Charging batteries inside an appliance

[richardghole@yahoo.com]

Hi

A while back I was discussing charging batteries up inside appliances
and received a couple of responses on the thread on Tues, Mar 14 2006
at 3:34 pm. However, I am not sure what battery charger to use if
there is any available. It would have to be a slow charging rate
charger. Many digital cameras are rated at 3 volts but AA batteries are
normally 2.5 volts for 2 AA batteries. Therefore, 3 volts should be
enough to charge them and would not be too high for the camera.
However, I would have to be careful that the batteries did not get too
hot for the camera so a slow charge would be needed.

Are there any battery charges that are suitable or would one have to be
modified? How many hours would a charger have to take so that it would
be safe?

I do have some Nickel Cadmium battery chargers that charge slowly over
about 16 hours but I heard that Nickel Metal Hydride are better for
cameras. I can't understand why Nickel Cadmium chargers cannot be
used for Nickel Metal Hydride batteries. Do you think that the Nickel
Cadmium battery chargers that I have could be easily modified to slowly
charge Nickel Metal Hydride batteries?

I heard that cameras do drain a small amount of power from the battery
even when they are switched off. Rechargeable batteries also discharge
quickly so if a camera is not used for a few months the batteries would
be flat and this would prevent the camera being used quickly.

I am about to make an order from http://www.electusdistribution.com.au/
and am wondering if any of the below charges would work for this
purpose?
MB3520
MB3505.

Your help is appreciated,
Regards Richard.

 

[David L. Jones]

richardghole@yahoo.com wrote:

Hi

A while back I was discussing charging batteries up inside appliances
and received a couple of responses on the thread on Tues, Mar 14 2006
at 3:34 pm. However, I am not sure what battery charger to use if
there is any available. It would have to be a slow charging rate
charger. Many digital cameras are rated at 3 volts but AA batteries are
normally 2.5 volts for 2 AA batteries. Therefore, 3 volts should be
enough to charge them and would not be too high for the camera.
However, I would have to be careful that the batteries did not get too
hot for the camera so a slow charge would be needed.

Why would you want to butcher a camera to slow charge standard AA's
inside??
Why not just take them out and sit them on a commercial trickle
charger?
Put some Alkalines in the camera in the mean time to keep the time/date
going.

Cameras that have a docking cradle will often let you recharge the
batteries in-situ. Does your camera support this?

Are there any battery charges that are suitable or would one have to be
modified? How many hours would a charger have to take so that it would
be safe?

I do have some Nickel Cadmium battery chargers that charge slowly over
about 16 hours but I heard that Nickel Metal Hydride are better for
cameras. I can't understand why Nickel Cadmium chargers cannot be
used for Nickel Metal Hydride batteries. Do you think that the Nickel
Cadmium battery chargers that I have could be easily modified to slowly
charge Nickel Metal Hydride batteries?

There is essentially no difference between the two chargers. You can
use a Nicd charger to charge NiMH's.

I heard that cameras do drain a small amount of power from the battery
even when they are switched off. Rechargeable batteries also discharge
quickly so if a camera is not used for a few months the batteries would
be flat and this would prevent the camera being used quickly.

Yes, the camera takes an almost unmeasurable amount to keep the
time/date clock going. A pair of Alkaline AA's in there will probably
last half the shelf life.

I am about to make an order from http://www.electusdistribution.com.au/
and am wondering if any of the below charges would work for this
purpose?
MB3520
MB3505.

I can't see why you want to do this, why not just take the batteries
out?
Keep them on a wall trickle charger next to the camera and simply pick
them up when you want to use the camera. A few seconds to insert them
and away you go.

Dave

 

[richardghole@yahoo.com]

Hi Dave or whoever can help,

Thanks for the reply.

With the digital camera I have it is very hard and time consuming to
open the battery case. It is a very tight fit. Also it is very easy to
forget to put the batteries in if they are taken out. Having to put
them in would take crucial time if the photograph had to be taken
urgently. For example, I plan to take weather phenomenon that can only
occur for a few seconds at times without notice.

There are some cameras that charge the batteries internally but they
are rare and may not do what I want.

On my Nickel Cadmium charger they warn that it can only be used for
Nickel Cadmium batteries.

Do you know of any suitable charger?

Regards Richard.



