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Old Aug 6, 2003, 9:34 PM   #1
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Default NiMH service life

I just bought a used camera off e-Bay, and the seller included 16 NiMH AA cells with a charger. My Minolta Dimage 7 uses 4 at a time. When I pop these puppies in the charger, they seem to charge fine. I measure them with a VOM, and they show 1.21 Volts. When I put them in the camera, though, they last about 15 minutes before the camera shuts down on low charge. Are these batteries toast? I'm considering going to disposable lithiums since they're supposed to last longer. My shooting style is that I use the camera a LOT in a single day, and then don't use it again for a few weeks. Will the lithiums have the shelf life to last for months with this type of use, or am I better off buying fresh NiMH (batteries and/or charger, whichever I need)? Alternately, should I just stick a fresh set of Alkaline AAs in every time I want a day's work and discard them at the end of the day? Enquiring minds want to know <G>
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Old Aug 6, 2003, 10:25 PM   #2
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You could try a deep cycle on the batteries. I've heard some people clame that it helps after some reasonable set of charging (5 or so? Don't recall.) It doesn't cost you much to do it, and it might help.

Does the charger have individual circuits so the batteries can be tested and controlled independantly? Or does it charge in pairs? If its in pairs, then one might not be well charged. I guess if you test each battery after the charge you clearly know that the charge is complete... but its something that came to mind.

They could also just have a really low mAh rating.

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Old Aug 6, 2003, 10:44 PM   #3
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Hi Eric! Thanks for the prompt response. The batteries are Powerex units rated at 1800 mAh (about typical for NiMHs). My charger is 2-at-a-time or 4-at-a-time no-name unit. I guess that to deep cycle these, I'd need to short circuit them via a low resistance resistor till they were very dead. That would not be a problem. The batteries claim to be "rechargable up to 1000 times." Since I don't know their history, I'll try killing them & then recharging. Thanks again.
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Old Aug 8, 2003, 2:13 PM   #4
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My shooting style is that I use the camera a LOT in a single day, and then don't use it again for a few weeks.
Some people put in Alkalines/Lithium during camera storage (low self discharge, fine for the camera's low power backup drain in storage)

I hear the Dimage is a bit thirsty, but your experience seems excessive. As mentioned, you only need 1 out of 4 batts to be faulty, and 2 will not fully charge if the charger is running in pairs.

First off, number all your batteries uniquely and any new you buy from now on. Date them as well. Charge 1 pair at a time. Buy a small single AA batt torch and time approx how long it takes to disharge each fully charged batt. From the bulb rating you can work out a theoretical figure, but don't expect to get 100% out. Do this for each battery, If your discharge time is way out then those batts are the ones to work on. Alternatively, put the 4 'suspect fully charged' batts in the torch and time the discharge for each - you might learn something!

The thing about the fast chargers, despite many posts and suspicion about their treatment of batteries, is you know by the temperature after charging, that energy has gone in! Whereas trickle charging doesn't give up many clues at the end of charge. Voltage alone is not reliable. Hope this helps - VOX
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