Circuit Lake

The purpose of the project is to build lead-acid batteries charger using solar panel in small and portable applications. The charger will stop charging once a pre-set voltage (temperature compensated) has been reached, and resume charging when the voltage has dropped off sufficiently. The load is disconnected when the battery voltage drops below 11V and reconnected when it gets back to 12.5V. The customary diode that prevents the battery from discharging through the solar panel has been replaced by a FET-comparator combination.

Project features:

• Charges until Vbat = 13.8V (adjustable), then float charges;
• Shuts down load when Vbat < 11V (adjustable), resets at 12.5V;
• Burns less than 20mW in FETs when charging at 0,5A.
• Will work with cheap and readily available components like LM393 comparators and BUZ11 FETs;
• Uses less than 0.5mA when using TLC393 comparators;
• Temperature compensation;