The only time you're likely to think about your car battery is when you turn the ignition key and nothing happens. But a little knowledge about batteries can help you get more life out of them.
If you've ever lifted a car battery, you know how heavy it is. That's because much of it is made of lead, a very dense material. Inside a battery's plastic housing are thin plates of lead and lead dioxide, bathed in a solution of sulfuric acid and water. The chemical reaction of these elements leads to a charge. This design has been around since Gaston Planté invented it in 1859.
Many people believe that batteries shouldn't be stored on concrete because it will drain them. Like many myths, this one has a toehold on the truth. Years ago, when battery cases were made of wood and glass, moisture in concrete could swell the wood and crack the glass, causing fluid to leak out. When hard rubber replaced wood, the current from the battery could sometimes conduct out through a moist concrete floor. But today's polypropylene cases insulate batteries so well that it's OK to leave them on concrete.
A typical "flooded" lead-acid battery has removable caps on top to allow for checking the fluid level. Making sure the fluid level is topped off, so that it covers the lead plates, is really the only maintenance these batteries require. "A battery generates heat as it's charging, so fluid gasses off," says Rich Brandt, sales manager at Interstate All Battery Center in Everett.
He advises checking the fluid level every six months, and using only distilled water to top off the reservoir. Tap water contains minerals, which stick to the plates and cause shorting (a bad thing). Be careful about how much water you add, because excess fluid can slosh out of the caps and onto the battery, battery tray and terminals. The water is OK, but the sulfuric acid that'll mix with it is caustic and nasty to clean up.
If you have an aversion to maintenance and can spend more money, a sealed battery might be more to your liking. These are designed to be maintenance free and to charge faster, says Brett Cooper of the Northgate branch of Batteries Plus. They also have longer warranties.
But the warranty doesn't mean the sealed battery will last longer, Brandt says. Most batteries, regardless of type, last about five years on the west side of the Cascade Range, he says, and about a year less on the east side because of greater temperature variation. Seattle's mild weather puts us in "battery nirvana," Brandt says, so fluid loss is minimal.
Both Brandt and Cooper agree that the worst thing for a battery is to let a car sit idle for days or weeks, and then drive it for a short trip. In that case, the battery doesn't have a chance to fully recharge.
"A battery likes to be exercised," Cooper says. "It will atrophy if you don't use it."
For cars that sit idle for more than two weeks at a time, a battery tender can help maintain a charge. The computer-controlled, AC-powered devices are designed to continually monitor a battery's charge and turn off when it's full. Cooper says that regular battery chargers can "cook the battery" if left on too long.
A dirty battery can self-discharge more rapidly, so it helps to keep the top of the battery clean, including the metal terminals. Using a battery-terminal cleaner — a special tool that uses wire brushes to strip grime off the terminals — and a solution of baking soda and water will do a good job of cleaning the top.
How do you know when a battery is near the end of its life? The only sure way to know is to have a battery specialist or mechanic test it for you. The tests are usually free and quick.
Since lead is toxic, dead batteries should never be put in the garbage. Fortunately, lead-acid batteries are about 98 percent recyclable. Any retailer that sells batteries is required to accept them for recycling. For other recycling options, visit kingcounty.gov and search for "batteries."
If Planté were alive today, he'd probably be flabbergasted by how ubiquitous his invention is — and very wealthy.