Ground (battery to engine) wire crimp failure/meltdown

[renzoreba]

This was a very close call.... We experienced ground wire meltdown coming back from our trip over the weekend. We had been out sailing for 4 days.

Some background info:

Engine is a Honda BF50.
Meltdown occurred on original wiring job (1997 or so).
Recently replaced a faulty regulator/rectifier.
Batteries are 2 Optimas D31M

Last couple of times or so that we went out I noticed I had to hold ignition contact for about 4 seconds before the starter motor would turn the engine, as opposed to the immediate turn of the engine it should normally give with a fully charged battery. I attributed this to a probable faulty starter engine.

Next failure was the engine lift, right at meltdown it would raise up very, very slowly. The tilt switch at the throttle began making a hissing sound when I would press it, and I knew immediately I was dealing with a short. When I went below deck to inspect (I thought at first the problem was inside the console), I noticed a faint burnt rubber smell. I traced the smell all the way to a panel in the aft berth alongside what would be the inside of the transom, were some very thick engine wires run through. I immediately unscrewed such panel, and I found this:



Immediately shut down the engine and disconnected the battery terminals. Glad I had my TowBoatUS membership current

Turns out it is the negative wire that runs from the batteries to the engine. Meltdown occurred at the crimp site. So now in hindsight I am guessing that the starter failed because it wasn't getting enough current due to a faulty crimp. Same for engine tilt.

This is a pic of the positive engine wire, which did not burn. It is the black wire that runs horizontally throughout the middle of the pic. To the right is the negative wire which I cut to remove the damaged segment:



The inside diameter (only the copper threads) of both the positive and negative cables that run from the battery up to this point is about 11 mm (cable says 2 gauge UL). They are crimped to a thinner cable with an inside diameter of about 6 mm (sorry I have no wire gauge and cable does not indicate gauge at that point). This cables run parallel to the engine to the starter and starter solenoid I believe.

I recently replaced a faulty regulator and this was our first trip out after this. I am trying to figure out whether this failure was caused solely by a crimp job gone bad, or maybe something else??

I am assuming that it is not a good idea to crimp a thicker gauge cable to one that is roughly half its diameter, as this would create resistance, especially in applications were higher than usual amp draws are required. Wouldn't it be better to just run 4 AWG cables from the battery to the engine? Why bother crimping them down halfway?

This is also 1997 wiring running from the battery to the engine, very likely not intended for an AGM battery output and in need of upgrade.

My knowledge of electricity is very basic, so please excuse me if I cannot follow very technical explanations. Thanks for any input and suggestions!

[raycarlson]

sounds like original owner did a shoddy repair. a new motor usually comes with a set of 10-12 foot battery power cables with no splices anywhere in their length.Just a splice if done properly would not create enough resistance to create that much heat to melt wire,but add 10-15 years of oxidation and salt corrosion and that would surely do the trick as you have found out. Don't skimp run new cable from motor all the way to battery or fuse with zero splices this time.

[RobertB]

I noticed on my a splice in the cables running to the engine in the aft berth area - not waterproof and occasionally sitting in water. I can see these failing the same way someday. I promptly sealed the splices. Lets hear if for MAC Factory sales!

[renzoreba]

Still waiting for the electrician to come by and give his assessment... Still bothered by the fact that I put great care in rewiring all wires from battery to comfort devices (new LED's, refrigerator, new stereo, fans, spotlight, etc) using only tinned wires and waterproof, heat shrinking crimps. However, I somehow neglected the most important wiring, the one that goes from the batteries to the engines, which are the ones that handle the greatest loads. They looked good on visual inspection, but I guess that is not enough, as I failed to recognize the signals the engine was giving me of an impending electrical failure. Granted, this wiring is 16 years old; I am thinking that maybe the crimping of gauge 2 to gauge 4 or 6 wire halfway through was to bring greater amperage closer to the engine. The metal crimp ring used to join both wires looks rusted; I can more or less assume that the integrity of the heat-shrink wrap that protects such crimp failed over time, allowing water to seep through and rust the crimp ring. A more or less loose connection ensued, which began offering more resistance over time + overheating, which eventually led to a complete failure. I am very grateful this did not end up in a fire. I suggest all Mac owners check the wiring that leads from the battery to the engine, in particular the positive and negative wires, and check for crimps. Have somebody start the engine, or raise it and lower it, while somebody else makes sure those crimps stay cool. That can be most safely done with an infrared thermometer device, but plain touch should also work. Make sure cables don't sit in an area where water can pool, and that they are not tied together to other cables as they can melt them also in the event of failure. If this crimps are necessary for engine wiring then they must be redone every so often. But I think for all practical purposes there should be a single high quality cable with no crimps at all.

