Quote:
Originally Posted by Drake
I have a different opinion on this than KosMos, personally I would store them with whatever charge they have left: rechargeable batteries will naturally shed their charge slowly over time and there's no real need or benefit from storing them 'empty' -- in fact, if their charge drops too low (i.e., fully discharged then stored for a long time) some of the cells might reverse polarity (which will potentially kill your pack unless you have a good charger and really know what you're doing).
Then just charge your pack up before the game. If its been stored for a long time (more than a few months) you might want to charge, discharge then re-charge it and let it trickle charge for a while after.
As for measuring how much juice is left in a pack, L473ncy is right (or L473ncy's mom, I guess): trying to measure the amps with a multimeter won't give you a usable result, but you can estimate charge from voltage. A 1.2v cell when fully charged will give off about 1.3v (so a 9.6v pack will usually read around 10.4v, sometimes even more if they're high capacity cells). "Discharged" cells show about 0.9v (you don't want to let cells drop below 0.9v, that's when bad things start happening), so your 9.6v pack will show something between 7.2 and 9.6v depending how drained it is.
If you had a "pretty empty" pack showing close to 7.2v and you knew you were going to store it for several months (like over winter), I'd actually charge it a bit before putting it away: just trickle charge it for a few hours, so that when it drains itself over time the cells don't drop below 0.9v.
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0.9v is for NiMh chemistry. NiCd work differently and fully discharging (to 0v) is preferable, otherwise it forces a "memory" effect into the pack. Always discharging to 0.9v would actually be bad in this case.
The reason for the shorting wire is that the cells will also recover over time, some cells will do faster than others. That means that it can cause a cell to reverse itself if the other cells gain enough juice before it. Shorting the pack makes sure that there is nothing, no positive or negative power in the pack.
You really should have a good charger if you consider using this method to store your packs, because the "wake-up" can be hard if you need to charge them with a crappy charger that will not work when voltage is too low (like most cheap "universal" chargers, they just don't detect a battery plugged and never start)