Re: [Amel Yacht Owners] Onan Generator and Starting Battery

eric freedman


As bill mentioned the Generator/engine start battery negative should not be connected to the house bank.

The generator has a floating ground which means as soon as the generator is started the generator is disconnected from the battery, The only thing that is connected to the battery when the generator is running is the Isolated ground Alternator.


Did you check to see where the leads for the Blue Seas volt meter are connected?

If it has its ground hooked to the generator you will get an erroneous reading as it is no longer connected to the battery. What reading do you get when the engine is running?

Make sure that the voltmeter is connected both negative and positive directly to the battery.

I believe this might be your problem.

Fair Winds


Kimberlite Amel Super Maramu #376



From: amelyachtowners@... [mailto:amelyachtowners@...]
Sent: Monday, April 25, 2016 8:51 PM
To: amelyachtowners@...
Subject: Re: [Amel Yacht Owners] Onan Generator and Starting Battery




I think the only person(s) capable of answering your start battery question is the previous owner and/or the person that installed that Bluesea battery monitor because Amel did not. Assuming that it is installed correctly (it sounds like that could require a leap of faith), you probably have a short in the 12vdc alternator on the generator... But that is a wild guess.

And, the starting battery is 12vdc and the house battery system is 24vdc. They should be isolated from each other.

Have you located the shunt on the negative side of the starting battery? Where is it? Take a photo? I think you probably have an installation problem with your monitor.

Bill Rouse
BeBe Amel 53 #387
Sent from my tablet
+1832-380-4970 USA Voice Mail

On Apr 25, 2016 7:12 PM, "ldesalvo@... [amelyachtowners]" <amelyachtowners@...> wrote:


Hello Group

I have a question regarding my 6.5 KW Onan Generator and the voltage
reading of my starting battery when the Generator is running. When my
generator is off and not running the starting battery voltage reading on
my Bluesea system monitor reads 12.8 volts but when I turn the generator
on the voltage reading is only 3.5 volts. Also it appears that when I
turn the glow plugs on prior to starting the generator the grounding
relay is activated and once the generator is started the grounding relay
turns off. Does anyone have an idea why my Bluesea monitor is reading
low starting battery voltage when the generator is running and how to
correct it?

Also should the starting battery negative terminal be connected to the
negative terminal of the house batteries? I do not see a link between
the two at this time.

Thank you for your help in advance.
Jim, S/V Liebling SM #207
Puerto Vallarta, Mexico


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