David L. Jones wrote:

richardghole@yahoo.com wrote:
Hi

A while back I was discussing charging batteries up inside appliances
and received a couple of responses on the thread on Tues, Mar 14 2006
at 3:34 pm. However, I am not sure what battery charger to use if
there is any available. It would have to be a slow charging rate
charger. Many digital cameras are rated at 3 volts but AA batteries are
normally 2.5 volts for 2 AA batteries. Therefore, 3 volts should be
enough to charge them and would not be too high for the camera.
However, I would have to be careful that the batteries did not get too
hot for the camera so a slow charge would be needed.

Why would you want to butcher a camera to slow charge standard AA's
inside??
Why not just take them out and sit them on a commercial trickle
charger?
Put some Alkalines in the camera in the mean time to keep the time/date
going.

Cameras that have a docking cradle will often let you recharge the
batteries in-situ. Does your camera support this?

Are there any battery charges that are suitable or would one have to be
modified? How many hours would a charger have to take so that it would
be safe?

I do have some Nickel Cadmium battery chargers that charge slowly over
about 16 hours but I heard that Nickel Metal Hydride are better for
cameras. I can't understand why Nickel Cadmium chargers cannot be
used for Nickel Metal Hydride batteries. Do you think that the Nickel
Cadmium battery chargers that I have could be easily modified to slowly
charge Nickel Metal Hydride batteries?

There is essentially no difference between the two chargers. You can
use a Nicd charger to charge NiMH's.

I heard that cameras do drain a small amount of power from the battery
even when they are switched off. Rechargeable batteries also discharge
quickly so if a camera is not used for a few months the batteries would
be flat and this would prevent the camera being used quickly.

Yes, the camera takes an almost unmeasurable amount to keep the
time/date clock going. A pair of Alkaline AA's in there will probably
last half the shelf life.

I am about to make an order from http://www.electusdistribution.com.au/
and am wondering if any of the below charges would work for this
purpose?
MB3520
MB3505.

I can't see why you want to do this, why not just take the batteries
out?
Keep them on a wall trickle charger next to the camera and simply pick
them up when you want to use the camera. A few seconds to insert them
and away you go.

Dave

 

[David L. Jones]

richardghole@yahoo.com wrote:

Hi Dave or whoever can help,

Thanks for the reply.

With the digital camera I have it is very hard and time consuming to
open the battery case. It is a very tight fit. Also it is very easy to
forget to put the batteries in if they are taken out. Having to put
them in would take crucial time if the photograph had to be taken
urgently. For example, I plan to take weather phenomenon that can only
occur for a few seconds at times without notice.

In that case I would seriously consider primary batteries. Alkalines
are fine if you don't take too many shots, otherwise the new Lithium
AA's are the go. Quite expensive, but if you only use infrequently then
probably OK. They have the advantage of working in cold climates too if
that is an issue.
With rechargables you can always forget to charge them, but with
primaries you will always be ready to go.

I keep a pair of AA Alkalines in my old camera in the glove box, always
ready to go no matter what.

There are some cameras that charge the batteries internally but they
are rare and may not do what I want.

On my Nickel Cadmium charger they warn that it can only be used for
Nickel Cadmium batteries.

Ignore it, that is typical manufacturer rubbish. It will work fine with
NiMH's.

Do you know of any suitable charger?

Without knowing your camera I am hesitant to suggest anything.

Incidently, how are you going to modify the camera to take the
connector, sounds real messy...

BTW, if it's crucial that you know the batteries are charged, you'd
better have a charge indicator light on the charger that detects actual
trickle charge current. Otherwise if your custom fitted socket gets a
loose contact, you won't know if the batteries are charged or not.

Dave

 

[Pete]

David L. Jones wrote:

There is essentially no difference between the two chargers. You can
use a Nicd charger to charge NiMH's.

Please don't make stuff up and present it as fact if you don't know the
answer. Your answer couldn't be further from the truth, and if
followed, will likely cause the original poster to needlessly shorten
the life of his cells. NiMh cells do not tolerate over charging, and
most NiCd chargers will overcharge NiMh cells.

However, *generally* an NiMh charger will work for both cell types.

If you want the technical details of why this is the case, just ask. Or
check out the web sites of any manufacturer of NiCd and NiMh cells.

