1. Please use the specified battery charger which is with Over-charge protection to charge the battery, the max voltage output is 4.25V
2. When charging the batteries, please put them in an open space and keep away from any inflammable goods such as Carpets, sofa, bed and etc.
3. Please don't use high current USB adapter charger that higher than 2A to charge the battery.
4. When changing the battery, don't pull hard when the battery is stuck, otherwise you may destroy the wire of battery and its inner structure, which will cause battery fire when charging!
5. If the battery swells, please discard it and don't use again!
4-in-1 Battery Charger: Input: 5V-2A, Output: 4.2V
Battery: 3.7V 650mAh, 2.41Wh
Battery quantity: 4 Pcs