This is a Generic charger that is made by many brands, the circuit is an approximation of all. Some improvements suggested. Some brands in europe and usa also use this circuit. This works well, but may not be in the best interest of battery life. The cost of the charger needs to be low. So this design or configuration is popular.
Battery Level Indicator The more care you show in the charger’s battery charging and discharging; the longer its life. Today i manage my UPS batteries manually, both charge and discharge. The batteries are expensive, there is no better way, that is affordable.