Regards, Peter

 

[richardghole@yahoo.com]

Hi

What if I connected the NiCd charger to a common electric timer that
perhaps left the charger on for half an hour and one hour off in
repeated regular cycles? Perhaps the charger could be turned on for
less time and done less frequently.

I plan on buying another camera as the one I have is a little old. I am
trying to decide on which one.

People who sell the cameras do not recommend AA Alkalines as they say
that they do not last long and are too low an amperage.

Regards Richard.

 

[David L. Jones]

Pete wrote:

David L. Jones wrote:

There is essentially no difference between the two chargers. You can
use a Nicd charger to charge NiMH's.

Please don't make stuff up and present it as fact if you don't know the
answer. Your answer couldn't be further from the truth, and if
followed, will likely cause the original poster to needlessly shorten
the life of his cells. NiMh cells do not tolerate over charging, and
most NiCd chargers will overcharge NiMh cells.

I'm not making stuff up, what I said is perfectly correct for the slow
charging the OP is after. Perhaps I should have made that point clear.
We are not talking about a fast charger here, or even a regular
charger, the OP wants a slow charger to avoid heating the cells while
inside the camera.
Most NiCD chargers are just a constant current source (with cutoff
functions), and CC is a pefectly valid way to charge a NiMH. The life
won't be shortened at all if the OP uses a sufficiently low NiCd
trickle charger on a NiMH.
The OP will be forced to use a very slow trickle charger unless he
wants to put a temp sensor in the camera as well.

However, *generally* an NiMh charger will work for both cell types.

If you want the technical details of why this is the case, just ask. Or
check out the web sites of any manufacturer of NiCd and NiMh cells.

I know all about it already thanks.

Dave

 

[David L. Jones]

richardghole@yahoo.com wrote:

Hi

What if I connected the NiCd charger to a common electric timer that
perhaps left the charger on for half an hour and one hour off in
repeated regular cycles? Perhaps the charger could be turned on for
less time and done less frequently.

Not a good idea, you'll almost certainly overcharge the cells and
shorten their life, unless you use a very low current "trickle"
charger.
You really need a temperature sensor inside the camera to detect if the
cells are being over charged. It's all looking like a pain in the butt
really.

I plan on buying another camera as the one I have is a little old. I am
trying to decide on which one.

Problem solved then, get one with a charging cradle and you can leave
it charging indefinitely.

People who sell the cameras do not recommend AA Alkalines as they say
that they do not last long and are too low an amperage.

Correct.
For high drain devices like cameras the capacity of standard Alkalines
is very poor compared to 2500mAh NiMH. In most cases you are lucky to
get half the number of shots you get with the NiMH's.
Energizer for instance quote the AA 2500mAh NiMH capacity rated at
500mA drain (to 1.0V), where as the AA Alkalines are rated at 25mA
drain to 0.8V. At 500mA drain the Alkalines capacity is only about
1400mAh, and that's to 0.8V, not 1.0V. Most cameras are designed for
NiMh use, so they won't drain down to 0.8V, so you loose even more
capacity there on Alkalines. That's why you'll get roughly half the
number of shots on Alkalines.
Lithium AA's on the other hand are rated at 3000mAh at 250mA drain to
1.0V, so you'll get similar performance to the NiMH's. They are much
more expensive though, but it means you can leave the camera lying
around for years without being charged and it will be ready to go when
needed, guaranteed.

Dave

 

[richardghole@yahoo.com]

Hi

Thanks for the letter.

How slow a battery charger would I need and what output should it have?
I think the NiCad one that I have takes about 16 hours to charge the
batteries.

Why wouldn't the common electronic timer work because if it switches
the charger off for periods, wouldn't it have the same affect as a
slower charger if it does not remain on for long? The timer could even
only switch the charger on for half an hour a day if that is best.

It is unlikely a camera with a charging cradle would have the features
I want as they are rare.

I heard that cameras do drain a small amount of power from the battery
even when they are switched off. This is for the clock etc. So I doubt
that the batteries would last years even for a lithium battery from
what I have read others say.

What do you think about the below non rechargeable battery? They cost
about 10 dollars a pair.

AA Size Lithium Long Lasting Batteries 1.5V - Pk. 2

The worlds longest lasting AA battery. The perfect power source for
high drain appliances, such as cameras, camcorders, personal stereos,
mobile phones, palm top computers and TV's.- Up to 3 times the life of
any alkaline battery.- Up to 10 times the life of ordinary carbon zinc
battery- Guaranteed shelf life up to 10 years.- 1.5V, 1.4Amp hour.-
Pack of 2

Your help is appreciated,
Regards Richard.

