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Old 06-26-2010, 11:30 PM   #1
SwedishBee
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Default Why is my battery cable getting so hot?

Why would my positive battery cable and clamps get so hot you cant even touch them, the rubber insulation is getting so hot its on the verge of melting.

The car seemed fine, I only noticed it because I needed to borrow the battery for a different volvo and that car ran it fine.
Is it possible the alternator went bad and is overcharging? Or do I have a short somewhere...
Maybe the starter?

This is a shame because I have sold this car and was getting close to delivering it.

This is the 95 960
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Old 06-26-2010, 11:37 PM   #2
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Could be a number of problems.

Why did you need a battery from another car?
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Old 06-26-2010, 11:40 PM   #3
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Im short on batterys so whenever I need to move cars around I have to play musical batterys.

I borrowed the battery that was in this 960 for my 242...
While pulling the 960 battery after a 5 minute drive, is when I noticed the problem.

Hopefully that makes sense... Im tired
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Old 06-26-2010, 11:43 PM   #4
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Maybe the positive battery cable is corroded inside the insulation.
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Old 06-26-2010, 11:45 PM   #5
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Im sure it is, so what does this mean?
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Old 06-26-2010, 11:50 PM   #6
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Buy some cable and make a new one.
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Old 06-26-2010, 11:50 PM   #7
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Most of the wires are gone, which gives the cable a smaller wire size and higher resistance. It now can't handle as much current.
Try measuring voltage drop across the cable. Higher voltage drops will make the cable get hot.
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Old 06-27-2010, 12:07 AM   #8
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well here is the rest of the story, when I first got the car together a few months ago, The car drained the battery in the first day or 2, and it turned out being a loose alternator cable nut.
The alternator cable got hot then and melted some insulation near the alternator. I tightened it up and have driven 1500 miles since.. I dont think the alternator wire was hot this time, just the main battery cable...

Should I replace the alternator to starter cable and get a new positive battery cable?
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Old 06-27-2010, 12:08 AM   #9
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Quote:
Originally Posted by vlvman View Post
Most of the wires are gone, which gives the cable a smaller wire size and higher resistance. It now can't handle as much current.
Try measuring voltage drop across the cable. Higher voltage drops will make the cable get hot.
Another thought, if the positive cable clamp is not tight on the battery, would it get hot like this?
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Old 06-27-2010, 12:11 AM   #10
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Quote:
Originally Posted by SwedishBee View Post
Another thought, if the positive cable clamp is not tight on the battery, would it get hot like this?
Yes that could create more resistance as well since it's not clamped down tightly.
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Old 06-27-2010, 01:55 AM   #11
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Check voltage when the 960 is running?
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Old 06-27-2010, 01:57 AM   #12
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Battery cables are cheap, but a new one.
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Old 06-27-2010, 09:11 AM   #13
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Resistance of the battery cable is to high for the current draw being applied to it. You may need a new cable, you may also have a short somewhere. Does the terminal make a noticeable spark when you connect the battery?

Quote:
Originally Posted by SwedishBee View Post
Another thought, if the positive cable clamp is not tight on the battery, would it get hot like this?
No, that would not cause the cable to get hot.

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Originally Posted by holtzboy View Post
Yes that could create more resistance as well since it's not clamped down tightly.
Read above.

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Battery cables are cheap, but a new one.
Yes.
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Old 06-27-2010, 12:38 PM   #14
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I also should of mention I broke my voltmeter recently so I need to get a new one...
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Old 06-27-2010, 02:34 PM   #15
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Quote:
Originally Posted by SwedishBee View Post
Another thought, if the positive cable clamp is not tight on the battery, would it get hot like this?
Mainly at the terminal. If the starter pulls enough juice, you can melt the lead.
Also if the starter is going bad... I though one of the batts on my diesel was going out awhile back, stopped at the parts store, and had em load tested. Both were fine, but my starter was pulling 400 Amps to get maybe 6 RPM, and it got hot enough to weld the lockwasher on the starter terminal back into a flat one.
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Old 06-27-2010, 06:43 PM   #16
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Damn. It has always turned over slowly. The last time I drove it I drove 200 miles in a day,
Maybe I will change out the alt>starter cable and the starter>battery cable and also the starter itself.
Thoughts?

