Second Leisure Battery (1 Viewer)

Oct 1, 2013
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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
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
1,038
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Emsworth
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Bailey 740
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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.

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JJ

Mágica
May 1, 2008
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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
381
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knaus van ti 600mg
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What age is your transit? You should be able to find out what power output your alternator has!
 
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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.

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Sep 16, 2013
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Horncastle, UK
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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?

Yes he is (probably).

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

Broken Link Removed
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
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I am thinking abut another two leisure battery's and alternator up grade with more solar
 
Sep 16, 2013
2,217
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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:
Broken Link Removed
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:

Battery_400A_Setup_CTEK_MASTER.png

(although no Smartcom now as I went with a compressor fridge)
 
Nov 18, 2011
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thanks that is very clear instructions thank you
bill

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pappajohn

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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.

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Aug 6, 2013
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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

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May 5, 2010
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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:
Broken Link Removed
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:

Battery_400A_Setup_CTEK_MASTER.png

(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?

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Sep 23, 2013
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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:

Battery_400A_Setup_CTEK_MASTER.png

(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.
 
Sep 23, 2013
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Why did you exclude solar from the BM1 monitoring ?
Given the way the two CTEK units work together, I don't think it is excluded. The input from all sources is combined by the CTEK & passed to the live side of the battery bank - which is linked to the BM1
 

hilldweller

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Dec 5, 2008
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Given the way the two CTEK units work together, I don't think it is excluded. The input from all sources is combined by the CTEK & passed to the live side of the battery bank - which is linked to the BM1

Well that's not the way I read your circuit. None of the solar current passes through the BM1 shunt so it does not see it. Of course the if the BM1 registers solar charge then I'm wrong or your diagram is.



PS........ I see it's not your diagram now.

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Sep 23, 2013
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Well that's not the way I read your circuit. None of the solar current passes through the BM1 shunt so it does not see it. Of course the if the BM1 registers solar charge then I'm wrong or your diagram is.



PS........ I see it's not your diagram now.
I agree that it's not obvious just from looking at the diagram. I have the advantage of having the manual for the two units in front of me.

The input from the solar panel comes into the top unit to the top left connection. It passes through the inbuilt MPPT regulator & is then passed via a busbar which connects the bottom left connector of the top unit to the top left of the bottom unit. At this point it is combined with the input from the alternator. The combined feed is output via the connector at the top right of the bottom unit.

The busbar connections that link the units are not in red on the diagram, so it's not obvious what they are. That part of the diagram is pretty much straight from the manual - which is all in black & white.

You're right - it's not my diagram. Time I learned to do things like that. It's an impressive piece of work - at least I think it is - if I could do it too I might not be so impressed! :laughing:
 
Sep 23, 2013
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On second thoughts, we are both over complicating things. :(

The shunt is in the negative line, so everything flowing through the circuit is going through it, no matter what the source.
 
Oct 4, 2020
151
182
North West England
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76,535
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Mercedes Cipro 55 CI
Exp
since 2015
Was bored so did a drawing anyway :)

Broken Link Removed
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.

Subscribers  do not see these advertisements

 
Oct 4, 2020
151
182
North West England
Funster No
76,535
MH
Mercedes Cipro 55 CI
Exp
since 2015
Was bored so did a drawing anyway :)

Broken Link Removed
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.
 
Oct 4, 2020
151
182
North West England
Funster No
76,535
MH
Mercedes Cipro 55 CI
Exp
since 2015
just a quick question, can i use another leisure battery to run the fridge when the engine is off ? i think the ehu charges the 120amp lithium leisure battery, and possibly the alternator also charges it when the engine is running, i would like to use another battery just to run the 12v side of the fridge an then possibly recharge it when the engine is running,
 

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