Batteries in parallel

[BobA]

Could any of the forum experts advise me if it feasible to connect two 110 ah batteries in parallel but located approx 6feet apart. I also need to know what size cable would be needed to accomplish this without any loss of power.
Thanks in advance
Bob

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[discovery2]

Yes it is feasible - a third battery was wired like this on my boat, and I would use the same size (thickness) cable as that already used for the starter motor.

David

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[snowleopard]

the cable needs to be able to cope with the largest load that could be put on the system. if you are using them for cranking then it's starter cable, otherwise go with the same size as is currently used to connect the battery to the load.

would advise against parallelling an old battery with a new on, they should be the same type and similar age. having got that condition, parallel batteries will give a longer life than two operated alternately.

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[cliff]

Another little tip FWIW, Take the positive feed form the battery that does not have the return lead.

er, I mean, neg feed to neg on battery 1 and pos feed to pos on battery 2

 

[Trevor_swfyc]

Would it be worth considering fitting a split charge diode a 1 in 2 out is only £25 for one rated at 70A see PBO Sailboats.co.uk advert. This will stop the weaker battery drawing down from the stronger if my understanding is correct.

Trevor.

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[Mudhook]

I think the cable to specify is 25mm2 (2 as in squared). That's big enough for most starters; a smaller cable will suffice if you are just feeding the distribution board and don't have bow thrusters, anchor winches, etc, fitted. But remember that voltage drop, which we try to keep within low limits, is a function of total circuit length as well as cable size. Within reason, you can't have cables that are too big (just too expensive!), but too small is a no-no.

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[Mudhook]

I think the cable to specify is 25mm2 (2 as in squared). That's big enough for most starters; a smaller cable will suffice if you are just feeding the distribution board and don't have bow thrusters, anchor winches, etc, fitted. But remember that voltage drop, which we try to keep within low limits, is a function of total circuit length as well as cable size. Within reason, you can't have cables that are too big (just too expensive!), but too small is a no-no.

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[LeonF]

Please could you elaborate ? This was suggested by someone on the Merlin stand at the boatshow but two electrics experts at my sailing club
said it wasn't neccessary.

<hr width=100% size=1>L.A.R.Ferguson