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Old 10-01-2010, 09:56 PM   #1
Bus Nut
Join Date: Sep 2009
Location: MASS
Posts: 449
Year: 1993
Coachwork: THOMAS
Engine: CAT 3116
Rated Cap: 83
Seperate battery or starting battery for gen

I'm trying to decide if I should use a seperate battery for the 6.5 Onan Genset generator. Or just run cables off of my chassis starting batteries to start the generator?


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Old 10-01-2010, 10:48 PM   #2
Bus Crazy
Join Date: Jan 2008
Location: Upstate NY (Mohawk Valley)
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Re: Seperate battery or starting battery for gen

It probably will come down to mounting concerns and not purely electrical concerns. Is there room for a genset battery? Will the cables to the engine battery be too long? Do the genset controls draw from its battery when on standby? If they do, how will you keep a separate battery charged when there are long pauses between runs?

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Someone said "Making good decisions comes from experience, experience comes from bad decisions." I say there are three kinds of people: those who learn from their mistakes, those who learn from the mistakes of others, and those who never learn.
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Old 10-02-2010, 02:25 PM   #3
Join Date: Sep 2010
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Year: 1993
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Chassis: Ford B600
Engine: 5.9 Cummins/ 5spd
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Re: Seperate battery or starting battery for gen

I've been thinking about this myself. I decided an aux battery just for starting the genset was the way to go, if for some odd reason you run your house/starting batteries to nothing you can still fire the genset which will in turn enable you to charge the house/bud starting batteries.
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Old 10-03-2010, 07:07 PM   #4
Bus Nut
Join Date: Sep 2009
Location: MASS
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Year: 1993
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Engine: CAT 3116
Rated Cap: 83
Re: Seperate battery or starting battery for gen

Smitty, I really didn't want to run it off of the house batteries because those are not designed for quick amperage draw (like the chassis batteries). I do see your point in just getting a seperate battery because it will be cheaper.

The generator charges the battery at 1 1/2 amps. And there is a diode in the gen wiring to prevent rundown of the battery while the gen is not in use.

I definately have plenty of room to mount a seperate battery. But Redbear has a good point. How will the battery stay charged while the genny is not in use? (Which probably won't be too often).

The cons of running off of chassis batteries are..

I have a significant length between genny and chassis batteries. (genny will be midship on passenger side and chassis batteries are rear on driver side).

And if the diode fails in the genny, my chassis batteries could be run down to nothing.
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Old 10-12-2010, 09:24 PM   #5
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Join Date: May 2006
Location: mid Mo.
Posts: 241
Year: 1976
Coachwork: bluebird
Chassis: F33695
Engine: 427 chevy
Rated Cap: 84
Re: Seperate battery or starting battery for gen

I have 4 batteries in my bus: one engine, two house and one gen. I have my house batteries in with my engine battery and I installed a solenoid and switch it from my control panel to charge the house batteries with the alternator when running down the road. In an emergency I can jump the solenoid with a wire to charge the engine battery while running the gen, on shore power or start the engine from my house batteries if need be (the solenoid doesn't work when my key is off or during cranking, you don't want this solenoid work all the time or you will run your engine battery down when you forget to turn the switch off). The gen is a stand alone battery and works quite well all alone. It can sit for months and start right up, nothing to drain it like radio memory, engine computer etc. Worse case scenario is you want the generator to start no matter what, everything else is secondary .I also installed a battery disconnect switch (like race cars and caterpillars use) so when I walk out of the bus I throw it and I know everything is dead and not pulling my house batteries down. We blew up the engine one xmas and the generator is the only thing that kept up from freezing. sportyrick
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