 

[David L. Jones]

richardghole@yahoo.com wrote:

Hi

Thanks for the letter.

How slow a battery charger would I need and what output should it have?

It would need to be designed for 2 series AA's (i.e. about 2.4V), and
off the top of my head I would say about 50mA would be fine if you are
going to pulse it on and off as you suggest, then it'll take a few days
to full charge from flat.
If you use higher current you have to be a lot more careful with cycle
times.
Your problem is you won't really know how much charge is left in the
batteries and without overcharge protection you could damage the
batteries.
Like I've said, it's getting messy, I really wouldn't bother doing it.
Have you even thought about how you are going to *reliably* modify the
camera to take a socket and internal wiring to do this? If reliability
and instant readiness of your camera is the #1 priority then the last
thing I would do is modify the battery connections.

I think the NiCad one that I have takes about 16 hours to charge the
batteries.

Why wouldn't the common electronic timer work because if it switches
the charger off for periods, wouldn't it have the same affect as a
slower charger if it does not remain on for long? The timer could even
only switch the charger on for half an hour a day if that is best.

Yes, that can be made to work given the right current.

It is unlikely a camera with a charging cradle would have the features
I want as they are rare.

I would hardly say they are rare. A lot of cameras with Li-Ion
batteries will have internal charging features.
What features do you need?

I heard that cameras do drain a small amount of power from the battery
even when they are switched off. This is for the clock etc. So I doubt
that the batteries would last years even for a lithium battery from
what I have read others say.

They should last for years. The clock takes in the order of microamps
of current. Measure it with a meter if you want to be sure.
My Fuji for example takes about 30uA, so the batteries will last for
essentially the shelf life.
Actually, the camera takes a "gulp" when the bateries are first
inserted, this is to charge the super cap that retains the clock power
while the batteries are replaced.

What do you think about the below non rechargeable battery? They cost
about 10 dollars a pair.

AA Size Lithium Long Lasting Batteries 1.5V - Pk. 2

The worlds longest lasting AA battery. The perfect power source for
high drain appliances, such as cameras, camcorders, personal stereos,
mobile phones, palm top computers and TV's.- Up to 3 times the life of
any alkaline battery.- Up to 10 times the life of ordinary carbon zinc
battery- Guaranteed shelf life up to 10 years.- 1.5V, 1.4Amp hour.-
Pack of 2

Like I said in my other post, Lithium AA's will last as long or longer
than fully charged 2500mAh NiMH's. Modern cameras can get hundreds of
shots from such a set. 500+ shots is not uncommon.
If you only take a few shots here and there then they should last a
very long time and will be the best option.
If you take hundreds of shots in one sitting then you'd have to replace
them after every use.

Dave

 

[richardghole@yahoo.com]

Hi Dave

Thanks for the letter.

I heard that Li-Ion batteries are very expensive and may only last 2
years and that AA would be more economical. So buying a camera with a
charging cradle may be expensive to maintain.

I can try the batteries I described in my last post but it is just the
camera experts recommend rechargeable so I thought I could try both.

You state: "Your problem is you won't really know how much charge is
left in the
batteries and without overcharge protection you could damage the
batteries."
Wouldn't this problem be overcome if I use a Nickel Metal Hydride
charger as they are specially made for these batteries and are not
supposed to over charge them.


Your help is appreciated,
Regards Richard.

 

[David L. Jones]

richardghole@yahoo.com wrote:

Hi Dave

Thanks for the letter.

I heard that Li-Ion batteries are very expensive and may only last 2
years and that AA would be more economical. So buying a camera with a
charging cradle may be expensive to maintain.

Li-Ion are expensive only if you buy the name brand from the camera
houses. Li-Ion batteries for my Canon are about $2ea on eBay from the
US for a generic brand, and they work pretty well.
You should get more than 2 years use out of a Li-Ion.

I'm a big fan of AA's for all of my gear. It means that I can share
batteries between my camera, GPS, UHF radios, torch etc. Essential when
you are out in the field.

