AA NiMh charge rate

[Michael Aos]

Just purchased La Crosse BC-700 and La Crosse BC1000.

I've been refreshing a bunch of old NiMh batteries. Seems to be going great.

I see a lot of comments that say the "ideal" charge rate is between .5C and 1C, and then others that say between .25C and .5C. Along with that I've seen minimum of .33C.

Based on the capabilities of these specific units:

My question is, with a 1200mAh NiMh, which charging rate is "better"? -- .25C, .42C, or .58C? (I'd guess .42C)

Also for 2500mAh NiMh -- .28C, or .40C, or .60C? (I'd guess .40C).
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[Etsu]

I'd start around 0.5C, and go from there. If they don't get very warm at that rate (like Eneloops), you can go higher if you wish. 1C works fine with Eneloops, for example. But if they get hot during charge, then back off the charge rate. Older NiMH cells don't like to be charged very fast. Your 0.4C will probably be okay for them, and in my experience it's fast enough that the charge termination will properly detect the -dV. But if you find they are still charging after 3-4 hours, then remove them manually.

1200mAh sounds like very old cells. You may find they don't work too well, but it's worth a try.

 

[hiuintahs]

I see lots of concern about charging batteries at too low of current, yet I've been charging my Eneloop 2000mAh batteries at 500mA (.25C) for years now and have never missed a termination point. Maybe I'm just lucky.......who knows.

 

[Lynx_Arc]

I see lots of concern about charging batteries at too low of current, yet I've been charging my Eneloop 2000mAh batteries at 500mA (.25C) for years now and have never missed a termination point. Maybe I'm just lucky.......who knows.

I've been using a duracell mobile charger at about 500ma for years and none of the cells that register good on it (no blinking lights) have not terminated properly. I charge my rayovac hybrids and duraloops on it all the time with no issues whatsoever. I think if anything 500ma is probably safer with bad cells because if they don't terminate properly on 500ma then chances are they are bad cells to begin with and may also not terminate likewise at 1000ma either which would have them cooking a lot harder if not checked upon.