I have an 110 amp hour battery. I want to be able to put in the back of the car and charge it whilst driving solo. How can I do this please? Not too technical please? I have no wiring in the boot that I can see so do I go to a tow bar fitter or will my local garage do it? (It's a proper garage not a dealer!) (I've got the usual 2 sockets on the bar.
Charging the battery
- Thread starter waffler
- Start date
Chris there has been a posting on here recently re this but I cant remember where. Ill keep searching
Hi Chris,
So you don't have a 12 volt accessory socket (cigarette lighter type) in the boot?
It would make sense to get one fitted by the tow-bar guy - then you could plug in a set of leads and couple up the battery. Never use crocodile clips, you should use the caravan type battery clamps - and you may want a plastics battery box to protect the boot against spillages.
A tow-bar fitter will be 100% familiar with the 12 volt wiring in the boot / tow-bar area - I'd go with them.
I think it will be a good idea to connect the new 12 volt accessory socket to the switched live supply - then the socket will only be powered when the car engine is running.
If you have a GEL Leisure battery, then these should not be charged at a voltage greater than 13.5 volts - which should be the actual voltage on the "12 volt" supply.
Robert
So you don't have a 12 volt accessory socket (cigarette lighter type) in the boot?
It would make sense to get one fitted by the tow-bar guy - then you could plug in a set of leads and couple up the battery. Never use crocodile clips, you should use the caravan type battery clamps - and you may want a plastics battery box to protect the boot against spillages.
A tow-bar fitter will be 100% familiar with the 12 volt wiring in the boot / tow-bar area - I'd go with them.
I think it will be a good idea to connect the new 12 volt accessory socket to the switched live supply - then the socket will only be powered when the car engine is running.
If you have a GEL Leisure battery, then these should not be charged at a voltage greater than 13.5 volts - which should be the actual voltage on the "12 volt" supply.
Robert
Nominal 12v car alternators supply at 14.4v as do car-type battery chargers. Caravan power supplies provide 13.8v.
Any battery limited to just 13.5v is unsuitable for use with a car or caravan.
Any battery limited to just 13.5v is unsuitable for use with a car or caravan.
This is what I posted to this question in another post.
This next tip depends on how your 12s plug has been wired
If it has been wired up with a split relay you should have two 12volt supllies that operate only when the engine is running to pins 2 Blue and pin 6 Red cable.
Pin 2 Blue is the Battery charging circuit that charges the caravan battery whilst you travel.
Pin 6 Red operates the fridge whilst you travel ( it only keeps an already cold fridge cold so always either use the mains electric or gas to get it cold before traveling)once you turn the engine off both supplies are disconnected by the relay so the car battery is not flattened by the current drain to fridge and caravan battery.
If you have a split relay then connect to the blue cable in the car the red of a length of twin cable 2.5mm (red and black) connect the black to the car body earth and at the other end connect a polarity socket ( one that will only go in one way so you can not reverse the connection) with a matching plug. Connect another length of the same cable to the plug making sure you keep red to red, black to black. On the end of this connect a crockadile clip to the black, on the red connect an in line 15 amp fuse then a short length of the same cable to a crockadile clip. You will need a second battery and battery box you then connect the crockadile clips to the battery, red to + positive, Black to - negative of the battery. Always have the polarity socket is disconnected when connecting up AND MAKE SURE THE PLUG PINS ARE NOY TOUCHING SOMETHING METAL THAT COULD MAKE THEM SHORT OUT.
This now means that the new spare battery in your boot will be charged up whilst your driving the car so you can swap it with the battery in your caravan when it starts to run down and the run down battery will be charging up whilst your driving.
If your 12s plug is wired so it only has the fridge pin 6 operating when the car is running you will need to connect to the Red wire as above and not the blue wire AND YOU MUST NOT HAVE THE SPARE BATTERY CHARGING WHEN YOUR TRAVELING WITH THE VAN as the fridge and battery current could be to much for the red cable.
This next tip depends on how your 12s plug has been wired
If it has been wired up with a split relay you should have two 12volt supllies that operate only when the engine is running to pins 2 Blue and pin 6 Red cable.
Pin 2 Blue is the Battery charging circuit that charges the caravan battery whilst you travel.
Pin 6 Red operates the fridge whilst you travel ( it only keeps an already cold fridge cold so always either use the mains electric or gas to get it cold before traveling)once you turn the engine off both supplies are disconnected by the relay so the car battery is not flattened by the current drain to fridge and caravan battery.
