The Bosch 36 Volt Quick Charger can charge a used 36V and 4.0Ah battery in 45 minutes, and a 36V and 2.0Ah battery in just 35 minutes. The smallest and lightest charger in its class supplies the cells safely. This unit has battery protection systems: one is slow charging - the first 80% are charged very quickly, while the last 20% are charged at normal speed. The other is the cooling fan to prevent overheating during recharging. This charger is equipped with a charging status indicator, and is also compatible with Bosch 18V batteries.