12v Cab battery charging

Captain Yoghurtpot

Captain Yoghurtpot

Joined
Apr 13, 2019
Posts
2,269
Likes collected
54,599
Location
Nottinghamshire
Funster No
59,884
MH
VW 2005 T5 Campervan
Exp
Since September 2018
Hi folks
Does anyone know if it is possible to charge a 12v cab battery in the engine bay via a 12v cigarette socket in the Motorhome internal dashboard?
Thanks
 
Sort by date Sort by votes
Theoretically I think the answer is yes.
I have a small solar panel plugged into cig socket as it is always live in my old Ducato.
What I would be unsure of is the ampage it could hold.
And secondly, why you feel the need to do this? (not taking the p*ss, genuinely don't know why you would want to?)
 
Upvote 0
Only up to the rated amperage of the cig socket wiring/socket.
Either 10a or 15a normally
BUT..... forget to unplug before attempting a start and either the fuse, if fitted, or the wiring will suffer drastically.

Subscribers  do not see these advertisements

 
Upvote 0
If it's permanent live socket then yes but only up to the current rating of the socket wiring... Check the fuse for this circuit!
 
Upvote 0
Sorry, must have missed something here. Is the OP suggesting charging the engine battery from.......................... the engine battery? 'Cos my dash sockets are wired to the engine battery.
:xeek:​
 
Upvote 0
TerryL said:
Sorry, must have missed something here. Is the OP suggesting charging the engine battery from.......................... the engine battery? 'Cos my dash sockets are wired to the engine battery.
Click to expand...

I think (hope) Captain Yoghurtpot intends to put a male cig lighter plug on the output lead of his mains battery charger.
 
Last edited:
Upvote 0
Perhaps he's going to start the vehicle and power a battery charger from the ciggy socket :D :D

Subscribers  do not see these advertisements

 
Upvote 0
Lenny HB said:
It will work on a Ford but not on a Fiat as Fiat socket is only on with the ignition.
Click to expand...

I have 2 sockets on the dash. One is only on with ignition and the other is always on. The radio was also wired for always on but I changed that. I guess this is a mod as I found a cable with a 15a fuse attached directly to the battery and socket goes off if the fuse is removed.

For charging the starter battery I attached cables with a socket that came with my charger.
 
Upvote 0
Captain Yoghurtpot said:
Does anyone know if it is possible to charge a 12v cab battery in the engine bay via a 12v cigarette socket in the Motorhome internal dashboard?
Click to expand...
Yes, in theory that's possible. When I go away for more than a couple of weeks, I do exactly that with the car on the driveway. I use a smart charger that goes into float mode when fully charged. But a trickle charger could do the job instead.

This works in my car because the socket is always live, even with the ignition off. That's not true for many cars, and may not be true for your motorhome. But it's easy enough to check.

A permanently live socket from the cab battery is quite useful in other ways, so if you don't have one it's a good idea to fit one. Or rewire an existing one to a permanent live. Through a fuse, of course, if going directly from the battery itself.
 
Upvote 0
Ok folks and thanks for the advice, comments and questions.
Here is the full scenario.
Motorhome has an on board charger that will only charge the Hab battery and is not capable of doing the Cab battery at the same time.
12v cigarette lighter socket is permanently Live with ignition switched off.
Project is to be able to charge both Hab and Cab Batteries when in EHU to keep topped up when at home.
Idea was to purchase a reputable 12v trickle charger to be connected to my 230v 3pin plug socket and connect a male cig lighter plug into the cig lighter socket to charge , then maintain via float the Cab battery.
Hab battery would be therefore charging as a stand alone unit via the in board charger.
Problem to overcome: how to get the wires from the trickle charger to the engine bay internally.
I cannot for the life of me find a grommet or lug access to get wires through, hence the idea of going internally via the cig socket.
Will definitely check the fuse ratings but feel sure a 12v TRICKLE charger will be fairly low in amperage output.
I know I can fit a vanbitz but of kit, which I do like, but again I have the same problem getting the positive cable from the engine bay to inside the Motorhome.
Hope this makes sense.
PS someone did mention on a different thread that on the Fiat Ducato there is a positive and negative plug inside the engine bay which is directly attached to the terminals of the Cab battery, but I have no idea where this is.
 
