Inverter Fuses & Battery Shutoff Switches

[davidbrady]

Hi Mike,

4/0 is a larger diameter than 3/0. Wire gauges sizes from small to large go like: [small] 4, 3, 2, 1, 1/0, 2/0, 3/0, and 4/0 [large]. Something that Vantare did on my bus which I like a great deal is they used large copper bus bars. They take all the positive battery posts and connect them to the positive bus bar using equal length cables, then they do the same with the negative posts going to a negative bus bar with equal length cables. This ensures that all batteries see the same voltage when in the charge mode and the same voltage drop when in inverter mode. This helps to prolong the battery bank life and the wiring is so much cleaner and better organized.

Cutoff switches can be put on the positive post side or the negative or both. There may be some slightly better arguments supporting one side over the other.

[RetDA]

Ron:

Your before pics look like mine as it exists now. I have worried somewhat about mine and the need for upgrading and a cut-off switch, but not enough worry to do something about it especially after 75 K miles or so with no issues. Perhaps I need to move my worries up a notch or so, especially since I plan this fall on replacing my dead and obsolete Heart Inverter.

Thanks for the post and the pics.

[Mike Huggler]

Thank You for the info, I was really wondering whether I could use 3/0 at the panel as it will only be 1 ft from the battery connection on the neg. side. I plan to go to the Fuse then through the HD on/off switch mounted on a plexy back-plain. Short bends eaiser with the 3/0. I believe 3/0 is what the House batteries are wired with on the home runs?? They all seem to go to central busbars as mentioned about 2 ft away. Mr. Brady Are those 4/0 on the Vantaire? How do you like the Prevost vs. Large BB?

[davidbrady]

Hi Mike,

My complete electrical schematics for my bus, Vantare number 4620, can be found on our sister site, Prevost Gurus, over at Library->Converters->Vantare->Coaches->4620->4620 Service Manual.pdf, page 103 shows the battery banks, cutoff switches, bus bars, and inverter wiring.

You can see the wiring for the 12V bank is #2/0 while the wiring for the 24V bank is #2. The wires are short, maybe a couple of feet in length. At a max current draw of 200A per battery for the 12V and 100A per battery for the 24V banks the voltage drops are less than a tenth of a volt or well less than 1%, 0.8% for the 12V and 0.4% for the 24V, (if I did my math correctly). The NEC code specs a drop of no greater than 3% to 5% for a 12VDC/24VDC/120VAC single phase circuit. If you can keep your cables at less than half a dozen feet or so, #3/0 would most likely be fine. I believe my LXi ran #3/0 from the batteries.

The Prevost is quite good. I'm very pleased with the quality of the house and the chassis and the driving experience is markedly ahead. My only problem is it's difficult to keep my credit card in my wallet due to the easy access to service. Although I can do much of the routine service, I get lazy (and busy) and the appeal of letting the highly qualified Prevost Service Centers handle routine chores for me is overwhelming!