# fitting a second battery



## bubble63 (Sep 30, 2009)

hi 
I need to add a new battery to a CI carioca. circa 2007

The motorhome has a leisure battery fitted in a rack externally, I replaced it with an elecsol 110 ah 18 months ago.

Question, the best space I have is inside ,under the dinette, to fit a second battery.

I am happy how to do the work, [ I think 8O ]

but.... would it be ok to buy another elecsol and have a miss match on battery age, one outside and one inside,

or

buy two new matched batteries , cheaper variety.

what do you think?

thanks in advance

neill


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## bubble63 (Sep 30, 2009)

I am bumping my own item :roll: 

same task, decided to order another elecsol same battery, 18 months older, and fit it in the dinette seat, with a battery box etc etc

read Clives artical about second battery fitting

but , what diameter cable to connect the batts

I have some 40amp/ 6mm copper, would that be OK for 2 meter run? to the other battery with 25 a fuses

thanks 
neill


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## rod_vw (May 10, 2005)

I don't know the layout of your van so I'm simply answering with very basic thoughts.

I would cable the second leisure battery back to the control point with at least 16mm cable (earth similar cross section but as short as possible). Secondly I would fuse it at 80A - 100A or at the same fuse value as the original. Done like this by removing either fuse I can run on either battery alone also I can easily isolate either for removing the battery. It's easy to forget that when batteries are connected in parallel the +ve lead is still live from the second battery when it's removed from the first! Fuses fitted as above can act as isolators. 

Re fuse sizes, in a modern vehicle with a high output alternator it is easy to blow a lower value fuse when charging a well discharged leisure battery. VW fuse the pair in a California with a 100A fuse in each +ve lead!

As for running two batteries of the same type but differing age. I cannot answer but one us may find out because that's exactly what I am running, two 100Ah Elecsols at about 12 months difference in age!

Rod


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## dolcefarniente (Jan 2, 2012)

Difference in battery age is irrelevant. Cable as suggested to link the batteries together but ask for 16mm2 not just 16mm (huge difference) . Depends where fuses are and what they're for. Cables to habitation circuits shouldn't need much above 20 - 25A. If charge is coming direct from alternator 100A if from a smart charger 25A.Hope it helps. Really you just need to install the second battery and then connect plus to plus and neg to neg making sure to route and insulate correctly. No real need for more fuses.


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## rosalan (Aug 24, 2009)

Perhaps, if you do not already have one, a Battery Master from Eddie Van-Bitz would complete the job if you have a Solar Panel. Of course with two large batteries you may consider an Inverter.
Money pit? 
What do you mean?

Alan


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## listerdiesel (Aug 3, 2012)

Battery age IS relevant, the older battery will self-discharge more quickly and will have less capacity.

In terms of connections, the heavier the cable the better, up to 50 sq mm, after that there is no real gain.

Fuse at 80A or 100A for safety.

Peter


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## bubble63 (Sep 30, 2009)

Thanks for all the replies

All I am doing in 'strapping two batteries together' for extra capacity, 220AH vs 110AH, solar panel , battery master etc already in place.

So I will be installing 'jump leads' across two batteries 2m apart, Clive Motts diagram shows 25 amp fuses close to both batteries live terminals, to protect against a short, but it doesnt spec he cable diameter for the 'jumpers'


regds neill


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## listerdiesel (Aug 3, 2012)

Use 25 sq mm or more, 25A fuse is probably OK once they are both up to charge, and as long as you haven't got any high-discharge items such as an inverter on board.

The problem with the smaller fuses is integrating them with the heavy cable.

Peter


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## dolcefarniente (Jan 2, 2012)

16mm square more than adequate for what you're doing. No more fuses needed. 50 mm cable will start a 14 ltr V8 8O


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