Upvote 0
SwissBob said:
I have 2 sockets on the dash. One is only on with ignition and the other is always on. The radio was also wired for always on but I changed that. I guess this is a mod as I found a cable with a 15a fuse attached directly to the battery and socket goes off if the fuse is removed.

For charging the starter battery I attached cables with a socket that came with my charger.
Click to expand...
My fiat Ducato has a live cig socket with ignition off but can’t find a way to get cables through the bulkhead to the engine bay to connect direct to the battery.
Thanks for the advice though.
 
Upvote 0
TerryL said:
Sorry, must have missed something here. Is the OP suggesting charging the engine battery from.......................... the engine battery? 'Cos my dash sockets are wired to the engine battery.
:xeek:​
Click to expand...
See further explanation, cheers.
 
Upvote 0
If you buy an optimate 2 or similar, it comes with a small lead to go on the battery with a connector to disconnect it. The engine battery is under the floor in the cab so it's super easy to wire it on. Then the plug sits under the drivers seat when not in use.

Subscribers  do not see these advertisements

 
Upvote 0
pappajohn said:
Only up to the rated amperage of the cig socket wiring/socket.
Either 10a or 15a normally
BUT..... forget to unplug before attempting a start and either the fuse, if fitted, or the wiring will suffer drastically.
Click to expand...
Yes Mr. Pappajohn, got that but would have a sticker or similar warning notice to avoid that scenario, but good advice all the same thanks.
 
Upvote 0
Richard and Ann said:
If you buy an optimate 2 or similar, it comes with a small lead to go on the battery with a connector to disconnect it. The engine battery is under the floor in the cab so it's super easy to wire it on. Then the plug sits under the drivers seat when not in use.
Click to expand...
No my battery is in the engine bay not under the floor.
My van is a 2000/2001 model. 18 years old.
But optimists is a range I have been looking at , thanks for the thought.
 
Upvote 0
Jev88 said:
Theoretically I think the answer is yes.
I have a small solar panel plugged into cig socket as it is always live in my old Ducato.
What I would be unsure of is the ampage it could hold.
And secondly, why you feel the need to do this? (not taking the p*ss, genuinely don't know why you would want to?)
Click to expand...
Thanks for the comment.
Please see further explanation.
Cheers.
 
Upvote 0
I'd fit a second cig lighter in the hab section, wired direct to the vehicle battery.
After retiring I used to help out a pal who fitted car electrical accessories. He used to get a power supply into the cab part by removing a wire (any wire that went direct to inside the engine bay) from inside the cab/dashboard, attaching two new wires to it and pulling the original wire (identified by the colour coding on the original wire) from the cab through to the inside of engine bay together with the two new wires. They find their own way through the bulkhead.
Only one of the new wires was needed for the extra cig lighter as the cig lighter's 'Earth' could be connected to the body inside the cab.
One end of one of the new wires was connected to the vehicle battery (with a fuse) and the other end connected to the cig lighter in the cab. The other new wire was pulled back into the cab, using it just as a 'mouse' together with the original wire which he refitted to where it had previously been removed.
You do need a bit of courage though, and be sure to attach the two new wires very securely to the original wire or if they come adrift you'll end up worse than before. He used to solder them all together and put heat shrink tube over where the three wires were joined to prevent the join from snagging as it passed though the bulkhead and help to secure them all together. Best to disconnect the vehicle battery before fiddling with the wires. You can get small quantities of heat shrink from accessory shops.

