I have following diagram on falstad
Top +5V is main PSU (12V 10A). Bottom +5V is battery (12V 2.3Ah). I have load about 2-3A so I dont think diode is good solution. Well I am trying to achieve following: While PSU is plugged then run circuit from PSU and charge battery. When it comes to power outage I would like to run circuit from battery.
What is not working? I dont know if its falstad issue or not but while PSU is active there is no current flowing to battery via resistor. Also I forgot to mention if there is power outage on PSU I definitely not want to charge PSU from battery (thats why there is mosfet) because behind mosfet will be 2 resistors to measure voltage by IC to notify user there is power outage.