Charging battery bank

ras108ras108 Registered Users Posts: 2
I have a 200ah battery bank I use for off grid camping. Having problems charging from my generator. What I have now is an inverter 3500w connected to my battery. And a generator 3500w inverter generator. I'm charging with a 5.0 amp noco charger plugged to my generator. Battery gets to about 50% and seems to stop taking charge. Is it just as simple as getting a bigger charger? And what voltage do I want to see on my meter when charging?


  • BB.BB. Super Moderators, Administrators Posts: 32,006 admin
    Welcome to the forum ras108,

    Can you tell us more about your setup?

    Battery bank? 200 AH @ xx volts? What type of battery (lead acid, Li Ion, etc.)?

    What voltage are you seeing at the battery bank terminals (12.0, 13.8, 14.5, etc.)?

    How do you "know" it is charging at 50%?

    A 5 amp AC charger is pretty small for what you are doing... A 50% discharged 200 AH battery bank would need ~100 AH to fill:
    • 100 AH / 5 amps = 20 hours of genset runtime... That is a lot of fuel/noise/smoke
    A typical charger for that setup (not knowing the battery "details") would be 10% to 20% rate of charge or 20 to 40 amps
    • 100 AH / 20 amps = 5 hours (plus absorb time, if lead acid)
    • 100 AH / 40 amps = 2.5 hours (plus absorb time, if lead acid)
    Of course, the larger charger will draw more from the genset... If you have a small genset (like a Honda eu1000i)--A 40 Amp @ 12 volt battery charger may be on the "large load" side for the small genset.

    However, if you have a larger genset, then even a 40 amp charger should not be much of an issue.


    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • ras108ras108 Registered Users Posts: 2
    200ah 12v agm battery, my gen set is a generac iq3500 inverter generator. The reason I'm led to believe I'm only getting to 50% is from the inverter battery monitor. When charging at 100% off my home electric I'm getting around 14.5v. I didnt have the chance yet to look at it off my gen.
  • PhotowhitPhotowhit Solar Expert Posts: 5,650 ✭✭✭✭✭
    No magic involved, you are charging a 200 amp battery bank with a 5 amp battery while running your 3500 watt inverter charger.

    If we convert to watts you have a 5 amp charger at 12 volts or 60 watts, Do you know what your inverter charger uses while on? I've seen 60 watt loads and even higher, at idle for inexpensive inverters!

    You just don't have much charging going on. Even without an additional load, a 5 amp charger would take 20 hours to charge 100 amps without any load or losses. Your AGM battery is likely 90-95% efficient, so you could bump that up too 24 hours with losses. Noco makes pretty god chargers, but they have too compare with others, so it is likely a 5 amp charger at 12 volts, but less amperage at higher voltages...

    What do you charge with at home? The same charger? Not seeing the same results? Find out what the idle load is on your inverter.
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former, 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
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