Since my previous charger said farewell today, I have decided to build a 48V 100A solar PWM charger (for LFP cells, ie. CC-CV) myself. I don't need MPPT because I have already well-balanced PV and battery voltage. I would have to operate an MPPT charger for decades until the additional cost/effort for MMPT pays off through its modest efficiency gain.
So I would like to educate myself about PWM chargers. In principle the charger's job seems pretty straightforward:
- connect the PV modules directly to the battery if its voltage is below its final value (CC mode)
- disconnect the battery as soon as final charging voltage is reached
- reconnect the battery with some hysteresis if it falls slightly below the upper limit (CV mode)
It is simple enough so that I could do these steps by manually operating the main battery switch, but even though my time is not too precious, I would like to spend some time with my family every now and then. You get the idea, I don't require 1 MHz switching frequency.
Choosing a microcontroller and an appropriately sized MOSFET doesn't seem to be too difficult. Soldering the latter to big copper bars or mounting them to an even bigger heat sink, neither. Yet I would still need some education about how to properly control a 10V MOSFET from a 5V micro (sadly, there don't seem to be too many logic-level MOSFETS at that performance level). Over-/undervoltage protection would not be an issue, because I already own a separate BMS. The only safety thing I would strongly prioritize is that the charger does not burn my house down, nor that it triggers my neighbour's love toys.
Is there a single source (book, website) where I can find that basic knowledge about a PWM plain vanilla "reference design" with appropriate electric safety?