Inverter Installation Trouble

I managed to poke quite a few holes through when I had an 80, just through the rubber grommet, inverter, UHF, etc
NickR

Hi Alex

Stick with the 4G cable. My Jaycar Cat. lists it at $5.95/m retail

While its not the best practise, you do only technically need 1 wire
with the other going to a good body earth.

But I wouldn't suggest this unless you feel you can make a good
connection and test it.
Where I do this I use two wires to two seperate points. I.E. 2 X 8g
instead of 1 by 4G. (sometimes this can help get thru firewall to)

In my car, Nissan Patrol, body earths are used now and near the front seat
where handbrake goes to floor are some really good bolts into bodywork
for doing this.

Robin Miller

Hi Alex

12mm thick, Bloody hell. why?

Admittedly my inverter is only 150watt PSW. I have it installed on the dash, velcroed to the dash mat. It is covered by a colour coded towel to keep the heat of the sun off it :-D Towel is removed when inverter in use.

I extended the same size wires to the Pos and Negative of my aux Batt and the extra earth to the body.

Have had capacitor blow outs but that is because my laptop is too power hungry for the inverter(bad advice from jaycar salesman)

No other issues.

My thinking is that anything stored under the seat should not be electronic as all manner of debris collects there...and if you negotiate lots of water crossings, that is another worry.

Cheers

Alex, I am with Willem, not under the seat please. If you doa water crossing and the inverter is on, water into car, 240 volts running around car, not good. Sure it is fused, but.......... Don't worry, I did the same to once, then relocated it when I thought about it more.

Man, your not simple job is my dream run. Whenever I attempt a new car project I could only wish for a few simple problems like this, in my case I usually end up breaking some inportant part of the car, end up with 'spare parts', snap plastic clips so the plastic part wont go back in without glue, have mechical components out that cant be refitted without a special part from the shops which are now closed (because the job has taken me over 5:00pm) or the part is in another state, I have to work the next day and the car is undrivable, I am bleeding from every knuckle and skin is all over the floor and oil is in my cuts, my wife is angry because the new expensive thing I wanted do do cost to much, and is not compatible, the new item also needed to be modified and I accidently broke it making the long term use of it annoying (unlike everyone else who's thing just went it like the directions say!) and I am feeling frustrated and annoyed after having to risen to every challenge all day long, being positive against all opposition and now dont have any mental ability to overcome the last fatal problem knowing I cannot finnish this short half hour job in the space of 1 day. Also I didnt mow, clean up the house, fix the roof and all the other things I was going to start at 10:00am having started my job at 9:30am giving half hour to finnish. BTW, try fitting it in the passenger foot well under the dash, its high up and out of the way.

Alex, you have a couple of things conspiring against you here. First, the size of the inverter and therfore the current it will draw at maximum load. Second the distance you plan on placing the inverter from the battery.

I have a similar set up, with inverter permanently wired to deep cycle battery in engine bay and positioned just behind the front passenger seat, but up off the floor (we have removed our rear seat). But I only have a 300W inverter that is never used anywhere near it's full capacity. I was therefore able to get away with 4 guage (I think that's what it is, possibly a bit bigger) wire which is protected by a 20 Amp fuse. Fuse will blow well below inverters maximum capacity.

If you are going to ever use your inverter at or near it's capacity, you will need to use heavier cable, but I doubt that you will need cable that is 12mm thick, particularly if you mean 2 @ 12mm. Sounds way too big. Because of all the different ways of specifying cables, it is hard to say. This article by Collyn Rivers covers this issue:
www.motorhomesaustralia.net/cable.html

I tend to always talk in terms of mm squared of conductor. I'd have thought 10mm squared cable (which is about 8mm overall diameter) would be plenty big enough for your purpose. Smaller if you will never use the inverter at full capacity (and you protect the cable with an appropriate fuse).

As for getting through the fire wall, I just found a gromett where other cable went through. Pushed a piece of wire through it (like a wire coat hanger), tape your cable to it and pull through.

