The new Bosch 18 Volt 4.0 Ah lithium-Ion CoolPack batteries with built-in cooling technology prevent heat damage, give upto a 65% longer run time and upto 100% longer life**. The 4.0 Ah CoolPack cells have finer \'windings than 3.0 Ah allowing more power density (fuel (Ah)) in the same pack size and less electrical resistance, this means a more fuel efficient battery and less frequent charges. All Batteries have a charge time of just 45 minutes. The unique casing of the Bosch CoolPack battery allows for an even displacement of heat inside and out. This protects the cells inside the battery from heat damage which can kill cells and lead to decreased battery life. Its the smallest battery pack in its class meaning its light and compact allowing for ease of use in same voltage class Bosch Blue Li-lon tools. Features: - CoolPack technology. - High power contacts with sliver coating. - Capacity indicator with 3 LEDs. - In-built temperature sensor. - Robust casing can survive a 3m drop. **in comparison with batteries without Coolpack technology. Specification Battery Voltage:18 Volt. Battery Capacity: 4.0Ah. Weight: 600g.