Forum Discussion

rich85704's avatar
rich85704
Explorer
Jan 25, 2015

Question on accessory outlet for inverter

I got a small pure sine wave inverter to use for sensitive electronics; I'm planning to do a fair amount of video and audio work in the rig this summer. It's a 400W unit, which is enough to power the gear I intend to use. I asked my RV mechanic to run wiring from the battery bank (2 12V in parallel) into the compartment where the inverter will be. (it's a Wagan "Elite 400W Pro" PSW model)

The inverter comes with 2 sets of cables: one with a 12V "cigarette lighter" style connector, and one with clamps to attach directly to the battery. The manufacturer cautions that a standard automotive accessory circuit will only handle about 15 amps, giving approximately 140 watts of AC out of the inverter. Fair enough. The manufacturer says that if you want the full 400W output, you should run a 12V accessory outlet, fused at 50amps, directly to the battery.

Long build-up to the question: my tech says that the outlet itself is the limiting factor here, and that it won't handle more than 15 amps even if connected directly to the battery, and that even if the inverter were wired direct, it should be fused at 25 amps max "because of surges." The inverter will handle an 800W surge, according to spec.

Opinions? I want to be able to use the full 400W if the need arises. Are there special "heavy duty" 12V accessory outlets? The wiring run from the inverter location to the batteries is less than 6 feet... what gauge wire would y'all suggest?

Thanks!

Rich
Class C
  • pianotuna's avatar
    pianotuna
    Nomad III
    Jan 25, 2015
    Hi,

    I'd suggest placing the inverter as close to the inverter as humanly possible without it being in the same compartment and using a minimum of #8 wire (thicker would be even better).

    Run a 120 volt line to where you need the power.

    Remember that 400 watts on the inverter may translate to about 40 amps of draw @ 12 volts on the battery bank.
  • tenbear's avatar
    tenbear
    Explorer
    Jan 26, 2015
    If the inverter is wired directly to the battery with no connector in the circuit you will be limited only by the wire size and any terminals used to make the connection. You should be able to run the full 400 watts, about 40 Amps.

    Pianotuna is absolutely right. Keep the wire between the battery and the inverter as short as possible. 10' of two #8 wires will cause a 0.5v drop. 5' would only have a 0.25v drop.
  • ScottG's avatar
    ScottG
    Nomad
    Jan 26, 2015
    It will work as long as your load is very small.
    Otherwise you need to hard wire it.
  • Golden_HVAC's avatar
    Golden_HVAC
    Explorer
    Jan 26, 2015
    HI,

    #8 wire can safely be fused at 40 amps, and #6 wire at 60 amps. Your inverter is rated for 50 amp input fuse, and you can use any wire size larger than #6 and fuse it at 50 amps. #4 wire will offer less voltage drop, and that can matter if the cables are more than say 6 feet long.

    It is much better to have a long 120 volt extension cord, than to extend the 12 volt wiring. However it is nice if you can have the inverter in a place that you can turn it on and off, to save battery power by leaving it off as much as possible.

    I would also recommend a non-lighted power distributor. 6 plugs with a 4-6' long power cord that plugs into one receptacle of the inverter. That way you can plug in several things. Your 120 volt output is limited to about 4 amps.

    Your 400 watt input can use about 40 amps at 12 volts (480 volts in X80% efficiency). So it 'could' be fused at 40 amps, but you might accidentally trip the fuse when a larger surge is put through it. 50 amps is better.

    If your RV mechanic is not 'comfortable' with installing some #6 wire and a 50 amp fuse, I would find another mechanic or electrician to do the job. For me, it is a really simple 2 hour (maximum) job.

    Good luck,

    Fred.
  • rich85704's avatar
    rich85704
    Explorer
    Jan 27, 2015
    I let this thread run for a few days to see who'd chime in. Thanks, all -- the input is really helpful!

    The run from the inverter to the battery is very short. I'd planned on the strategy which @pianotuna and @golden_hvac suggest: distribute on AC within the rig from the inverter location. I don't need this for regular operations, although I do plan to run battery chargers for the laptop and the electric bike off the inverter while I'm driving. They can be placed in the same cabinet as the inverter.

    Again, thanks!'

    Rich

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