The battery interconnect length only matters IF there are more than two jars. When there are an odd number of batteries only method #3 will balance them and cable lengths should all be identical.
You should go with the best practise and connect all loads to just one positive post.
http://www.smartgauge.co.uk/batt_con.htmlbrulaz wrote:
The general rule is that when wiring two 12V battery banks in parallel, you take the pos lead off one bank and the neg off the other.
But what if the battery interconnect cabling is much heavier (and shorter) than external leads?
Does it matter as much then?
In particular, my parallel 12V banks are interconnected with 8-12" of #1 cable, and I want to attach a #10-12 lead from my electric jack. One bank already has a neg lead to frame. I'm thinking that in this case it doesn't really matter which bank I connect the pos lead from the jack to.