A long time ago I bought a flexible solar panel (the type you stick on
boats or strap to the boom).
Just to play with.
It is a Uni-Solar 5W(!) panel.

I soon found that you have to have something to stop the panel drawing
current when the sun doesn't shine.
Back in the box for a bit (where a bit is of undefined length).

I'm now thinking of playing with it again and am looking for a simple
controller.

There are loads of apparently different brands on Amazon for around £10
upwards.

https://www.amazon.co.uk/solar-panel...?k=solar+panel
+controller

A remarkable number seem to have the LCD screen, USB ports, buttons etc.
all in identical places which suggests that they may all be one product
(or at least underlying board).

https://www.amazon.com/solar-panel-controller/s?k=solar+panel+controller

seems to show this more markedly.

Does anyone have any experience of these, perhaps enough to make a
recommendation?

Still only playing.

Cheers



Dave R

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On 27 Jun 2020 11:41:06 GMT, David wrote:

snip

Does anyone have any experience of these, perhaps enough to make a
recommendation?


Sort of.

Daughter had an electric fence around a rabbit hutch, powered by a 12V
17Ah sealed battery. On every night and if the area wasn't attended (=
my Mum was away g) and the battery would last (safely) over a week.

I added a 5W solar panel and one of the LCD / USB controllers you
mentioned and the battery would then last nearer 3 weeks.

The reason it wasn't more was mainly down to the fact the panel wasn't
anywhere near optimally mounted, in fact it would only be exposed to
any real sunlight for a couple of hours each day.

The real reason for adding the controller was it allowed the electric
fence to run automatically only dusk to dawn and protected the battery
from over discharge.

The 'problem' with any of these controllers and smaller panels is the
parasitic energy they draw to run themselves.

I could have re-orientated the panel, got a bigger panel or put
another panel at the other end of the building (to catch the sun later
in the day) but it was easier to just swap the battery for it's
partner and on an Optimate 2 charge / maintainer.

So, unless you know the overall balance of the system (worst case
energy in V typical energy out) is 'suitable' for your needs and so if
a controller is 'worth it', you may be better off with just an
anti-discharge protection diode.

Whilst a controller is a must to protect a battery from overcharge, if
the panel can deliver more current (and voltage) than the battery
should get once fully charged, the use of one with smaller panels
(where the ability of the panel is offset by the self discharge of the
controller) only really works to protect the battery from over
discharge, ironically, partially caused by the controller itself.

Cheers, T i m

On 27 Jun 2020 11:41:06 GMT, David wrote:

A remarkable number seem to have the LCD screen, USB ports, buttons etc.

Stikes me as a good way to use all the 5W (in bright direct sunlight)
output of the panel, giving no nett benefit...

all in identical places which suggests that they may all be one product
(or at least underlying board).

Wouldn't be surprised, lots of gadgets are based on the same
underlying chipset if not board.

Still only playing.

The "controller" in my small solar panel is nothing more than a
series schotty diode and a self flashing blue LED. When the LED is on
the battery doesn't get charged unless the panel is well illuminated.
Schotty diode as they have less forward volt drop than silicon.

--
Cheers
Dave.

On Saturday, 27 June 2020 12:41:09 UTC+1, David WE Roberts (Google) wrote:
A long time ago I bought a flexible solar panel (the type you stick on
boats or strap to the boom).
Just to play with.
It is a Uni-Solar 5W(!) panel.

I soon found that you have to have something to stop the panel drawing
current when the sun doesn't shine.
Back in the box for a bit (where a bit is of undefined length).

I'm now thinking of playing with it again and am looking for a simple
controller.

There are loads of apparently different brands on Amazon for around £10
upwards.

https://www.amazon.co.uk/solar-panel...?k=solar+panel
+controller

A remarkable number seem to have the LCD screen, USB ports, buttons etc.
all in identical places which suggests that they may all be one product
(or at least underlying board).

https://www.amazon.com/solar-panel-controller/s?k=solar+panel+controller

seems to show this more markedly.

Does anyone have any experience of these, perhaps enough to make a
recommendation?

Still only playing.

Cheers



Dave R

Assuming you're charging a lead acid battery and it's not SLA, 5w is not enough to need a controller. A diode stops any discharge.


NT

On Sat, 27 Jun 2020 07:22:11 -0700 (PDT), wrote:
true

Assuming you're charging a lead acid battery and it's not SLA, 5w is not enough to need a controller. A diode stops any discharge.

