Oops! Sent the last post before I had finished it! I want to be able to charge a second leisure battery in the boot of my towcar. I understand that I can plug it into the cigarette lighter socket but that socket is permanently live. And so is the fridge pin on the 7-pin socket. I may have to connect direct to the alternator and run the wire right back to the boot. Does anyone have any thoughts on this please? I shall anchor the battery in the boot and use quick release clamps on the terminals. If it is at all relevant I have a Mk III Mondeo TDCi and a Lunar Quasar 525. Any assistance will be gratefully received.
Second battery in towcar
- Thread starter David_374469452
- Start date
Hi David,
Firstly, your fridge pin shouldn't be permanently live otherwise you would probably come back to a flat battery if you had a stop much over an hour. It should only become live when the alternator is putting out a charge so in effect, if your engine tick-over was slow enough for the alternator light to come on, the feed to the fridge would switch off.
Firstly, your fridge pin shouldn't be permanently live otherwise you would probably come back to a flat battery if you had a stop much over an hour. It should only become live when the alternator is putting out a charge so in effect, if your engine tick-over was slow enough for the alternator light to come on, the feed to the fridge would switch off.
We did this for years when we used CLs
I had 2 battery boxes made with plastic bread bins fitted with round plugs and sockets(bulgin I think)and well scured in the boot or caravan
The fused power for charging was taken from the fridge circuit which as Tony has said should only be live when the car ignition is on
If you have the quick release clamps on the van it would be just as easy to have them fitted in the car as well but with some provision to prevent accidental contact between the 2 when the battery was not connected to them!!
Perhaps a mobile phone case etc on the +ve lead
Use heavy cable to avoid voltage drop
I had 2 battery boxes made with plastic bread bins fitted with round plugs and sockets(bulgin I think)and well scured in the boot or caravan
The fused power for charging was taken from the fridge circuit which as Tony has said should only be live when the car ignition is on
If you have the quick release clamps on the van it would be just as easy to have them fitted in the car as well but with some provision to prevent accidental contact between the 2 when the battery was not connected to them!!
Perhaps a mobile phone case etc on the +ve lead
Use heavy cable to avoid voltage drop
Hello David,
Do not attempt to charge a battery using the cigarette lighter socket. The possible currents may blow any protection fuse, and even if the fuse does remain intact, the quality of the electrical contacts are poor and tend to over heat. I have had a socket actually melt because of poor contact over heating with as little as 2A flowing. Batteries can take 10 to 15A quite easily.
You need a close-able box to hold the battery and secure it during transit. The top of the box needs to be vented to the outside using a plastic hose or pipe to allow any hydrogen gas to escape when the battery is charging.
The electrical connection should be made using s a 12S plug. Using the fridge power circuit, or the split charge circuit, connect a pair of battery clamps with 2.5mm cable. You must also fuse the positive lead, and for added protection I recommend fusing the negative as well.
The cable should pass through the soft seal around the boot/tailgate and into the battery box.
The battery will charge when the engine is running and the alternator is producing enough power.
Do not attempt to charge a battery using the cigarette lighter socket. The possible currents may blow any protection fuse, and even if the fuse does remain intact, the quality of the electrical contacts are poor and tend to over heat. I have had a socket actually melt because of poor contact over heating with as little as 2A flowing. Batteries can take 10 to 15A quite easily.
You need a close-able box to hold the battery and secure it during transit. The top of the box needs to be vented to the outside using a plastic hose or pipe to allow any hydrogen gas to escape when the battery is charging.
The electrical connection should be made using s a 12S plug. Using the fridge power circuit, or the split charge circuit, connect a pair of battery clamps with 2.5mm cable. You must also fuse the positive lead, and for added protection I recommend fusing the negative as well.
The cable should pass through the soft seal around the boot/tailgate and into the battery box.
The battery will charge when the engine is running and the alternator is producing enough power.
I agree with John's comments about cigar plugs ---we had a fire in the boot and the plug melted due to damage to an accessory lead when cargo shifted
I would wire into the 12S socket myself either where the wires from the relay go to the socket or at the socket terminal
You would then be able to charge up on tow as well if you had 2 batteries as we used to do
I would wire into the 12S socket myself either where the wires from the relay go to the socket or at the socket terminal
You would then be able to charge up on tow as well if you had 2 batteries as we used to do
Thank you Tony...just as I thought. The towbar and electrics were professionally fitted so I will be taking it back to the fitter for an explanation. Many thanks!!! David
Thank you JohnL. I was a bit wary about using the cigarette lighter socket anyway, so that's definitely out! The 2.5mm cable, I assume I could use household 2.5mm if I took out the unsleeved earth wire? Thank you for your help. David
Thanks again John. I think I am the right track at last! The car is booked in for Monday next to get the wiring sorted, then its off to the market to get a bread bin or something similar! Thank you all for your most helpful posts, perhaps we will meet up on site somewhere. If I don't get this right you will recognise me, I'll be the one with the boot on fire!!! Best wishes to you all, David.
My wife and I go to all British Superbikes where hook ups are a non event. Its either a generator or battery power. The dreaded genny gets on my nerves especially if its someone elses at about 11.30 at night.
So, I got another leisure battery and connected it in paralell with the main leisure battery, and fitted it under the front seat next to the main battery compartment. They charge simultaneously while I am hooked up at home between meetings, and of course while travelling. I regularly do 4 and 5 nights without problems, thats using tv's as well. Works well for me.
So, I got another leisure battery and connected it in paralell with the main leisure battery, and fitted it under the front seat next to the main battery compartment. They charge simultaneously while I am hooked up at home between meetings, and of course while travelling. I regularly do 4 and 5 nights without problems, thats using tv's as well. Works well for me.
Hi 250bob,
I hope you have your second battery both securely strapped down and contained in a splash proof container with a vent to the outside.
These large leisure batteries do not take kindly to poor charging techniques and will vent hydrogen gas and Sulfuric acid.
When you connect batteries together in parallel, it is important that they are of similar capacity, and level of charge, other wise heavy currents can flow between the batteries leading to overheating of cables and the internal plates. In extreme cases batteries have been known to explode.
I hope you have your second battery both securely strapped down and contained in a splash proof container with a vent to the outside.
These large leisure batteries do not take kindly to poor charging techniques and will vent hydrogen gas and Sulfuric acid.
When you connect batteries together in parallel, it is important that they are of similar capacity, and level of charge, other wise heavy currents can flow between the batteries leading to overheating of cables and the internal plates. In extreme cases batteries have been known to explode.
David
I have just caught up with your comment about the 2.5 cable.
I do not recommend the use of stripped twin and earth, as this is solid conductor, and both difficult to handle, and is prone to breaking after being bent a few times, and at connection points inside plugs.
Go for multi-strand flexible cables, like an appliance flex.
I have just caught up with your comment about the 2.5 cable.
I do not recommend the use of stripped twin and earth, as this is solid conductor, and both difficult to handle, and is prone to breaking after being bent a few times, and at connection points inside plugs.
Go for multi-strand flexible cables, like an appliance flex.
I missed that too
Definitely as John says use flexible stranded cable preferably from Halfords etc and tell them what you want it for
The thicker the cable the less voltage drop
I used cable similar to the motor mover wiring with red for live and black for earth
Definitely as John says use flexible stranded cable preferably from Halfords etc and tell them what you want it for
The thicker the cable the less voltage drop
I used cable similar to the motor mover wiring with red for live and black for earth
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