duh
I just remembered that I pulled this engine from a smashed car at the junkyard, they couldnt even get the battery out of it. I came along and cut it out... maybe the starter got burned up from shorting out in the wreck.
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Old 06-27-2010, 08:50 PM   #17
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dude just upgrade the big three cables under ur hood... look it up. BTW Bad Religion is the bomb diggity
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Old 06-27-2010, 09:52 PM   #18
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Quote:
Originally Posted by SwedishBee View Post
Damn. It has always turned over slowly. The last time I drove it I drove 200 miles in a day,
Maybe I will change out the alt>starter cable and the starter>battery cable and also the starter itself.
Thoughts?

duh
I just remembered that I pulled this engine from a smashed car at the junkyard, they couldnt even get the battery out of it. I came along and cut it out... maybe the starter got burned up from shorting out in the wreck.
Or, you could save yourself the hassle/money and just replace the cables.
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Old 06-27-2010, 11:18 PM   #19
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I already have another starter. If there is any chance of it being the problem I think I should just swap it...
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Old 06-28-2010, 01:07 AM   #20
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You are making this very complicated and it is not.

Are both cables getting hot?

Yes, then both cables may have to much resistance for the current going through them or both cables-connections may be bad. Connect an amp meter up to either one to verify the loop current and go from there. A current of over 15-25 amps with the lights off and blower off is too high. If the battery is shorted and drawing too much current then the alternator is over working and it should be quite warm too. What is the voltage at the battery with the engine at idle?

If one cable is only getting hot then you need to clean the connection on both ends and/or replace the cable.

Any excessive resistance of a cable will dissipate heat. Once copper gets too hot it will always have an increased resistance.

No, the starter should not cause the heat in the cable.
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Old 06-28-2010, 01:45 PM   #21
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I was waiting for your reply moxy, I will let you know what I find.
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Old 04-07-2013, 12:49 PM   #22
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Quote:
Originally Posted by moxy123 View Post
You are making this very complicated and it is not.

Are both cables getting hot?

Yes, then both cables may have to much resistance for the current going through them or both cables-connections may be bad. Connect an amp meter up to either one to verify the loop current and go from there. A current of over 15-25 amps with the lights off and blower off is too high. If the battery is shorted and drawing too much current then the alternator is over working and it should be quite warm too. What is the voltage at the battery with the engine at idle?

If one cable is only getting hot then you need to clean the connection on both ends and/or replace the cable.

Any excessive resistance of a cable will dissipate heat. Once copper gets too hot it will always have an increased resistance.

No, the starter should not cause the heat in the cable.
I came across this thread when searching because I have a very hot POS cable. The NEG is fine. 1998 Volvo V70.

Anyways the amps going to the battery are 35 at idle with low beams on - no other accessories. With my fan, fog lights, heated seats etc I am seeing 65 amps.

The voltage between POS and NEG at idle is 13.8v and 12.3v with the car off.

I dont know what else to test for!!!

But I need to figure out when my POS cable is so hot. I cant even touch it with my hand. It is also extremely hot at the fuse box connection. I can only drive for 5-10 minutes at a time just to be safe.
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Old 04-07-2013, 12:53 PM   #23
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Test while the car is running from one end of the positive cable to the other.
More than likely you need to repair or replace the POS cable.
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Old 04-07-2013, 01:06 PM   #24
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Thick positive cable should only see current when the starter is cranking(still charged during driving)
Check how hot the cable is closer to the starter.
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Old 04-07-2013, 01:07 PM   #25
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Quote:
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Test while the car is running from one end of the positive cable to the other.
More than likely you need to repair or replace the POS cable.

I have now done the following checks (all while car is idling, no accessories):

-POS lead multimeter to POS alternator > NEG lead multimeter to POS starter = 0V
-POS lead multimeter to POS starter > NEG lead multimeter to POS battery = 0.9V (seems like a voltage drop)
-POS lead multimeter to POS starter > NEG lead multimeter to POS fuse box = 1.2V (even more of a voltage drop)

Can I just run a new battery cable from my starter to POS battery without removing the old one? I can still bolt it to terminal where it runs to fuse box. The current cable is tucked well away in behind the fan. From what I understand electricity will follow the path of least resistance so I don't see this being a problem.
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