Simple Lead Acid Float Charger

[nickelflippr]

These shunt chargers have been talked about a lot. I just wanted to pass this schematic by and see if any mistakes, before soldering it up. The battery is a 12V flooded lead acid, 65ah deep cycle marine. Namely this is a band aid, so as to not boil out the water, until something more sophisticated is developed.

 

[nickelflippr]

Went ahead and breadboarded it, good thing, as the R1, R2 resister divider values were backward. Also the output from the TL431 cathode was opposite from what I thought, so an inverter circuit was added.

 

[nickelflippr]

there are 12V float chargers everywhere, but i want to build a 24V charger. please give me the schematic

The TL431 is an adjustable precision shunt regulator. Apply the formula, from the above schematic, to get your required charge voltage. The Vout or charge voltage can vary from Vref - 36V, and is set by R1 and R2. If you have a 24V rated panel then it should work. If you want something driven from the mains supply, look elsewhere.