Positive terminal turned black?

[Spool]

Hey Guys.
73 c20.

I notice my positive terminal on the battery has turned black. Any one have experience in this?

[Irish_Alley]

black would be from too much heat. what color was it before?

[bd]

Probably a redox reaction between one of the metals in the alloy and a corrosive agent like battery acid or baking soda.  Post a pic.

[Spool]

Apologies. Late reply due to long work hours.

I've attached a photo of the black terminal battery.

I also tried to take a reading with a Multimeter I have, but couldn't figure it out.
Choose DCV and it's reading 55.3 with nothing touched. Tested the car battery and it sparked as the cables got warm.
Is my multimeter strong enough? Wrong setting?

[bd]

The black discoloration on the battery post and terminal is probably a complex of lead oxide and lead sulfate.  It's unlikely that the metallic lead will oxidize or corrode any further if left alone.  However, terminal corrosion is evident.  I recommend that you use a nylon bristle brush and "gentle" stream of plain tap water from a garden hose to thoroughly rinse the accumulation of acidic electrolyte off the top and sides of the battery case.  DO NOT use baking soda or any other neutralizing agent!  Be very careful to wash any resulting splash off of vehicle paint and wear safety goggles to keep the solution out of your eyes.  Remove the battery cables and clean the posts and terminal ends using an appropriate battery terminal brush (such as imaged below).  Liberally coat the posts and terminals with lithium grease before reinstalling the cables to slow moisture penetration of the connections. 

At some point, replace those clamp-to-cable terminal ends (they are highly susceptible to corrosion and connection degradation problems) with crimped and soldered ends, or better, upgrade the complete cable assemblies to 2-AWG all-copper cables.

If you were trying to measure DC volts with the meter configured as pictured, the red lead is plugged into the wrong meter socket.  It is not at all surprising the meter indicated nonsensical reading.  The red (positive) lead should be plugged into the "red" socket for all measurements EXCEPT the 10 Amps DC selection at 7:00 o'clock.

[Dr_Snooz]

Why not silicone grease?

[bd]

Silicone dielectric grease will work at five times the cost.  I discovered many eons ago that non-moly chassis grease works superbly, adheres well and provides excellent moisture rejection at a fraction of the investment when compared to any "specialty" product.

[Spool]

Thanks guys. I'll be getting to cleaning everything as instructed tomorrow and also replacing the +/- cables & connections.

I may have pushed it to far with work though. As of today, the truck has a hard time starting up.
Sounds as if it's almost in slow motion before it speeds up and then finally rolls over. I think it's electrical, battery to starter issue.

I wanted to test my battery today with the multi-meter I have but still wasn't sure of the correct mode to measure the truck battery.
I had the negative plugged black (in the center) and the positive plugged red (to the right) but when I chose the '1oclock' position at "DCV", it wouldn't sit at zero.
Should I be using the '8oclock position' "DCmA"?

[bd]

I had the negative plugged black (in the center) and the positive plugged red (to the right) but when I chose the '1oclock' position at "DCV", it wouldn't sit at zero.
Should I be using the '8oclock position' "DCmA"?

Per your description, regarding the pertinent measurements, the test leads are connected to the meter correctly.

What exactly are you attempting to do? 

If you want to measure voltage, select "DCV" (1:00 o'clock position) - shorting the probes together should indicate zero on the display*.  Connect the test leads: red-to-positive, black-to-negative.  If you want to perform a battery load test (more likely a battery conductance test, using a DMM), select "BATTERY LOAD TEST - 12V" (9:00 o'clock position) and connect the meter across the battery terminals, as above.  The LEDs will indicate battery condition:  Green = GOOD, Yellow = MARGINAL/WEAK and Red = REPLACE.

----------------------------
* From Innova's website, regarding the 3320 DMM you're using:

Why do the numbers keep fluctuating when I'm not testing anything?

This is a normal function of the Auto Ranging feature of the 3320 DMM. It is simply picking up signals from the environment around it. You can zero it out by touching the two test leads together. When conducting a test, the meter will automatically zero out before giving a reading.


To determine whether there are continuity issues through the battery cables connecting the battery to starter, measure the voltage drop across each battery cable.  Set the meter to DCV and connect the test leads: red-to-battery positive post, black-to-3/8" battery cable stud on the starter solenoid, then have an assistant crank the engine while you monitor the meter.  Repeat the process with the test leads connected: red-to-bare metal on the starter motor case, black-to-battery negative post.  If the meter measures greater than 0.5 volt in either test, there are battery cable related problems that need to be corrected before pursuing subsequent tests.

[Spool]

Got it. Thanks BD.

I was attempting to get a read on my truck battery to see if it's dying on me.

I'll give it another go soon.

[Spool]

Thanks again.
Worked perfectly.

12.87 on the battery and then 13.50 with the truck running.