Author: Qualified mechanic John Cunningham. Published: 2021/11/10 at 6:33 pm.
This page is dedicated to helping you correctly identify battery polarity. Here, you’ll find a short video covering how to identify your battery terminals (battery cable and post identification); I’ve added a few extra mechanics tips below, including links to tools to help battery charging or boost starting foolproof.
Battery Polarity Critical
Battery polarity is crucial; if you’re boost starting, connecting a battery charger, swapping out a battery, or just testing a battery, you’ll need to get the polarity correct. You already know serious damage may occur if the polarity is reversed accidentally.
If you’re attempting to jump-start your vehicle, I’ve covered that subject, including a stepped guide here, or check out the jump-start video here.
If you’re attempting to swap out a battery, I’ve covered that here in this post, or you can check out the changing a battery video here.
I’ve included tools below that will prevent accidental reversal when boost starting – a foolproof set of jumper cables and a reverse polarity safe jumper pack.
Checking Battery Polarity – Mechanics Tips
Most battery cables and all battery casings are clearly marked. The plus or minus symbol is often embossed onto a plastic battery terminal cover and or color is also used to help identify polarity.
Positive
- Color RED
- Positive or plus (+) symbol
Negative
- Color Black or Green
- Negative or minus (-) symbol
There is another way to help identify or help confirm your identification is correct.
Following the negative battery terminal, it will lead to the vehicle’s metal chassis. The negative is the ground side of the circuit, and it connects to the chassis, usually pretty close to the battery.
Following the positive battery terminal, it will lead to the fuse box and also to the starter motor.
Boost Starting – Connect in order 1, 2, 3, and 4. Start the flat vehicle and remove cables in reverse order (with vehicles running) 4, 3, 2, and 1.
Tools
The NOCO jump starter pack is a serious tool; don’t let its size fool you. This little guy fights way above its weight. Capable of starting a diesel truck engine and yet small enough to fit in your glove box.
It features smart design and technology; it won’t allow you to connect its backways, and it features no spark technology, meaning it doesn’t arc when connected to the battery. It’s powered by the latest technology lithium battery.
But it’s got a few more tricks; it’s a fast charger, too (2 hours), which means you can use it to charge your car, truck, boat, mower, or snow blower battery as well as jump-start them. Other features include – a charge port for charging your phone or iPad, comes with an eight-mode hand lamp (500 lumens), a 12v 15amp port to power air pumps, or whatever.
This is a superset of jumpers for those who are unsure of the jumpstart polarity. The smart jumpers employ an integrated light to indicate incorrect jumper location. In addition, the light panel lets you know the battery state of charge and how well the alternator is performing.
The NOCO genius battery charger is what’s known as a smart charger, also known as a battery maintainer or trickle charger. They are smart because they detect the battery’s state of charge and automatically turn it off and on as needed.
If you are troubleshooting with the ignition system on, it kills the battery especially higher-end vehicles, to prevent this we use a battery maintainer. Picture links to Amazon.com.
The Topdon is a very capable and inexpensive battery tester. I covered battery testing using the Topdon battery tester and you can check that out here “Best battery tester for home use”.
Schumacher OBD-L Memory Saver or KAM tool. It is important to fit the memory tool before disconnecting the battery. Modern cars don’t like being without power. The Schumacher is easy to use with its 3 steps guided procedure.
Battery post and terminal cleaner. Dirty terminals are the root cause of a ton of electrical issues. Stainless steel cone wire brush side for terminal cleaning and internal brush for the battery posts. Suits top and side post batteries. Picture links to Amazon.com.
Proudly made in the USA, this anti-corrosive oil-based paste for battery terminals will prevent corrosion which is a very common cause of poor starts and premature battery failure.
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John Cunningham is an Automotive Technician and writer on Rustyautos.com. He’s been a mechanic for over twenty-five years and has worked for GM, Volvo, Volkswagen, Land Rover, and Jaguar dealerships.
John uses his know-how and experience to write articles that help fellow gearheads with all aspects of vehicle ownership, including maintenance, repair, and troubleshooting.