In message , Mr. Benn
writes
"OG" wrote in message
...

"john hamiliton" wrote in message
...
My pocket sized DAB radio eats AAA size batteries like there is no
tomorrow.

Maplin are selling so called 'Hybrid' rechargable AAA 800 mAh at
four for £10.99. Whilst Argos are selling four 'ordinary
rechargable' AAA 850 mAh at £5.99 (and 1000 mAh AAA at £14.99,
which seems a big jump in proportional price for another 150 mAh ? )

In this DAB radio situation, would so called *Hybrids* be of any
extra advantage, considering they are practically twice the price of
Argos?

Grateful for any advice on the latest state of play with these
rechargable batteries, and any info on where best to buy them from.
Thanks.

Hybrids are better than ordinary NiMH batteries because they provide
a slightly higher voltage for longer. As it's usually the drop off in
voltage that triggers the 'low battery' warning you may well find that
a 850mAh hybrid will be significantly better than a 1000mAh ordinary
one, at least that's what I've found with my digital camera.

Hybrids have slightly less capacity than regular NiMH batteries but
lower self-discharge rate and hence longer shelf life. For a DAB radio
that's not used infrequently, I'd be inclined to use regular cells.

Are 'modern' DAB radios designed to work with the lower voltage you get
from NiMH (1.2V compared with 1.5V for non-rechargeable)? I've not tried
it lately, but I recall that my DAB radio (my ONLY DAB radio) doesn't
last long on rechargeables - maybe only an hour or two. After that, it
will keep going for some time on FM.
--
Ian

On Tue, 15 Jun 2010, Ian Jackson wrote:


Are 'modern' DAB radios designed to work with the lower voltage you get from
NiMH (1.2V compared with 1.5V for non-rechargeable)? I've not tried it
lately, but I recall that my DAB radio (my ONLY DAB radio) doesn't last long
on rechargeables - maybe only an hour or two. After that, it will keep going
for some time on FM.


I have one that takes C size cells and it just doesn't work with
rechargable. I tried with some old nicads. It works if I put an extra
two into the circuit.

I have a couple of Roberts dab radios that have a switch to select battery
type. These seem OK.

Alan

In message ford.ac,
Alan Clifford writes
On Tue, 15 Jun 2010, Ian Jackson wrote:


Are 'modern' DAB radios designed to work with the lower voltage you
get from NiMH (1.2V compared with 1.5V for non-rechargeable)? I've
not tried it lately, but I recall that my DAB radio (my ONLY DAB
radio) doesn't last long on rechargeables - maybe only an hour or
two. After that, it will keep going for some time on FM.


I have one that takes C size cells and it just doesn't work with
rechargable. I tried with some old nicads. It works if I put an extra
two into the circuit.

I have a couple of Roberts dab radios that have a switch to select
battery type. These seem OK.

Noted. Thanks.
Of course, in most sets, you can't simply add a couple more batteries.
--
Ian

"Ian Jackson" wrote in message
...
In message ford.ac,
Alan Clifford writes
On Tue, 15 Jun 2010, Ian Jackson wrote:
snip
Noted. Thanks.
Of course, in most sets, you can't simply add a couple more batteries.
Ian

It depends on the battery case layout.
e.g. a series pair of AA can be substituted with 3 x 2/3rd AA

and C cells can be had in 2/3 3/5, etc. sizes

http://www.powerstream.com/Size.htm

Steve Terry
--
Welcome Sign-up Bonus of £1 when you signup free at:
http://www.topcashback.co.uk/ref/G4WWK

Ian Jackson wrote:

Are 'modern' DAB radios designed to work with the lower voltage you get
from NiMH (1.2V compared with 1.5V for non-rechargeable)? I've not tried
it lately, but I recall that my DAB radio (my ONLY DAB radio) doesn't
last long on rechargeables - maybe only an hour or two. After that, it
will keep going for some time on FM.

That's going to be expensive on non-rechargeables! The end point
voltage for alkalines is about 0.9 volts, and they spend quite a lot of
their life below 1.2.

