charging 12v when gennie is on in my custom mobile office

Hi, I am making a mobile office out of a 7x10' trailer. The plan is to have a few things that can run off a pure sine inverter on 12v deep cycle for when the generator isnt on. The generator is mainly to run the mini-split for when its too hot or cold inside...

I'll be drawing a few hundred watts off the inverter for LED lighting, laptop, a charging phone, maybe the 12" fan... and there's a couple DC direct loads like a little water pump and a 50W car audio amp.
And I'd like the generator to bulk then float the battery when I either need some air conditioning or the inverter (or separate voltage readout) is telling me I need some DC charging.

It seems like my loads will try to draw off a charger if I simply wire one from the AC of the gennie right to the 12v and over-tax it.

My goal is to not interrupt drawing off the 12v system when its needing to be brought back up by the charging system.
Is this possible without say, needing to get into a A & B battery bank setup?

I know that somehow solar/wind/turbine off-grid feeds the bank while people are using the power. How do I best set this up between just my Champion A/C inverter generator and my 12v deep cycle(s)?

thank you for your inputs,
Ron M


  • mcgivormcgivor Solar Expert Posts: 3,854 ✭✭✭✭✭✭
    edited December 2020 #2
    An inverter charger would be the best solution aseverything would be automatically taken care of with a single device. Inverter chargers are able to pass through power to support loads as well as keeping the battery charged. All loads can be powered by the inverter and transfer automatically occurs when the generator is started.

    Keeping the system separate from the vehicle battery will prevent possible imbalance problems leading to the vehicle battery being depleted, resulting in starting issues. Here is an example of such an inverter charger
    There are many options, once you establish your loads the capacity of both the inverter and battery can be calculated, don't impulse buy before having a plan.
    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery with Battery Bodyguard BMS 
    Second system 1890W  3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah LFP 24V nominal battery with Daly BMS, used for water pumping and day time air conditioning.  
    5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
  • prefercreateprefercreate Registered Users Posts: 2
    Got it! Thank you, mcgivor. I like that I don't need to have 2 sets of plugs also with this. And it seems to have a setting where it will favor the battery bank even when it senses the gennie is on. Nice flexibility.

    And as its just a trailer, the only battery is the one on the inverter-charger so there's no worry about getting in a situation where my truck can't start...

    I am wondering a bit about grounding. I do have a sink in there and my plan to keep myself safe is just using GFI outlets and not connecting anything, either the gen or the battery, to the frame of the trailer. "Floating" it, as i've been reading...

    Now I just need to think a bit on sizing my battery so its not draining so often as to be annoying. I think the samlex charging rate should be just enough. Great recommend. Thanks again,

    Ron M
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