But for other people Li-Ion and a charging cradle is the way to go, as
it's a "no-fuss" solution.
Look at *your* needs and how you will use the camera and then determine
what is best for you.
Don't let anything you read about the pros or cons a battery technology
drive your decision, NiMH and Li-Ion are both mature and excellent
solutions for camera use.

I can try the batteries I described in my last post but it is just the
camera experts recommend rechargeable so I thought I could try both.

Of course they recommend rechargables, that's because primary Lithiums
are expensive, and for the average user it's much cheaper and better to
use NiMH. Don't listen to the generic recommendations from the "camera
experts", look at *your* usage pattern and determine if Lithiums would
be a better solution. I recon there is a very good chance they would be
best for your "emergency use" application.

You state: "Your problem is you won't really know how much charge is
left in the
batteries and without overcharge protection you could damage the
batteries."
Wouldn't this problem be overcome if I use a Nickel Metal Hydride
charger as they are specially made for these batteries and are not
supposed to over charge them.

That's not the complete story.
A proper NiMH charger will have over-temperature protection as an
additional (and fail-safe) measure of battery overcharging, and this is
built into the charger cradle. When charging external batteries this
means you would need to install a temperature sensor inside the camera
next to the batteries. Not a trivial thing to do.

Have I convinced you to give up the idea yet? ;->

Dave

 

[richardghole@yahoo.com]

Hi

I think I was quoted about $70 for a Li-Ion battery and not a great
deal less for a generic one. So I would be surprised if something about
the cost you stated would be any good or be the correct battery for the
purpose.

I can't see how the battery would overheat if a proper charger is
used and it is at a very slow rate. The temperature could be measured
with a thermometer. I should think that the temperature would be
consistent. What is the highest temperature that would be acceptable
and is the main temperature risk to do with the camera?

So do you think that I should try the below battery first as they are
from a company I plan to order from? They cost about 10 dollars a pair.


AA Size Lithium Long Lasting Batteries 1.5V - Pk. 2
The worlds longest lasting AA battery. The perfect power source for
high drain appliances, such as cameras, camcorders, personal stereos,
mobile phones, palm top computers and TV's.- Up to 3 times the life of
any alkaline battery.- Up to 10 times the life of ordinary carbon zinc
battery- Guaranteed shelf life up to 10 years.- 1.5V, 1.4Amp hour.-
Pack of 2.

Your help is appreciated,
Regards Richard.

 

[David L. Jones]

richardghole@yahoo.com wrote:

Hi

I think I was quoted about $70 for a Li-Ion battery and not a great
deal less for a generic one. So I would be surprised if something about
the cost you stated would be any good or be the correct battery for the
purpose.

What's the battery model number? You can almost certainly get it a lot
cheaper on eBay.
Where did you get the quote from?

I can't see how the battery would overheat if a proper charger is
used and it is at a very slow rate. The temperature could be measured
with a thermometer. I should think that the temperature would be
consistent. What is the highest temperature that would be acceptable
and is the main temperature risk to do with the camera?

I've said it numerous times before, if the current is low enough then
yes, you can continously charge the batteries without a problem. But
the charge current will be so low (less than 1/10th C) that it will
take many days to fully charge the battery.
If that is acceptable to you then great, go for it.

But if you want the batteries to be charged at a reasonable rate and
then have the charger switch to "trickle charge" mode, you will most
likely need the temperature sensor inside the camera and hooked up to
the charger. The charger uses the rapid rise in temperature to detect
that that the battery is full.
If you want to use a charger without a temp cutoff and only relies on
voltage detection then you run the risk of damaging the batteries.

It's a bad idea all round, and you haven't even addressed the
reliability issue I raised!

So do you think that I should try the below battery first as they are
from a company I plan to order from? They cost about 10 dollars a pair.

AA Size Lithium Long Lasting Batteries 1.5V - Pk. 2
The worlds longest lasting AA battery. The perfect power source for
high drain appliances, such as cameras, camcorders, personal stereos,
mobile phones, palm top computers and TV's.- Up to 3 times the life of
any alkaline battery.- Up to 10 times the life of ordinary carbon zinc
battery- Guaranteed shelf life up to 10 years.- 1.5V, 1.4Amp hour.-
Pack of 2.

Your help is appreciated,
Regards Richard.

For god sake, yes, try them, they are purpose designed for high drain
devices like cameras!

