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Al_The_Pal

Member Since: 09 Feb 2015
Location: Near the bottom on the right
Posts: 146

2015 Defender 110 Puma 2.2 XS CSW Corris Grey

Connecting external leisure battery pack

I’ve got a greenbox leisure battery box, I’d like to charge this while traveling, the greenbox already has a Car Go split charge relay in it.

I’m aiming to connect via Anderson SB 50s, with one plug permanently fitted to the car.

Question is, what cable should I run from the car battery to my Anderson connector, and what fusing should I go for.

What sort of amps am I needing to deal with between the car battery and the Split charge relay.

Click image to enlarge

6th Apr 2019 2:03pm

DSC-off

Member Since: 16 Oct 2014
Location: North East
Posts: 1350

2015 Defender 110 Puma 2.2 XS CSW Aintree Green

Hi Al, I've been following this, hoping you get an answer, because I've been wanting to do the same.
I figured the connection between the 2 batteries should be able to handle the full output of the alternator, should it ever have cause to put it all to the leisure battery.
Something else in the back of my mind said caravan type split charge systems wouldn't handle the full alternator power, so maybe it's not necessary?
I've not found a definite answer and haven't tried anything yet.

Sorry, I've not helped answer the question. Hope someone can enlighten us both.
Cheers!

11th Apr 2019 7:51pm

Al_The_Pal

Member Since: 09 Feb 2015
Location: Near the bottom on the right
Posts: 146

Just bought a solar panel to keep it topped up on site until I work out what’s needed.

I’ve had a recommendation to a local auto electrician... so hopefully he’ll work it out for us.

11th Apr 2019 8:12pm

leeds

Member Since: 28 Dec 2009
Location: West Yorkshire
Posts: 8578

If you are thinking of having an Anderson connector permanent on your Defender I would suggest a SB175 which is rated at continuous 175 amps. That would need 35mm2 cable feeding the SB175. That would mean you could plug jump leads into the SB 175.

Now heavy duty cable you would be looking at about 7 amps/mm2

Max output from a standard alternator is about 100 amps. So assume 50% of that maximum is available for charging the extra battery so that would be about 50 amps

Now fast battery chargers can charge a battery at about 40 amps

Yes am working on high current figures.

This would mean at least 6mm2 cable

Now SB 50 are rated at 50 amp continuous

SB50 are available with either 6mm2 or 13mm2 contacts

Hope that all makes sense, but I do tend to work with good safety factors

Standard chargers work on about 2-7 amps so about 2mm2 cable.

You can do a convertor from SB 175 to a SB 50

HTH and makes sense

Brendan

11th Apr 2019 8:50pm

DSC-off

Member Since: 16 Oct 2014
Location: North East
Posts: 1350

Thanks Brendan. Will look into those wire sizes.
Cheers.

13th Apr 2019 5:54am

Al_The_Pal

Member Since: 09 Feb 2015
Location: Near the bottom on the right
Posts: 146

Done. SB175 to SB50 with 16mm cable, probably overkill but found genuine Anderson terminals for that size so seemed appropriate.

Click image to enlarge

8th May 2019 5:38pm

Scoobeenut

Member Since: 04 Mar 2015
Location: West London
Posts: 310

2010 Defender 90 Puma 2.4 SW Santorini Black

Al_The_Pal would be very interested to see some pictures of your finished install as I am thinking of going down this route myself.

24th May 2019 8:12am

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