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Author Topic:   Smoking Battery Cables
Florida15 posted 07-19-2006 05:23 PM ET (US)   Profile for Florida15   Send Email to Florida15  
Are the terminals on battery cables supposed to be hot? I mean, I know they are connected to a power source but are they supposed to be hot to the touch? I noticed the other day that there was even a little smoke coming off them. Is it time for new cables? What would cause this?
bobeson posted 07-19-2006 05:55 PM ET (US)     Profile for bobeson  Send Email to bobeson     
No, they are not supposed to be hot. The fact that they are means you have a serious, potentially deadly problem on your hands. Do not use this boat again until you have at least taken the cables off and thoroughly cleaned the terminals to remove all traces of crud, leaving only bare metal-to-metal contact surfaces. They should not generate significant amounts of heat during normal use. If cleaning the contacts does not eliminate the excess heat problem, then you might need to replace the cables, or at least replace the terminals on the cables.

The cause of this problem is power dissipation in the form of heat. Any time you have current flowing through a resistance, you get power dissipation. On high-current connections like battery cables, even relatively small amounts of resistance cause significant heating, which is why battery cables need to be so big - to lower their resistance, and therefor lower the amount of heat they generate. Exposed terminals tend to build up oxides and other crud, which form resistance in the connections, which causes more heat to be generated. This is a significant source of electrical fires, because with the right amount of resistance you can generate heat much faster than you can dissipate it, and yet the current is still below the threshold that would trip a circuit breaker.

Because of the nature of marine electrical installations, I highly recommend spending the extra money for proper marine-grade wire, connectors, crimps, and adhesive shrink tubing, which are designed to significantly reduce the effects of corrosion on exposed metal conductors and therefore avoid deadly electrical fires. You might get away with cheating on low-current accessories, but for high-current battery connections, don't play with fire!

Florida15 posted 07-19-2006 06:16 PM ET (US)     Profile for Florida15  Send Email to Florida15     
Thanks for the reply. I've cleaned my terminals and they are still hot so maybe it's a break or corrosion under the insulation. I've called around and will have to order new cables so I will probably do that tomorrow. I was also wondering, why do different motors need different cables? Seems like as long as they provide a link from point A to point B and they are large enough to handle the load, they would work. I have a 1982 Johnson 35 and the cables are relatively small in diameter. I guess so they can fit through the hole in the cowling. Actually, I would be more comfortable with larger cables but I don't see how they would fit through the hole. It's tight as it is.
ratherwhalering posted 07-19-2006 06:30 PM ET (US)     Profile for ratherwhalering  Send Email to ratherwhalering     
In an emergency when the cables are overheating or don't supply enough power to turn over the engine, pour coca-cola on the terminals. No kidding.

You'll have to properly clean the terminals later, but it'll work in a pinch.

Royboy posted 07-19-2006 09:39 PM ET (US)     Profile for Royboy  Send Email to Royboy     
Something is wired wrong somewhere. Cables should not just spontaniously start getting hot all of a sudden. Likely the last thing you hooked up or "fixed" has a crossed wire or there is something grounding out a power wire.


Florida15 posted 07-20-2006 02:12 PM ET (US)     Profile for Florida15  Send Email to Florida15     
Roy, the only thing I did was take the cables off under the engine and scrape them with a wire brush. Could I have somehow caused a short that way, maybe nicked the insulation or something ? I was going to go order some new cables today at lunch but had to attend a meeting so didn't get away. I think I'll take another look when I get home but it might be best just to put new cables on since I've got a feeling those are the originals (1982) I was quoted about $36 and 3 days to get them from the local Johnson dealer.

Which brings up another question. My cables are together except at both ends where they attach to the engine or the battery and they are split. On the ends where they connect to the battery, both terminals have a + on them. That makes no sense. Why wouldn't they have a + and a - ? They aren't two separate cables that a previous owner mismatched. They are bonded together.

