Dual Battery Q's/ VSR

[Cutty Sark]

Ok Got the battery switch with VSR for Christmas and I am ready to install. I am dizzy from reading Nigel Calders book and would appreciate some help. First off let me say at this point Im not adding any other electrical components or loads, I am just adding a second battery to handle house loads and my loads are fairly small: vhf, downriggers, gps wallas etc...First question is Cable sizing, is 4 AWG large enough to use from battery to battery switch or do I need to go all the way to 2 Awg. Second question: right now the positive to the DC panel in the cabin comes through a thermal circuit breaker and into the cabin. There are a couple items wired directly to the battery terminals( downriggers/wallas/ 2 bilge pumps). Now I want to add a positive buss along with the negative that I am already doing to clean up the terminals a bit. So should I (a) run the positve through the thermal breaker then to the positive buss and branch all electonics from there, (b) run the positive to the postive buss then to the thermal circuit breaker or (c) run two seperate positives, one to the thermal cicuit breaker one to the positive buss? Does this make sense? I guess my question really is that some items want to be wired direct to the battery, namely the downriggers , bilge pumps and the wallas. So should I make an always hot buss since these have their own fuses or should they be behind the thermal circuit breaker for the house too? And if it's always hot should I run the buss straight from the battery or is it ok to have it just upcircuit from the thermal circuit breaker. And lastly in the diagram from blue sea it has an optional fuse from the house battery to the swtch, does anyone use this setup?

See diagram here

http://www.c-brats.com/modules.php?set_albumName=album534&id=wiring_diagram&op=modload&name=gallery&file=index&include=view_photo.php

[Rock'nMyShoe]

Try these concepts to help with your wiring decisions:

Fusing (circuit breaker, thermal breaker, glass fuse, ATC fuse etc.) protects wiring first and the device second. Place the fuses as close to the battery or power source as possible. Any wiring before the fuse is subject to meltdown. Route, secure and protect unfused wiring with extreme care.

If using 2 or 4 gauge to positive bus bar, consider fusing the heavy wire near the battery (or battery selector switch) if the run to the bus is long, hard to protect or out of sight. This heavy supply wire will require a large fuse (say 60 to 100 amp, depending on the total load possible at the bus bar).

Once at the bus bar, consider placing smaller fuses, sized for the size of wire leading to the device, right at the bus bar. This way the wire to device is protected by say a 15 amp fuse for 14 gauge wire. The big fuse by the battery (that 60 to 100 amp) will not protect 14 gauge wire from meltdown. Note also, the fuse in the device only protects the device, not the wire leading to it. A side note, negative wiring needs to match the size of the positive wire of the same circuit.

PS The West Marine catalog has nice wire size chart for selecting wire for different amp draws over short or long distances. It has helped me many times. You may find a 6 or 8 gauge wire is quite OK to power the bus bar if your loads off the bar total no more than 40 or 50 amps. Remember when sizing wire versus amps versus length of run, to include the length of the negative wire as well.

[Pat Anderson]

Oh, yeah...I am just the guy to ask! Want me to come over and help? Maybe I can blow up your batteries too!

[Cutty Sark]

[dotnmarty]

Hey Sark- Nice job pluggin' up the holes. Thanks for posting the pictures
here
http://www.c-brats.com/modules.php?set_albumName=album534&op=modload&name=gallery&file=index&include=view_album.php

That's enough for one day! Happy New Year