Solar regulator doesnt reconnect the inverter

John1111John1111 Registered Users Posts: 1
Solar charger regulator must cut off at a certain point during the night but when it recharges in the morning it doesnt reconnect or the inverter is not reconnecting when i get back out to the block im having to turn the inverter off then back on to restart the power to the inverter.

Just a basic 300w inverter running off 120amh deep cycle battery running to a 20amp charge controller to a 160watt solar panel in hot sunny all day weather.

Its running a small irrigation box and occasionally if i can an electric fence unit


  • BB.BB. Super Moderators Posts: 27,055 admin
    Need to know a bit more details about your setup, how you run it, and exactly what is happening... However, a guess.

    Many (most?) AC inverters will shut down when the hit the Low Battery Cutoff Voltage (LBCO). Typically around 10.5 volts for a 12 volt system. And, if the inverter enters LBCO, then it stays shutdown until the battery power is turned off and back on to reset the inverter input controller.

    Some AC inverters will automatically restart if battery bus voltage goes over >~13.x volts--Check the manual (and how well the battery is being recharged).

    So--It would sound like your inverter is draining the battery to zero state of charge (0%). Taking a lead acid battery much below 11.5 volts is hard on a battery, and taking it to 10.5 volts can damage/ruin the battery pretty quickly (days/weeks of usage).

    The possible issues are--AC inverter is "too large" for the battery bank (draining battery in a few hours or faster). The AC loads are too large (again quickly draining the battery). The battery is not getting recharged to near 100% full the next day. And/or the battery has been damaged (taken dead, sulfated from storing at less than ~75% state of charge, not recharged >90% the next day, etc.).

    If the solar charge controller is not "reconnecting/restarting" in the morning--If the battery is below ~10 or 9 volts, many charge controllers will not start until they are connected to a "non-dead" battery (back over 9-10 volts or so).

    Regarding loads...  More or less, a 300 Watt inverter running a 150 Watt load will take:
    • 150 Watts * 1/0.85 inverter eff * 1/12 volts nominal DC voltage = 14.7 amps on 12 volt DC bus
    You normally want to run the battery to no more than 50% state of charge (longer battery life):
    • 120 AH * 0.50 max discharge * 1/14.7 amp (12 vdc load from inverter) = 4 hours of nominal run time from battery
    Now, to recharge the battery 50% to 100% full... Brisbane Australia, fixed array:

    Average Solar Insolation figures

    Measured in kWh/m2/day onto a solar panel set at a 62° angle from vertical:
    (For best year-round performance)
    Jan Feb Mar Apr May Jun
    Jul Aug Sep Oct Nov Dec
    January ~5.65 hours of sun per day:
    • 14.7 amps load * 12 volts * 4 hours = 706 Watt*Hours (DC) daily energy usage
    • 706 WH per day * 1/0.77 solar panel+controller losses * 1/5.65 hours of sun (Jan) = 163 Watt panel "break even"

    So, with your 160 Watt panel, on a typical January day, your system will (barely) recharge a 1/2 discharged battery (mythical 4 hour load * 150 Watt).

    Anyway--Just some math to see if we can figure out what is going on. In reality, if your battery was taken dead, it would take 2-3 days to fully recharge.


    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
Sign In or Register to comment.