jimh posted 07-20-2006 07:27 PM ET (US)     Profile for jimh  Send Email to jimh     
It sounds like you need to clearly mark and identify the positive and negative cables from the motor so that there cannot be any confusion when connecting them to the battery. I recommend using Scotch-35 vinyl electrical tape; it is available in RED and YELLOW colors. Mark the positive cable with RED and the negative cable with YELLOW. Also mark the battery terminals.
Florida15 posted 07-21-2006 10:32 AM ET (US)     Profile for Florida15  Send Email to Florida15     
Jim, that was the first thing I did when I bought the boat.
I took the battery out to charge it and when I went to put it back in I noticed both were marked +. I followed them into the engine to make sure I had them correct and marked them.
I stopped by Sam's this morning and bought a new Energizer cranking battery and I'm going to order some cables at noon.
On the old cables, I've cleaned the terminals on both ends but have noticed some green corrosion where the terminals begin to be insulated. I may cut back some of the insulation and see what's going on there. With battery cables that old, they could easily be messed up somewhere under the insulation.
jimh posted 07-21-2006 01:40 PM ET (US)     Profile for jimh  Send Email to jimh     
If in the cable itself, back a ways from the ends and under the insulation, enough copper (conductor) has turned into cuprous oxide (semi-conductor), the resistance could be too high.
davej14 posted 07-22-2006 12:27 PM ET (US)     Profile for davej14  Send Email to davej14     
At $36.00 for OEM cables just replace the originals that are now 24 years old. If you still have overheating then you need to look for another cause. In normal operation, except for cranking the motor, there shouldn't be enough current flowing to heat the connections.
Florida15 posted 07-23-2006 11:37 AM ET (US)     Profile for Florida15  Send Email to Florida15     
Looks like I'm going to have to take it to my mechanic. Yesterday I went out and hooked up the new battery, turned the key and got absolutely nothing. Turned it again and got a couple of clicks. So, I hooked up jumper cables and bypassed the battery cables. Good thing I had the cowling off because a wire started smoking. So, there's a short somewhere or something. It's beyond my limited knowledge so I'm taking it to the mechanic next week.
Florida15 posted 07-28-2006 02:18 PM ET (US)     Profile for Florida15  Send Email to Florida15     
Got it back from the mechanic today. It now starts up immediately and purrs like a kitten.
Turned out the problem was corrosion in the ignition switch.
I asked him if that would cause the cables to get hot and he said not likely but he checked everything out and they aren't hot now so problem solved.
Jerry Townsend posted 07-29-2006 12:13 PM ET (US)     Profile for Jerry Townsend  Send Email to Jerry Townsend     
Florida15 - I suspect that you also have a problem in your battery cables and suggest that you consider replacing them. The reason - the hot cable you mentioned can ONLY happen if there is resistance (electrical) at that point. The ignition switch corroded contacts effectively shorted a circuit, which caused electrical current flow - and with no or little electrical resistance, there would be no problem at that point - but with more than normal resistance, that component will tend to heat up and with a lot of resistance, it will get 'smokin' hot.

But, this is a good lesson for everyone - to find components where there is resistance - simply touch and feel each component until you find the hot one.

Your mechanic is correct in stating that the corroded switch would not cause the hot cable - except as described above.

I am a bit surprised that you didn't have a problem with your battery being discharged - over time, but then, you may be using your boat enough to have kept the battery charged. ------------ Jerry/Idaho

Florida15 posted 08-01-2006 10:49 AM ET (US)     Profile for Florida15  Send Email to Florida15     
Jerry, he tested the cables and said they were fine BUT I think I will replace them. I'm sure they are probably the originals.
Actually, it's just the opposite - I use my boat very little so I always have to charge my battery before using.
I just bought a new battery so I'm going to keep the cables off it when not in use. I figure that will prolong the life of the battery.
davej14 posted 08-02-2006 12:54 PM ET (US)     Profile for davej14  Send Email to davej14     
How often do you use your boat? Unless it is less than once every two months you should not have to be charging your battery before each use (this assumes that you do not have a bilge pump running during periods of storage). You must have something drawing current when it is stored and it would probably be a good idea to figure out what it is. A battery switch would be a better alternative to disconnection the battery.

If you really have prolonged periods of storage then I recommend an AGM type battery. My favorite is the Optima brand. This battery construction has low internal leakage and will not discharge over prolonged periods of storage. I put mine in the basement for 6+ winter months and it is still ready to go when I launch.

