Good Sam Club Open Roads Forum: Travel Trailers: Onan Generator Question
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 > Onan Generator Question

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McGrew

Anderson

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Posted: 09/29/19 12:41pm Link  |  Quote  |  Print  |  Notify Moderator

Hello folks, new guy here. I searched the web for an answer to mu question, and came up with little valuable info. I hope I put this in the right category, as this question is generic, but the generator in question did come from a travel trailer.

I recently acquired an Onan CMM 7000 generator. It has low hours, and runs great! I converted it to be back up power to my house bu building a Cart for to and adding a rack for the battery and fuel tank. My question is in regard to charging the battery that starts it. I have read there are different versions that have this circuit, and some do not. When I start the generator and monitor battery voltage, the battery voltage drops when the starter is engaged, I know this is normal, but the voltage seems to rise very slowly after running for a few minutes. I have not run it long enough to see if the battery fully recovers.
The model number is 7HGJAE-2132A. Can anyone tell me if this unit is supposed to charge the battery? Thank you!

enblethen

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Posted: 09/29/19 01:00pm Link  |  Quote  |  Print  |  Notify Moderator

The 12 volt battery charge rate is very low on most RV gensets. They rely more on the converter or inverter charge to replenish the battery.
I would use a standard battery charge to get the battery up and then for normal operating connect a battery maintainer from a house circuit.


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McGrew

Anderson

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Posted: 09/29/19 05:11pm Link  |  Quote  |  Print  |  Notify Moderator

Thank you for the reply! My plan is to keep a trickle charger on the battery until the generator is needed. This generator is around 17 years old, and I have not been able to find any documentation on this exact model number. Cummins Onan sells a generator that looks identical under the same part number, but is is now called a QG 7000. The spec sheet on this generator says it has a 5 amp supply for charging the battery. I believe if the unit I have had a 5 amp supply, the battery voltage would rise much quicker... I am still hoping someone can confirm this unit does or does not have a circuit to charge the battery. I don’t want to keep trying to fix a problem that does not exist! Thanks again!

STBRetired

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Posted: 09/29/19 05:33pm Link  |  Quote  |  Print  |  Notify Moderator

According to the Onan spec sheet, it does have a 5A battery charging circuit. Don't forget that it also draws power to run the control circuitry and ignition, so net output to battery is only a couple amps. I would add an external charger to get the battery back up to full charge and keep it there. Nothing big, maybe a 10A charger.


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McGrew

Anderson

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Posted: 09/29/19 08:50pm Link  |  Quote  |  Print  |  Notify Moderator

Thank you! The battery I am using is a new group 78. It has plenty of amperage to start the generator and run the ignition and control circuits. I just wanted to be sure I was not missing a blown fuse or other problem. It sounds like all is working as it should. Thank you for confirming my suspicions!

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