David Woolley wrote:

Ian Jackson wrote:

Are 'modern' DAB radios designed to work with the lower voltage you
get from NiMH

That's going to be expensive on non-rechargeables! The end point voltage
for alkalines is about 0.9 volts, and they spend quite a lot of their
life below 1.2.

My Pure Evoke3 can either take C-Cells or a rechargeable battery pack,
it worked OK on normal NiMH C-Cells but I kept forgetting to take them
out and recharge them, so I bought their special pack (which contains
NiMH C cells and a small PCB and connects to a dedicated charging socket
not the battery terminals) this worked ok, but their charging circuit
absolutely cooked the NiMHs they were hot all the time, and didn't last
long, reluctantly I bought their newer rechargeable battery pack, which
is a LiPo and seems to charge sensibly ...

In message , Steve Terry
writes
"Ian Jackson" wrote in message
...
In message ford.ac,
Alan Clifford writes
On Tue, 15 Jun 2010, Ian Jackson wrote:
snip
Noted. Thanks.
Of course, in most sets, you can't simply add a couple more batteries.
Ian

It depends on the battery case layout.
e.g. a series pair of AA can be substituted with 3 x 2/3rd AA

and C cells can be had in 2/3 3/5, etc. sizes

http://www.powerstream.com/Size.htm

I know that 'shortened' battery sizes exist, but I've never used them
myself. As they are non-standard, they are not so readily-available, and
(although I haven't checked yet), guess that they are more expensive.
--
Ian

On Tue, 15 Jun 2010, Steve Terry wrote:

"Ian Jackson" wrote in message
...
In message ford.ac,
Alan Clifford writes
On Tue, 15 Jun 2010, Ian Jackson wrote:
snip
Noted. Thanks.
Of course, in most sets, you can't simply add a couple more batteries.
Ian

It depends on the battery case layout.
e.g. a series pair of AA can be substituted with 3 x 2/3rd AA

and C cells can be had in 2/3 3/5, etc. sizes


My solution was rather more heath-Robinson than that. Your information
about battery sizes stored away for future reference though.

We keep that radio plugged into the mains in the kitchen and pretend it
isn't a portable because it isn't really.

Alan

"David Woolley" wrote in message
...
Ian Jackson wrote:

Are 'modern' DAB radios designed to work with the lower voltage you get
from NiMH (1.2V compared with 1.5V for non-rechargeable)? I've not tried
it lately, but I recall that my DAB radio (my ONLY DAB radio) doesn't
last long on rechargeables - maybe only an hour or two. After that, it
will keep going for some time on FM.

That's going to be expensive on non-rechargeables! The end point voltage
for alkalines is about 0.9 volts, and they spend quite a lot of their life
below 1.2.

Indeed.

There is an appallingly large amount of equipment around doesn't get
anywhere near using all the available energy in the expensive batteries that
power it.

I've had particularly bad experiences with digital cameras.

--

Brian Gregory. (In the UK)

To email me remove the letter vee.

"Andy Burns" wrote in message
o.uk...
David Woolley wrote:

Ian Jackson wrote:

Are 'modern' DAB radios designed to work with the lower voltage you
get from NiMH

That's going to be expensive on non-rechargeables! The end point voltage
for alkalines is about 0.9 volts, and they spend quite a lot of their
life below 1.2.

My Pure Evoke3 can either take C-Cells or a rechargeable battery pack, it
worked OK on normal NiMH C-Cells but I kept forgetting to take them out
and recharge them, so I bought their special pack (which contains NiMH C
cells and a small PCB and connects to a dedicated charging socket not the
battery terminals) this worked ok, but their charging circuit absolutely
cooked the NiMHs they were hot all the time, and didn't last long,
reluctantly I bought their newer rechargeable battery pack, which is a
LiPo and seems to charge sensibly ...

It's much easier to detect when a LiPo cell is fully charged.
And thank goodness it is because they tend to explode if you overcharge
them.

--

Brian Gregory. (In the UK)

To email me remove the letter vee.

