Lithium-ion Battery for B1 500 AirTTL from Profoto will give you up to 220 full power flashes and thousands of minimum power flashes on a 2 hour charge from the 2.8A multi-voltage charger. The 4.5A quick charger shortens that time to 1 hour. Fuel gauge-type LEDs on the battery and both the optional chargers allow you to monitor charge progress.