Onan Generator Problems

[Gary RVRoamer]

I agree with Mike - something is overloading the inverter that is pushing the 80+ amps and it shuts itself down. Typically that would mean a shorted cell in one or more of the batteries, but any short in the battery wiring could do it to.

[slabman]

Are you guys of the opinion 80+ amps is too high? When I had the old batteries in there I'd always get from 80-110 amps going into those batts. I don't think this is the real problem, though. I've cut the charge amps down to 40-50 amps and the inverters/chargers still do the same thing with these new batteries.

[hamguy]

Bob, how did you reduce the charge current?

Originally Posted by slabman

Are you guys of the opinion 80+ amps is too high? When I had the old batteries in there I'd always get from 80-110 amps going into those batts. I don't think this is the real problem, though. I've cut the charge amps down to 40-50 amps and the inverters/chargers still do the same thing with these new batteries.

[Gary RVRoamer]

80 amps is a bit high for bulk charge mode on a 4 battery bank - typically a 400 amp-hour battery bank should charge at about 50 amps in the preliminary (bulk) charge phase. Different experts have different numbers, but most say the max charge rate should be between C/10 and C/5, where C is the total amp-hours in the battery bank. 80A would be about C/5. The fact that you say it sailed right up to 80A-90A suggested to me that it was headed beyond that and quickly shut itself down. Had it stabilized at 80A I would have raised an eyebrow but probably not commented on it.

I notice you also say the inverters switch from charging to inverting and back. That seems bizarre. If shore or genset power is present, they should not indicate "inverting". If you see 80A and "inverting", that means to me the Magnum is pulling power from the batteries at a rate of 80A. Comments?

[slabman]

For Hamguy...there is a setting called "percent charge" on the Magnum control panel and I can simply change that setting to around 50% and the charging amperage drops accordingly.

Gary, perhaps I didn't make myself clear. I wouldn't want to check/verify generator function when plugged in....so no, the 80 amps related to CHARGING is current going into the batteries from the generator. I think I also mentioned I have checked this problem using charge input amperages ranging from 20 to the max, which happens to be a bit over 100A. When the coach was new I would regularly find amps over 100 under charge, so I didn't think this was anything too out of the ordinary. The tech people at Travel Supreme said this was fine, although I'm with you...I'd like to keep it at C/5 to C/10.

Bottom line...The point I'm trying to make is it doesn't matter where I set those charging amps from the generator, the inverters/chargers cycle on and off for some reason and I don't know why. It seems the Magnums just don't like something, either input or output and are cycling from charge to invert as a result. To me, this would be consistent to an overload or error condition and this is some kind of self-protective measure built into them. And again, the Magnum guys were convinced this was NOT a Magnum product problem as their products either work or they don't.

[slabman]

I finally got under there and pulled the covers to both Magnums. With shore power off and the gen running, I measured 118.0v and 121.5 V RMS on the respective inverter inputs from the generator. Frequency was 60.5 HZ. Output voltages were essentially the same voltage...maybe a tenth less.

So then I went in and turned off the inverters and found the system to be charging continuously-the inverters not tripping out and the roof A/C's running, other loads applied, etc. But when turning the inverters to "on", they trip on/off, of course. Then I turned off the two 30 amp breakers downstream of the inverters' output and they still cycled on/off....however, for a brief second one of the remote display panels flashed in RED the words "A/C Overload". Again, this was with generator running and no shore power, inverters on and both downstream subpanel breakers (load) off.

So this appears to tell me the generator is OK, the transfer switch is fine, wiring to the inverters is OK, but something perhaps in the Magnums is amiss. If turning off the load downstream from the inverters doesn't help, it would appear downstream wiring is also OK.

Does this shed any light on the situation? I think I need to call Magnum once again and see what they think.
_________________
Bob J. from TX 2007 Travel Supreme Alante 45MS14 2006 Lexus LX 470 Toad Report Post

[RV Wizard]

Your getting warmer!

[slabman]

I finally got to talk to another guy at Magnum who went through settings on my remote display panel. He had me lower the normal settings for "A/C Cutout Voltage" from 100V to 80V. Now under generator power the inverters/chargers run just fine with no cutting in/out. While I'm ecstatic the issue seems to be resolved, I'm a little miffed the first two guys I spoke with DID NOT find anything wrong with those settings I was operating under. I asked him why I should think to operate under such a low figure as 80V. when clearly the generator was putting out about 120V...who woulda thunk it? He said that was just the way it was and sometimes that is what was required to make the inverters perform properly. So be it......

My thanks go out to all on this board who exerted their brain power in trying to resolve this issue-I truly appreciate all the input. It's nice to have so many offering their sincere efforts to resolve issues such as this....

[RV Wizard]

Glad to hear that you have it working Bob. Keep us up dated if anything changes.