- Some older rechargeable batteries use a nickel and cadmium electrodes. These batteries require particular care during charging. Some old NiCd chargers will not shut off power after fully charging batteries, resulting in an overcharge. NiCd batteries also suffer from a memory effect, reducing their length if charged before completely drained. If you camera still uses a NiCd battery, remove it from the charger promptly to avoid overcharging.
- Newer varieties of rechargeable batteries, including Nickel-Metal Hydride and Lithium Ion batteries, do not suffer from the same issues as NiCd batteries. Chargers designed for NiMH and Li-Ion batteries will automatically shut off after charging, preventing overcharge. Even if you charge your battery inside the camera and use it while plugged in, the circuit will disengage the battery after filling up to prevent overcharging. These batteries also don't have a memory effect, and in fact should never be drained completely.
- If you do use NiCd batteries, leaving them in a charger that doesn't shut off can have several negative effects. An overcharged NiCd may experience reduced capacity. In extreme cases, the battery may completely stop working. These effects build over time: overcharging a battery one time won't necessarily ruin it, but letting it overcharge by several hours multiple times may.
- While NiMH and Li-Ion batteries cannot normally overcharge, they may if used with an improper or defective charger. Using a charger designed for NiCd batteries, for example, can quickly destroy a NiMH battery. To keep your camera battery alive, always charge it with your camera's included charger and power cord. If your camera takes rechargeable AA batteries, make sure the battery and charger types match. When replacing an old camera battery, match it by part number to ensure compatibility.