I just can't seem to get my arms around this. All I want to do is use an Arduino to at least monitor the charging for 12V batteries from solar panels.
At first, I wanted to build an Arduino controlled MPPT charger. I've seen several sets of schematics but they all seem to either have problems doing what they were designed to do, or are simply too weak. I want to attach only 200 Watts of solar panel, but many of the schematics were designed for only 20 or 50 watts. Getting the right sized MOSFETs and inductor coils seems to be the biggest challenge for most of these designs.
Eventually, I decided to Abandon that idea and use a commercial charger but put the Arduino Sensors in front of the charger. From the solar oanel, through the Arduino sensor, to the input of the charger. From the charger, through the Arduino sensor, into the battery. Same thing for load. As sensors, I wanted to use the INA219. I procured three INA219s and designed a circuit which provided the correct shunt.
I built the board and when I connected it I realised it wouldnt work! The chargers all seem to have common plus connectors (solar panel, battery, and load). To monitor the voltage and amps, I have to connect each INA219 to the Arduino ground and the negative side of the circuit to be measured (for example the solar Panel). That means, I would have a common rail on the negative side of all three circuits and a positive rail on all three circuits which obviously leads to trouble.
So, anyone got any brilliant ideas? How can I charge or at least monitor the charge/battery level/load of a 12V battery from 200 Watts of solar panels?
I've been working on this for six months and am getting no where! Any input or thoughts would be greatly appreciated.