"Brian Gregory [UK]" wrote in message
...
"David Woolley" wrote in message
...
Ian Jackson wrote:

Are 'modern' DAB radios designed to work with the lower voltage you get
from NiMH (1.2V compared with 1.5V for non-rechargeable)? I've not tried
it lately, but I recall that my DAB radio (my ONLY DAB radio) doesn't
last long on rechargeables - maybe only an hour or two. After that, it
will keep going for some time on FM.

That's going to be expensive on non-rechargeables! The end point voltage
for alkalines is about 0.9 volts, and they spend quite a lot of their
life below 1.2.

Indeed.

There is an appallingly large amount of equipment around doesn't get
anywhere near using all the available energy in the expensive batteries
that power it.

I've had particularly bad experiences with digital cameras.

If you use alkaline batteries, just keep the 'exhausted' ones and put them
in something else.

I find they run a quartz analogue clock for six months.

--
Max Demian

On Jun 17, 6:46*pm, Bodincus wrote:

And - by the way - since when is the voltage of a battery an indication
of the residual power in it?

http://www.farnell.com/datasheets/97133.pdf

MBQ

On Fri, 18 Jun 2010 03:17:27 -0700 (PDT), "Man at B&Q"
wrote:

On Jun 17, 6:46*pm, Bodincus wrote:

And - by the way - since when is the voltage of a battery an indication
of the residual power in it?

http://www.farnell.com/datasheets/97133.pdf

NiCD and NiMH have a pretty flat discharge curve so the voltage
remains fairly stable until they are about 90% discharged.

Therefore voltage is a fairly good, if crude, way of estimating the
charge left it these types. The same is not true for alkalis.
--
(\__/) M.
(='.'=) Due to the amount of spam posted via googlegroups and
(")_(") their inaction to the problem. I am blocking some articles
posted from there. If you wish your postings to be seen by
everyone you will need use a different method of posting.

On Jun 18, 12:57*pm, Mark
wrote:
On Fri, 18 Jun 2010 03:17:27 -0700 (PDT), "Man at B&Q"

wrote:
On Jun 17, 6:46 pm, Bodincus wrote:

And - by the way - since when is the voltage of a battery an indication
of the residual power in it?

http://www.farnell.com/datasheets/97133.pdf

NiCD and NiMH have a pretty flat discharge curve so the voltage
remains fairly stable until they are about 90% discharged.

Therefore voltage is a fairly good, if crude, way of estimating the
charge left it these types. *

By triggering on the sudden voltage drop.

The same is not true for alkalis.

The manufacturers data sheet seems to disagree with you. The voltage
drop is reasonably linear over service life. What could give a better
indication of remaining charge? It just requires a slightly different
sensing method.

MBQ

Bodincus wrote:


B) However, that proves my point. The relationship between voltage and
residual power is non-linear,

Correct

and the residual power inside the battery
- whatever type it is - is not related to the voltage between the dipoles.

Incorrect.


So WHY the devices are still using voltage as a value to measure if a
battery is still delivering the needed power?


Because it works.

"Mark" wrote in message
...
On Fri, 18 Jun 2010 03:17:27 -0700 (PDT), "Man at B&Q"
wrote:

On Jun 17, 6:46 pm, Bodincus wrote:

And - by the way - since when is the voltage of a battery an indication
of the residual power in it?

http://www.farnell.com/datasheets/97133.pdf

NiCD and NiMH have a pretty flat discharge curve so the voltage
remains fairly stable until they are about 90% discharged.

Therefore voltage is a fairly good, if crude, way of estimating the
charge left it these types. The same is not true for alkalis.

The voltage change is so small with Ni-Cad and Ni-MH that differences due to
ambient temperature changes and between individual cells (due to impurities
maybe, I don't know) can be nearly as much and can make any estimate of
charge left unreliable.

--

Brian Gregory. (In the UK)

To email me remove the letter vee.

"Man at B&Q" wrote in message
...
The same is not true for alkalis.

The manufacturers data sheet seems to disagree with you. The voltage
drop is reasonably linear over service life. What could give a better
indication of remaining charge? It just requires a slightly different
sensing method.

