1, the battery seems to be \"dead\
2, this \"dead\" to the battery, with the original charger is not charged (no current through), but with direct current equal to the battery design voltage to charge the battery will find that there is a relatively large current, and the charging current will slowly reduce, a few minutes later close to 0, which is good news: the battery voltage is returning to the design level.
Stop charging at this time, and then use a multimeter to measure the battery poles, whether there is a normal voltage
3, then, you can use the original charger to charge it.
4. In this way, I have repaired quite a few batteries, and many of them have been restored to about half their designed capacity.
5, in order to completely activate the battery, it is also necessary to thoroughly charge and discharge several times. The discharge circuit is composed of a resistor and a light-emitting diode, through which the discharge state can be estimated.
6, in my experience, this method for the first type of battery, very effective. The battery in the latter two cases is difficult to repair, and the information found on the Internet rarely has obvious effects. In particular, the third kind of \"can be charged, and the capacity is relatively sufficient, but the large current discharge voltage drops significantly (specific performance, such as: the shooting mode of the camera can only persist for a few minutes, and the mode of looking back can persist for a long time)\" this battery is a pity to discard.