Wiring 12V from the car to the van

Turners · Newbie

Wiring 12V from the car to the van

Phil C · Guru

Hi Turners welcome to the playground.

If you have no experience with electrics I would call in an auto electrician to do the work.

We have two large batteries on a solar panel in our van, so out in the sticks we can charge our batts on a sunny day. We use the water pump, TV and LED lighting for about 4 or 5 hours at night and all is sweet.

We also have a generator for the dark days.

Please remember that even 12 volts can cause a fire.

Take care, travel safe

Turners · Newbie

Hi Phil

Thank you for the information, we also have just purchased a generator. We are looking to do a round trip Central Coast to Darwin and return via Rockhampton next year so want to run our fridge and charge an aux battery at the same time.

PeterD · Guru

Brett, Is your fridge an absorption type (2 way fridge.) If it is then I suggest you keep it away from your house battery. If you don't then I suggest your experience will end up in wrecked batteries and tears. The current draw by the fridge will flatten your battery in quick time, running them on a battery is equivalent to running 2 high power driving lights. The 12 V input to absorption fridges is only meant to be supplied by the tow vehicles alternator (ie only switched on when your motor is running.)

It is best to use two cables from the tug to the van. One is a heavy cable for battery charging. The other is a cable not quite so heavy for the fridge, thjis cable should be controlled by a relay that is operated by your ignition switch (as Dometic recommend the fridges should be wired.) The JPG below is copied from one of Dometic's handbooks.

Dometic Fridge 12 V Wiring 2.PNG

-- Edited by PeterD on Tuesday 28th of October 2014 05:29:09 PM

Phil C · Guru

Peter, does the same current draw apply to 3 way fridges as well? We often pull over for a cuppa with everything connected, would hate to be in the middle of nowhere with a flat batt.

Cheers

Turners · Newbie

Phil & Peter

Thank you for your information, we have a 3 way fridge, I would only run it when the vehicle is running and i would swap it to gas LPG when we parked up, or of course run the generator

PeterD · Guru

Phil, You will probably get away running the fridge from your tugs battery on a fairly quick lunch stop if you have a 4WD. I have seen Falcons fail to start after a lunch stop. If you are one of those who unfortunately has the fridge across the vans battery and are diligent enough to switch it onto alternate power as you are unhitching then you are discharging the house battery unnecessarily. A fridge will last OK over rest stops without the `12 V running. In fact we don't unload the fridge when crossing the Bass straight on the ferry. We just shorten the time we store any contents in it.

Phil C · Guru

Thanks Peter

The circuit has no connection to the van's batts, just the aux pins on the ute. The worry is killing the ute batt when parked. It seems from what you say it should be OK.

I may try that relay idea, 10A contacts should be OK I recon.

Thanks for that
Cheers

-- Edited by Phil C on Tuesday 28th of October 2014 05:52:12 PM

PeterD · Guru

Phil C wrote:
I may try that relay idea, 10A contacts should be OK I recon.

The smallest fridge I know of draws 11 A. 16 - 20 A in the larger fridges is common. Consult your fridges handbook specifications. If you don't have a handbook you can download one, just put "(model number) handbook" into a search engine and you will find one or two entries offering PDF copies.

Relays are commonly 30 A capacity, don't skimp.

Phil C · Guru

Agree Peter, thanks for that. I will use a DPST with 30A contacts just to be sure.

Cheers again

Blue · Senior Member

Phil C wrote:
Agree Peter, thanks for that. I will use a DPST with 30A contacts just to be sure.

Cheers again

for a second Phil I thought that you were an electrician and couldn't believe that you didn't have a relay fitted to your car to protect its battery... wink

as been said... go 30 amp relay.. never run your absorption fridge off your van batteries it'll suck the life out of them... check specs that should be inside your fridge on a sticker...

even the little 90ltr fridge in our last van pulled 12 amps..

if we pull up for lunch or a stop for an hour or two we turn the gas on the fridge and try and open the door as little as possible

Blue · Senior Member

Turners wrote:
Hi Im looking for information in regards to installing a deep cycle battery into the front of our van and charging it from the car as we travel. also from the installed battery hooking up the van fridge and lights to the battery for use when we park up. Has anyone got some information and wiring instructions or know where I can get wiring instructions.

Thank you in advance

you would be far better fitting a solar panel battery charging kit for your vans batteries...

the more batteries you try and charge with your alternator... the more load you put on the motor and you'll lose fuel economy and also a little power from the motor..

it'll also prematurely wear out your alternator and depending on your vehicle could cost $500 to $800 big ones...

-- Edited by Blue on Tuesday 28th of October 2014 09:24:50 PM

Phil C · Guru

I certainly use to be an electrician Blue, just couldnt be stuffed putting a relay in. Call me lazy.... biggrin biggrin

Thank goodness I have a decent batt in my ute.

