As a follow on to what RC Ken said above, another good method would be to use a battery discharger and cycle the battery pack to see what the actual capacity is. This will do two things for you. It will give you a good idea of the real capacity (if it says 700 mah, then you should get around +/- 10% of capacity. The second benefit is that it will help rejuvinate (for lack of a better word) the battery if it is an older battery.

One of the top manufacturers and battery guru's said that he has rarely found a battey that was useless. He used this discharge/recharge cycle to actually rejuvinate or re-energize a battery that seems to be losing it's capabilities.

There are several on the market, the better chargers, ie. Triton or ICE for instance, have the discharge/recharge capability and will show you the current drained out during the discharge cycle. You can set these up for several cycles, over several days for instance, which will leave you with a very well prepared and peak charged battery pack. This goes for NiCad's as well as NiMH packs.

DS.