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Old 10-05-2016, 20:55   #1
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Voltage drop?

For the last couple of months, I found a voltage drop between my batteries and my circuit panel. If the batteries read 12.6, the panel may read 12.3 or lower. I've checked every wire I can and all seem nice and tight with no corrosion and all the screws are tight.
I had an electrician come by and after some testing, his claim is that the metal bar that runs down inside the panel that connects all the circuit breakers isn't conducting power as well as it should. It seems to drop in power the farther down the bar you go. It's been fine since I bought the boat 8 years ago and can't imagine what would have caused it (if it is the problem or he's just blowing smoke).
If I check at some of the buss bars it's even lower.
This all started shortly after I install a new chart plotter and updated my electronics merging my NMEA0183 and NMEA2000 into a network that would communicate with the new plotter(a B & G Vulcan 7).
Any suggestions?
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Old 10-05-2016, 21:08   #2
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Re: Voltage drop?

When you refer to the bar inside the panel you mean the metal (probably copper or copper alloy) that the main + cable from the battery connects and has many small screws where wires or breakers attach?

And if you measure the voltage at different points on that same, solid, copper bar you get different readings? Unless the metal itself has degraded due to stray current corrosion or something similar that just doesn't make sense to me at all.

Ignoring this issue for the moment, have you checked the ground side of the circuits? You checked all connections including removing the battery cables and cleaning the terminals and cable connections? What about the groundn side: main ground to the engine block or negative bus bar?

Another test, if all the above check out disconnect the main + and - wires at the panel and battery and check resistance on each end to end. Maybe do the same for that mysterious bar in the panel.
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Old 10-05-2016, 21:24   #3
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Re: Voltage drop?

Quote:
Originally Posted by mestrezat View Post
...This all started shortly after I install a new chart plotter and updated my electronics...
There you go.
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Old 10-05-2016, 23:15   #4
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Re: Voltage drop?

anyone who knows what they are doing could easly find where the drop is happening. and how much over each piece of wire. it will all add up to the total drop.

.3v is under 3% drop and is well within wiring spec for main battery wiring.
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Old 10-05-2016, 23:25   #5
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Re: Voltage drop?

Quote:
Originally Posted by mestrezat View Post
It seems to drop in power the farther down the bar you go. It's been fine since I bought the boat 8 years ago and can't imagine what would have caused it (if it is the problem or he's just blowing smoke).
If I check at some of the buss bars it's even lower.
This all started shortly after I install a new chart plotter and updated my electronics merging my NMEA0183 and NMEA2000 into a network that would communicate with the new plotter(a B & G Vulcan 7).
Any suggestions?
What's the size of this bar? Cross sectional area, is it warm with all the loading on? Sure it's copper?
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