Cheers

-- Edited by Phil C on Wednesday 29th of October 2014 08:52:58 AM

oldtrack123 · Guru

Turners wrote:
Hi Im looking for information in regards to installing a deep cycle battery into the front of our van and charging it from the car as we travel. also from the installed battery hooking up the van fridge and lights to the battery for use when we park up. Has anyone got some information and wiring instructions or know where I can get wiring instructions.

Thank you in advance

HI

[1]The First question we should ask is what type brand model# fridge you are going to use??

Is it a compressor fridge or an Absorption[ 3way ] fridges ooops, I see it is a 3way

MAKE & MODEL????

BIG differences in power requirements! smile

[2]From your post, it seems that you want to install TWO batterries in the van & when driving Charge BOTH from the vehicle Alternator

Clarifcation please?

No real problems with that with most older vehicled, but some late models do not put out sufficient voltage for direct charging

[3]So we also need to know what your tow vehicle is????""

If you can supply more info re [1] &[2],WE can more likely give you, more info that is realy relevant to YOUR case .

But certainly IT can be done ,has been done for many many years

Most Alternators will easily handle the load!

But If the fridge is a 3WAY IT SHOULD NOT BE RUN ON 12V unless the engine is running & IT should be supplied by it's own direct line from the tug[.NOT from the van batterries}

Again we can go into more detail when we know what you have biggrin

If you are realy interested in solar, it will depend on:

Your" expected daily [24h] usage

[a]how independent of mains power you wish to be

But solar to run the fridge while travelling

PeterQ

-- Edited by oldtrack123 on Wednesday 29th of October 2014 11:05:36 PM

-- Edited by oldtrack123 on Wednesday 29th of October 2014 11:08:34 PM

Phil C · Guru

Yeah, I took a look after ignoring it (I have a diesel) may cause a few issues. I pref to leave it, not enough knowledge to be playing games with the computer in the beast and may blow the new car warranty.

Thanks for the heads up, I tend to leave things alone nowdays unless I have 100% faith in what Im doing.

Cheers mate.

oldtrack123 · Guru

Phil C wrote:
Yeah, I took a look after ignoring it (I have a diesel) may cause a few issues. I pref to leave it, not enough knowledge to be playing games with the computer in the beast and may blow the new car warranty.

Thanks for the heads up, I tend to leave things alone nowdays unless I have 100% faith in what Im doing.

Cheers mate.

HI Phil

The basic arrangement that Peter D posted is still the way to do it,AND the way thousands are doing it

Even WITH diesels

EASY, SIMPLE, VIRTUALLY ANY ONE CAN DO

MaKe sure the Fridge Pos & the Coil Pos are fused as close as possible to their starting point

5A fuse for the coil 20< 30A fuse for the fridge depending on Wattage

It cannot fry, any thing

Simply find ANY positive line that is only live when ignition is turned. on & connect relay coil to that

IF the relay coil does not have spike suppression simply reverse connect a diode across the relay coil

One disadvantage is that the fridge will draw current immediately the key is turned start, If the crank battery is low or sick it may be to much for the engine to start [crank]

Some fridges have that isolation built in [AGAIN why model# are important] & just require a light gauge wire from tug D+terminal to D+ then heavy cables for the 12v heater from the tug battery

They depend on the actual voltage at that terminal & also act as a low voltage cutout

or you can use:

a voltage sensitive relay[my personal option]

Again voltage dependent & low voltage cut out to protect the CRANK battery& simple to fit

A fridge Switch in the van, depend on van movement [being in motion] to turn the fridge on

NOTHING GETS FRIED provided the correct sized cables are used

AND it would be a pretty poor alternator which could not take a 10<23A load in addition to normal running loads

YES, it will impose a small additional load on the engine ,like 120 to 230W depending again on FRIDGE model [lhp =750W[ from memory confuse ]

PeterQ

-- Edited by oldtrack123 on Wednesday 29th of October 2014 10:49:14 PM

Blue · Senior Member

dear lord.. what a mess.. blankstare

how anyone average grey nomad could follow the information in this thread would be a miracle..

there is talk of putting up stickies on this forum but from what I've seen of late, the information given is nothing short of confusing, with information full of holes in it, and to be honest, information that is outright dangerous that could possibly cause thousands of dollars of damage to your cars electronic systems with even the possibility of setting your car alight...

to advocate jacking power off any modern day electronic ignition system is nothing short of irresponsible... or just grabbing any old wire that's switched? confuse ... or for the average joe to start wring in diodes etc? confuse

struth...

there is a large difference between being able to do something in a particular way, OR, should be doing it in that particular way...

could you jack into your cars electronic system? yes

should you jack into your cars electronic system? NO NO NO

you should only ever jack into your cars "electric" side of the system and NEVER the electronic side where there is a possibility of frying your cars computer systems... depending on your car, you could have 3 or 4 computers in it that are very very expensive to replace..

-- Edited by Webmaster on Thursday 30th of October 2014 05:38:47 PM

exa41 · Guru

Your on the right track Blue, A VSR would do the trick through an external Anderson Plug , Very simple to wire , probably the best control of electrics to the van and easy to disconnect , relays with diodes and resistors are confusing to some . Use decent size cable to reduce voltage drop , don't forget to use fuses or circuit breakers .

oldtrack123 · Guru

Blue wrote:
[1]dear lord.. what a mess..