Dave

 

[jasen]

On 2006-06-19, richardghole@yahoo.com <richardghole@yahoo.com> wrote:

Hi Dave or whoever can help,

Thanks for the reply.

With the digital camera I have it is very hard and time consuming to
open the battery case. It is a very tight fit. Also it is very easy to
forget to put the batteries in if they are taken out. Having to put
them in would take crucial time if the photograph had to be taken
urgently. For example, I plan to take weather phenomenon that can only
occur for a few seconds at times without notice.

There are some cameras that charge the batteries internally but they
are rare and may not do what I want.

On my Nickel Cadmium charger they warn that it can only be used for
Nickel Cadmium batteries.

they bdon't want you using it primary cells. (dray cells, alkalines etc)

Do you know of any suitable charger?

I got one labeled "lenmar nomem pro" it's a fast-charger with a 12V plug
pack and a car adaptor, it'll charge 1000maH AA nicads in 100 minutes and
NiMHs in proportianately longer (and shut off automatically)

--

Bye.
Jasen

 

[Pete]

David L. Jones wrote:

Most NiCD chargers are just a constant current source (with cutoff
functions), and CC is a pefectly valid way to charge a NiMH. The life
won't be shortened at all if the OP uses a sufficiently low NiCd
trickle charger on a NiMH.

Here's a quote directly from the Panasonic web site: "Trickle charging
cannot be used with NiMh batteries."

Trickle charging NiMh cells *will* reduce their service life. I really
do suggest that you might like to update your knowledge with a visit to
the web sites of a few battery manufacturers.

I know all about it already thanks.

It's hard to be clearer than the quote above, directly from one of the
most respected battery manufacturers. Here's a link to the application
note that the quote is from:

http://www.panasonic.com/industrial/battery/oem/images/pdf/Panasonic_NIMH_Precautions.pdf

Regards, Peter

 

[David L. Jones]

Pete wrote:

David L. Jones wrote:

Most NiCD chargers are just a constant current source (with cutoff
functions), and CC is a pefectly valid way to charge a NiMH. The life
won't be shortened at all if the OP uses a sufficiently low NiCd
trickle charger on a NiMH.

Here's a quote directly from the Panasonic web site: "Trickle charging
cannot be used with NiMh batteries."

The next paragraph says:
"However, after applying a refresh charge using a rapid charge, use a
trickle charge of 0.033CmA to 0.05CmA"
It also goes on to recommend a timer just in case.
So it's actually telling you to use a trickle charge.
The quote not to use it is most likely referring to traditional NiCd
levels. The guy who wrote it probably got a bit confused.

Take a look at the Energizer application note:
http://data.energizer.com/PDFs/nickelmetalhydride_appman.pdf
Page 19:
"For charging schemes that then rely on a timed "topping' charge to
ensure complete charge, a rate of 0.1C appears to balance adequate
charge input with minimum adverse effects in overcharge.
Finally a maintenance (or trickle) charge rate of 0.025C (C/40) is
adequate to counter self-discharge and maintain cell capacity."

and Duracell:
http://www.duracell.com/oem/Pdf/others/TECHBULL.pdf
Page 16:
"A number of applications require the use of batteries which are
maintained in a fully-charged state. This is accomplished by trickle
charging at a rate that will replace the loss in capacity due to
self-discharge. In these applications, a trickle charge at a C/300 rate
is recommended. The preferred temperature range for trickle charging is
between 10°C to 35°C (50°F to
95°F). Trickle charge may be used following any of the previously
discussed charging methods."

So Energizer and Duracell fully endorse trickle charging, just like
many other manufacturers, and just like professional charger systems
have.

So it's perfectly OK to use a trickle charge, just make sure it's very
small, smaller than for NiCd.

BTW, I'd be willing to bet big time that Panasonic brand NiMH chargers
have a trickle charge mode too.

Trickle charging NiMh cells *will* reduce their service life. I really
do suggest that you might like to update your knowledge with a visit to
the web sites of a few battery manufacturers.

I have, and it's you who should update your knowledge.
You take one quote from one manufacturer that actually contradicts
itself in the next paragraph, and you take it as gospel.

Common industry knowledge is that NiMH's can be trickle charged, and
I've designed charging systems myself like this without any measurable
loss of capacity. There are many other factors which are more
detrimental to the service life of a NiMH than a high trickle charge
rate.

I know all about it already thanks.

