Battery Power Sharing

EssexBoy

EssexBoy

Joined
Feb 5, 2009
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South Essex
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5,558
MH
A Class
Exp
25yrs in Motorhomes and Caravans before that
Hi All
Just after some advice please on the possibility of charging one Van's hab battery from another vans hab battery....

The full story is that I will be going over to France immediately after Xmas for a week in my A class Euromobile and a friend has asked to tag along in their PVC.

The issue is that we will be likely staying on aires & my mates PVC only has one 90Ah hab battery & doesn't have any solar or B2B as it's usually used exclusively on sites in the UK.

So, as I have I have 3x 110Ah hab batteries, 400W of solar and a 30A B2B, I was wondering about "sharing" my van's 12V power with his van, should the need arise - in a safe and secure manner.

My thought was maybe to make a special lead (fused of course) to connect his towbar socket to mine (pin 9 - the permanent live)

Any one have any thoughts on how to achieve this sharing properly please?

Thank you
 
Connecting your towing sockets won't do anything for the hab battery.... That will connect the engine batteries.
Completely different circuits.
You could use something like jump leads or reasonably heavy wires and Croc clips to connect your battery bank to his battery.
Usual scenario.... Pos to Pos... Neg to Neg.
He would then share all the batteries with you
 
Last edited:
There may be a way to link the two independent circuits but it would mean you'd have to be 'tethered' which isn't ideal.

Would it be possible for you to make it so that one of your batteries can be removed and connected up to his system in place of his (ie just moving the cables off his to your 'loan' battery if the need arises)? Then when you are travelling return your battery back to its original position to charge it up again before putting it back in his vehicle assuming the travelling doesn't put enough charge back into his own battery.
 
pappajohn said:
Connecting your towing sockets won't do anything for the hab battery.... That will connect the engine batteries.
Completely different circuits.
Click to expand...
I agree the towing circuit will be linked the to cab not the hab bit.
 
pappajohn said:
You could use something like jump leads or reasonably heavy wires and Croc clips to connect your battery bank to his battery.
Usual scenario.... Pos to Pos... Neg to Neg.
He would then share all the batteries with you
Click to expand...
Stop editing when I've already quoted you! :D

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If You have a 12V to 240V Inverter You can use a 240V extension lead with a 12V battery charger from your high energy van to His low energy van.
I used to have a stand alone solar panel system in the back of My previous van with 2 extra leisure batteries and an inverter that I used to supply the front motor home standard batteries with power when they ran low.
 
Seems pointless inverting 12dcv to 230vac just to convert it back to 12vdc.
Couple of wires and Croc clips is more efficient and with an inverter you'd be running a flex between vans anyway
 
If you are good friends wouldn’t they (pvc) be in your large van most evenings when most of their power would be used for heating/lighting/tv..?

if your driving most days it would provide them with enough power for a “short” evening ...
 
Minxy Girl said:
There may be a way to link the two independent circuits but it would mean you'd have to be 'tethered' which isn't ideal.

Would it be possible for you to make it so that one of your batteries can be removed and connected up to his system in place of his (ie just moving the cables off his to your 'loan' battery if the need arises)? Then when you are travelling return your battery back to its original position to charge it up again before putting it back in his vehicle assuming the travelling doesn't put enough charge back into his own battery.
Click to expand...
That did cross my mind, but wasnt sure about humping heavy batteries about:D:D:D
 
pappajohn said:
Seems pointless inverting 12dcv to 230vac just to convert it back to 12vdc.
Couple of wires and Croc clips is more efficient and with an inverter you'd be running a flex between vans anyway
Click to expand...
12V may suffer from voltage drop if linking vans.
The 240V inverter method with a battery charger does work well especially if using long leads.
The Inverter should have large cables and a short run.
 
Just smiffy said:
If you are good friends wouldn’t they (pvc) be in your large van most evenings when most of their power would be used for heating/lighting/tv..?

if your driving most days it would provide them with enough power for a “short” evening ...
Click to expand...
This is what I am expecting to happen really... my worry is that my mate has never used his van "off grid", so just want to make sure I dont ruin it for him by his battery not lasting the distance...

