes in series. they
would start leaking somewhere below 3 V, and conduct pretty
strongly at 3.5 V.

You could also look a Schottky diodes and see what values of Vf
you see. If they start to conduct at .4 V, then 7 in series would
give you 2.8 V turn-on. You can get surface mount SOT23 dual
diodes wired in series, so that would only take 4 parts.

Jon
Sounds silly to me; why use the diodes in the forward bias
mode,when
the reverse bias mode seems far better?
That way, the capacitors are always reverse polarity protected.

Because the reverse breakdown voltage is not well specified. It is
guaranteed to be above some value, but where exactly will that be?
How many diodes do you know of that will protect a 2.7 volt cap when
the diode is reverse biased?

LEDs might be a good choice for forward biased protection. Some of
them work at 2.7 volts or so. Add a single Si diode and you will
get a very small amount of current flow in the cap working voltage
range with the knee in the I/V curve somewhere above 2.7 volts
depending on the color used.

You're whistling somewhere inappropriate if you think diodes are
going to match and track well enough.

Late generation high efficiency LEDs have incredibly sharp conduction
knees, amazing matching between components, and low internal
resistance. LED manufacturers have put lots of black magic into those
chips to break past normal efficiency limitations. Their only
imperfection as a shunt regulator is that the voltage drops with
temperature.

The problem of handling full inrush current after the caps have
self-discharged to different voltages remains unresolved. I still
think resistors would balance the best.


This is one of those annoying cases where the OP has vanished after
the initial post and is not answering questions. Without more info,
it's a wasted effort.

Something along the lines of Field's relay method post... maybe with
MOSFET's... is most likely to succeed... just needs the right
controls
:-}

...Jim Thompson


Jim... I haven't vanished, just out of town. I don't quite understand
what clairification you require... 10 caps in series to give 27VDC
total operating voltage.. each with "something" in parallel to prevent
over voltage... overvoltage will cause "super capacitors" to short and
fail..
that "something" must be such that it will not discharge the capacitors
when the 25 volts is removed, turned off, disconnected, not charging,
etc.

Bill
...with NOTHING to protect each one from reverse voltage?


Reverse polarity protection is important too, but what he is asking about
is individual cell overvoltage protection, for which he needs a 2.7 volt
shunt regulator across each cell, which will bypass a fully charged cell
while allowing the rest of the string to fully charge. The forward
polarity diode string others have suggested is a crude, high tempco shunt
regulator of sorts when used as suggested, but a much more precise and
stable voltage limit could be set with IC shunt regulators.

By replacing the resistor string with any variety of shunt regulator you
do also need to consider replacing the other feature of a resistor
string: preventing individual cell reverse polarity when the capacitor
string is fully discharged.

A resistor does NOTHING to prevent cell reverse polarity.



Actually, resistors do. You're missing the point of why resistors are
recommended.

The capacity of ultracaps is reasonably well matched. What's not well
matched is the internal leakage. Here's where you're in trouble:

- All 10 series caps are at 0V
- 25V is applied
- All caps charge to 2.5V +/- a tiny amount
- Disconnect charge/load and let them sit for a few days
- The voltages become extremely unbalanced from varying leakage
- Charging or discharging will cause OV or UV, possibly with enough
current for damage

Resistors would have brought them all down to 0V, a safe state.

--
Astraweb posts are filtered as spam
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Default Super Capacitor Voltage Protection Circuit

On Wed, 13 Aug 2014 18:37:24 -0700, Jim Thompson
wrote:

On Wed, 13 Aug 2014 18:02:27 -0700, John Larkin
wrote:
[snip]


This is one of those annoying cases where the OP has vanished after
the initial post and is not answering questions. Without more info,
it's a wasted effort.

Something along the lines of Field's relay method post... maybe with
MOSFET's... is most likely to succeed... just needs the right
controls
:-}

...Jim Thompson


Jim... I haven't vanished, just out of town. I don't quite understand
what clairification you require... 10 caps in series to give 27VDC total
operating voltage.. each with "something" in parallel to prevent over
voltage... overvoltage will cause "super capacitors" to short and fail..
that "something" must be such that it will not discharge the capacitors
when the 25 volts is removed, turned off, disconnected, not charging,
etc.

Bill


Do you know how much voltage is safe for those caps? Do you have a
voltage:current curve?


Do you have a clue? Not likely :-}

...Jim Thompson


You're repeating yourself, without content, as usual.