True, but it doesn't prevent any overdischarge of the battery?

The trick is to find a LVD solution that doesn't draw any significant
current itself, or find one where the LVD draws far less than any
potential load.

A latching relay / circuit might be such and could be used to
disconnect itself and the load when the LV threshold was detected.

Cheers, T i m

On Saturday, 27 June 2020 16:05:50 UTC+1, T i m wrote:
On Sat, 27 Jun 2020 07:22:11 -0700 (PDT), tabbypurr wrote:

true

Assuming you're charging a lead acid battery and it's not SLA, 5w is not enough to need a controller. A diode stops any discharge.

True, but it doesn't prevent any overdischarge of the battery?

yees

The trick is to find a LVD solution that doesn't draw any significant
current itself, or find one where the LVD draws far less than any
potential load.

A latching relay / circuit might be such and could be used to
disconnect itself and the load when the LV threshold was detected.

Cheers, T i m

I don't recall the op requesting a discharge protecting relay. If he wants one, I would not regard it as a trick in any way, just some basic electronics. A bistable relay can eliminate most of the current draw. Drive it with a low current opamp, 2 transistors or fets & 2 big caps and Robert's your relative.


NT

On Sat, 27 Jun 2020 10:58:18 -0700 (PDT), wrote:

On Saturday, 27 June 2020 16:05:50 UTC+1, T i m wrote:
On Sat, 27 Jun 2020 07:22:11 -0700 (PDT), tabbypurr wrote:

true

Assuming you're charging a lead acid battery and it's not SLA, 5w is not enough to need a controller. A diode stops any discharge.

True, but it doesn't prevent any overdischarge of the battery?

yees

So not provided by a simple diode.

The trick is to find a LVD solution that doesn't draw any significant
current itself, or find one where the LVD draws far less than any
potential load.

A latching relay / circuit might be such and could be used to
disconnect itself and the load when the LV threshold was detected.


I don't recall the op requesting a discharge protecting relay.

He didn't specifically request a lot of things but did request general
advice.

If he wants one, I would not regard it as a trick in any way, just some basic electronics.

'Basic electronics' that provides the LVD function whilst not
consuming any power itself?

A bistable relay can eliminate most of the current draw.

I know, I suggested it.

Drive it with a low current opamp, 2 transistors or fets & 2 big caps and Robert's your relative.

Schematic? ;-)

The point was, whilst a simple series diode can negate any self
discharge by the panel (and should be built into most panels in any
case), a big hole many fall into is wrecking a perfectly good /
expensive battery by over discharging it. So, it might be considered
'better' to have a less efficient system that protects the battery
than a more efficient one without.

The OP was looking for feedback from people who had experience of the
items he referenced, and I have ... and one of the 'virtues' is that
they typically protect the battery from over discharge.

Cheers, T i m

On Saturday, 27 June 2020 20:16:24 UTC+1, T i m wrote:
On Sat, 27 Jun 2020 10:58:18 -0700 (PDT), tabbypurr wrote:
On Saturday, 27 June 2020 16:05:50 UTC+1, T i m wrote:
On Sat, 27 Jun 2020 07:22:11 -0700 (PDT), tabbypurr wrote:

true

Assuming you're charging a lead acid battery and it's not SLA, 5w is not enough to need a controller. A diode stops any discharge.

True, but it doesn't prevent any overdischarge of the battery?

yees

So not provided by a simple diode.

ICBA to explain the obvious


The trick is to find a LVD solution that doesn't draw any significant
current itself, or find one where the LVD draws far less than any
potential load.

A latching relay / circuit might be such and could be used to
disconnect itself and the load when the LV threshold was detected.


I don't recall the op requesting a discharge protecting relay.

He didn't specifically request a lot of things but did request general
advice.

If he wants one, I would not regard it as a trick in any way, just some basic electronics.

'Basic electronics' that provides the LVD function whilst not
consuming any power itself?

If you manage to invent electronics tht uses no power I'm sure the world will be curious. Do you have any other silly requests?

A bistable relay can eliminate most of the current draw.

I know, I suggested it.

Drive it with a low current opamp, 2 transistors or fets & 2 big caps and Robert's your relative.

Schematic? ;-)

feel free.

