Own MPPT solar controller.

This year I rented a car garage. It is big enough for my needs and rent is reasonably priced. The only drawback is that it is not connected to electricity. In the garage I need only light. I have a fuel powered AC generator for tools, but for everyday use I needed some light.

Decision was easy - I bought 12V/20Ah LiFePO4 battery and a few 12 V lamps. It is enough to use light inside and one lamp activated with PIR sensor outside for about 2-3 weeks. I decided that I'll try to mount small PV panel to charge battery and be able to use light without charging battery at home twice a month.

I bought a photovoltaic panel (10W, 12V) and started looking for a charging controller. I found a reasonably priced device from Victron Energy that I was going to buy, but... That would be too easy!

Of course, it would be very ambitious to design my own charging controller implementing MPPT (Maximum Power Point Tracking), but I am experienced enough to know that it's not an easy thing to do. I found some open source design of MMPT charging controller that has much higher allowed voltage and power than I needed. Author of this design uses it to power his private lab and did a few revisions of the device. I decided to give it a try.

PCB and original firmware

Update: 7th October

I've ordered PCBs from PCBWay and soldered them. Here I found several issues. Electronic parts that are easily available in Thailand (the place where design's author come from) are not necessarily aviailable in Europe. I'm mostly ordering parts from TME, because it's in Poland and delivery is cheap, but some parts I had to order from Farnell. I had to order XL7007, DC/DC isolator and a few others from AliExpress. They look fine.

I have also decided to buy second (same) photovoltaic panel and connect it in series to boost voltage on input.