Can’t tell which is positive or negative on battery

Very basic(but important) question here. Which end is positive and which is negative? There are no markings on the sides as far as I can tell. I tried wiping down the tape to see if red was hidden, but no red to be found.

I’m embarrassed to ask this.I’m not not good with automotive maintenance, but I’d like to do more myself.

Hey Kevin, don't sweat it, it's a good question. Usually there's a big "+" and "-" embossed into the plastic itself.

But if not, look where the wiring goes. When you trace it to the point where the wire is bolted to the frame of the vehicle, that's the negative.

Good on you trying to learn more about this. It will save you tons of money down the road.

Douglas Alpenstock wrote:Hey Kevin, don't sweat it, it's a good question. Usually there's a big "+" and "-" embossed into the plastic itself.

But if not, look where the wiring goes. When you trace it to the point where the wire is bolted to the frame of the vehicle, that's the negative.

Good on you trying to learn more about this. It will save you tons of money down the road.

Thanks for the response Douglas. I was hoping someone would mention tracing where they connect because there are no +, -, pos, neg, etc. in the plastic. I checked the top and sides several times. I had someone else look too.

I want to jump start it because it does nothing when I turn the ignition. I have a portable jump starter. Haven’t used it yet. I’ll trace the wiring tomorrow and check back if I have any doubts.

Another way is to look at the battery connectors. As the photo shows, the positive connector is larger and bulkier than the negative.

The plus or minus marks are probably under the terminals.
You might have to remove them to see the + -.
Otherwise you can look for an M24 battery and see where the posts are.

Or hold the bare end of a wire to a battery post and then briefly touch the bare other end to an unpainted place on the frame or engine.
If it sparks it's not the ground post.

Howdy,

If you have a volt meter, when you touch the leads up backwards, black to pos and red to neg., the voltage will read -12 volts or whatever/-11.5 v,etc. If red lead is to pos. and black lead is to neg it will read +12 or whatever. When the reading is on the + scale, it is telling you which terminal is +/pos and which is -/neg.

Some older autos did have Positive grounded systems.

In general automotive batteries have the positive on the left as you look at the battery and the terminals are close to you. UNLESS it is marked with an F or a R after the BCI group number. The battery you have is a group 24 (BCI number)  The F stands for Ford and the R stands for reversed terminals.  There are other suffix letters that designate different terminal size but you probably won't encounter them in normal cars. It appears  in the picture that the terminal  on the right is larger in diameter so that would be a group 24F, that f might be hidden by the hold down.

craig howard wrote: The plus or minus marks are probably under the terminals.
You might have to remove them to see the + -.
Otherwise you can look for an M24 battery and see where the posts are.

Or hold the bare end of a wire to a battery post and then briefly touch the bare other end to an unpainted place on the frame or engine.
If it sparks it's not the ground post.

Craig was right, the +/- are hidden under the terminals. Thanks Craig.

It appears  in the picture that the terminal  on the right is larger in diameter so that would be a group 24F, that f might be hidden by the hold down.

also correct, there is an “F” hidden under there.

Thanks for giving me multiple ways to confirm this guys. Now to see if I can actually start the truck.

I'm an auto mechanic by trade. Positive post is slightly bigger than the negative. In your case, it looks like the positive is on the left side of the picture. As others said, wiring from the negative terminal runs to the body at some point. A voltmeter will show correct polarity too.

I saw what you did there.

After a bit of cleaning, even with just water and a brush, the top should be more readable.
The OP will probably need to get the proper wrenches and remove the negative battery terminal. The thing the wires are hooked to.
While staying away from the positive post.
When messing with the negative terminal, the wrench can touch ground and nothing will happen.
Not so if you are messing with the positive post.

 To reset the ECU: After I removed the negative terminal completely from the negative post,
I touch it on the positive terminal for about 10 seconds.
To drain any capacitors. Setting the negative and positive connections to the same level.
Some people forget this part and just disconnect the battery.
I know touching neg to pos sounds crazy but without the negative cable attached to the battery, no current can flow from the battery.
There shouldn't be any big sparks.
I suppose there are exceptions like if you have 2 batteries.

This is helpful. Don’t be embarrassed. Bad is not to ask and damaged the vehicle, that is embarrassed.😞

I can think of several ways to check, but you've been told most of them. (And some I hadn't known!) I'd like to add:
1) Ground a test light to the frame or body and probe both posts. On a negative ground vehicle only the positive post will light. (The vast majority of vehicles, at least here are negative ground . I don't think I've ever seen a positive ground, though I've always heard they exist.)
2) Get (or make) an adapter that clamps to your battery posts and adds a cigarette lighter type receptacle. Hook it up and plug in anything with an LED to indicate power. LED is Light Emitting Diode. Electricity can only pass one way through a diode. If it lights, the polarity is right, and the red clamp is on the positive post. If it doesn't light, switch the battery clamps.

If you use LEDs for testing, make sure you try them with reversed connections. Some are now wired to be "smart" and will light up either way. That was not the case in the past.