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Old Sep 13, 2003, 2:30 PM   #1
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Default How long should NiMh Batteries hold their charge

Hi All

Just a question on how long NiMh batteries should hold their charge.

I was out today taking pics when my battery warning flashed up, so I inserted the spare set of batteries I had charged previously.

Imagine my horror on turning my Canon A70 back on to have the message flash up "replace battery pack" !!

I had charged these batteries but not topped them up. I don't know how long ago I charged them - somewhere between 2-5 weeks I would guess but they have not been used at all since.

Would they really be expected to loose ALL their charge ? or is there something wrong with my batteries or charger ?

Batteries : Powerex 1800 NimH
Charger : Maha 401


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Old Sep 13, 2003, 4:20 PM   #2
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Default Not normal

I carry a set of charged batteries in my bag till my camera needs them. Then, they go in the camera and the drained ones get charged that night and go in the bag. Sounds like your process. Nothing like this has ever happened to me. I've quit counting but I get around 300 pictures with no problem.

My uninformed opinion is that either something is wrong with the batteries or you forgot to charge them.
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Old Sep 13, 2003, 5:52 PM   #3
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NiMH cells have a self discharge rate of around 30% per month at room temperature. The highest discharge rate happens during the first day after a full charge. The rate of discharge levels off after that.

Its best to top off batteries that have been sitting around for a while right before you take off on a photo shoot.
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Old Sep 13, 2003, 10:43 PM   #4
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this depends on the mah (mili amp hours) and the power drain of the camera (screen on, slr, compact, foucs asist light)
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Old Sep 14, 2003, 2:26 AM   #5
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Default Re: How long should NiMh Batteries hold their charge

Originally Posted by stefank
how long NiMh batteries should hold their charge?
Based on years of struggles with camcorders before I got my digicam, I suggest topping up spare Ni-MH batteries routinely before use, because their one serious drawback is self-discharge.

My digicam batteries last so long that I find it easy to forget to do this. I'd have your problem of failed second set all the time, unless I had the camcorder lesson to remind me. It's always longer than I thought since the last day out - life flies by, doesn't it?

Sealed lead-acid batteries were a good but heavy alternative to Ni-CD before Ni-MH came along. They could be trickle charged routinely at constant voltage, just like car starter batteries, and always be ready for use.
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Old Sep 14, 2003, 2:38 PM   #6
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Most good intelligent microprocessor chargers will continuouslly slow trickle at end of charge. The best thing with NimH's which are not being used, is to keep them in the charger. I have a set of 4 that live permanently connected to the charger which is kept powered. I know they trickle charge 'cos if I turn off the mains to force a re-charge, it only takes 10's of minutes to complete. And I believe that is probably down to error in charge measurement.

If you want to keep the camera memory alive for months out of use, then those with AA Bat cams advocate installing temporary high output alkalines until ready for use.

There are some cams using proprietary battery packs with (too clever) sensing circuits that actually tell the wrong story about charge condition.

If the batts are stored when it's been very hot they will discharge faster. Usually most battery technologies will lose less charge if they are stored in the fridge. However, with NIMh you must get them back to normal temp to get their full charge out. VOX
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Old Sep 14, 2003, 3:30 PM   #7
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Thanks for all the replies guys

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Old Sep 18, 2003, 5:26 PM   #8
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I can tell you from my experence using AA's NMH batteries, once in awhile I use my old sanyo digital camera, it uses two of these batteries and I have 12 of them in my bag all charged.
I go to use the camera a month later and all of them are just about dead, they have to be charged just before you use them, like a day or two, but don't wait too long after charging them. 8)
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Old Sep 18, 2003, 6:47 PM   #9
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left on there own a NiMh AA battery taken off the charger generally looses about 20% of it charge in the first 24 hrs. after that it is an incremental loss to real low over about 30 days.
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Old Sep 19, 2003, 7:44 PM   #10
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I was drawn to this thread because I've just received my first digicam -- Nikon CP2100. The kind person who gave it to included a 4 pack of Maxell NiMH 1850mAh & charger, labelled P2000 & P2001. (Yeah, two model numbers, kinda strange?)

I charged all four overnight, popped 'em in the CoolPix, and started playing in my home.

The first pair lasted 3 (three!) shots before the Battery Exhausted! warning shows. OK, I've read these batteries require cycling.

I swap those in to charge. The other first-cycle batteries lasted 4 shots. Another day, another try: one pair lasted 3 shots, the other pair lasted 1 shot.

Is this typical of the "breakin" phase? How many cycles do I go through before I can expect decent performance?

At what point would you veterans decide:

1) the charger isn't working (It does light up, but it has only one indicator light, not one for each cell.)
2) I have bogus batteries
3) Never use Maxell again
4) Something wrong with the camera.

My next step I guess is to experiment with the LiIon that came with the CP2100. How many shots should I get from that, if there's nothing wrong with the unit?
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