Why is my battery ground hot to the touch?

[cu440da]

I have a trunk mounted battery that grounds to the trunk latch bolt. Laid my hand across it and darn near burned my hand! I'm no electrician but I figure that can't be good!!


I have two main grounds, (both at least 2 gauge- at the trunk and at the engine) as well as at least 5 ground straps of various sizes and locations in the car. Main battery power (1 ga) goes through cutoff switch to starter relay. I have wired a bunch of cars like this previously and all worked fine.

Why is this happening?

Oh, is this related... starter acts like the battery is dead (slow crank, click, click, click...) even though the battery measures 14.5V?


Dave

[Jim_Lusk]

You have too much resistance where it is the hottest. If the whole cable is hot, then it is too small.

[farmington]

or you need to scrape some paint away so the ground strap gets to some good clean metal.

[68_Val_Sedan]

or you need to scrape some paint away so the ground strap gets to some good clean metal.

 

Move that ground.   Drill a hole in the trunk floor and frame rail flange, then clean the paint off of both sides. usea min of 3/8 bolt and then touch up the paint to keep corrosion at bay.

[flyboy01]

You need to get a few ground straps, one from the engine to the front inner fender, and one from the engine to the body (firewall), also clean that ground, but also it would be better to move it to a floor panel or frame rail. Use a dedicated bolt, not a shared bolt.

[eldubb440]

id run a heavy ground cable back to the engine and engine compartment.........the steel body isnt nearly as good of a conductor...... some would argue that the body is a giant resistor.....i remember someone here making kind of a "bus bar" in the trunk for grounds, and running it back up to the front of the car. it was pretty trick.

[bOb shingler]

id run a heavy ground cable back to the engine and engine compartment.........the steel body isnt nearly as good of a conductor...... some would argue that the body is a giant resistor.....i remember someone here making kind of a "bus bar" in the trunk for grounds, and running it back up to the front of the car. it was pretty trick.

[bOb shingler]

id run a heavy ground cable back to the engine and engine compartment.........the steel body isnt nearly as good of a conductor...... some would argue that the body is a giant resistor.....i remember someone here making kind of a "bus bar" in the trunk for grounds, and running it back up to the front of the car. it was pretty trick.

[NYrr496]

I like 200% grounds. I always run a ground to the block. Then block to firewall, block to frame... That click ckick will go away when you do that. It doesn't matter if your battery has 12 or 20 volts, if the power can't make a complete path, the starter won't see enough of it.

[68_Val_Sedan]

The electrons (power) flow on the surface of the metal they are connected to,  the frame rail has way more surface area than any battery cable you could put in .... not to mention it is welded to the rest of the car which also acts as a conductor. There is no need to run a ground cable to the front .... the factory never did on any of the trunk mount cars including the 13.5 to 1 compression max wedge cars ...

[flyboy01]

If the terminal itself is hot, then there can only be two problems, too small a cable for the current you are running, or a bad connection to the frame. If it is going through the trunk striker plate then it has to go though the plating of the bolt (and dirt or rust), then it goes into a painted/plated striker plate (and dirt or rust), then is goes into the bracket which was spot welded to the trunk pan 40 years ago. Not an ideal scenario.

[thebankerstoy]

The electrons (power) flow on the surface of the metal they are connected to,  the frame rail has way more surface area than any battery cable you could put in .... not to mention it is welded to the rest of the car which also acts as a conductor. There is no need to run a ground cable to the front .... the factory never did on any of the trunk mount cars including the 13.5 to 1 compression max wedge cars ...

 , you do not need to run a long negative cable up to the front of the car. The battery is mounted in the trunk of my 66 Coronet and while I do use a large gauge, heavy duty, solid copper, positive battery cable to the front of the car, I use a nice short heavy duty ground cable, that is bolted to a heavy metal brace in my car's trunk. I'll post a picture below, but I'm not sure it's large enough to see the mounting point of my ground cable. As mentioned above, you really need to make SURE that you remove ALL of the paint, primer, dirt, or any other materials from the surface where your cable contacts the metal in your trunk. I would also agree with what Jim Lusk said about the possibility of your ground cable being to small, as far as wire gauge size goes.

Richard

[attachment deleted by admin]

[Dart67]

Here's my grounding system.

