Onan GenSet: 16V to Batteries


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Old 12-22-16, 10:06 PM
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Onan GenSet: 16V to Batteries

I have a 7.5KW Onan liquid-cooled diesel generator in my service truck. When it's running, there's anything from 14-16V coming off my truck's batteries. The less load the higher the voltage. Is this going to damage anything? If so I'm probably just going to disconnect the alternator. I don't want to ruin 4 6 month old batteries.
 
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Old 12-23-16, 03:08 AM
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It would be borderline. Why do you have it connected to the truck in the first place? If it is for starting, I would isolate a battery just for that purpose and not have it conjoined to the truck.
 
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Old 12-23-16, 09:56 AM
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While vehicle batteries are commonly called 12 volt, the system and charging voltages are higher.
 
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Old 01-02-17, 08:41 PM
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Thanks for your replies, sorry I'm taking so long to respond.

It would be borderline. Why do you have it connected to the truck in the first place? If it is for starting, I would isolate a battery just for that purpose and not have it conjoined to the truck.
I have it connected to the truck so I wouldn't have to buy 2 more batteries, and lose more compartment space. It was really easy to run another 2/0 from the battery isolator switch to the generator.

While vehicle batteries are commonly called 12 volt, the system and charging voltages are higher.
But 16V? Ive never seen a battery charger get above 14.5-15V.
 
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Old 01-02-17, 08:51 PM
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If there's a battery charge regulator.... maybe it's shot.
 
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Old 01-02-17, 08:56 PM
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If there's a battery charge regulator.... maybe it's shot.
Where would this be located? The alternator is like a mini automotive alternator.
 
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Old 01-02-17, 09:01 PM
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If it's only a single heavy wire or a single heavy wire and one smaller wire it could be an internally regulated alternator.

Do you have a model number for that unit ?
 
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Old 01-02-17, 09:20 PM
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Here's the data plate. I didn't get any service manuals when I got the unit, it came off a 1997 Pierce fire truck.Name:  14159939_1119063748172855_1102747085_n.jpg
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Size:  27.1 KB
 
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Old 01-02-17, 09:39 PM
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There is currently a video on you tube of that genny from another fire department.

Shows a regulator for 12vdc. part # 185-2252.

Name:  regulator.jpg
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Some good manuals....
onan 7.5 dkdfj parts manual_pdf
 
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Old 01-02-17, 11:06 PM
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There is currently a video on you tube of that genny from another fire department.

Shows a regulator for 12vdc. part # 185-2252.

Attachment 75203
Thanks! I'll check that out, if I'm lucky something just vibrated loose.
 
 

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