GenSet Alternator

jlp0217 · May 8, 2016

Maybe I misunderstand, but it sounds like you're trying to charge full batteries if you genset alternator is able to fool your charger. If your batteries were low enough to accept a reasonable charge rate, the genset alternator would not be able to bring your batteries up to 14.4 volts or whatever you're trying to charge to, and the charger should jump in and do it. Another possible problem is how these charging sources are sensing voltage, and whether the wiring is large enough to not have significant voltage loss. Check your voltage at the battery while trying to charge with whatever source - it should be something around 14.4 volts depending on battery type and charger settings. If low, the check it at the charger and alternator.

Terry Cox · May 8, 2016

Our Onan 8kw Genset 30 amp alternator generates AC and terminates on the same AC power buss as the Genset. Makes sense, so I left it connected. Perhaps you have the same setup. Something to check. Our start battery serves both the Genset and main propulsion engines. Our arrangement, built by Hunter, seems to work well.

Bill Roosa · May 8, 2016

So alternator (boat motor) and alternator (genset AC output) and alternator genset (DC to charge a start battery) are confusing me
Let me see if I have the situation correct;
the only starter battery is pulling duel duty for the boat motor and genset motor
When you fire up the genset it produces AC and that makes the AC powered battery charger turn off??????
I'm thinking you really mean that when you fire up the genset it produces AC (an alternator!!!) to power the battery charger and has its own alternator to produce DC to charge its (not currently installed) starter battery. The DC alternator output from the genset is causing the AC powered battery charger to turn off due to some odd reason.
With that said, just disconnect the genset DC alternator and make sure the field coil and output wires are disconnected. once electrically uttered it will spin just fine without harm. It does make another mechanical thing to break however but I'd not be overly concerned.

Bill Roosa · May 8, 2016

When they started calling a DC producing device an "alternator" they set us all up.
I'd confirm that disconnecting the genset DC alternator actually fixes the problem. Just disconnect the genset DC alternator + 12 volt output (make sure it does not ground while doing this) and try again. Once you are sure that is the problem (should not actually be a problem but ....) I'd find the genset DC alternator field coil and disable it and disconnect the + 12 volt output (again making sure you don't ground the wires)
Good luck

Stu Jackson · May 8, 2016

Bill Roosa said:
Just disconnect the genset DC alternator + 12 volt output (make sure it does not ground while doing this) and try again.

NO, don't do this. NEVER disconnect an alternator output. You'll fry the diodes and kill the alternator.

What you must learn is where the regulator is and disconnect the regulator (which sends the signal to the alternator to provide DC output).

Essentially what Bill suggested, only the second thing he said to do is the first and only thing you need to do.

Your third post (#6) better explained it.

Good luck.

Benny17441 · May 8, 2016

What is the state of charge of the battery bank when you are conducting your test. With batteries up to full charge and a trickle current being produced by the alternator I do not see a problem with the charger not providing any measurable output.

Maine Sail · May 9, 2016

Set up a custom charge profile for genset charging of 14.7V absorb & 14.6V float. This will put the charger voltage .2V above the gen alt. In bulk both will produce full current in absorbtion the charger will now shut down the tiny alt..

JamesG161 · May 9, 2016

Maine Sail said:
This will put the charger voltage .2V above the gen alt.

This begs the question....
Do most standard Alternator's have a "standard" voltage regulator cut off voltage?
Jim...

PS: My Hunter has an engine/genset start battery and of course both have alternators of different Amp size. I assume they don't "fight" each other.

sailcrazy1 · May 9, 2016

We rewired our setup so the Engine alternator provides power to the house bank, and the genset alternator provides power to the isolated start battery(one battery provides start power for both the main eng and the genset. That start battery is also maintained via a 1-way Duo-Charge, which will allow the main house bank to recharge the start battery if the start batt is low. And, as a back-up we have a parallel switch, which will connect the house and start batteries together......but have never had to use it. The system has worked flawlessly now for 6 years of cruising.

Maine Sail · May 10, 2016

GonzoF1 said:
I think I understand it now (thought about it for 2 days now ) ... So there won't really be a "float charge" achieved when running the genset under this profile. A profile I will need to change with the remote (or maybe only on the charger's front panel). I don't think I could run it long enough to get them to a float state anyway after a day at anchor. Or maybe I am misunderstanding it... Still, I am basically just bulk charging it similarly to running the main engine alternators while underway when in this profile.

Please tell me I am right or correct me if I am wrong.

THANKS!

This is correct. When back at the dock you change profiles. You don't want a charger run off a genset dropping to float so its often easiest to trick it into not dropping into float.

Maine Sail · May 11, 2016

GonzoF1 said:
One final question and I will be done:

1) There is a LiFePO4-Lithium profile in the presets. Would that work as an option? It shows 14.6V for High Charge and Float w/Maintenance at 13.2 (Does maintenance charge even matter?)

Ooops... 2 questions, sorry.

No it won't work. It takes a few seconds to set up a custom profile. Ignore the words it is the VOLTAGE that matters..

GenSet Alternator

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SBO Weather and Forecasting Forum Jim & John

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