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Compass Marine How To | all galleries >> Welcome To >> Alternators & Voltage Sensing - Why It's Important > Volt Sense Blunder - FAIL !!!!!
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Volt Sense Blunder - FAIL !!!!!

"Roh-roh Raggy we rav rah roblem." Scooby does not like this at all, and he's right... Follow the orange line and try to figure out where we've made a mistake?

#1 The regulator is sensing voltage at the HOUSE bank and waiting to see a change.

#2 The alternator is feeding directly to the START battery but the voltage being sensed by the regulator is not budging, on the house bank, and why would it?

#3 In this scenario the regulator remains in FULL FIELD (full output mode) driving the voltage of bank 2 through the roof! We have an alternator being told to stay in bulk charging and a START battery that was nearly full to begin with. The result is the bank 2 voltage rising uncontrolled and frying the battery...

I have seen far too many batteries destroyed by this blunder over the years and the manuals apparently do not make this clear enough, for all installers.

other sizes: small medium original auto
Mark Hayward 08-Jun-2015 00:39
I have an yanmar 3ym30 with electromaax 120 amp alternator and a balmar 614. The house bank is 2 6 volt batteries 232 amp hrs.I am getting higher momentary increases in voltage when I startup the engine. The regulator seems to be hunting for a proper voltage. You can hear the alternator putting load on the engine and on the voltage meter I can see a momentary rise to at the extreme to 15.5 volts. Then the regulator drops the voltage to 13.9 volts. On my Victron Battery monitor the alternator is displaying approx 60amps output.
Re the wiring. I have the Balmar 614 grounded to the alternator case. The battery sense wire is attached to the house battery positive(Recommended by Electormaxx). Originally I had it wired to the common at the switch. Battery 2 to start then I would switch to both. After shut down my procedure is to switch to 1 or my house bank. Because they requested I connect the sense wire directly to the house bank I now can only start the engine with the switch on both so that the starting battery remains charged.
Do you have any idea what might me causing the momentary voltage fluctuations. Is it a result of sense wire being in the wrong place. Or perhaps because I grounded the regulator to the Alternator case. Btw after the alternator has run a bit a high output to replenish the batteries the voltage no longer spikes.
Thanks for any suggestions you might help my situation.