Proper house battery grounding & fusing

roach711 · 01-10-2012, 10:38 AM

I'm planning on installing two Trojan T-105's (225ah for the pair) as house batteries. I'll add a new positive cable from the chasis batteries to the house batteries with some sort of isolater switch between them. Cable run between battery banks is about 7 feet and alternator output is 130amps. I figure on using 1/0 gage cables to connect the house batteries to give me a bit of headroom.

Can I ground the house batteries directly to the frame near the house bank or will this create ground potential issues? The shorter cable run to the frame would certainly be cheaper.

As far as fusing the batteries goes, I'm thinking that a 200 amp fuse would be greater than the charging amperage and lower than the max ampacity of the batteries and cables. Is this the proper approach?

Also, does it make a difference whether the fuse is on the positive or negative side? I can't think of a reason why it would but what do I know?

lornaschinske · 01-10-2012, 12:56 PM

http://www.amplepower.com/primer/ Download as a PDF and read it if you dare since it comes from "outside" this forum. shockingly enough, it's one of the best "books" on batteries written. You can learn the basics of batteries and how to put together a system. Ample Power is geared more towards deep water boating than anything else. You don't have to buy their products but for everyone of their products is a lower priced and less reliable version. Personally, I go with standard market stuff over theirs because I really won't ever been out in the middle of a deep vast ocean. But great info.

roach711 · 01-10-2012, 01:49 PM

Are we even allowed to look at a boating site??????? They're not like us, you know.

chev49 · 01-10-2012, 02:26 PM

Just make your bus into a boat like they did on "Top Gear" UK version... 264 direct tv channel..

positive side always fused... normal battery isolator should work fine..

the boat site is a good one...

bus-bro · 01-10-2012, 06:52 PM

Quote:

Originally Posted by roach711

Can I ground the house batteries directly to the frame near the house bank or will this create ground potential issues? The shorter cable run to the frame would certainly be cheaper.

As far as fusing the batteries goes, I'm thinking that a 200 amp fuse would be greater than the charging amperage and lower than the max ampacity of the batteries and cables. Is this the proper approach?

Also, does it make a difference whether the fuse is on the positive or negative side? I can't think of a reason why it would but what do I know?

All great questions. I'm at the same stage.

I would think a single point for ground is the preferred. I'd size the amps per applicable NEC table. It's traditional to fuse the positive.

Check out this fuse block, it bolts on the battery terminal, uses the pictured fuse (a seperate item): http://www.westmarine.com/webapp/wcs/st ... &langId=-1

roach711 · 01-11-2012, 11:09 AM

I like that fuse block. It will save building another short (and expensive) battery cable.

Since my bus has a fiberglass body I'll be running all my device ground wires back to a bus bar in the electrical closet. That makes the house bank frame ground useful for alternator charging only. The only issue I can visualize is that the different ground potential might cause the two battery banks to charge differently since they'll both be fed from the same positive from the alternator.

Is this just my imagination or a real issue?

icnivad · 01-11-2012, 12:26 PM

Generally you fuse the positive, because the ground is more likely to short out somewhere, thus bypassing the fuse. For example, notice how most cars have a rubber cover over the positive battery terminal, but not the ground. If the ground shorts out, it's no big deal. Also, lots of devices (like my inverter) have their cases grounded, which would bypass a ground fuse.

I've grounded my deep cycle batteries to the chassis for years. In theory, I think it's better to run a cable, but I couldn't justify the cost and haven't had any problems.

roach711 · 01-11-2012, 02:21 PM

Thanx for the explanation. Makes sense now.

chev49 · 01-11-2012, 04:37 PM

Cables are only expensive if you buy new ones.. Old commercial welding cables (50') are what I have used since around 1966..first used them on street rods for the battery in the trunk, and always for the long runs in the 4 ones i have done, and the one im working on now. They are great for battery connections, but you gotta buy new ends at the electrical supply house and solder them in.

roach711 · 01-12-2012, 09:55 AM

Yeah, the cost of custom built cables is STUNNING.

I'll be building my own cables so I've been watching ebay for welding cable and also looked at waytekwire.com. Waytek has everything I need at one place. Unless I get lucky on ebay in the next week or so I'll buy it all from Waytek.

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