No Engine Battery Charge from Generator

[Huyck, Van]

I have an '05 Montery-C9 Cat, 8kw Onan diesel Generator, and Xantrex RS2000 Inverter/Charger.  When connected to shore power, the inverter charges the engine batteries to about 13.5 Volts.  When dry camping, if I run the generator, the inverter charges the house batteries, but not the engine batteries.  I confirmed this with a plug in volt meter plugged into the cigarette lighter.  I turn off the engine batteries when not running the generator, but ultimately the charge on them gets low from starting the generator.  Even after running the generator for several hours, I get no charge on the engine electrical circuit.  The Inverter is showing "float" on the charge display.  Any idea why the RS2000 won't charge the engine batteries, when it is run on the generator?  Is there any way to fix this?

[Edward Buker]

You should take a look at how your chassis batteries are being charged when on shore power and measure the voltages directly on both the chassis batteries and the house batteries. Repeat that same test with the shore power disconnected and then again with the generator running and see what the voltage levels are. That voltage matrix should tell the story. You should not do these tests without some delay between them to let the battery voltages settle to a non charging state.

The only scenario that I can come up with that would cause a difference in charging, with genereator in operation, is if you had an echo charger and the voltage was raised by the generator alternator high enough to stop the echo charger but did not have enough output to charge the chassis batteries adequately. If that is the case there are other charging systems that are non echo types or systems that will connect and disconnect the chassis and house batteries together when charging is occuring. If you already have a continuous duty solenoid for connecting the house and chassis batteries already installed you could install a non momentary type switch and manually switch the solenoid on while the generator is running and then remember to turn it back off. You could also automate that process with a relay circuit. Hope this helps.

later Ed