Florida15 posted 08-04-2006 09:30 AM ET (US)     Profile for Florida15  Send Email to Florida15     
Dave, it just depends. Heck, I've gone a whole summer and only gotten out twice. Depends on how much rain we get and how fast my grass grows. (I spend a lot of time doing yard work)
My problem is I was fooling around with an old battery so I would always recharge it just in case. I bought a new one so I shouldn't have that problem anymore. Hope to take it out tomorrow.
I bought an Energizer battery at Sam's Club. That's the first time I've seen a cranking battery made by them. I figured they make good small batteries (AA,C,D) so I would give it a try.
brchubs posted 08-15-2006 05:16 PM ET (US)     Profile for brchubs  Send Email to brchubs     
would bad battery cables make the voltmeter on my instrument panel fluctuate?
DANO posted 08-15-2006 05:48 PM ET (US)     Profile for DANO  Send Email to DANO     
yes it can... you are measuring the amount of voltage in the battery. if your volt meter is connected between the battery and the draw, it will show erronious readings. an ammeter is what is used to measure the CHARGING SYSTEM. a volt meter merely measures voltage. not a very accurate tool for measuring the health of your overall charging system....


brchubs posted 08-15-2006 06:56 PM ET (US)     Profile for brchubs  Send Email to brchubs     
Thanks for the info.I'm trying to sort out an electrical problem with my boat, and I too have "smoking battery cables" only it's just on the positive side.I also have problems with most of my accessories,(DEPTH FINDER, RADIO,ETC.)I'll probably check and replace the battery cables, it seems that's probably where the problem is according to all that I've been reading.
DANO posted 08-15-2006 08:09 PM ET (US)     Profile for DANO  Send Email to DANO     
I would say that you can eliminate 85 % of electrical problems with a properly install primary system. but if you get into is a learning experience...just be open minded enough to realize that it is a fairly simple system... just think it through and you should be o k ... clean cables, of the right gauge (size), corrosion free, installed tightly, (not 150lb. ft. of torque but snugged up) and correctly,through a battery disconnect,(preferably).charged up batteries.(specific gravity tested, not just with a volt meter.) remember 8 d cell batteries have 12 volts. but not nough amps to start your motor. the same holds true for specific gravity. if the acid content of the batt. is not up to a "specific" (sorry, no pun intended) level all the charging and meticulious care in wiring is wasted. a load test on a suspect bat. is also a good window into your battery. after this is taken care of, your charging system takes over. hope this helps


brchubs posted 08-15-2006 10:04 PM ET (US)     Profile for brchubs  Send Email to brchubs     
I like the idea of a battery disonnect, and I think I'm going to add that with the new cables. Thanks for the help.
davej14 posted 08-16-2006 11:46 AM ET (US)     Profile for davej14  Send Email to davej14     
Can you explain a "battery disconnect" ?
brchubs posted 08-19-2006 10:37 AM ET (US)     Profile for brchubs  Send Email to brchubs     
What a great website, I replaced the battery cables and the ignition switch and everything seems to be working like it's brand new.Thanks for all your help everyone.
DANO posted 08-19-2006 09:10 PM ET (US)     Profile for DANO  Send Email to DANO     
DAVE...a battery disconnect is nothing more than a break between the positive terminal of your battery and the ENTIRE rest of your system. It would be the same as if you were to disconnect the positive cable from your batt. Obviously a switch is a much quicker, cleaner way to go. The most common mistake people make is to have too many other connections from their battery "upstream" of the disconnect that when they flip the switch but fail to turn of their stereo, nav. lights, instument lights etc. it doesn't work. The only thing that should be hard wired to your battery outside of your switch would be your bilge pump and float switch for reasons we both understand. Make sure you don't accidentaly turn your battery switch to the off position when your engine is running as you while suffer altenator and voltage regulator problems after this move. Some new multiple battery switches now have a built in saftey that will allow an inadvertant swing to "off" but it is a good practice to avoid this att all costs. the other reason for the swich is to charge and consequently discharge certain batteries at will..... ie. you have a "starting" battery for your heavy high amp needs and a deep cell battery for your night fishing either drifting with your nav. lights and fish finder on, or anchored on an overnighter with family or friends and you need to keep your anchor light on. you switch your batt. switch to #2 (provided that is your circuit for the deep cycle) when you start your engine the following day, you switch to the starting batt. (#1) and then turn your switch THROUGH the "both" setting to the #2 setting to charge your deep cycle or you can leave it at "both" and your charging circuit will charge both batts as long as they will accept the charge...


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