Electrical Gremlins

Captainscall

Member
Sep 4, 2018
53
Boat Info
1988 300 Sundancer
Engines
350 Mercruisers w/Alpha Drives
Spent my first night on the hook in our new to us 88 300DA with an Onan 4kw gen.

First weird thing is that the battery charger/converter trips it’s breaker every time when using the gen and it really pulls the rpm down on the gen. The weird thing is the charger/converter works fine off shore power.

Second weird thing is the gen ran for about 12 hours then randomly shut down. It would barely crank over like the battery was dead. Started both main engines and the gen started up immediately and ran fine the whole way home with the main engines running. I am guessing I have a bad voltage regulator or blown fuse on the generator.

I just wonder if somehow these 2 issues are related? I wouldn’t be so worried about the gen not charging it’s battery if I was able to charge the batteries using the charger/converter. Any ideas?

Thanks!!
 
check batteries first for voltage and condition ,check ac output from generator when running no load , check charging volts to generator battery with ac converter off and the gen set running ( if you can keep it running with the breaker in ) , check dc voltage from converter to batteries while using shore power as the ac electromotive seat ,what happens to generator when you load it with another appliance ? say water heater or ac system ,does it spool up to greet the load ? check the ac voltage while loading the set with other draws and see what the volts are when and if it spools ,try to eliminate easy things first, plus, you may not have a charge leg to your generator battery form the converter either . You need a good battery for generator ignition and when the voltage is poor the generator may shut down , if the generator is powering the converter and you have a fried battery , the converter may act the way you described . eliminate the potential of a bad battery first check to see if its hot to the touch check the water levels , The converter while utilizing shore ac as the electromotive seat may act differently as it is a more constant ac supply and not vulnerable to the loads on your boat like the generator is , when you try and push current through a faulty pathway (battery) you will overload the electromotive seat in this case the generator. just some thoughts. I have seen multiple things go positively ape due to bad batteries .
 
Thanks for all the ideas!

I have load tested the batteries and they were all good. I will back at the boat Nov 9 and will perform all the other tests. The generator handles large loads like the heat just fine. I just can’t get how the converter/charger seems to draw more load than the heat/Ac. Can’t wait to figure it out though!!
 
Could be a power factor issue - especially if the “converter charger” is an old inductive type and is failing.

As others have suggested, it could be a battery issue (less likely now you had them checked) - if they were really low, that could make the charger pull excess current...

Could also be a random wiring fault when the charger is on, injecting a voltage into something effecting engine speed, or causing a load dragging a voltage down effecting engine speed
 
It is the factory 88 charger.

I am hoping there is a blown fuse on the generator panel that is not allowing it to charge the generator battery.

Then I hope that it’s just an old style converter/charger freaking out the generator.

Those would be the easiest answers. I have a lot to check when I get back to the boat Nov 9.

Thanks!!
 
It’s been a while and I think I may have figured out my problems. I found that the generator was revving way too high and putting out 160 volts!! I am sure the hz were off too but I did not have a way to test that. Dialed it back to within Onan specs. Battery charger works just fine and does not trip breaker. The gen is much quieter and smoother now. After some research I found that the gen only outputs 1amp 12v to charge the cranking battery. The night the gen died I had the blowers running all night and I am sure they draw more than 1 amp. Now that I can run my charger with the gen I hope I am good to go.
 
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