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Why is my battery cable getting so hot?

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.
 
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.
 
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.
 
I had a battery cable get silly hot on an old MG one time when I had a bad ground. I touched the terminal and it burned me badly. Turned out the ground to the engine itself was in awful shape. The car would still start, just not as well as when I fixed it.
 
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)
Also test from cable end to battery terminal.

Recently had a year old battery short internally, and it heated itself to the point of boiling and smelling like burning railroad ties. I unplugged it, and kept dousing it with water till it discharged itself and cooled off(about 2 hours), then exchanged it for a new one in the morning.
 
Also test from cable end to battery terminal.

Recently had a year old battery short internally, and it heated itself to the point of boiling and smelling like burning railroad ties. I unplugged it, and kept dousing it with water till it discharged itself and cooled off(about 2 hours), then exchanged it for a new one in the morning.

Ya I did that. O.00V
 
V70 battery cables are notorious for going bad, it's not that hard to replace if you remove the airbox and some of the intake tubing, and even easier if you pull the fan out.
 
I don't know if this helps, but back in the 70's some chrysler products had a problem with battery cable lead terminals melting. Turned out the starters were the cause.
 
PERSONALLY I believe it to be the lavender eye shadow,
the see thru tube top and the fishnet tights but that's just my
Dirty Old Man side comin' out.....:badboy:
 
Ive got 0.5V lost between alt and fuse box.
-0.2V from alt to battery
-0.3V from battery to fuse box

Would the total of 0.5V cause my lights to flicker and battery cables to get hot?
 
see # * 2 * & * 4 * (for a start at sorting the Voltage drop)

repeat the VOLVO LEKTRIKAL MANTRA with me *ONE MORE TIME* !
1) clean / tight /correctly sized CONNECTIONS *EVERYWHERE*
2) look for "creeping blue/green CRUD *up under* insulation" on BATTERY CABLES
3) fuses scrubbed and cleaned "contacts bent SNUG (if porcelain type use the COPPER
coloured ones *NOT* the "tin ones")
4) alternator terminals clean snug and GROUNDED to the BLOCK side of the motor mount and safe to the alternator
5) repair / replace harness bits that are crumbly-insulated on the "notorious DEATH PERIOD for harnesses"
6) when in doubt VOLTAGE DROP TEST / check RESISTANCE ACROSS a CONNECTION
7) dielectric grease is an insulator..and that's as far as I'm gonna speak on the subject..I *DON'T* use it
on ANY electrical connection...I DO *seal* the back sides of connections to stop gas intrusion with it....EOS

once you've got the "wahrs sorted" you may proceed to testing VOLTAGE /
RESISTANCE / CAPACITANCE / INDUCTANCE / ETC....
 
Ive got 0.5V lost between alt and fuse box.
-0.2V from alt to battery
-0.3V from battery to fuse box

Would the total of 0.5V cause my lights to flicker and battery cables to get hot?

.5V is lost via resistance and making heat....
 
I never sealed the deal on this thread.
My issue was a loose nut for the alternator charge wire on the back of the alternator.
 
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