And if you want to design an elaborate protection circuit for an
expensive part that you don't understand, do that again, too.


--

John Larkin Highland Technology, Inc

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com



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Default Super Capacitor Voltage Protection Circuit

On 13 Aug 2014 04:31:20 GMT, EngineeringGuy
wrote:

[snip]


Jim... I haven't vanished, just out of town. I don't quite understand
what clairification you require... 10 caps in series to give 27VDC total
operating voltage.. each with "something" in parallel to prevent over
voltage... overvoltage will cause "super capacitors" to short and fail..
that "something" must be such that it will not discharge the capacitors
when the 25 volts is removed, turned off, disconnected, not charging,
etc.

Bill


How much shunt resistance across each cell is tolerable when _not_
charging?

...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| San Tan Valley, AZ 85142 Skype: skypeanalog | |
| Voice480)460-2350 Fax: Available upon request | Brass Rat |
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Default Super Capacitor Voltage Protection Circuit

On 08 Aug 2014 15:50:31 GMT, EngineeringGuy
wrote:

When connecting "super capacitors" in series to increase the working
voltage above the level of the individual capacitors, does anyone have an
active voltage clamp that would not discharge the capacitors when the power
supply is disconnected? Most "super" capacitors have a working voltage of
2.5 or 2.7 VDC... I would like to connect 10 capacitors in series for a 25
VDC capacitor stack. Most suggestions call for connecting equalizing
resistors in parallel with each capacitor, but I would rather have a
circuit that would not discharge the capacitors when the power is off...
anyone have any ideas?

Thanks,

Bill


Food for thought, see...

http://www.analog-innovations.com/SED/ChargeLimiter_SuperCap.png

Obviously the charging current doesn't need to go thru the LED's in
the OptoCouplers, but some means is needed to tell the TL431's to turn
off.

Perhaps parallel the LED's (with ballast resistors)?

...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| San Tan Valley, AZ 85142 Skype: skypeanalog | |
| Voice480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.
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Default Super Capacitor Voltage Protection Circuit

On Thu, 14 Aug 2014 12:36:24 -0700, Jim Thompson
wrote:

On 08 Aug 2014 15:50:31 GMT, EngineeringGuy
wrote:

When connecting "super capacitors" in series to increase the working
voltage above the level of the individual capacitors, does anyone have an
active voltage clamp that would not discharge the capacitors when the power
supply is disconnected? Most "super" capacitors have a working voltage of
2.5 or 2.7 VDC... I would like to connect 10 capacitors in series for a 25
VDC capacitor stack. Most suggestions call for connecting equalizing
resistors in parallel with each capacitor, but I would rather have a
circuit that would not discharge the capacitors when the power is off...
anyone have any ideas?

Thanks,

Bill


Food for thought, see...

http://www.analog-innovations.com/SED/ChargeLimiter_SuperCap.png

Obviously the charging current doesn't need to go thru the LED's in
the OptoCouplers, but some means is needed to tell the TL431's to turn
off.

Perhaps parallel the LED's (with ballast resistors)?

...Jim Thompson


As in...

http://www.analog-innovations.com/SED/ChargeLimiter_SuperCap_v2.png

...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| San Tan Valley, AZ 85142 Skype: skypeanalog | |
| Voice480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.
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Default Super Capacitor Voltage Protection Circuit

In article ,
Jim Thompson
wrote:

On 13 Aug 2014 04:31:20 GMT, EngineeringGuy
wrote:

[snip]


Jim... I haven't vanished, just out of town. I don't quite understand
what clairification you require... 10 caps in series to give 27VDC total
operating voltage.. each with "something" in parallel to prevent over
voltage... overvoltage will cause "super capacitors" to short and fail..
that "something" must be such that it will not discharge the capacitors
when the 25 volts is removed, turned off, disconnected, not charging,
etc.

Bill


How much shunt resistance across each cell is tolerable when _not_
charging?

...Jim Thompson


I've seen ratings of 2 to 10 microamps internal leakage per farad at
25C after holding the voltage for 72 hours. That's around 0 to 0.5V per
day self discharge? The working voltage depends on temperature so
getting them hot can take them 0.5V down from a full charge quickly.

I've used them to keep mobile solar devices working as they pass through
shade. They're hardly ideal capacitors since you're moving charges
around in two films of carbon gel soaked with electrolyte. Their
voltage fluctuates for a while after sudden charging or discharging.
Some models have an ESR so crazy low that 0.1V of residual charge can
weld the pins together.