If you have a split relay then connect to the blue cable in the car the red of a length of twin cable 2.5mm (red and black) connect the black to the car body earth and at the other end connect a polarity socket ( one that will only go in one way so you can not reverse the connection) with a matching plug. Connect another length of the same cable to the plug making sure you keep red to red, black to black. On the end of this connect a crockadile clip to the black, on the red connect an in line 15 amp fuse then a short length of the same cable to a crockadile clip. You will need a second battery and battery box you then connect the crockadile clips to the battery, red to + positive, Black to - negative of the battery. Always have the polarity socket is disconnected when connecting up AND MAKE SURE THE PLUG PINS ARE NOY TOUCHING SOMETHING METAL THAT COULD MAKE THEM SHORT OUT.
This now means that the new spare battery in your boot will be charged up whilst your driving the car so you can swap it with the battery in your caravan when it starts to run down and the run down battery will be charging up whilst your driving.
If your 12s plug is wired so it only has the fridge pin 6 operating when the car is running you will need to connect to the Red wire as above and not the blue wire AND YOU MUST NOT HAVE THE SPARE BATTERY CHARGING WHEN YOUR TRAVELING WITH THE VAN as the fridge and battery current could be to much for the red cable.
I really simple, none technical way is to plug an inverter into a cigar lighter and then plug a battery charger into that. No extra wiring or thought needed. Just make sure you have a battery charger that is designed for a leasure battery.
Pete
Pete
make it simplier still why bother with an invertor just connect wires to battery from cigerett lighter makeing sure theres a inline fuse from battery. Only connect battery once the engine is running.
Paul
As we tend to use CL's without a hook up, I have been thinking of getting a second battery and like Chris charging it in the back of the car.
Your nice, simple method of charging from the cigar lighter sounds attractive to non techies like me. The problem is, how do you know if you are overcharging the battery or is that not likely to be a problem? My second question is, will the voltage straight from the socket be OK?
The other alternative, but much more costly, is to take the car to an auto electrician and have a proper job done.
What would you advise?
Thanks
Clarky.
As we tend to use CL's without a hook up, I have been thinking of getting a second battery and like Chris charging it in the back of the car.
Your nice, simple method of charging from the cigar lighter sounds attractive to non techies like me. The problem is, how do you know if you are overcharging the battery or is that not likely to be a problem? My second question is, will the voltage straight from the socket be OK?
The other alternative, but much more costly, is to take the car to an auto electrician and have a proper job done.
What would you advise?
Thanks
Clarky.
You can't just plug the battery straigh into the lighter socket. It would, at best, over charge the battery as the car battery runs at a different voltage. All kinds of bad stuff would happen.
If you plug a battery charger into an inverter, you'll get all the battery care the charger manufacturers built in with no wiring, or fuses, or screwdrivers, or risk.
If you plug a battery charger into an inverter, you'll get all the battery care the charger manufacturers built in with no wiring, or fuses, or screwdrivers, or risk.
Hello Chris,
First of all a small but important warning, even 12V dc can be dangerous, so if you are not sure refere it an electrican.
I am a little concerned with some of the replies so far, I would not recommend using a ciarette type ligher socket as the are notoriious for developing poor connections, becuase of vibration or something tugging at the wire. With the relativly high currents that 12V systems can run at bad connections can over heat and melt.
I have used a realatively cheap but reliable solution. You already have the necessary sockets on your tow bar.
Have a cable made up that uses a 12S plug that picks up the 0v and split relay ciruit for battery charging or the fridge. Both +ve & -ve leads are fuse protected (10A),and the other end has two snap on battery connectors. The lead is long enough to be fed from the towbar socket through the soft seal of the boot lid to a secured battery box in the boot of the car.
This uses the right gauge of wiring, is protected in teh event of acidental short circuits or wrong connectoin, only charges when the alternator is running and can only be used when you are not towing. Job done, cost about
First of all a small but important warning, even 12V dc can be dangerous, so if you are not sure refere it an electrican.
I am a little concerned with some of the replies so far, I would not recommend using a ciarette type ligher socket as the are notoriious for developing poor connections, becuase of vibration or something tugging at the wire. With the relativly high currents that 12V systems can run at bad connections can over heat and melt.
I have used a realatively cheap but reliable solution. You already have the necessary sockets on your tow bar.
