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I am working on a step-van that has easily a dozen aftermarket electrical accessories. The electrical system "evolved over the years" and is a total mess, and there's an electrical drain that kills the battery. So I'm trying to redo the aftermarket stuff.

One of the annoyances is a very long positive battery cable down to the starter. Two other lines also go down there - the alternator and the "everything else" line, both with fusible links.

There is a nice location about 15" from the battery where I'd like to put a positive junction post, and bring in the line from the battery, a new, better-routed line to the starter, those two other lines, future aftermarket device connections, and cables running to front and rear bumpers for connectors for jumper cables.

I'm wondering - is this a thing I should be doing? Is it a mistake?

I would also like to have a battery shut-off switch, but I see no reason to switch the heavy starter and alternator lines (GM 3-wire alternator) - I just want to switch the loads. I want to do this with a professional and permanent installation. Is this a mistake? I hear a lot about the importance of putting shut-off switches on the negative battery terminal. Does that apply here, or not? Switching the negative would seem to force me to switch cranking current, and I'm not worried about current leakage from the starting motor.

  • I used one of these on my son's car when I relocated the battery to the trunk. Used this to tie all of the power up front together and for a place to connect the pos battery cable in. Working great so far ... this doesn't answer your whole question, so leaving as a comment. – Pᴀᴜʟsᴛᴇʀ2 Aug 31 '17 at 23:46
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Without knowing how many and how large your loads are I can only suggest a search for "12volt battery multiple output terminal". Select a model that fits your load requirements. As far as switching goes, traditional (old school) Ford starter relays are reliable, can carry high loads and relatively inexpensive. You could mount a bank of these under the hood. The relays require a 12 volt source to activate them. You can make this source either "constant on" from the battery or an "ignition on" source. Either of these could be further controlled by a toggle switch in the cab. You'll want to add some circuit protection (fuse or circuit breaker) to each load.

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You'll need a fuse block and BLUE SEA SYSTEMS is where to look. Crimp connectors ALL MUST BE SOLDERED. Avoid Quick Disconnects, Ring terminals are easier to solder. Use #18 gauge wire for circuits fused at 10 amps or less. Because #16 is hard to find, use 14 and 12 gauge for heaver loads and protect these circuits with circuitbreakers. NEVER use wire made in China. If the fuse blok is mounted under the hood it MUST have a cover to exclude moist air. Document your work and keep it in the glove box.

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You can put an isolation switch on the positive line : make sure it is rated sufficiently (130A should be sufficient for all except the starter). Do think of those things that you may want to still work : clock for example or alarm...

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