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Onan Generator Question

McGrew
Explorer
Explorer
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!
4 REPLIES 4

McGrew
Explorer
Explorer
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!

STBRetired
Explorer
Explorer
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
Explorer
Explorer
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!

enblethen
Nomad
Nomad
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.

Bud
USAF Retired
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