Inline fuses, where, how many?

[matt s]

So I nearly burned my truck down today. The alternator wire slipped out of the crimp at the battery and grounded. 6-8 feet of burning wire and one scared owner. Luckily the damage was minor, but no longer will I ignore the lack of fuses and other shotty wiring from the previous owner.

I run a dual battery setup in parallel but will now be adding a manual isolation switch since I am re-wiring things anyway. It should come out similar to this diagram.

In this setup where would you put the in-line fuses? Also I was thinking of running #6 (bigger?) from the alternator so what size fuse on that line?

Thanks in advance.

EDIT: I stole this diagram from another thread, so thanks to who ever created it.

 

[Chazz Layne]

I'm probably a little overparanoid on such things, but I would do your split on the battery using terminals designed for that, then place your fuses as close as physically feasible to the battery. That will give you excellent protection early on for the main lines, and will make for a nice clean install.

I run #4 to the alternator, starter and factory fuse block (distance over wire is about 3 feet). As to what size fuse, you'll need to find out what sort of current draw those items take to see what size fuse you need (and to see if #4 wire is big enough).

I'm also partial to circuit breakers instead of fuses for that kind of current: http://www.powerwerx.com/fuse-holders-fuses/resettable-circuit-breaker-cooper-bussmann.html
They are a little pricey up front, but you don't have to replace them like fuses when they pop, and the convenience of flipping a switch to cut power is worth it.

 

[matt s]

Thanks Chazz, I got it mostly buttoned up today. Inline fuse off the alternator and added a fuse block just off the accessory battery to handle all other stuff and move the fuses close to the power supply.

I did pick up two different battery isolation switches and am "marinating" on just how I want to employ them.

 

[dzzz]

That's the old type of system. If your house battery has similiar charging to the starting battery, this will work better:

 

[AxeAngel]

Nice use of the blueseas ACR unit Don.

Similar to what I have but I use the ML series with remote switch and LEDs to monitor.

For battery connections use MilSpec terminals. I use 2GA wire from alternator to battery, 2Ga for both grounds, 2Ga to main fuse box, 4Ga to rear fuse box(Fridge, Inverter(400W), OBA, Dual cigarette lighter) with a 60A fuse 9" from the accessory battery. Accessory battery powers all aftermarket toys(above mentioned + CB, winch, lights, lasers)
-Sam

 

[failsafefabrication]

Re; Fuses

I cannot recommend the Blue Sea ML relay enough, I went through (read fried) several solenoids before I went to this system and it is safe, redundant (if you get the unit with the manual option; http://bluesea.com/category/2/productline/388 ) and it will keep you happy years down the road. This is a manual charge version so you will need to engage/disengage it, however unlike the automatic version you can use your spare battery bank to jump your starter.
As for fuses; rule of thumb is that if you have a run from a power source-eg your battery you will want to fuse it as close to that source as possible. So a breaker or fuse between the feed going to your house battery and the battery itself; also IMPORTANT: one right at the terminal on the house battery side. As you are creating an isolated line either battery can create a shorted condition and fry the wire. Breakers of good quality will save you many $$ if you ever do blow a fuse as a 200A fuse will run you over $40 for a good quality blade style. Make sure that you use an AWG guide on wire sizing to cross check your wire sizes against your fuse ratings in order to safely protect the conductors. Breakers-marine style that have a manual trip can serve many uses when working on your system because you can use them as a manual disconnect to protect yourself when attaching the house battery (s). Fire is no fun and in a vehicle it can be a total loss, don't feel bad about toasting the wire, just feel happy you were not injured and there was no real fire. Good luck!