It's hard to be clearer than the quote above, directly from one of the
most respected battery manufacturers.

Energizer and Duracell are respected manufacturers, and both of them
say I am right and you are wrong.
I'd suggest you check out a few more references next time before you go
taking one manufacturers quote as gospel.

Regards
Dave

 

[Pete]

David L. Jones wrote:

The quote not to use it is most likely referring to traditional NiCd
levels. The guy who wrote it probably got a bit confused.

C30 to C50 is a maintenance charge, not the typical C10 trickle charge
used with NiCds. A maintenance charge is intended to keep a cell
charged, not to charge it. The purpose is to simply counter
self-discharge, which is about three times higher with NiMh compared to
NiCd.

In fact, that's exactly what your energizer and duracell quotes are
saying too.

So Energizer and Duracell fully endorse trickle charging, just like
many other manufacturers, and just like professional charger systems
have.

No, they are endorsing a maintenance charge, at a much lower rate than a
typical C10 NiCd trickle charge rate. In fact, duracell is saying C300,
which will never charge a cell.

So it's perfectly OK to use a trickle charge, just make sure it's very
small, smaller than for NiCd.

No, read it your quotes again. Maintenance, not trickle charge. And at
a much lower level than a NiCd trickle charger.

BTW, I'd be willing to bet big time that Panasonic brand NiMH chargers
have a trickle charge mode too.

I'll take that bet. Cash or chocolate only, please.

Maintenance, possibly. Trickle, never.

I have, and it's you who should update your knowledge.
You take one quote from one manufacturer that actually contradicts
itself in the next paragraph, and you take it as gospel.

There is no contradiction. Instead, you appear to be confusing trickle
charging with maintenance charging. Your own quotes show this.

Common industry knowledge is that NiMH's can be trickle charged,

Your own quotes do not support your statement - they are clearly talking
about maintenance, not trickle charging. It appears that you cannot see
the difference.

From the Duracell data sheet you quote, at the bottom of page 19:

"Finally a maintenance (or trickle) charge rate of 0.025C (C/40) is
adequate to counter self-discharge and maintain cell capacity."

Clearly, what they're saying is that this "trickle" charge (to use the
word you like, and the word they add for people who don't understand
"maintenance" is not *charging* the battery, but merely overcoming
self-discharge. Again, they say the same thing on page 21, near the top.

On your "techbull.pdf" file (what a great filename, lol), Duracell are
saying exactly the same thing (top of page 17), but they are using your
term "trickle charge", when it's really just overcoming self-discharge.
They even say these exact words. C300 will never *charge* a cell, so
saying that this is trickle charging the cell is just plain silly.

A typical NiCd C10 trickle charger will fully charge a NiCd cell in
about 12-14 hours. Connect this same C10 charger to a NiMh cell for the
same time, and you'll probably not cause any problems.

*HOWEVER*, a typical NiCd C10 trickle charger does not have a timer, and
is often left on (by the user) for longer than 14 hours. At the C10
rate, you can virtually charge a NiCd cell forever without causing any
problems. Not so with NiMh cells. As you'll read in the data sheets
you quote, C10 for more than about 12 hours *will* overcharge a NiMh
cell, and NiMh cells *will* suffer a reduction in capacity because of
this overcharging. Measurable, and definite. *AND* is says so in the
data sheets.

Peter

 

[David L. Jones]

Pete wrote:

David L. Jones wrote:

The quote not to use it is most likely referring to traditional NiCd
levels. The guy who wrote it probably got a bit confused.

C30 to C50 is a maintenance charge, not the typical C10 trickle charge
used with NiCds. A maintenance charge is intended to keep a cell
charged, not to charge it. The purpose is to simply counter
self-discharge, which is about three times higher with NiMh compared to
NiCd.

In fact, that's exactly what your energizer and duracell quotes are
saying too.

So Energizer and Duracell fully endorse trickle charging, just like
many other manufacturers, and just like professional charger systems
have.

No, they are endorsing a maintenance charge, at a much lower rate than a
typical C10 NiCd trickle charge rate. In fact, duracell is saying C300,
which will never charge a cell.

So it's perfectly OK to use a trickle charge, just make sure it's very
small, smaller than for NiCd.

No, read it your quotes again. Maintenance, not trickle charge. And at
a much lower level than a NiCd trickle charger.

