12V supply to caravan - from dual battery

Submitted: Sunday, Oct 26, 2003 at 17:02
ThreadID: 8096 Views:3065 Replies:6 FollowUps:2
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Hi All, I have a caravan with a 12V circuit for use when 240V is not available - lights, fridge option, etc. Now this may sound like a silly question but how does it get the 12V power from the car ? Before I get a dual battery system fitted I am keen to know if there should be a specific wire in the connection to the car that should be permanently live - if so which one ? Or do I have to set up an entirely separate connection for this purpose ? Can anyone help please ?
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Reply By: Member - Bob L - Sunday, Oct 26, 2003 at 17:36

Sunday, Oct 26, 2003 at 17:36
You will not get a heavy enough connection via normal trailer connection.
I have dual batteries with controller, ie Main battery is isolated and takes priority with regards charging.
I then have a 8T cable from 2nd battery (both positive and ground) using an Anderson plug to attach to Tvan. I would recommend even heavier wire but in my case have protected same with 30 amp fuses on "Both" batteries As I only use van supply for lights it would appear sufficient to maintain charge. Could be in trouble if van battery was flat? If you are running a fridge you really need cable similar to standard battery cable with decent fuses for protection (against short circuit and fire)

Hope this gets you started in the right direction.
PS My Tvan came wired with heavy cable to hitch with an Anderson Connector and I only had to provide the other half. Purchased my bits from a friendly auto electrician.
Cheers Bob

AnswerID: 35158

Reply By: Member - Ross - Sunday, Oct 26, 2003 at 19:49

Sunday, Oct 26, 2003 at 19:49

Drawing through your trailer wiring connector to the van should be OK as long as you only intend running a flouro or similar low draw lighting.

The normal round and rectangular 7 pin plugs hava an aux connection point which is just for this purpose.

However always be mindful of the fact you are drawing from your starting battery ... until you install your dual setup.

As to which one (connector point)... I've been meaning to check this out myself as I intend installing a deep cycle battery in our camper trailer for lighting and as a backup in case its needed. Deep cycle batteries are not the ducks nuts as a starting battery but will do the job if needed. Check out the back of the plug packet at any retail outlet for which connection goes where ... and let me know when you find out :-}.

Also be aware you can charge your second battery by this method but you MUST have a relay setup in the wiring so it's disconnected during cranking to start. your truck.

Trying to draw 300-400 amps through even 6mm wiring over 6 or so metres would have interesting results .. to say the least.
AnswerID: 35166

Follow Up By: Mickl - Sunday, Oct 26, 2003 at 22:19

Sunday, Oct 26, 2003 at 22:19
The rectangular 7 pin numbers are 4723561, 7 pin round plugs read anti clockwise 123456 with 7 being the centre pin. (in both cases looking at the socket not the plug)

1 Left turn lamp yellow cable
2 Reverse lamp black
3 Earth white
4 Right turn lamp green
5 Electric brakes blue
6 Stop lamp Red
7 Tail lights brown

Australian Standard AS2513

FollowupID: 25421

Follow Up By: jeepy - Sunday, Oct 26, 2003 at 22:27

Sunday, Oct 26, 2003 at 22:27

FollowupID: 25422

Reply By: Blackie - Sunday, Oct 26, 2003 at 20:54

Sunday, Oct 26, 2003 at 20:54
There is lots of info on this topic on the
AnswerID: 35177

Reply By: Nav 80 - Monday, Oct 27, 2003 at 11:56

Monday, Oct 27, 2003 at 11:56
I installed a 12v battery in my van conected to the existing 12v curcuit from the vehicle but put in a diode from an altenator so the battery can receive charge but current can not be drawn back on start up,works well.
AnswerID: 35223

Reply By: Member - DOZER- Monday, Oct 27, 2003 at 15:42

Monday, Oct 27, 2003 at 15:42
Gday Mike
Plenty of different ways to set up the system, at the moment, power from main battery goes through the reversing pin to the van. (good guess)
Can buy 7 pin connecters with extra pins from van shops that cater for the van with a battery in it.
Have you considered putting the battery in the van instead of the car...then there is no need to keep the car connected when camping (one can drive car and the partner see to cook/read in the dark at thesame time)
When van disconnected, back to one battery.
Andrewwheredayathinkwer mike?
AnswerID: 35268

Reply By: Member - Toonfish - Tuesday, Oct 28, 2003 at 11:38

Tuesday, Oct 28, 2003 at 11:38
cheap anderson plugs on e-bay in several different sizes .
safer than 7 pin low voltage wires getting hot and losing power through drain.1999 NISSAN NAVARA DUALCAB
2 awestruck kids (dads driving!)
AnswerID: 35379

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