I want to make simple UPS with means of arduino, to learn the processes from it, and be able to record and monitor at PC. For the start i want to implement buffered usage charge mode. Logic is simple - when voltage is less than defined(say it battery voltage is less than 13.6V) - then gate should open and connect battery to charger. If voltage is greater then gate should close, disconnecting charger and preventing battery and load from excessive voltages. So, it would do kind of clever PWM. I am asking for a help, i dont know how to connect gate to arduino. If i explained bad please look at illustration:
After night of researching, i seems to figure out correct schematics for this by myself. Haven't tested this yet, but theoretically it should work. Only requires that N-mosfet gate open voltage is below +4 Vgs, and P-mosfet open is near -10 Vgs. Illustration is as following:
PS. For mosfet models seems i have to hunt powerful low-Rds models in TO220/247 cases, to diminish heat waste, because 0.2C charge current for 200Ah battery could be 40A. Something like IRF4905 P-FET should fit the task. Charging would require 550-600W charger and for P-FET with Rds=0.02Ohm, Vdrop would yield 0.8V and 30-35W would be dissipated as heat. And any cheap, even low power TO-92 N-FET, that opens somewhere at Vgs +2..+4V to control -10V P-FET's gate from +5V arduino PWM signal.