[chainring]

Originally Posted by jj2me

Didn't know smart chargers had a range different from other (slow?) chargers. I just followed the BC-900's instructions, which doesn't seem to take into account the batteries' capacity: "In general, 200 mA is a recommended charging current if rapid charging is not necessary. It is definitely safe and optimum to the rechargeable batteries."

Like I said, a true "slow" charger is dumb, in that it has no charge termination smarts other than a timer. "Smart" chargers, as they're known, have different methods of detecting a fully charged cell. The most popular is a change in voltage, known as delta V, or -dV (negative delta Voltage). If you plotted the voltage of the charge, it would eventually rise to a point, then fall. That fall is what the charger is looking for, and once seen it will end the charge cycle. To generate a sufficient drop in voltage most chargers need to be operated at the 0.5 - 1.0C range. Some are better than others, but they may also employ temperature to aid detection and as a safety.

Thanks again. This is terrific info you've given us in this thread.

No problemo, glad I could help.

Quite glad that I shouldn't be charging at 200 mA, since using the BC-900's "Refresh" cycle at 200 mA is an overnight experience with the worry of an exploding cell.

Stick with 0.5C charge rates and you won't damage the cell, nor will you be tying up the charger forever.

And really, losing 200 cycles because you fast charge? Is that really such a big deal for the average consumer, who might only go through 50 - 100 cycles/year? That's still 3 - 6 years (instead of 5 - 10).

I agree, it's not that big of a deal in the whole scheme of things, especially when weighing in the added convenience. If I were relying on some batteries for a business use, you'd be hard pressed to find me using the 15 min charger on them, but I don't have that sort of use... Keep a spare set of Eneloop's charged up and you won't be presented with that kind of situation in the first place.