Increase battery of a portable usb charger?
Li-ion 3.6V 1200 mAh
Input: DC 5V 400 mAh
Output: DC 5V 450 mAh
Can i add an old battery that has 3.7V and 1150mAh to the charger and increase the battery life of it?
Would it be safe to just hook up the the negs to negs and pos to pos?
Also what would be a better way to increase battery of the charger without buying a new unit?