How To

How do I......Replace my battery?

The 12-volt lead-acid batteries used in most vehicles – even pure electric models like Teslas – typically last between five and eight years.

The 12-volt lead-acid batteries used in most vehicles – even pure electric models like Teslas – typically last between five and eight years. Most garages and many auto parts stores have devices called “capacitance testers,” which can accurately determine battery health. Of course a battery that won’t hold a charge after boosting or recharging speaks for itself.

In most cases, replacing a battery is a simple task, though there is no uniformity on the battery location. It’s common to find it beneath plastic covers in the engine compartment. You may also find the battery in the trunk. Or maybe in the floor, or even beneath the back seat.

Regardless of location, there are some precautions needed and things to be aware of. Of course, the vehicle should be powered down with the ignition in the “off” position. With very rare exception, the negative terminal should be disconnected first and reconnected last. The tool required to undo the terminal clamps varies from vehicle to vehicle, ranging from your hands, to pliers or a spring clamp. Use caution not to touch both terminals — or the positive post and any metal part — with a tool at any time. All batteries have some form of hold-down that will need to be removed, whether a clamp retained with a bolt, a bracket with bolts or studs, or a strap secured with bolts.

Remember that batteries contain acid, so use appropriate skin and eye protection and avoid tipping the battery on its side while changing it. If the battery has a cloth or plastic insulator around it, be sure to transfer it to the new battery. Use a terminal brush to clean the clamps before reinstalling, and don’t over-tighten clamps or bolts.

If the battery isn’t already dead, you may run into issues if the vehicle loses power during replacement. Some systems require re-initializing, or even security codes, when the battery dies. This part of the process maybe best left to a professional. For example, removal of the audio/nav unit to access a serial number (to give to the dealer) is necessary for getting the codes for Hondas.

Batteries come in many standardized sizes and terminal positions, also known as “groups,” and several key types (traditional flooded cell, AGM, and gel are the most common). Be sure to match the group and meet or exceed the original’s “Cold Cranking Amps” spec (a standardized measure of cold-temperature performance). The batteries used in models with auto-stop/start, hybrids, and EVs should always be replaced with the same type to ensure proper function.

Brian Early is a longtime Wheels contributor and a Red Seal automotive technician with over 25 years experience.

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