Those graphs are for a highly artificial case of a constant discharge.

You'll probably find quite a variation in the voltage of a cell with, say,
50% of it's energy left depending on how quickly it was discharged to that
point.

--

Brian Gregory. (In the UK)

To email me remove the letter vee.

"Bodincus" wrote in message
news:wGJSn.71497$nW1.35752@hurricane...
(18/06/10 11:17), Man at B&Q:
On Jun 17, 6:46 pm, wrote:

And - by the way - since when is the voltage of a battery an indication
of the residual power in it?

http://www.farnell.com/datasheets/97133.pdf

MBQ


A) That's for alkaline batteries, not rechargeables, and we know the
pattern is massively different. Rechargeables have a voltage peak at the
beginning, then they settle to an average for longer than normal
batteries, then they fall sharply (sharper than that graphs).

B) However, that proves my point. The relationship between voltage and
residual power is non-linear, and the residual power inside the battery -
whatever type it is - is not related to the voltage between the dipoles.

There is some relationship it's just not an exact relationship.

Also whether it's linear or not has nothing to do with it, one can easily
adjust for any non linearity of the relationship.

--

Brian Gregory. (In the UK)

To email me remove the letter vee.

On Fri, 18 Jun 2010 13:31:24 +0100, Bodincus
wrote:

B) However, that proves my point. The relationship between voltage and
residual power is non-linear, and the residual power inside the battery
- whatever type it is - is not related to the voltage between the dipoles.

So WHY the devices are still using voltage as a value to measure if a
battery is still delivering the needed power?

What else could they measure?

Bodincus wrote:
(18/06/10 11:17), Man at B&Q:
^^^^^^^^^^

On Jun 17, 6:46 pm, wrote:

And - by the way - since when is the voltage of a battery an indication
of the residual power in it?

http://www.farnell.com/datasheets/97133.pdf

MBQ



snip


BTW, just curious... what MBQ stand for? MegaBecquerel? ;-)


Man at B&Q?

or is that too obvious?
--

Terry

Brian Gregory [UK] wrote:
"Man at B&Q" wrote in message
...
The same is not true for alkalis.

The manufacturers data sheet seems to disagree with you. The voltage
drop is reasonably linear over service life. What could give a better
indication of remaining charge? It just requires a slightly different
sensing method.

Those graphs are for a highly artificial case of a constant discharge.

You'll probably find quite a variation in the voltage of a cell with, say,
50% of it's energy left depending on how quickly it was discharged to that
point.

No: what you find is variation with discharge rate on ON load voltage.
Off load the voltage on all secondary cells is a reliable, though non
linear, guide to charge state.


Primary cells are different. They 'recover' after a hard discharge as
they depolarise.

Chris Blunt wrote:
On Fri, 18 Jun 2010 13:31:24 +0100, Bodincus
wrote:

B) However, that proves my point. The relationship between voltage and
residual power is non-linear, and the residual power inside the battery
- whatever type it is - is not related to the voltage between the dipoles.

So WHY the devices are still using voltage as a value to measure if a
battery is still delivering the needed power?

What else could they measure?

weight. E=mc^2 and all that ;-) ;-)

On Fri, 18 Jun 2010 13:41:29 +0100, "Brian Gregory [UK]"
wrote:

"Mark" wrote in message
.. .
On Fri, 18 Jun 2010 03:17:27 -0700 (PDT), "Man at B&Q"
wrote:

On Jun 17, 6:46 pm, Bodincus wrote:

And - by the way - since when is the voltage of a battery an indication
of the residual power in it?

http://www.farnell.com/datasheets/97133.pdf

NiCD and NiMH have a pretty flat discharge curve so the voltage
remains fairly stable until they are about 90% discharged.

Therefore voltage is a fairly good, if crude, way of estimating the
charge left it these types. The same is not true for alkalis.

The voltage change is so small with Ni-Cad and Ni-MH that differences due to
ambient temperature changes and between individual cells (due to impurities
maybe, I don't know) can be nearly as much and can make any estimate of
charge left unreliable.

