If your battery packs are NiMH cells, then it will take about 4-5 charge-discharge cycles before they will hold their full capacity and allow you to discharge them fully. Charge them at about .025C (4-hour rate), and charge them at 0.10C (10-hour rate). Do this about 4-5 times. Then try a regular discharge to see what the capacity is. You continue to charge and then discharge until the capacity comes up.

NiCd cells don't need the slow charge/discharge cycling. Just give them a slow 24-hour charge for the first charge and they should be ready to go.

Also check your leads and connectors. Long leads of small-diameter wires can cause a significant voltage drop due to their resistance. Add a dirty connector and some bad solder joints in the connectors, and you have a recipe for bad charge/discharge numbers. Shorter leads, heavier-gauge wire, and good connections are the solution, here.