Can you put AAA rechargables in a recharger meant for AA batteries

I have a recharger and some AA batteries. The batteries are 2000 mAh. Can a person put AAA batteries in the recharger? I assume there are several issues that could be problems like

The AAAs may need electricity at a different rate than the AA do
The AAAs may have a different chemical reaction inside the batteries than the AA (I don’t know how likely this one is though)

So what would happen if I put the AAA in the AA charger, assuming they fit. Will the electricity only go in as fast as the battery can absorb it or is it best to just get a different charger and some AAAs to go along with that one.

They won’t fit. Spend $ 10.00 and get a AAA recharger at Radio Shack.

Or go one better and buy a charger that can handle both AAA and AAs.

After saying that, (because I own one that does both) I realized I have no idea how to recharge AAA batteries in the thing. I verified that it will charge them, but I just don’t know how I’d make em fit. Huh.

It’s more trouble than its worth, but you could do it with a cheap charger. I’ll assume we’re talking about NiCads or NiMH rechargables here - I don’t know about alkaline rechargables.

The chemical reaction in the AA or AAA batteries is the same, but the AAA battery has a smaller electrode area. This means that it has a smaller allowable peak charging rate, and a smaller allowable “overcharging” rate. It also has a smaller capacity, of course.

NiCad/NiMH rechargers tend to use a constant, controlled trickle current to recharge. The cheapest rechargers are the ones where you just put the batteries in and leave them for about 14 hours. They have no automatic cut-off - the charging rate is below the allowable “overcharging” rate. NiCads and NiMH can tolerate being “overcharged” to a degree - the energy is just converted to heat when the battery is full. It is safe to leave the batteries “overcharging” in the charger when the 14 hours is up, but it will shorten their life.

If you put your AAAs into a cheap trickle charger, the charging rate would be okay while the batteries were actually charging up since the allowable “overcharging” rate for AAs is small compared with the maximum charging rates of either.

However, the current would be a tad high for the “overcharging” once the batteries were full. So you’d have to be sure to disconnect them smartly after the appropriate time, which you’d have to calculate from the capacity of your AAAs compared with your AAs. Plus you’d have to rig up some Heath Robinson (Rube Goldburg, to you!) method of extending the length of the battery, since the AAAs will be too short to fit directly into an AA bay. Like I said, more trouble than its worth, and I’d only do it in an emergency, once or twice.

More expensive chargers blast current into the AAs as fast as they can take it, detect when they are full and switch to super-slow trickle charge. The charging rate is undesirably high for AAAs, and the charger may get confused and not cut them off when they are full, which could lead to them leaking. (Or if you believe in health and safety paranoia, “exploding”.)