Maybe I did not phrase my point well. What I meant was an absolute
voltage threshold is a useful way of detecting when a NiCD or NiMH is
nearly fully discharged. It's the way my digital camera uses. This
method is not good when Alkali batteries are used since the voltage
gradually drops as it discharges and the camera will report a dead
battery when there is plenty of life left in it.
--
(\__/) M.
(='.'=) Due to the amount of spam posted via googlegroups and
(")_(") their inaction to the problem. I am blocking some articles
posted from there. If you wish your postings to be seen by
everyone you will need use a different method of posting.

On Jun 18, 2:58*pm, Mark
wrote:
On Fri, 18 Jun 2010 13:41:29 +0100, "Brian Gregory [UK]"



wrote:
"Mark" wrote in message
.. .
On Fri, 18 Jun 2010 03:17:27 -0700 (PDT), "Man at B&Q"
wrote:

On Jun 17, 6:46 pm, Bodincus wrote:

And - by the way - since when is the voltage of a battery an indication
of the residual power in it?

http://www.farnell.com/datasheets/97133.pdf

NiCD and NiMH have a pretty flat discharge curve so the voltage
remains fairly stable until they are about 90% discharged.

Therefore voltage is a fairly good, if crude, way of estimating the
charge left it these types. *The same is not true for alkalis.

The voltage change is so small with Ni-Cad and Ni-MH that differences due to
ambient temperature changes and between individual cells (due to impurities
maybe, I don't know) can be nearly as much and can make any estimate of
charge left unreliable.

Maybe I did not phrase my point well. *What I meant was an absolute
voltage threshold is a useful way of detecting when a NiCD or NiMH is
nearly fully discharged. *It's the way my digital camera uses. *This
method is not good when Alkali batteries are used since the voltage
gradually drops as it discharges and the camera will report a dead
battery when there is plenty of life left in it.

But only because the wrong threshold is being used for the type of
battery.

MBQ

On Jun 18, 2:06*pm, Terry Casey wrote:
Bodincus wrote:
(18/06/10 11:17), Man at B&Q:

* * * * * * * * * * *^^^^^^^^^^

On Jun 17, 6:46 pm, *wrote:

And - by the way - since when is the voltage of a battery an indication
of the residual power in it?

http://www.farnell.com/datasheets/97133.pdf

MBQ

snip



BTW, just curious... what MBQ stand for? MegaBecquerel? ;-)

Man at B&Q?

Correct.

Anyone old enough to remember the Man at C&A adverts will understand
the joke.

MBQ

On Fri, 18 Jun 2010 07:23:17 -0700 (PDT), "Man at B&Q"
wrote:

On Jun 18, 2:58*pm, Mark
wrote:
On Fri, 18 Jun 2010 13:41:29 +0100, "Brian Gregory [UK]"



wrote:
"Mark" wrote in message
.. .
On Fri, 18 Jun 2010 03:17:27 -0700 (PDT), "Man at B&Q"
wrote:

On Jun 17, 6:46 pm, Bodincus wrote:

And - by the way - since when is the voltage of a battery an indication
of the residual power in it?

http://www.farnell.com/datasheets/97133.pdf

NiCD and NiMH have a pretty flat discharge curve so the voltage
remains fairly stable until they are about 90% discharged.

Therefore voltage is a fairly good, if crude, way of estimating the
charge left it these types. *The same is not true for alkalis.

The voltage change is so small with Ni-Cad and Ni-MH that differences due to
ambient temperature changes and between individual cells (due to impurities
maybe, I don't know) can be nearly as much and can make any estimate of
charge left unreliable.

Maybe I did not phrase my point well. *What I meant was an absolute
voltage threshold is a useful way of detecting when a NiCD or NiMH is
nearly fully discharged. *It's the way my digital camera uses. *This
method is not good when Alkali batteries are used since the voltage
gradually drops as it discharges and the camera will report a dead
battery when there is plenty of life left in it.

But only because the wrong threshold is being used for the type of
battery.

