12 volt charger

[tonyb2]

Hi . I want to charge my spare caravan battery [used when i use CLs] from the car. I have a 12 volt socket in the back of the car and can safely stow the battery. Is there a gadget available that will run from a 12 volt supply to charge a 12 volt battery. Any ideas appreciated
tony

 

[Arryvanpulla]

Hello tony,there is a product you can purchase but I suspect it may be just a box to put the batterie in to keep it secure,
I have seen on a couple of occasions it being done by using a plug into the grey socket (12s) and a length of flex with clamps onto the batterie inside the vehicle .Sorry I can't be more specific regarding which terminals in the plug you need to use or. Size of flex (twin core is all you need) it might be wise to put a fuse in line as well,
Have a word with you're local towbar fitter and he will be able to advise ,and make up the piece of gear for you.
PS you will have to make sure the batterie clamps are connected before you plug in !.

 

[emmerson]

Tony, I've done this to charge Herself's 24v scooter from the car.
All you need is a 300w inverter (Maplins, about £30). They come with a cigar lighter plug, but these don't last long, so I hard-wired into the lighter socket wiring, via a 10amp fuse. You then simply plug your 12v charger into the inverter, hey presto, mobile battery charger.Make sure though, that you connect through the ignition or alternator circuit, so that you cannot leave it on when the engine's off.
I've used this method for many years now, and I've never needed to mains charge since I set it up.
,

 

[RogerL]

If the 12v car socket is only live when ignition is on, then just run a twin cable from the socket to the battery - no need to involve inverters/chargers.
The 12v car socket will supply 14.4v when engine is running, well a bit less with voltage drop, so will charge the battery nicely.
The above won't be suitable if the 12v socket is live all the time.

 

[emmerson]

Agreed, Roger, but I needed 24v, and the inverter is useful for all sorts of other things.

 

[JTQ]

The inverter and appropriate charger is also better for proper Leisure/deep cycling batteries as then the regulation is specific for that type of battery. This is very different to the requirements of the starter battery for which the vehicles regulation is set up.
I have done it for years via an inverter. Agreed its not so efficient but with a 200hp engine at my disposal this is hardly relevent.

 

[drsorento]

emmerson, you may need 24v but he only wants to charge a 12v battery as he stated in the OP so going through the long winded and by far more expensive option with inverters etc is both more complex and pointless,
keep it simple as already said just connect into the power socket.

 

[JTQ]

so going through the long winded and by far more expensive option with inverters etc is both more complex and pointless,
keep it simple as already said just connect into the power socket.

If its a true "deep cycling" or even a reasonable quality "Leisure" battery then recharging it via an inverter and appropriate charger is anything but "pointless".
The point of doing it correctly is as I said earlier, the car's alternator regulating system is designed to rapily charge the vehicles "starter" battery, a different technology to a deep cycling battery.
Clearly if you only use starter batteries for your caravan then no problem in treating them as starter batteries..

 

[Arryvanpulla]

So jtq do you use starter batteries ? Because when you connect your van to you're tow vehicle the van battery is being charged by the tow vehicle charging system......!!!

 

[JTQ]

So jtq do you use starter batteries ? Because when you connect your van to you're tow vehicle the van battery is being charged by the tow vehicle charging system......!!!

Well I don’t use starter batteries simply because I use the batteries in a true Leisure role as we rarely go on hook ups.
Your assumption that by connecting to the car when towing my van’s battery is charge managed by the alternator is in my case a flawed assumption.
Unlike many cheaper systems my van has a Schaudt controller/charger which takes the power incoming from the car and operates as a “smart” charger regulating the charge rates and voltages to specifically suit the GEL VRLA battery I use. Its is further smart enough to achieve this from inputs as low as 10.5volts through to 15.5 so compensating for voltage drops and the car's regulation.
In the crude arrangement where the caravan battery is directly connected to the vehicles alternator regulator, as you assumed I had, then the voltage drop in the lengthy wiring under potentially high currents gives some level of protection to the van battery. Clearly the lower resistance the wiring from alternator to battery is, as in spare battery in boot rather than caravan the lower that inherent protection would be.

 

[emmerson]

So, to coin a phrase, "ye pays yer money and takes yer choice!"

 

[Arryvanpulla]

Hi Tony ,as drsorento says "keep it simple " I have been charging my batteries for over 35 years from the cars system ,my present battery is over 7 years old Elecsol carbon fibre plates is still going and holding charge .I certainly would not go down the route of extra waisted money on more extra weight.