OT: electronics/battery questions

[dg]

I have a solar phone charger from Maplin (

) which charges 5 AAA batteries, which can then be used to recharge portable devices (phone, mp3 etc)

Batteries are in series within the device

Oddly one or sometimes two of the AAA batteries will get completely drained - this could be different batteries, placed in different slots. This will happen if I pre-charge the batteries before putting them into the solar charger, and it will occur if the solar charger is used to charge the batteries - i.e. it won't charge them.

So what would cause individual batteries connected in series to become drained?

Secondly, I have a similar device which charges an internal battery but uses a small wind turbine (

The problem with this one is that there is no way to know it's state of charge. So is there a simple way, or a piece of circuitry with LED's say, which I can use to determine how much percentage of charge is left in the battery?

Cheers

dg

[meow2222]

)

If the 5 cells are really in series, the only answer is one cell more leaky than the others. Normally NiCds should, ideally, get an equalisation charge now and then. This would resolve the problem for a while - maybe the solar charger doesnt output enough juice to do an equalisation charge. If so, just charge them in a mains charger when it happens.

NT

[Dave Plowman (News)]

Cells should only be charged in series if they're identical and in an identical state of discharge. Ie as in a drill battery pack. And even then it would be better to charge them individually.

[Andy Dingley]

Or they're Li-Po batteries and you need a firelighter! NiCds don't enjoy series charging, Li-Po _will_ overheat and burst reliably first time it's attempted, quite probably with ignition too.