I just bought a camping/expedition type trailer with its own in built leisure battery for lights, webasto, water pump etc. The battery has a lead connected for charging but just for attachment to a normal charger ie the leads just end up as bare wire terminals to attach crocodile clips to.

Now I am no expert with regards tow bar electrics at all so please be kind!!!

If I connect up this cable to a tow bar connector to go to the white plug on my towbar will this charge the battery potentially at the cost of draining the one in the car if its left connected? If this is the case I guess this is the reason people use split chargers to protect the car battery?

I dont really want to mess about with the wiring in the car itself but could I connect a split charger or something similar in the trailer itself so the leisure battery only charges if the car battery is fully charged? Whats the easiest solution? I suppose I could just wire it up and make sure I disconnect when left hitched but car stopped overnight or something?

Whats the general consensus?

And why so many pins in the white connector? What else goes through this?

T

EDIT:
Just found this:
http://www.pfjones.co.uk/tow-bar-electrics.html

So does that mean if my car has a twin electrics tow bar fitted that the 7 pin secondary socket is already protected by a split charging relay? I am sorry but dont know who fitted the towbar electrics as was on when I got it but it looks standard (Westphalia?) so can I check somewhere for presence of the relay?

Funnily enough Tom, i bought a new trailer yesterday with a winch and battery fitted and was wanting to know exactly the same as you, so if you find anymore info not posted on here would you kindly share it with me

No worries will do. There must be something in the air. Personally driving halfway down the country to spend a lot of money was better than dodging the masses obsessed with hitting a small ball with a stick that has taken over this part of the world!

http://www.westerntowing.co.uk/acatalog/Ca...agram.html

connect to blue terminal on diagram for power for charging the battery, this will then only run when the ignition is on



check to see if you have the standard LR wiring in the drivers side boot cubby, there should be a small white box about the size of a fag packet, follow the wires they should go under the boot floor and out to through a grommet to the tow bar wiring socket. these are how it looks if gen.

Click image to enlarge

Ah the plot thickens a little! Mine has the white box as shown but the connector was disconnected. When connected the trailer lights work fine but when the trailer itself is disconnected the trailer warning light keeps coming on and off on dashboard even at rest (no jolting) and sometimes the indicator goes double speed and sometimes not. Maybe a loose connection somewhere or dodgy relay?

Anyway with the white box there does that mean when working well that the secondary connector will charge a trailer battery but only if the main car one is ok?

T

Yes, basically.

I use mine all the time with a caravan, it has a mover on it which is used to get it into position for hitching up, plug the van into the car and the battery recharges while we drive, the charging circuits are disabled when the ignition is off, not 100% sure but i think it charges both at the same time. Its never caused an issue for me and my van battery is 110ah so pretty big.

It could be that the unit needs coding to the car.... Though it should work. Chances are though there is a dodgy connection somewhere in the back of the 12n (black) socket. If not the fag packet part is available off the bay or from dan. There is nothing that can't be fixed with a hammer😜😜
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KIA E-Niro 4+
2010 LR D4 Commercial 2.7 TDV6

You can always get a nice little £10 solar panel and keep a trickle on the battery all the time

Regardless of the electric being genuine or not, on the supplementary socket (white cover) pin 4 is positive for battery charging and pin 3 is the earth for it. That has always been standard.

The genuine electrics do include a primitive split charge relay. Not sure about non genuine.

If you have a new Jaeger 13 pin socket, pin 10 is positive and pin 11 is earth. These are commonly referred to as being for the fridge but they are only functional when the engine is running, hence another primitive split charge system.

^^^^
Afaik (and ive wired a few) pin 4 is direct feed from battery and a constant live? On pre 1997 wiring pin 2 is the charging circuit, post 1997 it should be a spare switched 12v

The reason being that in 1997/98 the internal wiring in a caravan changed to regulate the charging function internally, it will draw the power from pin 4 but only when the switched live is on. Hence no battery drain when the car is off. Prior to this the charging was regulated by the towing vehicle via pin 2. But now it is redundant due to the charging function being internal. However it should still be able to provide a charging circuit. It is basically the wiring in the caravan which has changed rather than the car.

So yes charging is now provided via pin 4 but only when the caravan senses a feed on the fridge circuit on
Pin 6.

On a 13 pin euro the charging is provided the same way via pin 9 when a voltage recognised on pin 10.

Tomthevet should check if the feed on 2 is switched, if he were to wire the battery directly to pin 4 it would be wired directly in series with the car battery. It would charge but wouldnt stop when the car was off, and if under charge may draw power from the car battery even when the engine wasnt running, as there would be no internal wiring on the trailer as there is on a caravan to regulate the charge function. There is nothing that can't be fixed with a hammer😜😜
FFRR 4.4 SDV8 Autobiography Santorini Black.
KIA E-Niro 4+
2010 LR D4 Commercial 2.7 TDV6

This is all brilliant info. I knew you guys would know! I will check for switched live. Cheers

The control unit for the 13 pin or white 7 pin socket should only allow charge when the alternator is providing over 13 volts, ie when the car is running. It isolates trailer below that TDV8 Vogue SE 2009.
TDV8 Sport. Gone. Loved it but it didn't love me!
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