KA9PDK Solar Charge Controller
Here is the schematic of my current solar controller. It seems to work fairly well as all the smarts are in the arduino controller. On one of the several I have built, i actually paralleled 2 MOSFET to ease the burden on them. Jury still out on if it was worth it. The T for thermistor was a big help on keeping things from going to crazy. A standard 10K thermistor does quite well at monitoring heat sink temp. I just use a small drop of mixed up epoxy to mount it on heat sink next to the MOSFET. After much reading, it seemed to me, that while most folks insisted on charging a SLA or AGM battery using a current limiting circuit, some also pointed out that if voltage monitoring could be utilized, then put the charge to the battery until it was full and then cut back. This is my approach and I charge until battery reads a certain voltage and then drop back to a float voltage. Been working fine for me since beginning of year or was it late last year. Time flies and I have too many projects to remember. Note also that I use a NRF24L01 radio transceiver to send a status report to my central controller. You could cut that part out of the attached program if not utilized. Get back to me for more info on utilizing the radio section if needed. Have 10 different one one running here on the homestead. Note also that this should work for any kind of charging voltage input.
arduino sketch for the controller