[DaveB]

Cables will deterate in short time if battery charges a short cell in one of your batteries.
Green liquid on terminals is first indication you have a bad cell.
Remember if you have one bad cell in a group it will prevent charging to others, as it takes up all the charging.
Dave

sounds like original owner did a shoddy repair. a new motor usually comes with a set of 10-12 foot battery power cables with no splices anywhere in their length.Just a splice if done properly would not create enough resistance to create that much heat to melt wire,but add 10-15 years of oxidation and salt corrosion and that would surely do the trick as you have found out. Don't skimp run new cable from motor all the way to battery or fuse with zero splices this time.

[raycarlson]

renzoreba, no need to feel cables and check for heat when raising motor. You need to buy an inexpensive little multi-meter and learn to use it correctly, it will let you see inside of your wires for problems or corrosion by using the resistance check feature and seeing the level of ohm's it takes to push current through your cable. Really every boater should have a muli-meter on board their boat and be semi familiar with its use. You can pick up a little cheapy for under ten dollars at harbor freight. Not quite sure about what the other poster is talking about green liquid on top of your battery, as I've had many batterys with bad cells that still would hold 12.3 - 12.4 volts(half charge) and never have witnessed green liquid on or near battery unless I spilled some sour apple martini while troubleshooting.

[JohnCFI]

renzoreba, no need to feel cables and check for heat when raising motor. You need to buy an inexpensive little multi-meter and learn to use it correctly, it will let you see inside of your wires for problems or corrosion by using the resistance check feature and seeing the level of ohm's it takes to push current through your cable. Really every boater should have a muli-meter on board their boat and be semi familiar with its use. You can pick up a little cheapy for under ten dollars at harbor freight. Not quite sure about what the other poster is talking about green liquid on top of your battery, as I've had many batterys with bad cells that still would hold 12.3 - 12.4 volts(half charge) and never have witnessed green liquid on or near battery unless I spilled some sour apple martini while troubleshooting.

Probably meant 'green powdery' ..... corrosion.

[seahouse]

Good suggestion Ray; those multimeters are very handy to have around the boat, car, home.

I'm thinking, renzo, to check the resistance of heavy battery cable you would need better resolution at very low resistance (say, below 10 ohms) than these meters would give you. For that you would need a device called a "megger", or megohm meter, which also measures very high resistance accurately, such as for checking the insulation integrity. It's really not something you would do on a regular basis to check the condition of the heavy conductors on your boat, though. And a megger is not something you would find in a DIYer's tool kit.

The environment on a boat is severe on any electrical connection (they have a finite life - check the electrical connections on any old boat that hasn't been redone), so the obvious way to minimize problems is, as you mention, to minimize the number of splices and make single line runs wherever possible. There are products on the market that help reduce corrosion at terminals and connections, of various effectiveness. One I use with success is No-ox-id. Hard to find on the consumer market, but an electrical supply place will carry it - it's with persuing. As well, some professional-type electrical connectors have a gel built in that protects the joint from the elements and corrosion in one step. Significant, but not as important on copper wire, because the oxides are conductive, compared to aluminum wire, where the oxides are not (= higher resistance and heating).

The "green" is the result of the metal copper reacting with the mists from the corrosive battery electrolyte that result during charging. Some batteries (car, motorcycle etc) have a vent tube that, when used to vent to the exterior of the battery compartment completely eliminate it. The terminals on such batteries will look brand new and shiny until their dying days years later, even if no anti-corrosion grease is used. Other batteries have porous caps that capture and recover the corrosive mist.
- Brian.

[mastreb]

renzoreba, no need to feel cables and check for heat when raising motor. You need to buy an inexpensive little multi-meter and learn to use it correctly, it will let you see inside of your wires for problems or corrosion by using the resistance check feature and seeing the level of ohm's it takes to push current through your cable. Really every boater should have a muli-meter on board their boat and be semi familiar with its use. You can pick up a little cheapy for under ten dollars at harbor freight. Not quite sure about what the other poster is talking about green liquid on top of your battery, as I've had many batterys with bad cells that still would hold 12.3 - 12.4 volts(half charge) and never have witnessed green liquid on or near battery unless I spilled some sour apple martini while troubleshooting.

+1. I've always carried one. I use it instead of an installed voltmeter for the battery as well (although when running the motor also reports voltage to my chartplotter).

[renzoreba]

Thanks for the advice. The good thing about sailing your boat frequently is that it forces you to keep her up in good shape. As boundaries get pushed, "weak links" break, and if you survive it, or if you do a good inspection prior to it and catch the "weak link" before it breaks, then in a way you succeed in making your boat a tad safer.

[renzoreba]

Quick update here, no electrical damage found and things are back to normal after replacing both positive and negative wires with a continuous 4 gauge tinned wire run from battery to engine. Truth of the matter is, when you pay somebody to run cables for you, if they run out of wire halfway through they are just gonna grab another spool of wire, crimp, and finish the job. All they care about is THEIR bottom line, not yours. Crimps do not belong in boats. Specially on high amp wires.