Test whether battery will still take a charge

Is there an easy test to see whether a battery (NiCd, NiMH and Gel) will still take a charge? (like with a multimeter)

I have an opportunity to buy used batteries at a really low price but I want to make sure they will still take a charge. I'm assuming the batteries I want to test have sat on a shelf long enough to be fully discharged.

For Ni Cd (my guess, so don't blame me if anything goes wrong), if the cells are AA in size, you can zap em with 5 amps for like 3 seconds. Check the voltage before and after the zap. If there is an increase and the voltage remains steady after the zap (meaning they don't fall at 0.01 volts every second) the battery should be good to hold a charge. Try the same for ni mh, but with 3 amps for 5 seconds.

Don't know about gel batts...

Gels are easy. If they're really dead, they will probably be at below 11 volts for a 12v battery, or say 5.5 for a 6v battery. Either way, you've got a damaged battery, maybe a bad cell. I might be being picky, but if a sealed lead acid battery has been sitting around with no charge on it for a long time, it's at a fraction of it's design capacity, and my experience with batteries like this hasn't been good.

A lot of used batteries have been in service for close to their design lifetime, and for nicad/nimh, possibly not treated well. This is just MHO, but I wouldn't pay more than 5% of the new battery price for used batteries, and would view it as a gamble. (But if they're close to free, then why not!)

how do I zap the batteries with 3 or 5 Amps? I think I understand zapping with a voltage but how do I zap it with current? is there a URL with the circuit?

thanks

Eh, why not just hook up a few rechargable (Read: 3 or 4 cells) AA or C cells and short circuit em to one battery. AA promises at least 6 amps flowing throw, C cells can go up to 30 amps... but just don't get too crazy....

Stay away from the used gel cells. They only are good for a couple of years if the are not being charged once in a while. Other than that what Albany to says is right on. A check you can do with nicad cells is measure the resistance. Nicads tend to short out when they die. Packs will read like they are one or more cells short if they have shorted cells. You can pop these cells and get them to work by passing a high current pulse through them, but they probly well do it again.