Have a cable made up that uses a 12S plug that picks up the 0v and split relay ciruit for battery charging or the fridge. Both +ve & -ve leads are fuse protected (10A),and the other end has two snap on battery connectors. The lead is long enough to be fed from the towbar socket through the soft seal of the boot lid to a secured battery box in the boot of the car.
This uses the right gauge of wiring, is protected in teh event of acidental short circuits or wrong connectoin, only charges when the alternator is running and can only be used when you are not towing. Job done, cost about
sorry Clarky I was being sarcastic I would not do it that way, the only way I would do it is as I described using the 12s wiring.
Sorry Pete your incorrect the battery would not over charge its getting the same voltage as the car battery from the alternator it would only over charge if the alternator circuits were faulty.
using an invertor can create all sorts of problems is it big enough to charge the battery quickly what about the loses involved is the cigar lighter socket capable of supplying the neccesery current.
Thanks for this. I do have 12 v output in the boot. Do you say I can cahrge the battery from that?
Thanks to all folks who have replied. I need to explore just what I have got, e.g if the van battery does charge when towing, and where the wires actually run.
PaulA, The car battery is a different type than a leasure battry. So, if the lighter socket was coming off the same circuit, it would overheat the leasure battery plates.
That's OK though as the lighter sockets are on a different ciruit than the battery charger. Either case plugging the battery into the lighter will not work.
The inverter howerver does. I know this because I use this method to charge an elecric scooter in the boot while driving and to charge the van battery up when not on mains hookup as a way of filling the van battery up from the car battery.
That's OK though as the lighter sockets are on a different ciruit than the battery charger. Either case plugging the battery into the lighter will not work.
The inverter howerver does. I know this because I use this method to charge an elecric scooter in the boot while driving and to charge the van battery up when not on mains hookup as a way of filling the van battery up from the car battery.
Pete from your posting your wrong yet again on several points all I can do is qoute your comments ON OUR WEB SITE to the moderator thread.
8 Feb 2006 08:36 PM
"Better to be a joke than a sad git who talks about things he doesn't know"
8 Feb 2006 08:36 PM
"Better to be a joke than a sad git who talks about things he doesn't know"
Hello again Chris,
Please ignore Pete's suggestion of using a cigarette lighter socket to charge a caravan battery, it will simply not be man enough to cope with the ammount of current and will be in danger of over heating.
also Petes suggestion of using an inverter is misleading. An inverter takes 12Vdc and produces 230Vac for running small wattage equipement. You would need to convert the 230V ac back to 12V by using in addition to the inverter a'battery charger' what a lot of equiepment to do what your car alternator and caravan wiring is already set up to do.
Another point is that even using an inverter the current drain will still be there on the cigarette lighter circuit, infact there will be more, becuase of the inefficencies of the inverter and the battery charger.
Cigarete lighter circuits for charging large batteries is a definate NO NO. They are ok for the small chargers for scooters.
Please ignore Pete's suggestion of using a cigarette lighter socket to charge a caravan battery, it will simply not be man enough to cope with the ammount of current and will be in danger of over heating.
also Petes suggestion of using an inverter is misleading. An inverter takes 12Vdc and produces 230Vac for running small wattage equipement. You would need to convert the 230V ac back to 12V by using in addition to the inverter a'battery charger' what a lot of equiepment to do what your car alternator and caravan wiring is already set up to do.
Another point is that even using an inverter the current drain will still be there on the cigarette lighter circuit, infact there will be more, becuase of the inefficencies of the inverter and the battery charger.
Cigarete lighter circuits for charging large batteries is a definate NO NO. They are ok for the small chargers for scooters.
Charging Batteries in the boot of a car presents some serious hazards and should not be entered into casually. Unless these hazards are know, understood and countered it is wrong to advise others to do it, and much I read here worries me. The more obvious hazards to take into account are:
Sorry about the spelling above; that is most certainly not an area I am any expert in. Hope you still understand the content. john
JTQ I agree with the common sense advice about securing the battery in a battery box in the boot.
However your technical advise is wrong.
Qoute
I opt to do it via an inverter and a proper leisure battery charger, as it's the only way I know of controlling the charging currents and those in the car wiring. Personally I would dismiss on the spot any technique linking the battery directly to the cars 12volt system. I know that will charge the battery, but it will not be either voltage or current regulated. I also know that the gassing is greatly minimised with a properly controlled charger. The car charging system is designed only to suit a starter battery needs not a remote leisure batteries requirement.
