VIRTUE N-CHARGE RECHARGEABLE BATTERY PACK - SPIRE, CTRL & ROTORThe VIRTUE N Charge is an easy to install rechargeable battery pack providing better performance over traditional AA batteries in a lightweight package. Never buy batteries again thanks to the easy USB charging port. Recharge on the fly using your phone charger, laptop, or external battery pack. Never wonder again if your AA batteries have enough juice to get you through the next game. With the N Charge, simply press the built in battery indicator