Software based on ARM mbed library for the LibreSolar 20 A MPPT solar charge controller
The charge management is implemented using a state machine with the following states:
Initial state of the charge controller. If the solar voltage is high enough and the battery is not full, charging in CC mode is started.
The battery is charged with maximum possible current (MPPT algorithm is active) until the CV voltage limit is reached.
Lead-acid batteries are charged for some time using a slightly higher charge voltage. After a current cutoff limit or a time limit is reached, the charger goes into trickle or equalization mode for lead-acid batteries or back into Standby for Li-ion batteries.
This mode is kept forever for a lead-acid battery and keeps the battery at full state of charge. If too much power is drawn from the battery, the charger switches back into CC / bulk charging mode.
This mode is only used for lead-acid batteries after several deep-discharge cycles or a very long period of time with no equalization. Voltage is increased to 15V or above, so care must be taken for the other system components attached to the battery. (currently, no equalization charging is enabled in the software)
The PWM signal generation for the DC/DC controller inside the charge controller is done by a separate class HalfBridge. Most of the dangerous functions which could blow up your MOSFETs are implemented here.