The point was, whilst a simple series diode can negate any self
discharge by the panel (and should be built into most panels in any
case),

There are sound reasons why they aren't. If you run panels in series you don't benefit from multiple V drops. There are also ways to prevent discharge that don't drop a volt or so under load.

a big hole many fall into is wrecking a perfectly good /
expensive battery by over discharging it.

Yes. And some are more careful. And in some situations it's better to run it low on infrequent occasion than cut off early etc.


So, it might be considered
'better' to have a less efficient system that protects the battery
than a more efficient one without.

The OP was looking for feedback from people who had experience of the
items he referenced, and I have ... and one of the 'virtues' is that
they typically protect the battery from over discharge.

Cheers, T i m

It's hard to know what the op wants without enough detail.


NT

wrote:
On Saturday, 27 June 2020 16:05:50 UTC+1, T i m wrote:
On Sat, 27 Jun 2020 07:22:11 -0700 (PDT), tabbypurr wrote:

true

Assuming you're charging a lead acid battery and it's not SLA, 5w is not enough to need a controller. A diode stops any discharge.

True, but it doesn't prevent any overdischarge of the battery?

yees

The trick is to find a LVD solution that doesn't draw any significant
current itself, or find one where the LVD draws far less than any
potential load.

A latching relay / circuit might be such and could be used to
disconnect itself and the load when the LV threshold was detected.

Cheers, T i m

I don't recall the op requesting a discharge protecting relay. If he wants one, I would not regard it as a trick in any way, just some basic electronics. A bistable relay can eliminate most of the current draw. Drive it with a low current opamp, 2 transistors or fets & 2 big caps and Robert's your relative.


NT

https://www.briandorey.com/post/low-...-using-max8212

https://datasheets.maximintegrated.c...11-MAX8212.pdf

The leakage current isn't zero, but it's a relatively simple circuit.

The version here is non-recovering, and you press a reset button
after a battery-rundown event. Not very convenient.

https://www.maximintegrated.com/en/d...tes/9/926.html

Paul

On 27/06/2020 22:08, Paul wrote:

https://www.briandorey.com/post/low-...-using-max8212

https://datasheets.maximintegrated.c...11-MAX8212.pdf

The leakage current isn't zero, but it's a relatively simple circuit.

I wonder if it oscillates around the cut off point. 0.3V hysteresis
seems too low.
Battery under load gets to 12.4V and the circuit cuts off the output.
Battery no longer under load and recovers to 12.7V and circuit restores
output.
Battery now under load at 12.4V and ..........

Any circuit that requires a heat sink in such a small enclosed die cast
box is going to run at elevated temperatures. I personally would have
chosen a capacitor temperature rated at 105C




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On Sat, 27 Jun 2020 17:08:27 -0400, Paul
wrote:

snip

https://www.briandorey.com/post/low-...-using-max8212

https://datasheets.maximintegrated.c...11-MAX8212.pdf

The leakage current isn't zero, but it's a relatively simple circuit.

The version here is non-recovering, and you press a reset button
after a battery-rundown event. Not very convenient.

https://www.maximintegrated.com/en/d...tes/9/926.html

The chances are there is something like that built into the charge
controllers you referenced (there certainly was in the one with two
USB outlets as that's the one we used for a couple of years).

I went to turn the electric fence off and found it was already off.
Then I checked to battery voltage (LCD display) and realised why (it
had gone into LVD mode and it hadn't been sunny enough, long enough to
re-trigger it again).

When I was looking for a suitable charge controller (again, really for
the LDV function) I was looking for something 'lightweight' that might
have a correspondingly low parasitic load but couldn't find anything.

The thing is, if the charge to total load capability it's sufficient
to stop the battery flattening in the first place, not having it auto
reset may still be 'better' than destroying a battery?

I have re-cycled too many 'brand new, used a couple of times'
batteries from motorcycles and other roles from lack of maintenance to
know I'd rather avoid that over anything else.

Cheers, T i m

On 27/06/2020 12:41:06, David wrote:
A long time ago I bought a flexible solar panel (the type you stick on
boats or strap to the boom).
Just to play with.
It is a Uni-Solar 5W(!) panel.

That won't supply enough power for the controller's backlight.

Simple diode would be best.

On 27/06/2020 12:41, David wrote:
A long time ago I bought a flexible solar panel (the type you stick on
boats or strap to the boom).
Just to play with.
It is a Uni-Solar 5W(!) panel.

I soon found that you have to have something to stop the panel drawing
current when the sun doesn't shine.

A diode?


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