Battery Inter-Connect

[nitpik]

When connecting a number of 6-volt batteries to form a larger house bank, is it OK to use a slightly smaller gauge wire to join the pos. and neg. terminals of two batteries connected in series?
Details:
6 Lifeline GC-4CT's, set up as three series pairs, then paralleled, to give a 660 Ah house bank.
- 30 foot return trip from batteries to DC main panel, and projected load of 70 amps to a max of 150 amps, suggests 2/0 main battery cables.

Am I wrong to think that the inter-connecting cables within the house battery would be "sharing" the load, both during charge and discharge, and so could safely be AWG #1, or 1/0 cable?
Not a big deal, but it would make wiring a little easier.

[ExRonin]

Nitpick
Because of both the distance (I assume the 6V batteries are in close proximity and these are short connections) and due to the way current flows) the interconnect can be a smaller gauge. A good rule of thumb is 1 gauge smaller than your main bus wires. Understand this is only for the series connections. The parallel connections need to be the same gauge as you main bus. Hope is helps.

[sailing_jack]

I understand the logic, but I wouldn't do it. the conductor has to be able to carry the full load. As a rule, conductor size should only ever be reduced if there is a fuse protecting the smaller wire.

[sailing_jack]

exronin is right about the series connectors. that is a separate conductor.

[ExRonin]

Thanks Sailing Jack, you saved me the trouble of a reply detailing current flow in series and parallel connected batteries. <flowers>

[nitpik]

Thanks guys - I thought that was the case regarding the currents flowing in the series connections, but it is always a good idea to bounce it off other sailors.
Just thought of a possible exception - future 1500W windlass installation, wired to one end of the six-battery bank. The large current draw will be coming off the "top" of all the batteries. Will the full current then be passing through those series connections?

[ExRonin]

Quick crude drawing. Your windlass is "just another load" and should be connected (through a breaker) to the positive and negative busses, not direct to the batteries. Note that the path of the parallel connection is important.

[gmau]

Lots of good info and good reading on connecting battery banks at SmartGauge Electronics - Interconnecting multiple batteries to form one larger bank

Gordon