The key to using a meter with Nicads is to have one with a "load" on it. I strongly suggest you get a meter made by one of the hobby companies. A typical voltmeter from radioshack or whereever won't tell you what is really going on.

When people refer to "ESV"s, that's what they mean, though it's kind of a misnomer. (ESV stands for "expanded scale voltmeter". Having an "expanded scale" does not actually imply having a load on the circuit. I personally use a DVM (digital volt meter) that has a built in load (made by a hobby company). So it's not a ESV, since it has no "expanded scale", but it does have the load, so it works well. (and it doesn't break everytime I drop it like the cheap ESV's I had before)

This is because of the way Nicads work, they will show lots of voltage with out a load, then fall off dramatically with even a small load on them. Obviously, is the voltage under load we care about.

You can actually take a normal voltmeter from radio shack or wherever, and make up a test lead that has a resister built in to it correctly to apply the proper load. I did this for years, and the results are just as good, and more accurate (if you use a high quality meter) that the hobby meters. It's easier and cheaper these days to just get a meter made for this though.