1. Rechargeable batteries self-discharge faster than disposable batteries. A NiCd rechargeable can lose 10% of its charge in the first 24 hours, and about 10% per month following that.
2. Slow recharge (say, overnight) is better for battery life than fast recharge.
3. Use a “smart” battery charger that can detect when a rechargeable battery is “full.” Overcharging can damage a battery.