Tuesday 12 July 2016

Battery repair

One of the cells in one of my 4s, 10AH batteries was down to 2.7 volts. That's bad; I usually run them down to 3.2, maybe 3.0 exceptionally. And when I tried to recharge it, it wouldn't recharge.

I put it aside, and replaced it with a pair of 4s 5AH in parallel, but I didn't stop thinking about it. In the last week or so, I've got it back into action. What I did was balance the cells (which means discharging the cells that aren't the lowest voltage) and then charging, then balancing, then charging, and after a few iterations of this, I've got it back to 4.2 volts.

I'll use it next time I go out, to see if it really is fixed.

1 comment:

  1. Was this perchance on a battery pack with a swollen casing?

    You once said:

    "You must also learn about the care of Lipos. They are dangerous, no question. So, learn about the safe handling of Lipos. .....

    The two most important things for safety; 1) don't over-charge them (your charger should ensure that doesn't happen), 2) don't short circuit them by connecting a battery's positive to its negative (I designed my connectors to make that pretty much impossible). And I'd add a third, important not for safety but for keeping the batteries working, 3) don't let the voltage of any cell fall below 3.0 volts (I use 3.2 volts as a minimum)."

    There would seem to be a fourth important thing: 4) Do not leave in a fully charged state if not planning to use soon (within a couple of days).

    Anecdotally, battery cells left fully charged for extended period can emit gases which swell the casing / result in reduced capacity.

    Quality chargers have a Storage program setting which sets LiPo cells to 3.85 volts.

    Seems to be a compromise between battery longevity and being constantly available for immediate use.