I am not going to write an essasy on the subject I did enough of those over the 7 years I spent qualifing as an Electrical Engineer. The supply from your altenator to your car battery is regulated by the cars Regulator, and if you use the same common sense as at the start of your posting and ask your self if the 12s system causes the battery to over charge why is it used in all caravans to charge the battery on the van.
I am sorry but your advise is not correct
However your technical advise is wrong.
Qoute
I opt to do it via an inverter and a proper leisure battery charger, as it's the only way I know of controlling the charging currents and those in the car wiring. Personally I would dismiss on the spot any technique linking the battery directly to the cars 12volt system. I know that will charge the battery, but it will not be either voltage or current regulated. I also know that the gassing is greatly minimised with a properly controlled charger. The car charging system is designed only to suit a starter battery needs not a remote leisure batteries requirement.
I am not going to write an essasy on the subject I did enough of those over the 7 years I spent qualifing as an Electrical Engineer. The supply from your altenator to your car battery is regulated by the cars Regulator, and if you use the same common sense as at the start of your posting and ask your self if the 12s system causes the battery to over charge why is it used in all caravans to charge the battery on the van.
I am sorry but your advise is not correct
With reference to JTQ's (Pete by another name?)
If you look at my earlier reply, I already instructed the use of a secured battery, with fused leads. I also indicated that 12Vs systems can develop large currents, and that cigarette lighter sockets are not sufficiently durable. So your very long reply is basically confirming the points I have already made.
I agree that venting the battery gasses is a sensible action, but that would be necessary even with your system.
The process of charging a leisure battery from the car is well established and is used through the 12S socket to charge most caravan batteries whilst towing. I would agree with you that the charging current is not regulated, but the voltage is, and in practice the charging circuit is usually fused at 10A, which is still a relatively small fraction of the sustained current transfer rate permitted for leisure batteries. This does not present a problem to the battery.
Your implication that the full current capacity of the alternator would present itself to leisure battery is entirely misleading. The current output from the alternator to any given circuit is determined by the potential difference between the alternator and in this case the leisure battery, and don't forget that all the other electrical services in the car will be drawing some share of the current capacity. It is likely that you would have at worst a 4.5V difference, which would automatically limit the current to significantly less than full 75A, and as the batteries terminal voltage rises the PD will diminish and so will the charge current.
I am not saying you are wrong to use an inverter and a charger, and it is one way of doing it. In my considered and experienced opinion it is unnecessarily complicated, and with the limited charge current you have it may not meet some caravanner's usage pattern, especially when the questioner has a 12S socket already available.
I would add that my solution is not a permanent or long term solution, but it should be safe and effective for a couple of days out travelling from the caravan to the beach etc.
If you look at my earlier reply, I already instructed the use of a secured battery, with fused leads. I also indicated that 12Vs systems can develop large currents, and that cigarette lighter sockets are not sufficiently durable. So your very long reply is basically confirming the points I have already made.
I agree that venting the battery gasses is a sensible action, but that would be necessary even with your system.
The process of charging a leisure battery from the car is well established and is used through the 12S socket to charge most caravan batteries whilst towing. I would agree with you that the charging current is not regulated, but the voltage is, and in practice the charging circuit is usually fused at 10A, which is still a relatively small fraction of the sustained current transfer rate permitted for leisure batteries. This does not present a problem to the battery.
Your implication that the full current capacity of the alternator would present itself to leisure battery is entirely misleading. The current output from the alternator to any given circuit is determined by the potential difference between the alternator and in this case the leisure battery, and don't forget that all the other electrical services in the car will be drawing some share of the current capacity. It is likely that you would have at worst a 4.5V difference, which would automatically limit the current to significantly less than full 75A, and as the batteries terminal voltage rises the PD will diminish and so will the charge current.
I am not saying you are wrong to use an inverter and a charger, and it is one way of doing it. In my considered and experienced opinion it is unnecessarily complicated, and with the limited charge current you have it may not meet some caravanner's usage pattern, especially when the questioner has a 12S socket already available.
I would add that my solution is not a permanent or long term solution, but it should be safe and effective for a couple of days out travelling from the caravan to the beach etc.
John I think your right it is him by another name. Its happening so often now that I dont know genuine questions and answers, so untill the powers that be sort this out I am no longer going to spend any more wasted time replying to questions in the technical forum. I dont suppose I'll be missed your more than capable and have the patience good luck.
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