1100mAh Battery fits Dell Axim X50 X50v X51 X51v series High Quality, high capacity, light weight rechargeable DC 3.7V Li-Ion 1100mAh battery. Longer battery life than the original battery that comes with the PDA. Best replacement for the original Dell Axim X50 X50v X51 X51v series battery pack. #No memory effect. Can be charged or discharged as needed without loss of capacity. Overcharge protection, with built-in battery life microchip.