Voltage drop...

[oldmako69]

12.64 and 12.62 read directly from the batts.

12 feet away where the battery cables join the YAM engine cables I'm reading 12.5 or so. IOW a loss of about .10-.15 at the connection.

Reasonable or reason for concern?

[Jason2tpa]

You've only given us 1 of the 2 required variables for determining acceptable resistance with a known length and gauge of copper wire.

Follow the web address below. Plug in the 2 variables and the calculator will spit out the resistance.

https://www.cirris.com/learning-cent...lculator-table

[panasonic]

And what condition the cables are in. Are they new or old with possibly some corrosion inside them.

[oldmako69]

2AWG. They are 12 years old. The battery ends are nearly perfect, clean as a whistle. Reasonable quality lugs and heat shrink. The two feet that I can see are like "new". The tag ends are also clean. Are they perfect? Probably not.

The boat was stored indoors, in a huge garage. The cables run inside a PVC pipe embedded under the ****pit sole.

I just installed two new DC group 31's, and two new Perko Batt switches. (1/2/BOTH/OFF). I am slowly rebuilding this %$#@*%!!! boat and in spite of judicious application of valuable green rectangles, I still have issues.

[fairdeal]

IOW a loss of about .10-.15 at the connection.

Reasonable or reason for concern?

I'm guessing that's a reading with no load?

What you really need to measure is the drop under load -

as Jason has posted, voltage drop is a function of current - the higher the current flow, the greater the drop

So when you are cranking - say, ~200 amps - that's when it matters most.

Here's another calculator:

Voltage Drop Calculator

Plugging in 12 feet (1 way) of 2 AWG, at 200 amp load you expect - best case -
a drop of 0.77 volts just for that section of conductor.

Corrosion & connections could drop it further.

[panasonic]

Like Mr Fair deal says the proof is in the pudding....do a voltage drop check when cranking that will help you determine the internal health of your cables.

Just like a stress test on your heart...same principle.

[oldmako69]

Many thanks for the info gents.

I either need to whip up a set of alligator clipped 10' leads for my VM or wire in a remote cranker at the eng. Or, find a comely lass with time to kill who enjoys standing around in her bikini nursing a ****tail. She can either take the readings or turn the key, her choice. Will get busy.



*** I've probably put 50-75 hours on these engines without a single fuel (starvation) problem.

[pstephens46]

I had to make a set of extended leads for the same purpose.

I searched high and low and can't find a link for the clips Fairdeal uses.....

They are larger and look easier to work with than my little silver alligator clips.

Maybe he will see this and I can save the link somewhere else on my computer.....

[dray0151]

Many thanks for the info gents.

I either need to whip up a set of alligator clipped 10' leads for my VM or wire in a remote cranker at the eng. Or, find a comely lass with time to kill who enjoys standing around in her bikini nursing a ****tail. She can either take the readings or turn the key, her choice. Will get busy.

how did you get a picture of my wife>>>>

[pstephens46]

how did you get a picture of my wife>>>>

Maybe you can buy her some better boating attire. Looks like she went shopping at JC Penny's in 1978.

[oldmako69]

Those clothes will look just fine once on the sole of the boat.