[2]how anyone average grey nomad could follow the information in this thread would be a miracle..

[3]there is talk of putting up stickies on this forum but from what I've seen of late, the information given is nothing short of confusing, with information full of holes in it, and to be honest, information that is outright dangerous that could possibly cause thousands of dollars of damage to your cars electronic systems with even the possibility of setting your car alight...

[4]im also confused about peter d and peter q ... is this the same person?

[5]to advocate jacking power off any modern day electronic ignition system is nothing short of irresponsible... or just grabbing any old wire that's switched? ... or for the average joe to start wring in diodes etc?
struth...

[6]here is a large difference between being able to do something in a particular way, OR, should be doing it in that particular way...

[7]could you jack into your cars electronic system? yes
[8] you should only ever jack into your cars "electric" side of the system and NEVER the electronic side where there is a possibility of frying your cars computer systems... depending on your car, you could have 3 or 4 computers in it that are very very expensive to replace..

HI Blue

You really do have problems & Again show your lack of knowledge

I do not know what you claim to be but the above is a pearl showing you lack of understanding

[1]I have tried to fully explain the options so ANYONE can make up their own minds on which way to go

If you find it difficult to understand YOU have a serious problem

[2]

IN my case, anyone who does not understand is welcome to come back asking for further explanations

[3]Ok .Point out where you believe it is wrong & out right dangerous!!

I am sure many of us will be interested in your corrections

So far any information you have given is to buy something

[4]

Perhaps you ask Cindy to check on that rather than nasty insinuations??

But you have shown your nasty streak elsewhere, have'nt you???

Perhaps PeterD & PeterQ are two different people with far wider knowledge than you

& are capable of explaining in detail

Perhaps YOU should highlight the fact that you are an Ebay seller [ among other things solar panel, & dangerous electrical lights[Since removed when I asked questions]

And your solar panel advert was full of crap & misrepresentation!!

Claims to be an expert in solar ,YET could not see the serious errors in his own advert!!

I do hope you do not claim an electrical background or you would have understood how dangerous those lights were

[5]Where has anybody suggesting "Jacking" of the electronic ignition system????

What has been said is simply taking a feed from any positive line which is switched by the ignition switch to a small relay coil

Why do you believe THAT is any different to ALL the other loads that are ignition switch controlled??

YOUR answer to that will be interesting

[6]VERY very true,but one really need to KNOW which is which.

SORT THE WHEAT FROM THE CHAFF

[7]Again PLEASE explain where anyone is "JACKING"in to the car electronics system??Including PeterD's original circuit

THe system of using the car run position of the ignition switch is being used/ has been for a wide range of purposes for a very looooong time

Strange that only you think it will be a disaster

WE ALL await your detailed explanations with bated breaths

It will be a chance for you to really shine or forever shut up!!!

BUt you had better be right, so think very carefully, before you post more crap .

By the way are you sending helpful??? PMs to members when a possible solar sale is involved ???

PeterQ

-- Edited by oldtrack123 on Thursday 30th of October 2014 01:47:41 PM

oldtrack123 · Guru

exa41 wrote:
Your on the right track Blue, A VSR would do the trick through an external Anderson Plug , Very simple to wire , probably the best control of electrics to the van and easy to disconnect , relays with diodes and resistors are confusing to some . Use decent size cable to reduce voltage drop , don't forget to use fuses or circuit breakers .

HI Exa

You may have noticed MY prefered option was A VSR!!

But Ignition switch controlled relays are still popular,

IN fact most VSR should be ignition switch controlled, &That is the way I would connect them

The diode is only an additional safegaurd

In fact most VSR have one fitted internally but they may/do have large coils capable of generating a high back voltage on opening

If a person is not capable of fitting a small diode across the relay coil ,they should not even attempt to make any changes or additions to ANY wiring

All that has to be done is ensure the diode is connected in the correct manner

That means that it blocks current [does not make a short circuit when the coil is energised, but shunts[sends] the voltage &current generated by the collapsing magnetic field back through the coil itself when power is removed

No voltage spikes feed back into the system,which could damage any electronics

Yes,

Detailed for those who are interested in learning rather than just being told smile biggrin

PeterQ

-- Edited by oldtrack123 on Thursday 30th of October 2014 01:00:16 PM

Phil C · Guru

HHHmmmmmmm

Battle on lads.

Im just watching at the side. I would like to remind you all, before the moderator does, be respectful and try hard not to piss people off with inflammatory comments and challenges.

Really doesn't matter a red rodents rectum who is right or wrong, this forum is not about that.

Have a nice day.

Webmaster · Guru

Hi all,
As Phil mentioned, please keep posts respectful and friendly. Also, as I noted in another thread in 'techies corner', it is important that people should seek qualified advice if they are undertaking any electrical work to their rigs.