I doubt they have the ability to detect the type of battery used.
--
(\__/) M.
(='.'=) Due to the amount of spam posted via googlegroups and
(")_(") their inaction to the problem. I am blocking some articles
posted from there. If you wish your postings to be seen by
everyone you will need use a different method of posting.

Bodincus wrote:
(18/06/10 13:58), Chris Blunt:
On Fri, 18 Jun 2010 13:31:24 +0100,
wrote:

B) However, that proves my point. The relationship between voltage and
residual power is non-linear, and the residual power inside the battery
- whatever type it is - is not related to the voltage between the
dipoles.

So WHY the devices are still using voltage as a value to measure if a
battery is still delivering the needed power?

What else could they measure?
During idle time, small bursts through a fixed resistance circuit to
measure both voltage (and its drop under load), and current.
A bit of computation and you can measure how much oomphf the cell has left.
BTW, I hereby claim Intellectual Property for this idea.

claim away.

Its nonsense.

Knowing what current you can draw is meaningless.

Man at B&Q wrote:
On Jun 18, 2:58 pm, Mark
wrote:
On Fri, 18 Jun 2010 13:41:29 +0100, "Brian Gregory [UK]"



wrote:
"Mark" wrote in message
...
On Fri, 18 Jun 2010 03:17:27 -0700 (PDT), "Man at B&Q"
wrote:
On Jun 17, 6:46 pm, Bodincus wrote:
And - by the way - since when is the voltage of a battery an indication
of the residual power in it?
http://www.farnell.com/datasheets/97133.pdf
NiCD and NiMH have a pretty flat discharge curve so the voltage
remains fairly stable until they are about 90% discharged.
Therefore voltage is a fairly good, if crude, way of estimating the
charge left it these types. The same is not true for alkalis.
The voltage change is so small with Ni-Cad and Ni-MH that differences due to
ambient temperature changes and between individual cells (due to impurities
maybe, I don't know) can be nearly as much and can make any estimate of
charge left unreliable.
Maybe I did not phrase my point well. What I meant was an absolute
voltage threshold is a useful way of detecting when a NiCD or NiMH is
nearly fully discharged. It's the way my digital camera uses. This
method is not good when Alkali batteries are used since the voltage
gradually drops as it discharges and the camera will report a dead
battery when there is plenty of life left in it.

But only because the wrong threshold is being used for the type of
battery.


google depolarisation of primary cell and see why it doesn't work.

MBQ

In article , The Natural Philosopher
wrote:
Bodincus wrote:
(18/06/10 13:58), Chris Blunt:
On Fri, 18 Jun 2010 13:31:24 +0100,
wrote:

B) However, that proves my point. The relationship between voltage
and residual power is non-linear, and the residual power inside the
battery - whatever type it is - is not related to the voltage
between the dipoles.

So WHY the devices are still using voltage as a value to measure if a
battery is still delivering the needed power?

What else could they measure?
During idle time, small bursts through a fixed resistance circuit to
measure both voltage (and its drop under load), and current. A bit of
computation and you can measure how much oomphf the cell has left. BTW,
I hereby claim Intellectual Property for this idea.

claim away.

Its nonsense.

Knowing what current you can draw is meaningless.

The way of testing partly discharged U2s (aka D-cells) at TVC was to put an
AVO on the 10 amp range across the battery terminals. It the needle kicked
up to 5 Amps, then they could go out again in a Uher; if not, they went in
a box marked 'Used', from which we helped ourselves.

