This is a simple lead-acid battery charger build for my own needs. Lead-acid batteries needs to be charged first at constant current and then at constant voltage. There are also some integrated circuits made for lead-acid batteries, but this simple circuit works fine for my purposes. It is built around L200 regulator. I tried LM317 also, but wasn’t pleased with it.
Circuit is mostly from L200 datasheet. It can be used with load connected to battery if load is smaller than charging current. Of course current is then shared with load and charging takes longer. Charging current can be set with R2. R3 is for voltage adjust with R1. D1 is to prevent battery discharging trough charger if charger will be switched off and battery still connected. Remember to use a heatsink with L200.
Circuit is simple:
Here is board I designed:
This board can be used as normal voltage regulator board also. Current sense resistor can be replaced with jump wire if you don’t want current limit. You can also drive some 2N3055 or similar transistors to get more current.