Smoking Battery Cables!

Anonymous Poster · May 30, 2002

hi,

i have a problem with my fiat 70-66DT, it doesn't start easily due to bad cranking. and the positive battery cable gets really hot and sometimes starts smoking!! could it be incorrect cable sizes?? the heat/ smoking is a sign of resistance isn't it?
any help would be greatly appreciated!

regards

gareth

s1120 · May 30, 2002

Sounds like a bad connection to me. Try removing the cables, and cleaning up where they attach. I bet that will work.

mbsil · May 30, 2002

Check the obvious stuff...corroded battery clamps (connectors), etc. Corrosion will "wick" its way up a cable.

I've seen corrosion travel 4 feet down a wire before.

Test the cable with an ohm meter. Anything over a couple of ohms on a cable this short means that the cable needs replacing as it is completely infiltrated with corrosion.

RoyJackson · May 30, 2002

"the heat/ smoking is a sign of resistance isn't it?"

Yepper!! You've got too much resistance on the line. This is your power (hot) lead, of course.
Have you added anything to your electrical system...more lights, by chance? Or higher wattage bulbs?
It could well be corrosion, as the other folks mentioned. I would replace the cable in it's entirety...ASAP! Before your tractor catches fire...

bgott · May 31, 2002

Do a voltage drop test. Set a DVOM on dc and touch on lead on the positive battery terminal and the other lead on the starter post. Crank the tractor and see how much voltage the meter shows. You will drop 3 or 4 volts with that much amperage going through the cable without any problem, I'll bet you show 6 volts or better. This loaded test is way better than a resistance test, all it takes is one connected strand in the cable to show zero ohms.

BB_TX · May 31, 2002

Corrosion will cause heating, but the heating would be at that point in the connection, not the cable itself. I would guess either the cable has been replaced with an undersized cable. Or the cable has a partial break somewhere under the insulation. Definitely replace the cable.

WVBill · May 31, 2002

Could be a combination of things: Maybe it's hard to start due to a weak spark (if gas engine) or something. Cranking it for a long time will heat up the battery cable. I had that happen on my motor home once and nearly melted the lead post connector on the cable in the process. When they say don't crank for more than 10 seconds (or whatever) between cool down cycles, I found out the reason...

hazmat · May 31, 2002

A loose connection will cause resistance which will increase amp draw which causes the wire to heat up.

Anonymous Poster · May 31, 2002

thanks guys,

my guess is that when we bought the tractor, they replaced the old battery cables for new thinner ones. they look new and cheap. another thing that i noticed is that both cables get hot, not only the positive one! corrosion is another problem i have. i will replace both cables with thicker ones and see!!

thanks for all the replies!!

regards

gareth

Gomez · May 31, 2002

<font color=blue>another thing that i noticed is that both cables get hot, not only the positive one!</font color=blue>

Makes sense, they are both carrying the same amount of current./w3tcompact/icons/smile.gif

BB_TX · Jun 3, 2002

<font color=blue>will cause resistance which will increase amp draw </font color=blue>
This is an often stated misconception of electricity. An increase in resistance causes a decrease in current flow. Ohm's law is V=IR (voltage = current times resistance). Or to rearrange, I=V/R (current = voltage divided by resistance). As resistance increases, there is a proportional decrease in current.
A bad connection does cause heating because of a voltage drop across that connection point. This can be thought of as the power loss across that connection. Power(in watts)=VA (volts time amps). Also Power=I(squared)R (current squared times resistance). If the connection were perfect (no resistance) there would be no power loss. As the resistance increases, the power loss is multiplied by the square of the current. That loss grows rapidly as the resistance increases, and thus the heating.
Not trying to stir anything up, just want to clear the issue./w3tcompact/icons/smile.gif

Soundguy · Jun 3, 2002

Actually, a higher resistance will lower the current flowing through the circuit... but a coroded cable connection will make the cable drop a good amount of voltage across it, making it more of a resistor than a conductor... and it will start disipating a decent amount of power as heat.

Someone probably put lawn mower cables on it or something similar.

Soundguy

hazmat · Jun 3, 2002

OK I'm an idiot and forgot that Voltage = Current * Resistance.

I was trying to quantify an experience I had with a loose connection getting hot. We had an inverter put in my dad's boat. They wired a switch so you could choose between shore power & inverted power (both 110V). They didn't tighten up on the connection & when turned on, the wire got hot & started to melt the insulator. When the connection was tightened up, no problem.

boustany · Jun 6, 2002

There are several likely reasons why your battery cables would be smoking:
1) undersized cables, corroded cables, etc., which don't have the current handling capacity and are therefore basically being heaters;
2) Too much load as a result of a starter motor malfunction (or load on the engine), which would put excessive draw on the battery and overload the cables
3) Undervoltage at the battery, which would not allow the starter motor to operate correctly and spin up to speed. This could be due to a defective battery, or one with insufficient cranking power.

2 & 3 are as a result of the fact that electric motors draw a lot of current before they get up to speed due to a lack of 'back emf'. A stalled motor, or close to it, is basically a short circuit. Undervoltage doesn't deliver enough power to spin the motor up, and surprisingly enough can lead to a burnt out motor due to excessive current draw. I would try replacing the cables (which are probably shot by now anyway), testing with a new battery (which can be borrowed) and then replacing the starter.

The worst possible thing is that the tractor engine is putting too much load on the starter. Hope its not that.

Tell us what the fix was!

turnkey4099 · Jun 6, 2002

And don't forget that the ground cable has connections on -both- ends. I had much the same problem and after many sessions trouble shooting I found the problem was the connection at the other end of the ground cable, not the battery end.

Harry K

Soundguy · Jun 6, 2002

You wouldn't believe how many ground connections I've seen made to a frame, etc, and the paint wasn't removed.. allowing only minute conduction ( if any ) threw the bolt face, etc.

Soundguy

chuckokie · May 29, 2011

Ok so I replace the postive battery cable, negative battery cable, the battery and the cable to the starter and a resistor and it still won't start. It kind of whines and the resistor gets pretty hot. I've checked all over looking for a short and don't see one. Any other hints. By the way I'm a novice at this and this is my first tractor.

Don87 · May 29, 2011

chuckokie said:
Ok so I replace the postive battery cable, negative battery cable, the battery and the cable to the starter and a resistor and it still won't start. It kind of whines and the resistor gets pretty hot. I've checked all over looking for a short and don't see one. Any other hints. By the way I'm a novice at this and this is my first tractor.

Congratulations, you are the winner...........you just replied to a 9 year old thread. Heck..........you even beat my record by 2 years:laughing::laughing::laughing:

Find the appropriate forum for the tractor that you own. Please list your location, model and year of your tractor........then post the problem.

You will get much faster responses and fixes this way.:thumbsup:

And welcome to TBN