Acceptable DC Voltage Drop?

Northeaster · 03-07-2009, 10:03

Hi Folks,

Just hooked the new 18" raydome up t omy Raymarine C80 display, and it is working fine.
However, I noticed that I had let's say 12.60 volts at my DC panel (using a meter accross the back posts of the old broken old analog battery gauge), whereas I only measured about 12.00 a few feet away at the connection block, where the Raymarine power is attached.

As I thought this drop seemed excessive, I temporairly connected in a larger (12Ga) wire from the DC panel, to the Raymarine power connection point only, and still had ablou the same drop.

Questions:

1. Is this normal, or easily explained?
2. Is the fact that I am metering voltage at the DC panel, with little of no amperage draw on it, giving me the higher reading, whereas a few feet away I am measuring with the power to the unit turned on?

The feed to the DC panel (from the battery switch) is original, and perhaps undersized, but since I didn't have any other circuits on at the panel, I would not think this would be an issue. I could see if I was running the cabin lights, water or bilge pump, etc at the same time, all over a possibly undersized feed!

Thoughts?

donradcliffe · 03-07-2009, 12:25

Try putting the meter between the positive on the panel to the positive on the back of the unit or connection block when the unit is on. Also measure between the negative on the panel and the negative at the unit. Somewhere you are losing 600mv, and it could be on the ground side.

Northeaster · 06-07-2009, 05:04

Don - Thanks for the advice. I forgot my meter, when I went to the boat this weekend. Will do more tests next time.

03-07-2009, 10:03	#1
Northeaster Registered User Join Date: Jan 2008 Location: Nova Scotia, Canada Boat: Seafarer 30 Impetuous Posts: 276	Acceptable DC Voltage Drop? Hi Folks, Just hooked the new 18" raydome up t omy Raymarine C80 display, and it is working fine. However, I noticed that I had let's say 12.60 volts at my DC panel (using a meter accross the back posts of the old broken old analog battery gauge), whereas I only measured about 12.00 a few feet away at the connection block, where the Raymarine power is attached. As I thought this drop seemed excessive, I temporairly connected in a larger (12Ga) wire from the DC panel, to the Raymarine power connection point only, and still had ablou the same drop. Questions: 1. Is this normal, or easily explained? 2. Is the fact that I am metering voltage at the DC panel, with little of no amperage draw on it, giving me the higher reading, whereas a few feet away I am measuring with the power to the unit turned on? The feed to the DC panel (from the battery switch) is original, and perhaps undersized, but since I didn't have any other circuits on at the panel, I would not think this would be an issue. I could see if I was running the cabin lights, water or bilge pump, etc at the same time, all over a possibly undersized feed! Thoughts?

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03-07-2009, 12:25	#2
donradcliffe Registered User Join Date: Mar 2007 Location: Santa Cruz for summer Boat: Beneteau First 456 Posts: 648	Try putting the meter between the positive on the panel to the positive on the back of the unit or connection block when the unit is on. Also measure between the negative on the panel and the negative at the unit. Somewhere you are losing 600mv, and it could be on the ground side.

06-07-2009, 05:04	#3
Northeaster Registered User Join Date: Jan 2008 Location: Nova Scotia, Canada Boat: Seafarer 30 Impetuous Posts: 276	Don - Thanks for the advice. I forgot my meter, when I went to the boat this weekend. Will do more tests next time.