BTW, I'd be willing to bet big time that Panasonic brand NiMH chargers
have a trickle charge mode too.

I'll take that bet. Cash or chocolate only, please.

Maintenance, possibly. Trickle, never.

I have, and it's you who should update your knowledge.
You take one quote from one manufacturer that actually contradicts
itself in the next paragraph, and you take it as gospel.

There is no contradiction. Instead, you appear to be confusing trickle
charging with maintenance charging. Your own quotes show this.

Common industry knowledge is that NiMH's can be trickle charged,

Your own quotes do not support your statement - they are clearly talking
about maintenance, not trickle charging. It appears that you cannot see
the difference.

From the Duracell data sheet you quote, at the bottom of page 19:

"Finally a maintenance (or trickle) charge rate of 0.025C (C/40) is
adequate to counter self-discharge and maintain cell capacity."

Clearly, what they're saying is that this "trickle" charge (to use the
word you like, and the word they add for people who don't understand
"maintenance" is not *charging* the battery, but merely overcoming
self-discharge. Again, they say the same thing on page 21, near the top.

So this "maintenance" charge value is such a precisely engineered value
that it *just* counteracts the self discharge?
What if you go 0.01C over the quoted maintenance rate, are you going to
eventually damage the cell? The answer of course is no.

On your "techbull.pdf" file (what a great filename, lol), Duracell are
saying exactly the same thing (top of page 17), but they are using your
term "trickle charge", when it's really just overcoming self-discharge.
They even say these exact words. C300 will never *charge* a cell, so
saying that this is trickle charging the cell is just plain silly.

I was not implying you use those exact figures to trickle charge the
cell.

A typical NiCd C10 trickle charger will fully charge a NiCd cell in
about 12-14 hours. Connect this same C10 charger to a NiMh cell for the
same time, and you'll probably not cause any problems.

*HOWEVER*, a typical NiCd C10 trickle charger does not have a timer, and
is often left on (by the user) for longer than 14 hours. At the C10
rate, you can virtually charge a NiCd cell forever without causing any
problems. Not so with NiMh cells. As you'll read in the data sheets
you quote, C10 for more than about 12 hours *will* overcharge a NiMh
cell, and NiMh cells *will* suffer a reduction in capacity because of
this overcharging. Measurable, and definite. *AND* is says so in the
data sheets.

Peter

Now this is just playing around with words and specific numbers.

Yes, a NiMH cell may have its service life reduced by a normal 0.1C
charger, due to overcharge, but you are talking specific values now.

It is possible to "trickle charge" a NiMH cell (at some rate between
0.1C and the "maintenance" charge rate for arguments sake) to
eventually fully charge a NiMH cell and not damage it. That's what I've
been saying all along.

You can dick around with exact C numbers all you like, the fact is in
practice you can do it sucessfully. I know, I've done it myself.
If you get too high a trickle charge rate you might shorten the life of
the cell, but even then it's not a big deal in many applications, you
can still get a good service life for your money.

Not everything is black and white as per the data sheet you know, not
all cells are the same either, nor are any two systems alike.
Build some real systems, test some real batteries, you'll find out.

Dave

 

[Pete]

David L. Jones wrote:

Now this is just playing around with words and specific numbers.

No it's not - the figures are from your data sheets.

Yes, a NiMH cell may have its service life reduced by a normal 0.1C
charger, due to overcharge, but you are talking specific values now.

Yes, specific because C10 is the typical rate used to trickle charge NiCd.

It is possible to "trickle charge" a NiMH cell (at some rate between
0.1C and the "maintenance" charge rate for arguments sake) to
eventually fully charge a NiMH cell and not damage it. That's what I've
been saying all along.

Surely now *you're* just "playing with words and specific numbers"

Your original statement was this:

There is essentially no difference between the two chargers.
You can use a Nicd charger to charge NiMH's.

Patently, that's untrue. And now you appear to even be agreeing that
you need to charge at a specific rate.

You can dick around with exact C numbers all you like, the fact is in
practice you can do it sucessfully. I know, I've done it myself.

The fact is, unless you "dick around with exact C numbers", you're in
danger of overcharging NiMh cells, and therefore reducing their service
life. Which is exactly what your data sheets all say, many times over.

Build some real systems, test some real batteries, you'll find out.

I've probably built more that you can imagine, Dave.

Peter