Appraising small rechargeable batteries

On Sep 7, 8:03=A0pm, JD wrote: > Hi Experts, >

It's fine to use a fast charger to run them up in

that's the only way i know of.

Get a cheap quartz clock and wire a 1.2v flashlight bulb (or a 4.7 ohm resistor) in parallel witn the battery holder, put each cell in and see how long the clock runs for. (should be less than 12 hours, the clock will tell you how long it ran for)

doesn't make much difference.

Just be sure they don't short out, this requires more care with "9V" and "lantern" batteries. than with AA and AAA

That's a neat idea. I used to check NiCd cells by measuring current vs time as I discharged them at some reasonable rate. (C/4?) It's a time consuming PITA. But that was back when I was a college student with more time than money.

George H.

This appeared on the groups awhile back and works pretty well:

You buy a cheap analog quartz clock, wire a dummy load resistor across the battery contacts, put a freshly charged battery into the holder and see where the clock stops - then calculate the capacity in amp hours.

A few refinements like a switch and outboard battery holders will work wonders. I test mine then use a "P-touch" label maker to put the actual capacity on the side of the battery.

Good question. If they are fully charged they just run down anyway if they aren't used. To get the most out of the batteries use them right after charging.

The newer slow self discharge ones are great - so great I threw out my standard NiMH types and bought all "pre charged" batteries - they hold a charge for many months, not just a week or two.

No reason not to store them together. That sounds like a myth.

You can refrigerate them to make the charge last longer though - providing there isn't a lot of water condensing on them.

Seriously: Switch to low self-discharge batteries! It saves a lot of aggravation.

Yes, but not chuck out the older style NiMH, kids love them for toys :)

I've got some of the new style charge holding batteries as they suit my usage patterns much better.

Another thing is use a decent charge that charges each cell individually, and do try to charge at the recommended C/10 rate (it's quoted on the battery), unless you're really in a hurry. Fast charging stresses the battery more. So I set my charger to charge 2100mAH AA cells at 200mA, rather then the default 1000mA which is the fast charge for those 2700mAH high self-discharge style AAs.

An overnight charge is usually okay. Found four of these I forgot I had, all measured over 1.2V no load after more than six months in storage.

Grant.

No kids . . .

Really. The old NiMH style are OK if you do something every day that uses batteries and you recharge/use them right away.

My wife had given up on NiMH due to the self discharge and unreliable capacity numbers. I tested some with the quartz clock gizmo and found some that were ~200 mah or 1/10 what they should have held. She was just using standard alkaline batteries and recharging them until they leaked then tossing them.

I gave her some low self discharge ones and she's a believer.

Very good point about the charger. I've an old Rayovac alkaline, Nicad, NiMH, AAA,AA charger that has four independent chargers, with leds to indicate which ones are finished charging.

The el cheapo more common chargers are just a lossy transformer and current limiting resistor/LED and charge the batteries two in series.

ad,

I use NiMH cells in my Canon camera. I don't think I've charged them

G=B2

My apologies for my belated reply. This was very helpful and enlightening. Have a great weekend :-)