A car battery can die out after a few years.
Car batteries weaken with time. In fact, according to BatteryStuff.com, only 30% of batteries sold today last a full four years. This is partly due to the numerous electrical appliances in today's cars. Fortunately, 80% of weak batteries got that way by a reversible process. This process, called "sulfation," is something you can even reverse on your own, at a fraction of the cost of getting a new battery.
Instructions
1. Put on safety eyewear and gloves. Sparks when the battery terminal and clamp are closed can ignite battery gas and blind you with the explosion. Put on rubber-soled shoes.
2. Remove the ignition key from the cylinder.
3. Unclamp the battery cables from the battery terminals. Place the battery somewhere ventilated.
4. Take the plastic cell caps off the top if it's a "serviceable" battery. If not, you'll have to drill holes into the plastic--one per cell. The battery should have little marks above each cell to tell you where to drill. Drill the holes wide enough to slide in a funnel. (Afterward you'll fill the holes with "hole caps." Pick them up at a hardware or auto supply store.)
5. Heat a liter (quart) of distilled water in the microwave, somewhere between lukewarm and boiling. Tap water won't work here. Its minerals coat the metal battery plates.
6. Dissolve 10 tablespoons of Epsom salts (magnesium sulfate) into a liter of distilled water.
7. Pour the saline solution into the six holes using a funnel. Marks on the battery side should tell you how high to fill.
8. Use a "smart charger" to recharge the battery overnight. It will vary the charge at varying rates to maximize the percentage of electrolytes that end up charged, without overcharging, which leads to further sulfation. Make sure the charger is a 3-step charger so you get a full charge. Charging the battery using only the car's alternator can leave 10% of the electrolytes uncharged, which leads to sulfation. You can get a 3-step charger online for as low as $40 (see Resources).
Tags: 3-step charger, distilled water, which leads