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itsjustgher 06-02-2013 03:15 PM

Series / Parallel Battery Jumper Sizing
1 Attachment(s)
First time boat owner here. 1982 Irwin Citation 40 MKII with 2 previous owners worth of headaches.

To start, I want to go through and ensure all cables are sized correctly and properly fused. I have a basic understanding of how to use voltage drop and ampacity tables, read and re-read Nigel Calder, but cant for the life of me grasp how to size the parallel and series jumpers. I have 4 6-volt 225 (20hr) Crown Deep Cycles. Currently sized with #2. I would like to replace, label, have install new properly sized lugs, adhesive heat shrink, etc. So if I should go bigger now is the time, if I should use #2 then I have some crimping tools to purchase.

How do I calculate the maximum amount of amps that will go through the jumpers? If the total bank is going to be 450Ah @12v should these jumpers be 0/4 and sized as high as I can get to 450Amps? Or does this have to do with the maximum load that will be place on the bank, i.e. the starter? Which I understand the recommendation is for a 200Amp fuse. While I understand bigger is better, being cost efficient prudent for this mariner.

I'll attach a photo of the fun I am about to have.


chef2sail 06-02-2013 04:09 PM

Re: Series / Parallel Battery Jumper Sizing
Battery Bank Wiring Diagrams - 6 Volt - 12 Volt - Series and Parallel

I used 2/0 on my battery connections which may be a little overkill. Cables from the HB also depend on distance back although most batteries are close to the source of charging and dc panel. Each boat is different though

Don't forget to fuse within 7 inches of the battery bank

Here is Mainesails advice....I follow his lead


deniseO30 06-02-2013 07:05 PM

Re: Series / Parallel Battery Jumper Sizing
Very short wires and cables carry much much more amperage when they are shorter. Amps and Wire Gauge - 12V Circuit

itsjustgher 06-02-2013 07:31 PM

Re: Series / Parallel Battery Jumper Sizing
1 Attachment(s)
If 0/2 is overkill then thats most likely what I will go with. :) I appreciate the input.

That first link brings up another question for me though. when wiring the batteries, I understand the benefit of positive off one end and negative off the other. But when series/paralleling 6 volt batteries does it matter what "series" of batteries the cables see first? For example (this is visualized in the attached diagram, sorry for the roughness) my current setup has four batteries in a row, two are together in a series and so are the other two. The paralleling cables will both hit the two batteries to the right first. Does this break the "rules"? If so, would having extra negative cable as in (A) be best. Or just have the cable come out on the other side as in (B)?

It helps to know that the panel and all other components are to the left of the batteries. Which is where I would like my positive and negative Busses to end up.

A second question that comes up, regards the placement of an echo charger, AC Battery Charger, and any other electrical components. Is it a horrible idea to mount these in the engine compartment close to the batteries? Not so worried about diesel fumes as much as corrosives from the batteries venting, oil, grease, etc.

Decisions Decisions.

Thank you for any and all input, it helps get the mind going. :)

Stu Jackson 06-04-2013 08:52 PM

Re: Series / Parallel Battery Jumper Sizing
You're not the only one:)

Golf Cart 6V Battery Wiring Golf Cart batts re-positioning & wiring diagrams

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