Extending battery bank - size of cables

[dulcibella]

At the moment I have a domestic battery bank consisting of two 110 AH 12V batteries (due for replacement) connected in parallel. I wish to increase the size of this bank to 4 X 110 AH. The only practicable site for the two extra batteries will involve a cable run of about 2 metres to the existing site. I guess that it is important to minimise resistance in these connections so that one pair of batteries is not preferentially depleted (or the other pair starved of charge). I am thinking in terms of 25 sq mm cable for these connections - will that be enough to make the resistance insignificant for practical purpose?

 

[prv]

I don't have my volt-drop table to hand to compute cable sizes, but I have a suggestion for the uneven-charge issue. Wire all your batteries up in parallel, but then instead of connecting the positive and negative feeds to the same battery at the end of the row, connect the positive to one bank and the negative to the other (will need extending over to your other compartment). This should even out the load across the two banks.

Pete

 

[pvb]

If it's just domestic use, 25 sq mm would be OK, however for a fiver or so extra I'd fit 35 sq mm. To minimise any imbalance in charging, you should connect the main positive to one end of the bank of 4 and the main negative to the other end of the bank.

 

[[70521]]

I've managed to find a 230 Ah battery, might save you some weight, space, wiring and should work out cheaper than 4 * 110 Ah.

 

[VicS]

I've managed to find a 230 Ah battery, ..........

Can you lift it though or is it a recipe for hernias or slipped discs

 

[prv]

Can you lift it though or is it a recipe for hernias or slipped discs

I manhandled my two 210Ah batteries on board and down the hatch on my own - then in and out of the locker several times!

Pete

 

[dulcibella]

Thanks everybody. Some helpful comments here before thread drift took over.