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Hard wiring inverter

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My next little project as part of tidying up my electrics is to hard wire my inverter to the battery box. The cables that come with it have crocodile clips so I presume there must be an internal fuse?!?

Anyway my thinking was to put a relay in the feed so that there is only power to the inverter when the ignition is on to save draining the battery. I thought if I drew one of the ignition feeds from behind the dash back into the battery box I could run that across the relay to earth to cut off power to the inverter as soon as the ignition went off. Presumably considering the current I would need one of the bigger 70 amp relays from VWP that I used on my headlight circuit.

I was also thinking it would be useful to put a switch in that ignition feed so that I could isolate power to the inverter when the engine is not on so that if it isn't being used then the power all stays in the battery box compartment, stopped at the relay. I was planning to run the cables out of the back of the battery box, up through the flat bit of the back bulkhead thing and then up to the inverter mounted at head height on the side panelling at the passenger side. I reckoned if the wires were inside some of the corrugated wiring conduit I got then that would keep it safe.

I have a sense from earlier suggestions regarding wiring that it would be better to provide a fused supply to the relay but what sort of fuse would I need?? It has one 13 amp socket on it.

Any thoughts or suggestions would be most welcome.



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I have my inverter a 350w, attached above the rear left side window [to left of the tail door] IIRC ran a power lead from batt bay along the chassis & upto the inverter power terminls & also ran a cable along the inner roof gutter down the B post to a double socket on the front face of the seatbox [passenger side], so I've mains power in the cab for my laptop & in the loadbay from the inverters onboard mains socket.

1st pic -- inverter, large red cable goes forward to double mains socket [see 2nd pic] the red/black cables in the far corner drop down to chassis level then from batt bay.

double socket has a built in circuit breaker & each socket is indivdually switched [switch are in upper corners -- in off position,so hard to see]



Edited by western
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I just switch my inverter on/off with it's own switch [the red rocker], hadn't thought about using a relay to switch it, if it's not being used to power anything then leaving it on shouldn't drop the battery very much, I've left mine on over a weekend & didn't have any starting problems when I needed to use my 110 after.

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I was more thinking of being stupid and leaving something plugged in, then leaving the truck and forgetting that it was on, so still drawing current.

I am not known as "belt and braces gibson" for just being very plump!

might be a worthwhile addition then <_< not sure where to connect the relay to though or which size relay to use, need a lekky type person for that, Where's Luke when he's needed :unsure:

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You could put a relay in the supply to the inverter, but it'd have to be pretty beefy - depending on your inverter. a 600w inverter is going to draw atleast 50A, for example.

It's worth checking though, if the inverter has a low voltage shut down, it may well have, to prevent accidental discharge of the battery.

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The inverter fitted to my work 130 has on several occasions drained the battery after long weekends of no usage (it was not left on), as a result i have had a relay fitted to isolate the supply when the ignition is off.

It is important to fit a fuse to the power cable that feeds the inverter, mainly to protect the cable in case of damage.

The inverters we use at work (we are on the forth type now) seem to go wrong regularly and being able to isolate it by turning the ignition off is very useful (not to mention a vital safety feature). Saying that we are using 1000watt versions and they normally run most of the working day so they have a hard life.

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OK, looking at all comments I wondered if this would be the right sort of setup. It is a 300W inverter so relatively small.

Connection from "dead side of the cutoff switch to a VWP midi fuse at 40 amps then to a VWP 70 amp relay (using a feed from the fuel pump starter solenoid on the "live" side of the cutoff switch to activate the relay circuit (so that when ignition is off the relay allows no current through). Then run 6 sq mm cable, which VWP rate at 50 amps from the relay back to the inverter - live from the relay and earth to battery.

By my reckoning this should allow the inverter to be isolated by the relay if the ignition is off and be completely isolated if the cutoff switch is off. I think this would be OK and would allow an upgrade of inverter if required without having to rewire. Or am I using a sledgehammer to crack a nut?

Thanks for any comments


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I have a 1500w inverter fitted under the nearside rear passenger seat of my 110.

It does have an on/off switch, however I also have a H/D cut-off switch on the positive circuit, fitted facing upwards just beside the front passenger seat set into the battery box towards the rear, adjacent to the door. Cables are 25mm sq.

As the inverter is for occasional operation (wife's hairdrier etc. :rolleyes::o ) the cut-off switch key is removed ensuring no battery drain when not in use.

It also prevents battery drain when kids press switch on (as they do!) even if there is no appliance plugged in.

If you go the relay route Durite do a 180amp version, the same as the one simonR uses in his Xcharge split charging kit.


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