Charging the batteries
BEFORE YOU CONSIDER CHARGING:
If you have a NiCd battery, it's best recommended to use a NiCd charger. You can use a NiMH charger, just be aware that the charging parameters may be different, unless if your charger says it supports both types of batteries, that should work the greatest.
If you have a NiMH battery, it's best recommended to use a NiMH charger. You shouldn't use a NiCd charger on NiMH batteries, as it would lead to damage to the battery or the charger.
If you have a NiCd battery and an original 2001 charger, simply plug the battery into the charger, and set a timer. If you're charging the battery after a while of not being in use, 3 to 3 1/2 hours should be good. Do NOT listen to the manual, saying to charge the battery for 6-10 hours, that is going to overcharge it! If you are going to charge the battery after your i-Cybie goes into the charging position, 45 minutes to an hour and a half should be good enough.
If you have a NiMH battery and an NiMH compatible smart charger with the specified connector, you can plug the battery in and charge it, until it detects when the battery is fully charged, by using some sort of indication. (edited)