To know the exact time it takes for your charger to recharge your batteries fully, you should know the type of batteries you are dealing with, such as AA, AAA, NiMH, or NiCd. You must also check the battery's capacity, measured in mAh, and the electric current output of the charger, measured in mA. You can also calculate. Rechargeable batteries start discharging when they are not being used. It is referred to as self-discharge. This means you must recharge it before using it because it happens quickly, too. A typical rechargeable battery gets. Each time you leave the batteries in the charger even after they are fully charged, they lose their capacity a little bit. This usually happens because. It would be best to look at the blinking colors while charging it. It served as an indicator if it was fully charged or not. Most chargers switch colors between “charging” mode and “charged” mode, so find its meaning in the manual. Yes, you can, but it damages the battery a little bit. It won't happen right away, and the damage won't be visible. Overcharging a battery eventually loses its capacity to recharge to 100 percent. It.