Can anyone advise on how I can recharge my spare 12v battery when using the tow car on trips out when camping. I have heard that you can charge the battery using the tow electrics and wonder if anyone has down this and is it safe etc. Also can I use a 12v cigar lighter to charge the battery?
12v Battery (spare) recharging using the tower car
- Thread starter Frank_374304655
- Start date
The battery is a very heavy lump to have loose in the car so on safety grounds make sure you can secure it before you think of recharging it this way.
Having said that I do and the way I do it is to have an inverter plugged into a 12 volt socket and use the inverter to power my CTEK Multi XS 3600 charger.
This achieves a high level of charge but I have not let the battery get very discharged before topping it.
Having said that I do and the way I do it is to have an inverter plugged into a 12 volt socket and use the inverter to power my CTEK Multi XS 3600 charger.
This achieves a high level of charge but I have not let the battery get very discharged before topping it.
Hi, two potentially cheaper suggestions. If I find myself in this position, when planning to go out, I start my car then swap batteries and within a very short time the van battery is charged. Or you can prepare a grey (12S) plug with twin flex (to the correct terminals for your car) and battery connectors on the other end. Put the battery in the boot and connect the terminals, plug the new lead into the socket, and drive around. This works in the same way as charging the battery in the van when travelling. Make sure the cables are suffiniently large to reduce power loss.
Hello Frank,
I have done this, but there are precautions you must take.
When a battery is charged it can produce hydrogen gas that in the right concentrations is highly explosive. Inside the boot of car, there is no natural ventilation, so it must be provided. Using a plastic box with a close fitting lid to contain the battery, and arranging for a plastic pipe to vent any excess gas to the outside is an effective method.
The box can also provide the security to prevent the battery from moving around or tipping, also if there is and acid spill it is contained in the box.
When charging a leisure or a car type battery the current needed can be quite high (10A or more) This is too much for a cigar lighter socket, and can cause them to over heat and melt. You must use a more robust contact, and the 12S towing socket is designed for this and is far better.
Check that the charging cable and gas vent pipe can pass through the boot lid or tail-gate seal without damage. They should also be no longer than necessary to prevent snagging on any passing objects or dragging on the road.
For safety both the positive and the negative connection leads to there target battery should be fused (10A in each), and the battery connectors should be insulated to prevent unintentional short circuits if a loose lead should come into a metal part of the car.
The charging cable should be connected to the target battery before it is connected to the 12S socket on the tow-bar.
I have done this, but there are precautions you must take.
When a battery is charged it can produce hydrogen gas that in the right concentrations is highly explosive. Inside the boot of car, there is no natural ventilation, so it must be provided. Using a plastic box with a close fitting lid to contain the battery, and arranging for a plastic pipe to vent any excess gas to the outside is an effective method.
The box can also provide the security to prevent the battery from moving around or tipping, also if there is and acid spill it is contained in the box.
When charging a leisure or a car type battery the current needed can be quite high (10A or more) This is too much for a cigar lighter socket, and can cause them to over heat and melt. You must use a more robust contact, and the 12S towing socket is designed for this and is far better.
Check that the charging cable and gas vent pipe can pass through the boot lid or tail-gate seal without damage. They should also be no longer than necessary to prevent snagging on any passing objects or dragging on the road.
For safety both the positive and the negative connection leads to there target battery should be fused (10A in each), and the battery connectors should be insulated to prevent unintentional short circuits if a loose lead should come into a metal part of the car.
The charging cable should be connected to the target battery before it is connected to the 12S socket on the tow-bar.
AlanW
"I start my car then swap batteries and within a very short time the van battery is charged"
I have to admit I find this a little worrying - an alternator is supposed to have a battery connected, there is a possibility of damaging the electrical system.
Also the thought of the charging current being available on a loose cable in the engine compartment with the engine running is even more worrying.
Much prefer your second solution or JTQs although you may want to take precautions against gassing.
Frank you mention charging the battery from a cigar lighter socket - I do not think this would work as I believe the 12V socket would have a regulated 12V supply, try checking it with a meter if you want to make sure.
"I start my car then swap batteries and within a very short time the van battery is charged"
I have to admit I find this a little worrying - an alternator is supposed to have a battery connected, there is a possibility of damaging the electrical system.
Also the thought of the charging current being available on a loose cable in the engine compartment with the engine running is even more worrying.
Much prefer your second solution or JTQs although you may want to take precautions against gassing.
Frank you mention charging the battery from a cigar lighter socket - I do not think this would work as I believe the 12V socket would have a regulated 12V supply, try checking it with a meter if you want to make sure.
Hi Garry, I have discussed the charging of a van battery with the franchised dealership who suggested this method, yes certainly, providing you don't short out the live lead whilst changing them, but you get a much higher charge current than you do throught the 12s socket and no problem about gassing.
I was under the impression that if you disconect the battery on a modern car you will have to reprogram the radio and possibly some other electronics on the car.
If the engine is running the alternator would power these, not something I am going to try though.
The battery acts like a big smoother and if it is not in circuit the dirtier supply could interfere with and possibly damage some electronics.
Cheaper and easier to get a second battery IMHO.
The battery acts like a big smoother and if it is not in circuit the dirtier supply could interfere with and possibly damage some electronics.
Cheaper and easier to get a second battery IMHO.
THE EASIEST AND MOST RELIABLE WAY I HAVE FOUND TO DO WHAT YOU WANT IS TO use a 30amp 4 pin relay mounted in the boot......Run 2 wires from the front on the car....one 35amp wire (with 25amp inline fuse) from the battery to terminal 30 on relay.....one 17.5 amp wire from the alternators no charge no charge wire( thats the one that goes to the light on your dash to let you know that the battery is charging)to terminal 86 on the relay.......earth terminal 85 to the body in the boot......that leaves terminal 87 to go to your battery that you want to charge in the boot ( ues 35amp wire for this one and also fit another 25 amp inline fuse)
Make sure the battery in the boot is fixed securely as you dont want it to slide about or spill!!!(JOB DONE)
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