Handling batteries

NiCad cells build up crystalline formations, as they are manufactured and later as they are cycled. These crystals cause tiny bridges to form between the plates inside the cell. The more crystal formations the harder it becomes for the cell to absorb and release energy effectively. This is refereed to as IR or Internal Resistance.

A "Zapper" is a transformer and capacitors that store up a large charge and then releases it through the cell in a couple microseconds. This tends to shatter the crystals breaking down the IR in the cell and making it more efficient. Commercial zappers are very expensive and can pass as much as 30,000kva through a cell. There are less expensive "maintenance" zappers that put up to 90volts at up to 1kva through a cell to help keep crystals from building up.

There is still some debate on whether or not zapping actually does anything for NiMH though. There is also still discussion on whether or not "Zapping" cells will shorten the life. People have shown as much as a 14% improvement in NiCad cell performance with high current draw (above 40amps) applications. But again it may shorten the cell life and number of times the cells can be cycled.

Memory Effect

Nicads in every application suffer "memory effect" to varying degrees, the newer sintered cells are affected less but NiMh do not suffer this phenomenon at all. The problem with NiMh is that for a given current the output voltage is less than NiCd, because of the voltage drop across the higher internal resistance of NiMh cells. That's why one or two extra cells are added to increase the voltage when using NiMh. Note that some NiMh cells are becoming available whose internal resistance is approaching that of NiCd cells.

By InvertedFlying and terrys01, here's a partial rundown about NiCad and NiMH batteries at this aero-robot site.

Here is an article about why car batteries fail quickly.

Here is a battery powered device called Zap-a-Pet that may be as immoral and inhumane as early electrical medical devices and are most probably illegal if this little firm were to be contacted by appropriate authorities such as the County or District Attorney in his region: Fairplay, CO 80440. This device has outrageous claims such as the ability to fix a retarded dog or a sick cat. Get this quote from this vendor site: "About halfway through the zapping, he relaxed and let his head rest on my arm. When I was done I let him go under the covers to hide. I came back a half hour later and zapped him again for 7 minutes. When I had finished he didn't go under the covers. He sat out and ‘smiled' and made eye contact, and seemed to be the best of his old self. I have no idea what was wrong with Walter, but it is clear that the Zapper made a dramatic change in him, like nothing I have seen before."