Second Leisure Battery

Oct 1, 2013
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Lanzarote
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Yesterday I was talking to a local man about fitting a second leisure battery to my Transit based camper.

I also want him to fit a split relay thingy, but he said the alternator wouldn't be big enough to charge both leisure batteries.

He suggested having 2 seperate batteries. One charged from van and one from EHU.

is he talking bollox?
 
OP
Yorick
Oct 1, 2013
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And a second question. Many moons ago the van battery flattened as we left the fridge on while not travelling. Sadly the leisure battery was not man enough to jump it off.

would this addition of a second battery provide the extra needed power to start the van in an emergency?

Thanks.
 
Jan 8, 2014
956
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Emsworth
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with regards to the fridge the van battery should not discharge as there should be a in line relay which only allows power to the fridge when the engine is running and shuts off when the engine stops. My van has two leisure batteries and is charged from the alternator or ehu - but in fairness i dont know what amps my alternator kicks out.
 

JJ

May 1, 2008
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Quinta Majay, Pinheiro Bordalo, Portugal
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over 40 years
Don't listen to me because others know far more but...

Your alternator can charge 2 leisure batteries but will take longer to fill them up.

Unless it is a compressor fridge then the fridge will quickly flatten your batteries.

The usual set up is you can only work your fridge on 12 volts when the engine is running (the fridge relay knows when the engine is running and connects the fridge).

The second leisure battery won't help very much with jump starting unless the connecting wires are nice and fat.

JJ :cool:
 
Jul 23, 2013
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Scotland
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knaus van ti 600mg
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Getting There since 2013
What age is your transit? You should be able to find out what power output your alternator has!
 
OP
Yorick
Oct 1, 2013
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Thanks. I forgot to mention that there is no fridge relay. Yet. That's next on list.
 
Sep 16, 2013
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North Wales
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Since 2006
Yesterday I was talking to a local man about fitting a second leisure battery to my Transit based camper.

I also want him to fit a split relay thingy, but he said the alternator wouldn't be big enough to charge both leisure batteries.

He suggested having 2 seperate batteries. One charged from van and one from EHU.

is he talking bollox?
Yes he is (probably).

I have a few minutes free, want a drawing of exactly what you need?
 
Sep 16, 2013
1,097
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North Wales
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Was bored so did a drawing anyway :)


This will give you a split charger for your leisure batteries and power your fridge correctly on 12v (so it just comes on when engine is running).

It will also allow you to jump the starter battery from the leisure batteries by by-passing the relay (I have a similar system fitted in my own van).

Because of the current needed to jump start you will need 25mm cable where shown.

Hope this helps.
 
Nov 18, 2011
10,019
19,336
I am thinking abut another two leisure battery's and alternator up grade with more solar
 
Sep 16, 2013
1,097
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North Wales
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Van Conversion
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I am thinking abut another two leisure battery's and alternator up grade with more solar
Assuming you already have two batteries , so want four, it's worth connecting them in a way that charges and discharges them equally. I have four in my own build and this is how they are connected:

What this does is splits the batteries into two banks diagonally, then joins the two banks diagonally. Looks complicated but it's just one extra cable.

I spent ages (mainly on marine forums) working out the best way of doing this in a motorhome. If interested this is my whole charging system:


(although no Smartcom now as I went with a compressor fridge)
 

pappajohn

LIFE MEMBER
Aug 26, 2007
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The simple answer is yes, he's talking bollox.

Many folks have 3 or even 4 batteries connected together as one and they charge ok.
 
Aug 6, 2013
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Kendal, Cumbria
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since 1999
Don't listen to me because others know far more but...

Your alternator can charge 2 leisure batteries but will take longer to fill them up.

Unless it is a compressor fridge then the fridge will quickly flatten your batteries.

The usual set up is you can only work your fridge on 12 volts when the engine is running (the fridge relay knows when the engine is running and connects the fridge).

The second leisure battery won't help very much with jump starting unless the connecting wires are nice and fat.

JJ :cool:
Absolutely correct. Alternator size is irrelevant and it will perform exactly as JJ says.
 

Chris

LIFE MEMBER
May 5, 2010
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kent
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Assuming you already have two batteries , so want four, it's worth connecting them in a way that charges and discharges them equally. I have four in my own build and this is how they are connected:

What this does is splits the batteries into two banks diagonally, then joins the two banks diagonally. Looks complicated but it's just one extra cable.

I spent ages (mainly on marine forums) working out the best way of doing this in a motorhome. If interested this is my whole charging system:


(although no Smartcom now as I went with a compressor fridge)
Thanks.

I think I might have a crack at that at the weekend.

Looks easy peasy to a man of my abilities.

Anyone got any idea of the value of a 2013 burnt out Autotrail Scout?
 
Sep 23, 2013
2,314
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Lincs
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Globecar Campscout PVC
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Since 2008 (started in a VW T4 campervan)
I spent ages (mainly on marine forums) working out the best way of doing this in a motorhome. If interested this is my whole charging system:


(although no Smartcom now as I went with a compressor fridge)
I don't think you can better this for a bare van conversion. The only thing I would do differently would be to feed at least one fuse box from the 12V 80A voltage regulated Consumer output on the SMARTPASS, rather than direct from the batteries. I would then put anything likely to suffer if supplied with the 14+V charging voltages on this fuse box. When in 'Recover' mode, the MXS 25 can be pushing out over 15V. This output also protects the batteries from over-discharge, because it shuts off if the batteries drop to critical levels.

I can't find the exact voltage that the Consumer output is regulated at, but I suspect it is limited to 13.5V max, because that's what CTEK mains chargers provide when in 'power supply' mode.
 
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