Battery terminals

Battery terminals are the electrical contacts used to connect a load or charger to a single cell or multiple-cell 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.

In recent years, the most common design was the SAE Post, 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.

General Motors, and other automobile manufacturers, have also begun using side-post battery terminals, which consist of two recessed female 3/8" threads (SAE 3/8-16) into which bolts or various battery terminal adapters are to be attached. These side posts are of the same size and do not prevent incorrect polarity connections.

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.

Some batteries sizes are available with terminals in two different configurations: 1) positive on left and negative on right, 2) negative on left and positive on right. Purchasing the wrong configuration may prevent battery cables from reaching the battery terminals.

Marine batteries typically have two posts, a 3/8"-16 threaded post for the positive terminal, and a 5/16"-18 threaded post for the negative terminal.

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Wikipedia