Lower Voltage when engine is running

pcmpetepcmpete Member Posts: 110 ✭✭
in Engine Discussions
Situation.

Ignition off 
Battery is 13.2volts

Engine off, ignition on:
Battery is 13.0volts
 Vessel View is 13.0volts

Engine Running
Battery is 12.8volts
Vesselview is 12.4volts

even if the alternator is not exited yet, why change is voltage readings while running?

Video 1 - Starboard Battery with Starboard engine Start
Video 2 - Starboard Battery with Port engine start


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Comments

  • LaReaLaRea Member, Moderator Posts: 7,765 mod
    Did you measure the input side of the battery isolator?  You lose 0.5 to 0.7 volts coming across the isolator.  If it's 12.8 volts on the output side, the input side is probably seeing 13.4 volts being produced by the alternator.  
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  • pcmpetepcmpete Member Posts: 110 ✭✭
    alternator side is 14.4v.
    but why the difference between battery and vesselview only when engine is running

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  • YYZRCYYZRC Member Posts: 5,142 ✭✭✭✭✭
    On my VV, one battery reads 14.4 and the other 12.x.  I swapped the starter batteries and the voltage readings didn’t follow. I assume a bad ground somewhere. 
    2008 350 EC on Georgian Bay
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  • LaReaLaRea Member, Moderator Posts: 7,765 mod
    VesselView is showing the voltage seen at the starter motor.  Check for corrosion in the + and - cables from the battery to the engine.  
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