Thanks Tom61 for the Pelican battery warning. (I had bought 2 of these, and they worked great at first.) Then one day it just stopped charging the Z! It didn't get hot or anything. It just stopped charging the Z. A quick check with the multimeter showed it putting out 5.6 volts. That's a little high, and I guess the Z has some kind of protection circuit built in, because it would not charge from the Pelican battery but still works fine with the AC adapter. Now I'm back to my 4 AA NiMH battery pack, which still works fine. It's just heavier, and I have to take the batteries out to charge them.