Product Description Size AA Lithium Ion (LiFePO4) 400mAH 3.2V Rechargeable Battery For Solar Light Model#14500 series (same length as AA standard batteries) - Especially fit for any solar lights or devices that uses 3.2V AA Lithium-Ion battery (must not be used on 1.2V light or devices) - Can be recharged up to 1,000 times - The mah refers to how much capacity a single battery can hold (the bigger the number the better as long as the devices use the 3.2 voltage) - Dimension: approx 2.0"Lx0.53"WCurrently most commonly used rechargeable batteries for Solar garden lights are as below:NiCD (other abbreviation: NiCD, NICad) 1.2VNiMH (other abbreviations: Ni-Mh) 1.2VLiFePO4 (other abbreviation: LiFe, Lithium-Ion Phosphate) 3.2V *Please do not use the regular rechargeable battery to replace the solar rechargeable battery. Since the regular rechargeable battery is 1.5V. They have different voltage. Only batteries of the same or equivalent type as ones in your solar lights or device are to be used. Do not mix new and old batteries. If you are not sure which batteries to purchase, first match your battery types and then the Voltage. The mAh is your own choice: if you want a light that can illuminate for a longer time, you should choose the higher number of mAh.