Hello, I've small 10W solar panel with 0.5A short circuit and about 23Voc, which I use to charge 7AH 12V gel battery.
Of course I need battery overvoltage protection, so I've designed such circuit using.. only 12V zenner diodes, optocoupler, mosfet, diodes to protect solar panel from battery at night.
Nowadays, in summer I geat easy 0.5A short circuit and this battery is charged in sunshine easy-I use it to make cell phone calls and as stand by for old Siemens cell phone, and it works-I've never charged my phone room wall socket, since I've made 4.15VDC voltage regulator to exchange with flammable Lion oryginal cell phone battery
However, looking into this answer:
It does not look like an MPPT controller so even if it will tolerate the possible 40+V from your panels (unlikely), it will be very inefficient.
... assuming I can track sun (I've my solar panel perpendicular to sun most of the daylight), how much more efficient can be controller using MPPT, instead of my solid state battery limiter, which doesn't draw any current when fully charged battery left at floating voltages between 13.5V-13.9V?
With a 12V nominal battery banks, you'll want MPPT controllers.
Why I might want MPPT controller, when I can track sun and I have my pannel perpendicular to the sun, which means that this panel can see Sun most of the day?
I've just managed to choos all elements for this small PCB to source-without any MPUs (microcontrollers, etc) just analog circuit can take care of 12V battery to limit its voltage to floating 13.5V-13.8V even in the middle of the day at full Sun.
Why I might want MPPT -maybe for winter days?
I've also bigger ~66W 1.2m x 0.6m pannels, which will be connected in series to create ~250 VDC under nominal load, so maybe some kind of MPPT will be needed, but to charge small battery like 7AH using 10W solar panel it looks like simply solid state battery limiter should work at good Sun light conditions like in the summer
I see no reason by something like this, which looks like simply battery limiter, etc , which costs more than 66W 1.2m x 0.6m solar panel, by make a few PCBs 1 in x 1 in (2.5cm x 2.5 cm) which should protect 12V battery, too
Coleman 7 Amp Solar Charge Controller with Rings by Sunforce - 60012
https://www.batterystuff.com/largerimage.html?id=566