DC Engine Bond point

wynkoop

Member II
At the moment there are 2 wires to the + on each of Silver Maiden's batteries. One is the heavy gauge wire to the battery switch, and the other is the + lead of the bilge pump through an automotive fuse holder. All other power connections are after the battery switch at the + bus bar, which really has very little there. One wire to the original fuse panel which has it's own bus and another wire to the SSB, via an automotive fuse holder.
 

Kenneth K

Sustaining Member
Blogs Author
For those of us who use their engines the starter draws more than the glow plugs. it's 1000 watts (~83 amps) if fully loaded....
As a related project, I'm installing MRBF type fuses atop the batteries. If the stater can draw 85A, then you add + 20A for the glow plugs + 5 for the engine panel + 5 for a couple of lights, I should never see more than 115A total draw.

Seems like a 150A MRBF fuse might be the best protection. Sure, a 1/0 battery cable might be properly "sized" for 200A or more, but why do I want to allow that much current to flow through a shorted wire before blowing the fuse when I know the normal draw should never exceed 115A?

Opinions? Thanks.
 

Tin Kicker

Member III
Sounds totally reasonable. Just because a cable can reach a certain load never means allowing it to do so is a good idea.
:geek:

btw -
After pulling my tank out to clean it was "interesting" to find the red battery cable sleeve chafed through - on the aluminum tank. It's the gray flat spot that the yellow wire runs behind.
 

Kenneth K

Sustaining Member
Blogs Author
After pulling my tank out to clean it was "interesting" to find the red battery cable sleeve chafed through - on the aluminum tank.
Nice catch! I'd say more "shocking" than "interesting!" Some of my battery cables were covered in cheap plastic tubing in that area. It looks cheesy, but I'm guessing it was put there to prevent chafing. I also had some large, pointy, unused screws poking out from the battery compartment towards the fuel tank and the battery cables. It's like Allstate's "mayhem" guy sleeping in that little compartment under the quarterberth.

Do you know what that small yellow wire is for? I have one like that too, but I haven't traced it yet.
 

Tom Metzger

Sustaining Partner
Brown/Yellow Stripe (BY) or Yellow (Y) - see noteBilge BlowersFuse or switch to blowers

NOTE: If yellow is used for DC negative, blower must be brown with yellow stripe.
No charge this time.
 

wynkoop

Member II
I have no idea who installed it. The original pump was not automatic. It was a water puppy sitting under the sink with a hose to the bilge. When it eventually died I replaced with a big RULE down in the bilge.
 

Tin Kicker

Member III
wynkoop - No surprise on the non-OEM wires on a 46 year old boat. In fact it's probably a good thing, which you made better.

Kenneth K - The yellow wire in my photo goes from the alternator to the regulator.
 
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