Charging batteries inside an appliance

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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.


Re: Charging batteries inside an appliance


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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?

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

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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.

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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 :)


Re: Charging batteries inside an appliance


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:
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Re: Charging batteries inside an appliance


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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.

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

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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 :)


Re: Charging batteries inside an appliance


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

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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

Re: Charging batteries inside an appliance



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Hi Jason

Thanks for your letter.

I thought that a rapid charger could possibly damage the camera or
overheat it and that a very slow rate of charging would be best used.
Do you think so?

What is the output voltage and current of the charger you refer to?

Your help is appreciated,
Regards Richard.


Re: Charging batteries inside an appliance


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You are correct!

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Don't even think about using the fast charger Jason is referring to.
You need either
1) a slow charger (<0.1C rate, that's < 250mA for 2500mAh NiMH),
or 2) a fast NiMH charger with voltage cutoff and preferably a temp
cutoff sensor in the camera. But NiMH cells can get very hot during
charging, so this is still a risky thing to do inside your camera.

The slow 16hr NiCD charger you have will work just fine, it will just
take a long time to charge the batteries.

Use those Lithium AA's you are getting and all will be right with the
world!

Dave :)


Re: Charging batteries inside an appliance


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yeah, i forgot you wanted to charge the batteries in-place

I'll stick a meter on the charger ans see what current it gives for a
"maintenance charge" after the cells are full.

Bye.
   Jasen

Re: Charging batteries inside an appliance


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20mA - seems a little high, full rate is 700mA

I'd go with the lowest charge rate quoted here C/300 - about 8mA


Bye.
   Jasen

Re: Charging batteries inside an appliance



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Rip the charging electronics out of a wireless optical mouse charging
cradle, these usually charge 2x AAA cells so they won't overheat AA cells.
In the UK I just bought such a mouse for only 5.99p - it'd be a close run
thing whether you could buy the individual components for less!



Re: Charging batteries inside an appliance



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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

Re: Charging batteries inside an appliance



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.


Re: Charging batteries inside an appliance


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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.

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

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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 :)


Re: Charging batteries inside an appliance


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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.

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I know all about it already thanks.

Dave :)


Re: Charging batteries inside an appliance


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.


Re: Charging batteries inside an appliance



snipped-for-privacy@yahoo.com wrote:
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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.

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

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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?

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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.

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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 :)


Re: Charging batteries inside an appliance


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.


Re: Charging batteries inside an appliance


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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.

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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.

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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 :)


Re: Charging batteries inside an appliance


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.


Re: Charging batteries inside an appliance


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

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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!

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


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