Nokia 6160 Owner's Manual page 79

Chargers & Other Accessories
Note: When a charger is not in use, disconnect it from the pow-
er source. Do not leave the battery connected to a charger for
longer than a week, since overcharging may shorten its life. If left
unused, a fully charged battery will discharge itself over time.
Standard Travel Charger
(ACP-7U)
Rapid Travel Charger (ACP-9U)