Mark Houlahan
Tech Editor, Mustang Monthly
May 22, 2012

One of the most feared aspects of car repair, maintenance, or even a restoration is the vehicle's electrical system. Watts, volts, ohms, and other terms swirl around most people's heads like sharks circling a bleeding surfer, and at the heart of that electrical system is one of the most misunderstood parts--the battery. In our Mustangs, be it vintage or late-model, the starting and charging system is based on a 12-volt negative ground service, so we're not going to bother with six-volt or positive ground systems for this story.

As the heart of your electrical system, your battery, must not only be able to start your Mustang by supplying enough power to the starter, but it also must be able to provide auxiliary power for key on and key off accessories (when the engine is not running and therefore the alternator not supplying the vehicle's power, for things like listening to the radio or the interior lights illuminating when the doors are opened). Lastly, the battery must be able to store this power between vehicle use (but not long-term storage) so that the car will start the next time you use it.

So why is it that this most important part of your electrical system is so often just left to fend for itself and never given maintenance until that fateful day when you get up early to head out to a car show and you find your Mustang in the garage with a dead battery? Your club members are meeting for the drive to the show in 20 minutes and you're standing there with the hood up wondering what you should do.

Taking care of your battery is really a simple process. It is something you need to add to your regular maintenance schedule. You check your engine's oil level on a regular basis right? You need to check your battery's level on a regular basis too. Keeping your battery properly charged not only means you'll be able to hop in and twist the key when you need it most, but the battery will last longer and save you money. Of course, there are a few preventive measures you can perform on your battery as well, and we'll go over those as well.

Battery Condition

Batteries do not last forever. They should be considered a consumable item. That being said, sometimes it is best to start off with a new battery if your battery is of a questionable history. Just bought a classic Mustang and there's no real indication of the battery's age? You might want to play it safe and simply buy a new battery. Depending upon location, you can often guestimate how close you are to needing a replacement battery. In hot climates like Florida, Arizona, and Texas, you're probably going to see three years max out of a high-quality battery.

Today's batteries are typically a sealed, maintenance-free design, so there's little you can do to service the battery except for keeping the terminals clean. Often an "eye" on the battery will tell you its condition. If your battery does have removable service caps to allow checking the battery's level, then you should check the level at regular intervals. Be sure to remove all jewelry before servicing your battery and wear eye and hand protection. Remove the caps and check the fluid level. The fluid level should allow for the battery's lead plates to be completely submersed. If not, you can carefully add distilled water to bring the level back up.

If you own and know how to use a hydrometer, you can also check the specific gravity of your cells if the caps are removable. The same can be said for the battery's open circuit voltage (measured across the terminals). If you own a volt-meter, you can check the voltage too. Use the above chart to determine your battery's state of charge.

Finally, external condition is just as important as the internal condition. Case damage, terminal damage, and more should all be things to look for on a regular basis. Of course, if your battery is properly secured, there's little chance of external damage, but we've seen cases nicked when being dropped into place, so be careful and don't rush things when installing your battery.

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