--
From KT24

Using a RISC OS computer running v5.16

Mark wrote:
On Fri, 18 Jun 2010 07:23:17 -0700 (PDT), "Man at B&Q"
wrote:

On Jun 18, 2:58 pm, Mark
wrote:
On Fri, 18 Jun 2010 13:41:29 +0100, "Brian Gregory [UK]"



wrote:
"Mark" wrote in message
...
On Fri, 18 Jun 2010 03:17:27 -0700 (PDT), "Man at B&Q"
wrote:
On Jun 17, 6:46 pm, Bodincus wrote:
And - by the way - since when is the voltage of a battery an indication
of the residual power in it?
http://www.farnell.com/datasheets/97133.pdf
NiCD and NiMH have a pretty flat discharge curve so the voltage
remains fairly stable until they are about 90% discharged.
Therefore voltage is a fairly good, if crude, way of estimating the
charge left it these types. The same is not true for alkalis.
The voltage change is so small with Ni-Cad and Ni-MH that differences due to
ambient temperature changes and between individual cells (due to impurities
maybe, I don't know) can be nearly as much and can make any estimate of
charge left unreliable.
Maybe I did not phrase my point well. What I meant was an absolute
voltage threshold is a useful way of detecting when a NiCD or NiMH is
nearly fully discharged. It's the way my digital camera uses. This
method is not good when Alkali batteries are used since the voltage
gradually drops as it discharges and the camera will report a dead
battery when there is plenty of life left in it.
But only because the wrong threshold is being used for the type of
battery.

I doubt they have the ability to detect the type of battery used.

Mine has a menu setting for the type of battery being used.

--
Adrian

charles wrote:
In article , The Natural Philosopher
wrote:
Bodincus wrote:
(18/06/10 13:58), Chris Blunt:
On Fri, 18 Jun 2010 13:31:24 +0100,
wrote:

B) However, that proves my point. The relationship between voltage
and residual power is non-linear, and the residual power inside the
battery - whatever type it is - is not related to the voltage
between the dipoles.

So WHY the devices are still using voltage as a value to measure if a
battery is still delivering the needed power?
What else could they measure?
During idle time, small bursts through a fixed resistance circuit to
measure both voltage (and its drop under load), and current. A bit of
computation and you can measure how much oomphf the cell has left. BTW,
I hereby claim Intellectual Property for this idea.

claim away.

Its nonsense.

Knowing what current you can draw is meaningless.

The way of testing partly discharged U2s (aka D-cells) at TVC was to put an
AVO on the 10 amp range across the battery terminals. It the needle kicked
up to 5 Amps, then they could go out again in a Uher; if not, they went in
a box marked 'Used', from which we helped ourselves.

Those are primary cells, not secondary cells.


Do that to Nickel or lithiums, and you risk a small explosion.

Bodincus wrote:
(18/06/10 15:38), The Natural Philosopher:
Bodincus wrote:
(18/06/10 13:58), Chris Blunt:
On Fri, 18 Jun 2010 13:31:24 +0100,
wrote:

B) However, that proves my point. The relationship between voltage and
residual power is non-linear, and the residual power inside the
battery
- whatever type it is - is not related to the voltage between the
dipoles.

So WHY the devices are still using voltage as a value to measure if a
battery is still delivering the needed power?

What else could they measure?
During idle time, small bursts through a fixed resistance circuit to
measure both voltage (and its drop under load), and current.
A bit of computation and you can measure how much oomphf the cell has
left.
BTW, I hereby claim Intellectual Property for this idea.

claim away.

Its nonsense.

Knowing what current you can draw is meaningless.
C'mon, New Scientist, enlighten us...
Why should it be meaningless???
Bah...


Because teh internal impedance of a secondary cell is not a function of
its charge state by and large, and measuring it is fraught with danger
of any serious current is drawn.


PLONK

"The Natural Philosopher" wrote in message
...
Brian Gregory [UK] wrote:
"Man at B&Q" wrote in message
...
The same is not true for alkalis.

The manufacturers data sheet seems to disagree with you. The voltage
drop is reasonably linear over service life. What could give a better
indication of remaining charge? It just requires a slightly different
sensing method.

Those graphs are for a highly artificial case of a constant discharge.

You'll probably find quite a variation in the voltage of a cell with,
say, 50% of it's energy left depending on how quickly it was discharged
to that point.

No: what you find is variation with discharge rate on ON load voltage. Off
load the voltage on all secondary cells is a reliable, though non linear,
guide to charge state.


Primary cells are different. They 'recover' after a hard discharge as they
depolarise.