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The simplest solution would be for him to buy a second battery and be frugal with his usage if necessary, once he has a 'taste' of what it's like to use aires and not having to pay out loads of dosh to use sites he's likely to want to continue! A little investment in a battery therefore will save him in the long run and give him more beer money! :beerchug:
 
Minxy Girl said:
The simplest solution would be for him to buy a second battery and be frugal with his usage if necessary, once he has a 'taste' of what it's like to use aires and not having to pay out loads of dosh to use sites he's likely to want to continue! A little investment in a battery therefore will save him in the long run and give him more beer money! :beerchug:
Click to expand...
That is the plan longer term. He is prepared to buy more batteries, solar, B2B etc. but Aires & off grid are such alien concepts right now, I dont want to put them off by making their first experience miserable :D :D :D
 
If you connect hab to hab every time you stop you don't need exceptionally heavy cables. EHU hook-up cable re-purposed with croc clips on each end would do the job. Under such circumstances the two batteries would remain adequately balanced and no heavy currents would flow in either direction unless one of you used an inverter.
 
eddievanbitz said:
Let him sit in your van!
Click to expand...
No way... I'm not having common PVC dwellers in my van... :D2:D2:D2:ROFLMAO::ROFLMAO::ROFLMAO:

Seriously though, I just want to make sure their battery doesn't run out overnight, the heating doesnt go off, and they dont freeze....
 
*Machzoneman* said:
12V may suffer from voltage drop if linking vans.
The 240V inverter method with a battery charger does work well especially if using long leads.
The Inverter should have large cables and a short run.
Click to expand...
Assuming the donor vehicle already has an inverter fitted, why not then use a standard EHU lead between the vans, with a 13A socket to 16A converter at the donor end, and the other end connected to the recipent's external EHU input. You won't need an additional charger for the recipient as the charger should be part of the EHU input connection. All you must ensure is the recipent only uses their 12V, and the donor, given longer run times and background drain on the inverter, limits how long the donation boost can operate.
 
As my 400w of solar is often in excess of my needs, I have thought I could provide a 'mains' ehu to another motorhome via the inverter. The necessary adapters I already carry, just need to stress to the recipient that only his charger must be on.
A 12v cable to connect would be a bit impractical through voltage drop, two adjacent places on an aire couldnt be guaranteed.
 
I agree with HandyAndy. he should buy a solar panel kit & fit the controller box in the van & just stand the panel outside,then at a later date fit the panel permanently on the roof...
I had a 40w panel with a 70ah battery when i had my vw T25 & could manage 3-4 days in the summer months.
 
We managed indefinitely with our 40w free standing panel, the battery was fully recharged by lunchtime. Made about 2.5 amps stood facing the sun. They are a reasonable size to put away too, about the size of a ceiling grid tile.

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EssexBoy said:
Seriously though, I just want to make sure their battery doesn't run out overnight, the heating doesnt go off, and they dont freeze....
Click to expand...
We never have our heating on overnight, ever, not even when stuck up a mountain in freezing temperatures, an extra duvet and a hoodie work wonders!

Others have suggested a small solar panel but that won't put much in during the winter I'm afraid.
 
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Kannon Fodda said:
Assuming the donor vehicle already has an inverter fitted, why not then use a standard EHU lead between the vans, with a 13A socket to 16A converter at the donor end, and the other end connected to the recipent's external EHU input. You won't need an additional charger for the recipient as the charger should be part of the EHU input connection. All you must ensure is the recipent only uses their 12V, and the donor, given longer run times and background drain on the inverter, limits how long the donation boost can operate.
Click to expand...
There's a way to minimise the background drain of an inverter, and provide a useful but not excessive feed to the other battery.

A small 150watt inverter will have a very low background drain. It can be hooked up with a mains extension lead to a 5 amp charger such as a CTEK MXS5.0, to charge the other battery. Because it's a smart charger it will stop drawing current when the other battery is charged. Power loss over a normal mains extension will be minimal compared to any direct 12V connection.
 
Reallyretired said:
A 12v cable to connect would be a bit impractical through voltage drop, two adjacent places on an aire couldnt be guaranteed.
Click to expand...
Nothing was said about non-adjacent places and to be honest I wouldn't want a 230v mains cable laid across exposed public ground. Anyone could drive over it.
Probably OK if you're both on the same side and can lay it out the way I suppose.
 
Still think KISS: A relatively thin (for DC) cable linking the two batteries would, provided it was connected 24/7, keep your friends battery charged. It's safe and simple. Incorporate a fuse at either end if you think it might get damaged but other than that it's the simple solution. Voltage drop over whatever length is irrelevant if it's connected full time.

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