Generator doing something weird...

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forsythesjohn

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May 25, 2022
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My Onan 5500 onboard generator is surging up and down about 9 amps every few seconds. Up and down and up and down.

I have "fixed" it a couple of times by resetting the battery cables, or by just using one battery at a time, but it only works as a solution until the next time I turn the generator on.

There is a clicking noise in my battery compartment that initiates the surge or the power down. Nothing in the trailer itself is turning on and off, so it seems like it is something having to do with the batteries.

Anyone have any experience with something like this?

I did recently replace two of the batteries that had gone dead, but changing to just one, or two, or just the old battery doesn't seem to help much.

Last bit of information--when it is doing it's surging trick, when I turn off the generator, it also shuts down the control panel and everything in the trailer. It starts right back up again a moment later. When I can get it cycling correctly after playing with the battery cables, it works correctly.
 

DonTom

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Auburn, CA or Reno, NV
My Onan 5500 onboard generator is surging up and down about 9 amps every few seconds.
Welcome!

But how does a genny surge up and down 9 amps? Clarification is needed.

But if you mean the RPMs, I wouldn't worry about it. Don't expect it to sound like a normal engine. It has to stay close to 3600 RPMs and keeps on self-correcting to stay close to there, unlike other engines. If you're close to 60 hz output, I wouldn't worry about it. Besides, if it goes too far off frequency (from 60 hz or 3600 RPMs) , the control board will shut it down anyway.

Every 60 RPMs is 1 hz. So 3600 RPMs is 60 hz. Normal operating range is around 55 to 65 hz. Off much more than that, the genny will shut down. Same thing happens if AC voltage is too high or too low.

If it's working fine, forget about how it sounds.

-Don- Reno, NV
 

Lou Schneider

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Mar 14, 2005
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9 amps is the power draw of a good sized converter running flat out. Does your 12 volt voltage change in relation to the current surges? If so, I'd look for something on the 12 volt side that's drawing lots of current and overloading the converter, making it cycle on and off.

You may have a second bad battery that's drawing lots of current.
 

John From Detroit

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Davison Michigan
I am with Lou. double down with the "Clicking in the battery compartment" (Thermal breaker turning on and off... Test your batteries DISCONNECT to test I suspect a shorted cell or 2.
 

Kirk

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Full-time , Escapee
I have "fixed" it a couple of times by resetting the battery cables, or by just using one battery at a time, but it only works as a solution until the next time I turn the generator on.
Just to add to what has previously been posted, look at what you are telling us and there is a big hint since removing batteries resolves the problem then there must be some connection between the batteries and the surging. Have you tried taking all but the new batteries out of the system to see what happens? And while you are looking at the batteries, make sure that everything is connected properly.
 

Mark_K5LXP

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Albuquerque, NM
It sounds a lot like your converter is working into a fault or overcurrent, and a self resetting breaker is tripping and resetting.

Mark B.
Albuquerque, NM
 

forsythesjohn

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May 25, 2022
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US
This morning I started the generator with the main breaker turned off, then tested each breaker.

When the converter is turned off, everything runs fine.

Does that point to a bad converter, or still bad batteries?
 

forsythesjohn

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I tested two of the batteries yesterday after they had been disconnected for several hours and they were both fine. All cables test fine. Thinking that third battery is new but I haven't checked it while disconnected yet.

I'd love for it to be the battery instead of the converter!
 

Henry J Fate

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I tested two of the batteries yesterday after they had been disconnected for several hours and they were both fine. All cables test fine. Thinking that third battery is new but I haven't checked it while disconnected yet.

I'd love for it to be the battery instead of the converter!
It would seem to be the converter but could be any of the batteries too. I would disconnect batteries and keep checking to eliminate a bad battery. If you have 6 volt series sets, removing in series sets becomes necessary.
 
Last edited:

CharlesinGA

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Oct 6, 2017
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50 miles south of Atlanta, GA
John is most likely correct, the clicking is an auto reset circuit breaker in the 12v system.

NWMTMBLG

This explains the sudden off and fairly shortly, comes back on. These are common in RV's

Charles
 

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