Positive battery connector is quite warm. Why? (1 Viewer)

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NE78FJ40

NE78FJ40

Joined
Apr 8, 2004
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Location
Gretna, NE
I'm getting very close to getting ready to start this 77 FJ40. I thought I would hook the battery up and just crank it over, but not start it yet. Turned the key a couple of times and then discovered that the battery might have been to low on volts. Just got a clicking sound. Went to remove the battery cables and found the positive battery cable to be a quite warm. Negative was fine. Anyone know what would cause this issue or is it even an issue?

Mark
 
There could be some corrosion between the battery terminal and the cable. ir it might not be doing good contact.
 
Could be-Undersized cable, corrosion in the cable breaking down the wire strands, poor connection between cable and cable end, poor connection between battery lug and cable end. Check both positive and negative cables and connections. Any or all of these could cause heating of battery lug and the clicking at the starter.
 
Both battery cables are new. They appear to be the same size as original. I'll check the connections next time. Could a bad ground on the negative cause it. Just a thought.
 
How many volts was the battery reading? FastEddy and the other guys are right, resistance is a concern. But that's just one part of Ohm's Law. Voltage is key too.

If you cut the voltage in half, you effectively double the current draw (amps) on the cables. So if your battery is at 9 volts, you're drawing 33% more amps to turn the engine over than if you were at 12 volts. All the cables are sized for current levels at 12 volts. An overloaded cable will heat up.

My advice, charge the battery, see if you still have any heat issues.
 
When I got home, the battery read 12.3 volts. The battery is on the charger right now. Will see what it does tonight. There was just a little bit of corrosion on the battery terminal, but if didn't think it was enough to cause a problem.


...via IH8MUD app
 
You have to read voltage off the charger. On the charger it will read the charge/float voltage. Let us know how it turns out.
 
My negative terminal used to get hot because it could not make a tight connection. I'm not saying anything anyone else hasn't said in this post as far as a lose connection being the culprit. I will say, that you should put the battery back in the truck, clean the terminals with a wire brush and make them tight. I believe it will start then.
 
NE78FJ40 said:
When I got home, the battery read 12.3 volts. The battery is on the charger right now. Will see what it does tonight. There was just a little bit of corrosion on the battery terminal, but if didn't think it was enough to cause a problem.
...via IH8MUD app
Click to expand...

Even the slightest trace of a white or grayish film can cause the problem you're describing.
Clean the battery studs with sandpaper 180 grit or so and do the same with the inside of the clamps.
When all works fine put some di-electric grease on it.
The white/gray film is caused by acid vapors. Clean the battery well with a soapy water to neutralize the acid traces.
The di-electric grease (or acid free vaseline aka petroleum jelly) prevents the vapors to start the corrosion process.
Battery-Terminals.jpg


mdsims said:
You have to read voltage off the charger. On the charger it will read the charge/float voltage. Let us know how it turns out.
Click to expand...

You have to read the battery voltage after a rest period of minimal 2 hours.
It's even better to do the reading when there is a light load on the battery. Just switch the key to the "on" position will tell if your battery is holding charge (11.8V or more), or is on his way out when the voltage is less than 11.8V.

Start with cleaning your battery studs and clamps.

Rudi
 
mdsims said:
How many volts was the battery reading? FastEddy and the other guys are right, resistance is a concern. But that's just one part of Ohm's Law. Voltage is key too.

If you cut the voltage in half, you effectively double the current draw (amps) on the cables. So if your battery is at 9 volts, you're drawing 33% more amps to turn the engine over than if you were at 12 volts. All the cables are sized for current levels at 12 volts. An overloaded cable will heat up.
Click to expand...

I think you make a little mistake here. Ohms law: I = V / R or Current = Voltage / Resistance
When you cut the Voltage in half you also cut the Current in half because the Resistance stays the same.
http://en.wikipedia.org/wiki/Ohm's_law

The cable is not overloaded. The contact between the battery stud and the cable clamp is not 0 (zero) ohm. This resistance creates a voltage drop over this connection. The combination of current, resistance and voltage drop is causing the bad connection to heat up.
This heat is conducted to the cable so the cable heats up.

Rudi
 
Last edited:
Don't rule out a defective "Brand New" cable. I got one once.
 
Heat comes from resistance to flow. You said that you were trying to start your 40, and that the cables got hot after doing so. As long as they're not smoking, I honestly don't see a problem. My cables get hot after winching, but it's to be expected with the amount of current that's flowed through the line. As most winches use some form of starter motor, you'd expect the same result from a starter motor. You can, to some extent, reduce the temperature by putting in thinner strand wire, and/or heavier gauge wire. But again, if it only gets hot after hard usage, there's little to fear.
 
I charged the battery all day yesterday and put in the 40 last night. Cleaned the connections and found the battery cable on the starter may not have fully tight. It cranks over good now.


...via IH8MUD app
 
And the positive terminal on the battery didn't get hot either.


...via IH8MUD app
 
NE78FJ40 said:
I charged the battery all day yesterday and put in the 40 last night. Cleaned the connections and found the battery cable on the starter may not have fully tight. It cranks over good now.


...via IH8MUD app
Click to expand...

Problem solved! :clap:

Rudi
 
bj40green said:
I think you make a little mistake here. Ohms law: I = V / R or Current = Voltage / Resistance
When you cut the Voltage in half you also cut the Current in half because the Resistance stays the same.
http://en.wikipedia.org/wiki/Ohm's_law

The cable is not overloaded. The contact between the battery stud and the cable clamp is not 0 (zero) ohm. This resistance creates a voltage drop over this connection. The combination of current, resistance and voltage drop is causing the bad connection to heat up.
This heat is conducted to the cable so the cable heats up.

Rudi
Click to expand...

I = V / R works for resistive loads where resistance is constant. My understanding is the starter is a motor, thus an inductive load. Inductive loads are essentially short circuits around a magnetic field and will try to draw more current if voltage goes down to maintain the same wattage consumed. The caveat to this: All DC loads appear as resistive in steady-state operation, but at start/stop such as cranking over the enigne, do contain/express their inductive properties. Thanks for the perspective though, I'm more of an AC guy, DC is something I've not put much thought into, but will now.

Glad the OP is up and running! :steer: and a :beer: when you get home.
 
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