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Hi,

We have a spare 75ah leisure battery and I wondered if it was possible to get a charger that would plug into the 12v socket in the boot of our x-trail? My thoughts were that we could, if using CL sites, keep one battery in the van and other in the boot of the car (strapped down) charging up as we are driving around i.e when not towing. As one gets low we could then switch them over. Is this a simple thing to do or should I just charge them both up before leaving home and then look for a site with a charging facility. We are interested is trying some CL's for the 1st time this year and thought it would be nice not to have to worry about EHU. Longer term I will be considering solar panels but at the moment can't afford it and as we have the extra battery wondered if we could use a system like this to keep us going while away. I don't really want to start rewiring the car so something that would plug into the socket is preferred......or is this not possible because the battery would draw too much power, etc ?

Hi, Thanks for this. I think it is only live when the ignition is switched on but need to check this as must admit I haven't used it before! So providing it is a switched socket I won't need to add any new in-line fuses or regulator, etc? I have no problem making up a plug and battery clips if this is all that is needed.......good point about the battery box! I did post the same question on another forum and some people were saying it would need new wires run back to the alternator ........which is a no go as this is only a short term solution! I think they were saying the battery might draw more current then suitable for the existing wiring...?

There has been much discussion in the past about this and the most sensible suggestion that I have seen was that if, as a trial, you simply wired up a plug with the same connections as a 12S plug but with only the wires connected that would charge the caravan battery and then ran that from the towbar socket into the boot and connected it with crocodile clips to the boot battery, then it would charge the boot battery in exactly the same way as the 12s socket chages the caravan battery when you are towing.
IE No 2 pin, battery charging Positive. No 3 pin Battery charging Negative.

At least this way, you are not changing any existing wiring before finding out if the idea is feasible.

Quote: Originally posted by LobeyDosser on 20/3/2012

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There has been much discussion in the past about this and the most sensible suggestion that I have seen was that if, as a trial, you simply wired up a plug with the same connections as a 12S plug but with only the wires connected that would charge the caravan battery and then ran that from the towbar socket into the boot and connected it with crocodile clips to the boot battery, then it would charge the boot battery in exactly the same way as the 12s socket chages the caravan battery when you are towing.
IE No 2 pin, battery charging Positive. No 3 pin Battery charging Negative.

At least this way, you are not changing any existing wiring before finding out if the idea is feasible.

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Hi, Wires from the 12S socket into car would be the better way to charge the battery, as most modern cars now have a live feed to the cigarette plug(s), and if these plug(s) used the battery would still try and draw power from the car battery when the car is not running, with the 12S connections from the split charge relay, battery will charge while car running, and charge to battery will cease when engine has stopped as it charges from the alternator (eliminating any chance of you forgetting to pull plug or switch of the attached battery), every time the engine is switched off.

Hi, ive been doing this for 5 years now, 20 amp  wires from towing relay (in the boot), battery clamps into battery box. I have fitted a 15 amp fuse in the + wire, which i remove when towing,

the live+ attatched to the grey plugs live port on the relay, which charges the vans battery when towing, negative to the relay negative;

Bobs ter uncle:)

Just buy a 13 pin plug and a short length of cable, say one meter. Then only wire the two wires that you need to charge the battery.

This way you are not changing anything on the car until you have tried this set up.

Okay, once you know that everything works and you can make use of the new set up, then you can think about hard wiring it into the existing wiring in the boot.

However, using the plug system, if you change your car, you will not have to also change the wiring.

Quote: Originally posted by mazza79 on 21/3/2012

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you'll need one of these or you'll flatten your car battery
one of these

I was offered to put a charging circuit in the boot of the car when i priced a towbar up

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Hi mazza, that is the charger relay, and that should already be fitted to his car when tow bar fitted with13pin socket, along with the caravan/trailer indication unit, if he has said he is towing a caravan.