An MPPT solar charge controller using Arduino as well as a homemade Li-Ion battery. Also an 18650 battery tester. So 3 projects simultaneously because they’re closely related.

I’m using a CC CV boost converter to convert solar energy to the voltage for a 7s Li-Ion battery. The arduino reads voltage and current and will try to adjust the CC value to obtain an optimal wattage. I have removed the CC potentiometer and replaced that with an Arduino PWM pin with voltage divider that sets the corresponding current limit. This way a relation between CC pwm duty cycle and solar output can be set.

DIY Li-Ion battery goes hand in hand with the solar project. I’m making a home battery out of salvaged laptop batteries. That requires a battery tester as well which I’m also making myself. The battery tester works by charging a battery with a TP4056 module and discharging as soon as it’s fully charged over a resistor while monitoring voltage/current over time. This happens 16x in parallel using multiplexers so 16 batteries can be tested simultaneously.

I’m also taking safety very seriously so all batteries are equipped with both thermal fuses and current fuses. That involves 3D modelling battery holders, printing them, spot welding/soldering etc. As well as an additional monitoring system on top of a commercial BMS so that the battery status can be monitored remotely. I intend to have a smoke detector, thermostats and an emergency cutoff switch controlled by that second BMS.

Once everything works to a somewhat satisfying degree I intend to post the projects in more detail.

Every project tends to explode in scope in terms of what it all requires so I’m not making as much progress as I want but it has been very educational.