Subscribers  do not see these advertisements

 
Last edited:
Upvote 0
Spriddler said:
I'd fit a second cig lighter in the hab section, wired direct to the vehicle battery.
After retiring I used to help out a pal who fitted car electrical accessories. He used to get a power supply into the cab part by removing a wire (any wire) from inside the cab/dashboard, attaching two new wires to it and pulling the original wire (identified by the colour coding on the original wire) from the cab through to the inside of engine bay together with the two new wires. They find their own way through the bulkhead.
Only one of the new wires was needed for the extra cig lighter as the cig lighter's 'Earth' could be connected to the body inside the cab.
One end of one of the new wires was connected to the vehicle battery (with a fuse) and the other end connected to the cig lighter in the cab. The other new wire was pulled back into the cab, using it just as a 'mouse' together with the original wire which he refitted to where it had previously been removed.
You do need a bit of courage though, and be sure to attach the two new wires very securely to the original wire or if they come adrift you'll end up worse than before. He used to solder them all together and put heat shrink tube over where the three wires were joined to prevent the join from snagging as it passed though the bulkhead and help to secure them all together. Best to disconnect the vehicle battery before fiddling with the wires. You can get small quantities of heat shrink from accessory shops.
Click to expand...
Hi Spriddler
Thanks but surely if my existing 12v cig lighter socket is a direct feed to the battery, why would I need a second one?
 
Upvote 0
Captain Yoghurtpot said:
Hi Spriddler
Thanks but surely if my existing 12v cig lighter socket is a direct feed to the battery, why would I need a second one?
Click to expand...
You don't need another one if your existing cig lighter is permanently live. If it isn't you could simply rewire it with a permanently live feed instead of via the ign switch.
It's sometimes handy to have a cig lighter socket back in the hab section. I have fitted one (admittedly connected to the leisure battery) in the rear of my hab part for a 12v supply, e.g. for charging 12v stuff.
 
Upvote 0
autorouter said:
I use a smart charger that goes into float mode when fully charged. But a trickle charger could do the job instead.
Click to expand...
I use a CTEK MXS5.0 smart charger. It has a special connector on the output wires. You can buy a range of ends that just plug into this connector. It comes with standard croc clips, but you can get cig lighter plug, terminal eyelets, extension wires etc. Not cheap but bomb-proof and plug-and-play.
CTEKMXS5.JPG

CTEKCigPlug.jpeg
I use the MXS5.0 because it has a mode to charge a motorbike battery as well as a car charge mode. You may not need that. It charges 200Ah of flat leisure battery no problem, it just takes a long time at 5 amps.
 
Upvote 0
Captain Yoghurtpot said:
Problem to overcome: how to get the wires from the trickle charger to the engine bay internally.
I cannot for the life of me find a grommet or lug access to get wires through, hence the idea of going internally via the cig socket.
Click to expand...
There are at least two possibilities. The 'split charge relay' connects the starter battery to leisure battery while the engine is running. The relay might be in the engine bay, or it might be near or inside the 12V electrics fuse box. You could make a connection to that.

Alternatively, there might be a fridge power relay, if the fridge is a 3-way or AES type. That is also directly connected back to the starter battery. You could connect to that. The fridge only takes power when the engine is running, so it won't cause any problems. That's how it's done in Hymers and anything with a Schaudt Electroblock.
 
Upvote 0
A battery master woul be your easiest and safest option.
Just 3 wires... One to hab Pos, one to cab Pos and one to chassis earth.
The one to CAB Pos can be to ANY permanent live wire from the CAB system....it doesn't have to go directly to the battery.
As long as the hab battery is ½v more than the engine battery then a couple of amps will be sent to the engine battery.
 
Upvote 0

Join us or log in to post a reply.

To join in you must be a member of MotorhomeFun

Join MotorhomeFun

Join us, it quick and easy!

Join us

Log in

Already a member? Log in here.

Latest journal entries

Back
Top