Hi Alex

Keep the inverter high as others have stated, the cargo barrier is a good place for inverters and HF radios if the water gets that high you will have other problems than the 240 volts. No holes are allowed to be drilled through the firewall, you have to use existing holes. The 4g wire should take the current unless you are going to draw 500watts constantly

Ray

Hi ALex : First, you are aware of the need to avoid voltage drop by using large cable - so you are ahead of the pack. The low voltage cut-out is a great feature to protect the inverter, but a PITA when it happens. A larger cable will avoid that.
Naturally the load on the inverter - and hence the 12V wiring - depends on the current draw of the 240V device you need to power. What is the 240V current needed? This may give you some room to use smaller cable.
Have you seen the articles and formulea on Collyn Rivers site :
Voltage drop equals (cable length (in metres) X current (in amps) X 0.017) divided by cable CROSS SECTION in mm.sq.
His site has numerous articles on all things electrical for camping, including wiring.
In particular - check out the 'wiring woes' article.
Site Link

So - if the device pulls 240watts, then DC current draw is a bit over 20 amps (inverters are never 100% efficient).
So - (4.5m + 4.5m) x say 20amps dc x .017 / 12mmsq = 0.255V drop.
Recommended maximum is 0.36V (3% of supply 12V). The inverter alarm/cutoff probably works around 11.5V

Finding access through the firewall can be a challenge.
On some vehicles, there is no option but to drill a new hole.
Have you checked out the grommets in the floor drain holes? This could be an alternative (& Silicon seals well).........Best of luck with the project - hang in there.
nb I use 18sqmm cable to my car anderson plugs, van battery and fridge. The old adage - do it once - do it right. (takes the same amount of time).....Keith.

Under the seat is a little vulnerable during river crossings.
A friend of mine lost his radio because of that!

I hear a lot of people have concerns about inverters under seats, and probably rightly so. I don't do many river crossings and haven't yet don't one that has come close. I guess as a precautionary measure, I can always unplug the inverter from the battery before attempting the crossing, just to make sure.

The earthing issue is easily solved by using a bulk head fitting as used in fibreglass boats - its a brass bolt about 50mm long threaded both ends with a thin hex 20mm from one end and a nut and spring washer on the other - you drill a 8mm hole in the firewall poke the long end through then fit the nut and washer, fit a battery type earth lead from the engine bay side to the point where neg battery lead attaches to the body you now have a threaded fitting inside the car to attach any earth returns this means you only have to run one positive cable through the firewall use a heavy cable and an insulated terminal block (also from boat) this gives you a distribution point inside the car as well all this cost less than $100.00
Regards kev

Hi Alex
I am using a 1500watt constant (3000w Peak) inverter with 2G cable attached to my cargo barrier, the cables passed along the sill cavity, and I have found a grommet in the floor under the passenger foot-well close to the sill cavity (Nissan Patrol), that will accomodate these cables (12mm each) after being sure they dont hang too low to be hung up on anything, and they are protected from chaffing by the grommet, they were sealed with a silastic compound to prevent water ingress and secured to the chassis to be sure they are very secure, and a cover plate fitted to the chassis to be sure to be sure as additional protection.

I calculated the wattage peak and decided that 4G was too small for the possible load. My setup has never caused me any concern due to VD or overheating.

So what I am saying is, with your 500w inverter 4G is correct, 8G I feel is too small for your task and would cause VD (Voltage Drop)and possible hating problems.

NB. I am not an auto electrician, this is just MHO.

Colin, On Patrol.

when I fit the inverter that I am yet to get, I will put it close to the battery and run the 240 volts to a socket in the cab. That way there is no loss on the 12v cable and of course there would be negligible on the 240v cable which can be any old extension lead. The unit is out of the way too.

Owen

Hi Alex

sorry so long getting back.

As a rule water does not get up in the engine bay unless you are doing a river crossing that I myself would never attempt. Some people love swimming their cars so I would recommend an isolation solenoid or manual switch (heavy duty) on the 12 volt feed for them. Also you can isolate it that way to stop losing amps when it's not being used. A bit of silastic might be worth applying to the plug for peace of mind.

A couple of replies suggested it is unsafe to run 240 through a car but they do it ships and boats and well, you know, I have it in my house and garage with the same considerations for safety. I reckon more water splashes around my kitchen and bathroom than my engine bay. You could even build an earth system into it in case of appliance shorts if you wished but most of the stuff we use does not require an earth.

Mounting a plug on or under the dash provides some minor problems but you could simply hang the plug that comes with the extension somewhere convenient and out of sight. If you use the typical wall plug make sure there are no exposed wires is all.

I suppose you should have a sparky look it over for peace of mind but that it your responsibility.

good luck

Owen