If you READ what I was commenting on you'll find it was primary cells I was
commenting on.

--

Brian Gregory. (In the UK)

To email me remove the letter vee.

"Bodincus" wrote in message
news:8AKSn.66732$D81.21518@hurricane...
(18/06/10 13:58), Chris Blunt:
On Fri, 18 Jun 2010 13:31:24 +0100,
wrote:

B) However, that proves my point. The relationship between voltage and
residual power is non-linear, and the residual power inside the battery
- whatever type it is - is not related to the voltage between the
dipoles.

So WHY the devices are still using voltage as a value to measure if a
battery is still delivering the needed power?

What else could they measure?
During idle time, small bursts through a fixed resistance circuit to
measure both voltage (and its drop under load), and current.
A bit of computation and you can measure how much oomphf the cell has
left.
BTW, I hereby claim Intellectual Property for this idea.

So when your camera suspects the battery is low it connects a resistor
across it and turns it from a suspicion into a fact?

:-)

--

Brian Gregory. (In the UK)

To email me remove the letter vee.

Brian Gregory [UK] wrote:
"Bodincus" wrote in message
news:8AKSn.66732$D81.21518@hurricane...
(18/06/10 13:58), Chris Blunt:
On Fri, 18 Jun 2010 13:31:24 +0100,
wrote:

B) However, that proves my point. The relationship between voltage and
residual power is non-linear, and the residual power inside the battery
- whatever type it is - is not related to the voltage between the
dipoles.

So WHY the devices are still using voltage as a value to measure if a
battery is still delivering the needed power?
What else could they measure?
During idle time, small bursts through a fixed resistance circuit to
measure both voltage (and its drop under load), and current.
A bit of computation and you can measure how much oomphf the cell has
left.
BTW, I hereby claim Intellectual Property for this idea.

So when your camera suspects the battery is low it connects a resistor
across it and turns it from a suspicion into a fact?

:-)

yeah. well. no more foolish thatn any other suggestion.

Are 'modern' DAB radios designed to work with the lower voltage you get
from NiMH (1.2V compared with 1.5V for non-rechargeable)? I've not tried
it lately, but I recall that my DAB radio (my ONLY DAB radio) doesn't
last long on rechargeables - maybe only an hour or two. After that, it
will keep going for some time on FM.
You're thinking of NiCads. NiMhs are 1.5V.

spacecadet wrote:

You're thinking of NiCads. NiMhs are 1.5V.

Err, no. NiCd and NiMH are ~1.2V, Zinc carbon and alkaline cells are 1.5V

spacecadet wrote:

Are 'modern' DAB radios designed to work with the lower voltage you
get from NiMH (1.2V compared with 1.5V for non-rechargeable)? I've not
tried it lately, but I recall that my DAB radio (my ONLY DAB radio)
doesn't last long on rechargeables - maybe only an hour or two. After
that, it will keep going for some time on FM.
You're thinking of NiCads. NiMhs are 1.5V.

No, they are not.

On Sat, 19 Jun 2010 09:31:25 +0100, spacecadet
wrote:

You're thinking of NiCads. NiMhs are 1.5V.

No. NiMhs are 1.2 - 1.3 Volts.

On Fri, 18 Jun 2010 14:32:52 +0100, Bodincus
wrote:

(18/06/10 13:58), Chris Blunt:
On Fri, 18 Jun 2010 13:31:24 +0100,
wrote:

B) However, that proves my point. The relationship between voltage and
residual power is non-linear, and the residual power inside the battery
- whatever type it is - is not related to the voltage between the dipoles.

So WHY the devices are still using voltage as a value to measure if a
battery is still delivering the needed power?

What else could they measure?
During idle time, small bursts through a fixed resistance circuit to
measure both voltage (and its drop under load), and current.
A bit of computation and you can measure how much oomphf the cell has left.

The additional components required to do that will all add additional
cost and weight to the device, as well as further draining the
battery. It doesn't make much sense to unnecessarily put extra load on
a battery when what you are trying to achieve is to squeeze as much
life out of it as possible.