Run A/C from inverter?

Anybody know from experience whether I can run a 13500 BTU/hr AC, (Dometic) with a soft-start installed off of a Victron 2000VA Multiplus Compact inverter ? Given enough battery capacity to make it worthwhile.  

Comments

  • BB.BB. Super Moderators, Administrators Posts: 31,081 admin
    Given that a Honda eu2000i is supposed to be capable of starting/running a 13.5 kBtu A/C -- Especially with a good soft start conversion--It certainly sound possible.

    If a flooded cell lead acid battery, suggest a minimum of 400 AH @ 24 volts for a 2 kWatt AC inverter.

    A 12 volt battery bank would have to be in the 800 AH range, and even then, getting much more than 1,800 Watt inverter running on 12 volts is a bit of a pain. 12 volt systems, design for ~0.5 volt drop for DC wiring, and the circuit should be designed for:
    • 1,800 Watt * 1/10.5 volt battery cutoff * 1/0.85 AC inverter eff = 202 Amps @ 12 volt battery bank (0.5 volt 12 VDC wiring drop max)
    • 2,000 Watt * 1/21.0 volt battery cutoff * 1/0.84 AC inverter eff = 112 Amps @ 24 volt battery bank (1.0 volt 24 VDC wiring drop max)
    Remember the typical good quality AC inverter will surge ~2x its name plate Watt rating.

    But from a practical point of view--I do not have any experience to answer yes or no... Hopefully somebody else here does.

    Given that this is an RV--You might be looking at LiFePO4 or similar batteries--The AH rating of a lithium bank would be much less needed to support the surge current--But you have to look at the battery bank specifications to ensure that it can handle the running and starting surge current. You might be able to get down to 200 AH @ 24 volts pretty easily with Li Ion (light/small battery, but nowhere close to inexpensive).

    Some of the newer RVs are using Li Ion banks and dumping propane all together and using induction cook tops--And then have enough energy/power to also run the A/C for a while just from the battery bank.

    If you look at some of the RV forums, you can probably find the answer there.

    Of course, a smaller AH battery bank will run less hours in a day than a big old heavy lead acid bank.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • mcgivormcgivor Solar Expert Posts: 3,558 ✭✭✭✭✭✭
    What is the running voltage /current of the A/C unit ? Theroitically it should be capable if the soft start significantly reduces inrush and initial surge. Not all A/C units consume the same amount of energy for a given BTU output, higher efficient refrigerants like R32 use significantly less than R34A or R410A for example so there is no blanket answer. Having two 9000 BTU myself  the  R32 running current is 2.6A, the R410 is 4.2A at 230V,  both can operate similtaniously on a 2500 VA inverter without issues, they are however  inverter based, so no inrush.

    The DC nominal voltage is important if 12V, which is often used in RV's, substantial conductors will be required to prevent voltage drop which could cause the inverter to shut down even if were' capable of supporting the load. The best way to find out if it will work is to try it out, assuming you have the inverter.



     
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  • addcoaddco Registered Users Posts: 11 ✭✭
    Thank you for the feedback. Time to get some real-world amp readings with the A/C running. 
  • Ralph DayRalph Day Solar Expert Posts: 927 ✭✭✭✭
    Or most importantly A/C starting amp readings
  • 706jim706jim Solar Expert Posts: 371 ✭✭✭✭
    I figure you could run your A/C off of the inverter but not for very long.
    Island cottage solar system with 2400 watts of panels, 1kw facing southeast 1kw facing southwest 400watt ancient Arco's facing south.Trace DR1524 MSW inverter, Outback Flexmax 80 MPPT charge controller 8 Trojan L16's. Insignia 11.5 cubic foot electric fridge. My 27th year.
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