240V or 120V generator charge efficiency

machinemanmachineman Solar Expert Posts: 124 ✭✭✭
My 7Kw 240V/120V single phase propane generator is dead and its time for a replacement.  My inverter/charger is a Magnum MS4024AE which uses both 120V legs (240V in) to charge my batteries. But it can charge with 120V only also.  I want to get a small generator maybe 3000 to 4000w but those are nearly all 120V only.  Do I loose some charging efficiency through the charger if I only charge with 120V instead of 240V?   I have a 24V 460ah battery bank

Comments

  • oil pan 4oil pan 4 Solar Expert Posts: 661 ✭✭✭✭
    Depending on your charger going down to 120v could limit your charging amps, which means more generator run time.
    Is there a difference in charging amps when powered by 120v power versus 240v power?

    Solar hybrid gasoline generator, 7kw gas, 180 watts of solar, Morningstar 15 amp MPPT, group 31 AGM, 900 watt kisae inverter.

    Solar roof top GMC suburban, a normal 3/4 ton suburban with 180 watts of panels on the roof and 10 amp genasun MPPT, 2000w samlex pure sine wave inverter, 12v gast and ARB air compressors.

  • EstragonEstragon Registered Users Posts: 1,809 ✭✭✭✭
    Spec for the charger is 15aac per leg input at 120/240v split phase. Using one leg (120vac single phase) would be 15x120v=1800w max. That would put output at ~ 1800w ÷ 28v x .85eff = about 55adc charging output in bulk.

    I don't think charging efficiency would be much different, but a 460ah FLA bank might take 75a or so in bulk, so run time would be longer than with the old 7.5kw genny.

    On the plus side, if you use an inverter type generator such as a Honda eu3000i with eco mode, you could charge in absorb much more fuel efficiently.
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
  • EstragonEstragon Registered Users Posts: 1,809 ✭✭✭✭
    A separate but related potential issue occurs to me. If applicable, you may want to check the inverter manual to clarify.

    I assume you have a 120/240v inverter to run 240v loads (pumps or HVAC)? The inverter likely just passes grid/generator power through to loads when available. There could be an internal autotransformer, but if not, 240v loads couldn't be run, and depending on wiring, 1/2 of your load panel may be dead while on generator power.
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
  • EstragonEstragon Registered Users Posts: 1,809 ✭✭✭✭
    Curiosity got the better of me and I checked what I think is the manual for your inverter.

    In the section covering 3-phase supply input, it suggests taking a single leg of the 3 (120v) will still allow 120/240v output (but inverter output has to be limited). Aside from the current linitation, this implies there isn't a problem with the concern in post #4 above.
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
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