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 ?
you might have to make one up, not seen a ready made one.
depending on how your socket works, IF it only comes on when the engine is running, then a simple cigar plug to battery clips (not croc clips, these can come off) would do the job.
If its live all the time, then a smart relay would fix it,
Failing either of those, if you only need it when not towing, I have a 12S socket, with just the charging connections made, that I use to charge the battery in the boot.
Also, get a battery box, you don't want acid getting in your boot.
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...?
I had this set up for over the winter, I just wired up a pair of quick release battery clamps with inline 15a fuse to the output on my TEC3M relay and just strapped it down and poked the vent tube through a rubber grommet in the spare wheel well. It did me good at keeping the battery topped up and I have been advise buy the manufacturer there's minimal chance of overcharging
Most lighter sockets only have thin wiring so, if your leisure battery is flat, too much current will be drawn and the wires or plug may melt - in my case it was the plug
Another option would to get an 350 watt inverter (or less) which would operate of the 12 volt socket, plug in a small car charger into the inverter, attach to the battery that is secured in the boot.
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
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.
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.
------------- If everything runs smoothly then I must have done something wrong
If in Doubt Check it Out.
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:)
------------- I Started with nothing and have most of it left!
Thanks everyone. I like the idea of using the towing socket when not in use and just plugging in and running the cable into the boot....that way I can use the electrics and the high rated cables our fitter put in that run back to the battery (as opposed to the lower rated cigerette socket in the boot). So next thing is where can I get something like this, I take it you can't buy one made up and would have to make one? Our car has the new 13pin socket if that makes a difference!
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
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
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.
------------- If everything runs smoothly then I must have done something wrong
If in Doubt Check it Out.
Dont be tempted to use the cig lighter socket , mine melted along with the wires, the only thing that stoped the car going on fire was the battery went flat before it could happen.
this was many years ago and i wouldnt dream of doing anything like that today.
Amazing family weekend with old steam engines, classic car displays, market stalls, and full catering and bar. And camping on site - Save £25 by booking in advance.
Topic: Charging spare leisure battery in boot?
