Planning on fitting twin elec to campervan so can power fridge whilst towing caravan, electrics for lights etc already fitted.

Having looked at my options and where to fit relay etc I don’t have many if any choices as where to put earth for relay, is it okay to fit earth wire to battery terminal ? (Earth from battery going straight to chassis) my battery is at the rear with the engine 😉

Many thanks in advance

Any metal part of the vehicle is an earth so how have you no good choices?
You probably dont want to earth to the battery as its a battery not an earth

Which battery starter or leisure? One in van one in caravan or two in van and one in caravan – I suspect your alternator and belt wont like you much.

What is the relay – split charger ?- how much current is going through it? Is it just the standard charging circuit for towing electrics?

Post a link to what you are trying to do and i will help but that is a bit unclear
Ta

Hi

Now I have time to explain

main battery to split relay but will only be using the fridge wire from the split relay to power the fridge in the caravan when on the move- no leisure battery in caravan

the negative of the battery strap goes straight to chassis

all other wiring easy was just wondering over the earth and thought keep it all close and use battery neg rather than drill somewhere

1985 vw t3

http://www.ebay.co.uk/itm/280591322805?_trksid=p2060353.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT

Short version use a separate earthing point not the battery/neutral.

Any bolt will work on your engine block for this purpose — Please dont use anything near your fuel line /carb etc !!!

Negative always go to the chassis as its the earth for the entire system. …. you can use that if you like – ie bolt to the same place that goes not bolt to the battery –

I would not go tot the battery for for reasons that are not worth going into for your needs.

Junkyard.

Where are chassis , engine or body earthed to if you don’t mind ?

The electrics are made complete by earthing – generally to the chassis or engine block- from the battery NEGATIVE

Essentially if you sent a live wire to any 12 volt thing and then “earthed it” to any part of the metal then it would work – you dont really need the negative. – Dont actually do this.

The charge circuit and the starter cranking amps are the ones that require serious earthing as they are large loads.

I think I earthed my tow bar to the one of the boot latch bolts. IT has no charging circuit

The car is NOT earthed as it has rubber tyres so its not actually grounded.

Boats need to have galvanic circuits to shed metal as they become an anode !
I built my own boat which is why I know about 12 volt electrics and charging circuits / split relays etc

And if he used a suitable sized cable to negative it would be grand ?

If you earthed everything in the car to metal bit but didn’t attach an earth strap back to negative terminal it won’t work

As far as I’m concerned, earth to either the negative battery terminal or to chassis/body, whichever is easiest. The only thing I would avoid is the smaller earth points near the dashboard/engine bay etc as they are often ‘signal earth’s’ for instrumentation rather than earth’s for power hungry components.

When I did my S socket I wired the permanent live to my leisure system so I could run lights in the trailer without fear of discharging the starter battery. Switched live (fridge) was wired the normal way via a relay and starter battery.

There isn’t really an earth in a caravan is there so it’s going to ground. Just make sure it’s a good one

trailrat if you have an opinion just express it rather than question me

Your points range from the broadly fair to blindingly obvious.

And if he used a suitable sized cable to negative it would be grand ?

yes but i still would not do it but it will work.

If you earthed everything in the car to metal bit but didn’t attach an earth strap back to negative terminal it won’t work

I think its safe to assume his vehicle has this strap

And I’m questioning why you wouldn’t and what the difference is so long as the cables sized accordingly.

Because at end of day it all goes to same place.

There are some loads I would not put through a vehicles earth strap either.

Such as if I was to wire in a winch to my landy. Direct wiring every time.

I’d say you’d be fine going straight to battery as long as you use a cable heavy enough for the load you’re going to put through it. If the battery is closer than the earth point then it’s the better option, that’s what I’d do.

And I’m questioning why you wouldn’t and what the difference is so long as the cables sized accordingly

Old split relays could overheat and the load through them for a charging current could be quite massive the run of THICK wire, back to the battery, meant that a localised earth was better/cheaper/easier
It won’t really matter with that unit but I would still just earth separately

IIRC the one on my boat took 120 amps – though i had an oversized alternator and a “charge system” to trick the alternator into delivering full load- as well – then again i had a 720Amph bank of 2 volt batteries to charge so i could do this.
The cost of cable to earth that [ and interconnect] was eye watering.

I guess habit and lack of need but yes the battery method will be fine with those loads.

In the end I used the bodywork as the earth !

Thanks one and all 🙂