rechargeable batteries?

question: is it possible to overcharge batteries?

i just bought me a recharger and batteries for my camera, and am curious.

the only reason i ask, i had (<----points to word to make it more obvious) a rechargeable flashlight, one of those 2 million candle jobs, i plugged it in to recharge, 2 days later, the top blew off..

i'd rather not have defective, or damaged batteries in my new camera.. does anyone have a clue?

Yes and no. It depends on the battery and the charger. Some are made to stop sending power to the batteries after they're charged, some keep going.

In a battery (rechargeable ones anyway) they have a crystal formation inside (sort of, its the easiest way to explain it). When you charge the battery this formation grows. Now, if the battery wasn't fully discharged it will create a new 'set' of crystals that aren't really connected to the rest of the crystal formation (thus, the battery doesn't last as long). I'm sure the rest of what it can do is fairly obvious.

Anyway, that should, at the very least, give you a shady answer.

most of that, i already knew, but thanx ol man :smile:

i have been googling since i posted, the only hits are entirely in either japanese or chinese, in any case, completely useless to me..

the panasonic site, doesn't even list the product so.. i guess i'll keep searching

Are the Li-Ion or Ni-Cadmium?

It is impossible to overcharge Li-ion batteries because they employ sophisticated protection circuitry. This is because the consequences of an overcharge are dire. They can literally explode, and not in a small way :biggrin:

For most other batteries extra charging time will simply result in allot of electricity being converted to heat. So, assuming the batteries you are using have a good thermal management system... no problem.

Crono - I think that may be dated information. It is my impression that most modern types of batteries do not suffer from this problem, but I'm not really sure.

NI-MH, is that bad?

No. Basically don't overcharge them. If it doesn't damage them straight away, it will shorten their lifespan. I'm pretty sure you can find a charger for any type of battery that will automatically stop charging when the batteries are done - they do cost more, but... well of course it's up to you :smile: Get a cheap charger and have to 'be there' when the time is up, or pay more and live a worry-free life (batteries wise anyway).

well, mines a cheapo model.. it says only in the documentation that it takes 20 hours to charge.. i can only assume thats from stone cold dead :/

so.. if i don't exceed 20 hours i should be OK?

Mine is like that, 17 hours. I think that means it's a trickle charger that just steadily pumps the electrons into the battery at the same low rate until (and after) it's full. A 'fast' charger pumps tons in at the beginning when the battery is empty, then reduces the charging rate as the battery approaches fully charged. If it's 20 hours and you left it for 22, I can't imagine there being a problem. If it's 20 hours and you leave it over the weekend, that could be a problem :smile:

well, thanx guys, hate to sound all noob, but up to now, my experience has been .. batteries blow.. my camera is a bit expensive to have that occur.. i was giving serious thought to sticking to disposables only..

thanx again.

I guess I'd go with Jeff's advice. I don't know much about Ni-MH chemistry. I know that for a Ni-H battery you wouldn't have to worry. However, I don't know how the fact of storing the hydrogen in a metal hydride affects the performance of the system.

Crono - I think that may be dated information. It is my impression that most modern types of batteries do not suffer from this problem, but I'm not really sure.

Probably, taking that all my knowledge of batteries comes from handset phones and the laptops I own. My laptop is 8 years old (ThinkPad 600), so you may be correct in that thinking.

However, I've noticed that every phone I've had which has a Lithium Ion battery has acted the way I described. But, whatever.

Li-Ion batteries loose capacity slowly over time regaurdles of your recharging habits. The electrolyte inside forms a solid barrier that keeps getting thicker and thicker over the lifetime of the cell untill finaly it just stops workling.

Wow! Never knew that... that explains 100% why my mobile phone battery started lasting a shorter and short time on a charge (eventually down to about 20 seconds of conversation).

Yeah, that's the s**tty thing about Li-ion technology. It's light, has excelent power-density, but has a fairly short usefull lifetime. The up-side is that there are no dangerous chemicals inside so disposal is a snap in comparison to the old cadmium and lead based cells.

on a much longer scale of course, the same is true for the old lead/acid batteries..

each time you use them, the life decreases, as well as the charge holding capacity..

most people think the battery is dead, when in fact its storage voltage has dropped below the starter/lights ability to use properly..

if you have it tested, it will most likely be just below 10 volts, still alot, but not enough to function as a car starting medium..

Yes, that happens in lead-acid cells, but for a different reason. What happens there is more akin to what was described earlier by someone (Jeff?). In each charge cycle a portion of lead is oxidized and then subsequently reduced. When it is reduced it tends to form dendrites (tree-like branching structures) on the electrode surfaces. these fragile formations can then break and drop off the electrode, taking away that much charge capacity.

omai, i have never learned so much about batteries in one reading.. ever...

Careful about letting Ni-MH run (Completely) out of power as well, or the polarities will reverse and it screws up the battery.