In order to eliminate a second (system) battery, I am investigating using a DC-DC converter.
This is a second attempt to use PIC microcontrollers in an SMPS controller function.
This implementation is a DC-DC converter for use as a battery maintenance system.
The PIC will be used to control the charging algorithm (4 modes) and constantly monitor the state of charge. The charger can be supplied from any external D.C. source with a voltage higher than the dropout of the voltage regulator. Future additions will include a battery impedance test and a capacity test.