Car Battery Polarity

A car battery has a polarity, which can be understood by the location of the terminals on its surface (usually on the cover). To determine the polarity correctly, the wide side of the battery with the terminals should be facing the person identifying the polarity. Polarity is considered 1 or straight when the battery “+” plus is on the left side of the battery, and the “-” minus is on the right. The terminals in the battery are indicated by the signs “+” (plus) and “-” (minus).

The diagram below can be used as a reference when informing the terminal layout required for your battery.

When determining terminal layout always face the terminal side (terminals closest to you) to avoid confusion and misinterpretation.

Polarity: 0 = Right Hand Positive (RHP), terminals on the wide side of the battery facing you
Polarity: 1 = Left Hand Positive (LHP), terminals on the wide side of the battery facing you

Convention for Identification

Polarity symbols are used where the polarity of a terminal must be identified. An electrical color code or other conventions may be used. In DC circuits, the positive pole is usually marked red (or “+”) and the negative pole is usually marked black (or “−”).

On a car battery, the positive pole usually has a larger diameter than the negative pole. Modern cars have the negative terminal of the battery connected to the vehicle’s body, and the positive terminal provides the live wire to the various systems. Older cars were built with the positive terminal of the battery bonded to the chassis.

Car Battery Terminals

Battery terminals are the electrical contacts used to connect a load or charger to a battery. These terminals have a wide variety of designs, sizes, and features that are often not well documented.

Automotive batteries typically have one of three types of terminals.

SAE is the most common design, consisting of two lead posts in the shape of truncated cones, positioned on the top of the battery, with slightly different diameters to ensure correct electrical polarity.
The “JIS” type is similar to the SAE but smaller, once again positive is larger than negative but both are smaller than their SAE counterparts. Most older Japanese cars were fitted with JIS terminals.
L terminals consist of an L-shaped post with a bolt hole through the vertical side. These are used on some European cars, motorcycles, lawn and garden devices, snowmobiles, and other light duty vehicles.

Terminals can also be both on the wide/long or narrow/short side of the battery, or diagonally opposed, or in the middle. Purchasing the wrong configuration may prevent battery cables from reaching the battery terminals.

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