The ground buss is made from a piece of 1/4" X 2" copper. It is drilled and tapped for 3/8" mounting and grounding bolts. It is bolted to the bracket that held the jack. The negative cable from the battery, the fuel pump ground, and two 6 guage stranded copper cables (one to the engine block and one to the front ground buss behind the passenger side kick panel. ALL of my grounds from the dash and engine bay go to the front buss.

Rear Ground Buss and Kill Switch




Front Ground Buss



Grounding is just as if not more important then the supply wiring. If the ground is bad funny things can and will happen with things.

Each thing that is grounded SHOULD go to its OWN screw, not stacked.

Herb

[eldubb440]

i remember someone here making kind of a "bus bar" in the trunk for grounds, and running it back up to the front of the car. it was pretty trick.

Here's my grounding system.

The ground buss is made from a piece of 1/4" X 2" copper. It is drilled and tapped for 3/8" mounting and grounding bolts. It is bolted to the bracket that held the jack. The negative cable from the battery, the fuel pump ground, and two 6 guage stranded copper cables (one to the engine block and one to the front ground buss behind the passenger side kick panel. ALL of my grounds from the dash and engine bay go to the front buss.

i think thats the one!

[cu440da]

I think the gauge of the cable is good enough, it's actually the old positive cable from the front. Looks like I'll start with a good cleaning and move the grounding point to the frame. I also have a 2ga cable from the engine to the k-frame, the factory ground strap from engine to firewall, 2 dash/instrument panel ground wires, gas tank grounding strap, alternator to engine strap, and the main one in back. I was planning on running the ground all the way up front later this season, if this doesn't clear it up I guess it'll happen sooner.

Thanks, I'll let you know how it works out.

Dave

[A13Dart]

You need to check the ground cable with an ohm meter. I have had cables that looked good, but were corroded under the insulation. If the cable measures low then check the cable to chassis resistance. The meter eliminates all guess work.



[attachment deleted by admin]

[cu440da]

I re-did the ground tonight. It's cool as a cucumber now.

Still having probs w/ battery acting like it's dead even though it has over 15v. I'm going to post a new topic for that one.

Thanks again,

Dave

[flyboy01]

Is the problem with cranking? If so, check the connection to the starter, also check the grounds between the engine and chassis if they are over 6 months old.

[375InStroke]

What does the voltage read while cranking?

[Bakaruda]

I have done electrical wiring for many years. All of the above are good points. I have to agree more withone thanany of the rest. It has been my experience that if the ground is hot it is to small and/or not grounded good. I would start over on the ground. First like one of the guys said drill a hole in the frame lip and clean both sides of the hole. Then ground it. I like the double your feed for a ground. I use 0 gauge weld cable. On my car I am welding the ground to the body while the car has no paint on it. Again just my 3 cents this time.

[375InStroke]

id run a heavy ground cable back to the engine and engine compartment.........the steel body isnt nearly as good of a conductor...... some would argue that the body is a giant resistor.....i remember someone here making kind of a "bus bar" in the trunk for grounds, and running it back up to the front of the car. it was pretty trick.

The electrons (power) flow on the surface of the metal they are connected to,  the frame rail has way more surface area than any battery cable you could put in .... not to mention it is welded to the rest of the car which also acts as a conductor. There is no need to run a ground cable to the front .... the factory never did on any of the trunk mount cars including the 13.5 to 1 compression max wedge cars ...

With AC, the magnetic field induced in the wire causes more impedence at the center of a wire than the surface, and this increases with frequency.  With DC, the frequency is zero, and the electrons move through the entire wire, not just the surface.  Steel isn't as good of a conductor as copper, but the cross sectional area of an entire car more than makes up for that.  Just like using aluminum wire instead of copper, where you go up in wire gauge to compensate for the extra resistance.  When using the car body for ground, only the welded structure is an adequate ground.  Parts bolted on are not good grounds, like doors, fenders, trunk lids, and trunk latches.  The ground from the battery should make contact directly to the steel structure, and not rely on the bolt for the conductive path.

[Bakaruda]

375instroker

You hit the nail on the head, thank you.

[redfastback]

during cranking, you should not drop more than 2 volts.  if it does, the battery does not have a good deep charge or its just old.  are you checking the battery after you turn the car off or after it has sat awhile?  try a known good battery.

[demon340v]

On my frame where there was a hole drilled from the factory i put a nut there wedled it and BAM! instant groundage!

best ground so far that i have had.

[Chris_Holliday]

I recently had a problem similar to this and found my alternator was not spinning fast enough to charge adequately at idle.  You need at least 13.5v to be charging.