RE: Energizer Rechargeable NiMH
garyo1954,
The biggest problems with batteries like this isn't the chemistry of the battery, but rather the battery form factor. Batteries like this without solder tabs on them can be VERY difficult to solder into a battery pack without damaging the batteries. Nimh batteries have a small plastic seal the seals the entire cell. If it gets too hot from soldering the seal will melt and then the battery will be ruined. It may still charge and give voltage, but it's now unreliable as it can fail at anytime like this. How much heat is too much. I can't give you the exact temperature, but I can tell you that 2-5 seconds of heat from a soldering iron can be too much for it. I'm not saying that it's impossible to solder batteries like this, but unless you can make a perfect (and quick) solder connection you're going to run a real risk of damaging the battery cell.
For those that want to build their own packs I recommend that they get batteries with solder tabs on them so that can avoid a lot of the problems I've listed above.
Ken