--
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Default Super Capacitor Voltage Protection Circuit

On Wed, 13 Aug 2014 18:37:24 -0700, Jim Thompson
wrote:

On Wed, 13 Aug 2014 18:02:27 -0700, John Larkin
wrote:
[snip]


This is one of those annoying cases where the OP has vanished after
the initial post and is not answering questions. Without more info,
it's a wasted effort.

Something along the lines of Field's relay method post... maybe with
MOSFET's... is most likely to succeed... just needs the right
controls
:-}

...Jim Thompson


Jim... I haven't vanished, just out of town. I don't quite understand
what clairification you require... 10 caps in series to give 27VDC total
operating voltage.. each with "something" in parallel to prevent over
voltage... overvoltage will cause "super capacitors" to short and fail..
that "something" must be such that it will not discharge the capacitors
when the 25 volts is removed, turned off, disconnected, not charging,
etc.

Bill


Do you know how much voltage is safe for those caps? Do you have a
voltage:current curve?


Do you have a clue? Not likely :-}

...Jim Thompson


Look at some supercap data sheets. On most, the only spec is operating voltage
and ESR. I've never see a voltage vs leakage current curve.

Seems to me that if you want to protect these things, you should know something
about them. And if it's not on the data sheet, measure a few. If I had any, I'd
measure them myself.

If they are charged by a modest constant current, do they go POP like a
film-foil cap, or do they just level off, like a wet electrolytic? [1] I'd
suspect the latter.

Would a series string self-equalize? A v:i curve might answer that question.

You seen to be promoting ignorance. Nothing new there.

[1] polymer electrolytics go POP!


--

John Larkin Highland Technology Inc
www.highlandtechnology.com jlarkin at highlandtechnology dot com

Precision electronic instrumentation


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Default Super Capacitor Voltage Protection Circuit

On Thu, 14 Aug 2014 12:52:10 -0700, Jim Thompson
wrote:

On Thu, 14 Aug 2014 12:36:24 -0700, Jim Thompson
wrote:

On 08 Aug 2014 15:50:31 GMT, EngineeringGuy
wrote:

When connecting "super capacitors" in series to increase the working
voltage above the level of the individual capacitors, does anyone have an
active voltage clamp that would not discharge the capacitors when the power
supply is disconnected? Most "super" capacitors have a working voltage of
2.5 or 2.7 VDC... I would like to connect 10 capacitors in series for a 25
VDC capacitor stack. Most suggestions call for connecting equalizing
resistors in parallel with each capacitor, but I would rather have a
circuit that would not discharge the capacitors when the power is off...
anyone have any ideas?

Thanks,

Bill


Food for thought, see...

http://www.analog-innovations.com/SED/ChargeLimiter_SuperCap.png

Obviously the charging current doesn't need to go thru the LED's in
the OptoCouplers, but some means is needed to tell the TL431's to turn
off.

Perhaps parallel the LED's (with ballast resistors)?

...Jim Thompson


As in...

http://www.analog-innovations.com/SED/ChargeLimiter_SuperCap_v2.png

...Jim Thompson


Less sensitivity to OptoCoupler CTR (current transfer ratio)...

http://www.analog-innovations.com/SED/ChargeLimiter_SuperCap_v3.png

...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| San Tan Valley, AZ 85142 Skype: skypeanalog | |
| Voice480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.
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Default Super Capacitor Voltage Protection Circuit

On Fri, 08 Aug 2014 15:50:31 +0000, EngineeringGuy wrote:

When connecting "super capacitors" in series to increase the working
voltage above the level of the individual capacitors, does anyone have
an active voltage clamp that would not discharge the capacitors when the
power supply is disconnected? Most "super" capacitors have a working
voltage of 2.5 or 2.7 VDC... I would like to connect 10 capacitors in
series for a 25 VDC capacitor stack. Most suggestions call for
connecting equalizing resistors in parallel with each capacitor, but I
would rather have a circuit that would not discharge the capacitors when
the power is off... anyone have any ideas?

Thanks,

Bill


There are commercial products for this purpose, for example: http://
www.aldinc.com/pdf/ALD8100xx.pdf. These also have a reverse diode built
in but they don't give any specs on it so you may need to be concerned
about that.

--
Jim Mueller

To get my real email address, replace wrongname with dadoheadman.
Then replace nospam with fastmail. Lastly, replace com with us.
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