Caring for your car battery
The last thing you need is a car that won’t start because the battery is dead. You can avoid that expensive service or tow charge (and the worry of being stranded!) by carrying out a 10-minute seasonal battery check along with a few maintenance tips.
In addition to a set of wrenches, you’ll only need a post cleaner or side terminal, a hydrometer and a cable puller, all available at auto parts stores. Keep in mind that you can skip the battery service if you make sure the mechanic does it during periodic servicing, but you’ll want to keep up with the regular maintenance.
Step 1: Clean the cables
Clean corrosion from the battery
Clean corrosion from the top of the auto battery first and then clean corrosion from around the battery cables with a post cleaner.
First clean the top of the battery and any corrosion from the cables using a tablespoon of baking soda, a cup of water and a nonmetallic brush. Flush with cool water. Now disconnect the cables, starting with the negative one to prevent your wrenches from arcing on a nearby ground. Loosen the battery cable clamp bolts and gently give them a twist. Use a cable puller if they’re stuck. Never pry on the auto battery posts. If you have a side post terminal (not shown), use a 5/16-in. box wrench to loosen the cables. With the cables removed, further clean off the corrosion around the auto battery terminals and cables with a post cleaner.
Step 2: Check the level of the electrolyte
Add water to fill holes, if necessary
If the battery needs water, use clean, distilled water and don’t over fill the cells.
If you have a no-maintenance battery, check to see if you have a green dot in the sight glass/charge indicator. Green means the battery is good. If it’s dark, it needs recharging. If it’s yellow or has no color at all, (inspect carefully and use a flashlight), replace the battery.
If you have preset radio stations or other memory functions in your car and want to keep them, go to your auto parts store and get a device like the one shown and a fresh 9-volt battery. Plug this into your cigarette lighter before you disconnect the cables. This will give you about one hour to clean the cables and test the battery charge.
Gently pry off the covers of the battery cells. (We discuss what to if you have a no-maintenance sealed battery later in this step.) The water and acid mixture in the battery (electrolyte) should be about 1/2 in. deep or to the bottom of the fill hole. If it needs water, use clean distilled water, being careful not to overfill the cells, and then inspect the battery case for cracks. If you find a crack, replace the battery. If you added water, let the water mix with the electrolyte for a few hours before the next step. (You may need to reconnect the battery to maintain your memory functions.)
Step 3: Check the condition and charge of the battery
Test the electrolyte in each cell with a hydrometer
To test the electrolyte in each cell, squeeze the ball on the hydrometer and draw the solution into the tester. Hold the test level, record the reading and squirt the solution back into the cell.
Test the electrolyte in each cell. Squeeze the ball and draw the solution into the tester. Carefully hold the tester level and write down the reading. Squirt the solution back into the same cell. The testers are calibrated assuming a battery is at 80 degrees F. Add .04 to each reading for every 10 degrees above 80 and subtract .04 for every 10 degrees below. If you get a cell reading that differs from the others by .05 or more, replace the battery. A fully charged battery should have a reading of 1.265 or higher. If all the readings show fair or low (1.200 is low) but are consistent, recharge the battery. Learn how to replace a car battery in our video tutorial.
Step 4: To drop in the new battery first remove the cables
Disconnecting negative cable first
Disconnect the negative cable first and then the positive
Remove your battery hold-down clamp. Disconnect the negative cable first, then the positive. Note: Always replace the battery with one that has a higher rating than the original.
Always wear eye protection and rubber gloves when working on batteries, and never smoke around them!
Step 5: Replace the battery
Lifting out old battery
Use the heavy-duty strap to carefully lift out the old battery
Tie a heavy-duty strap to the ears on the side of the battery and gently lift it out. Be careful; battery acid is dangerous. Don’t drop it. Once the battery is out, clean the battery tray and replace it if it’s badly corroded. Batteries are heavy and need solid support!
Step 6: Reinstall the clamp and cables
Connecting hold-down clamp
Connect the hold-down clamp before connecting the cable to the terminals
Carefully lift the new battery into place. Connect the hold-down clamp, then connect the cable to the positive terminal first and the negative last (for negative ground systems). Smear a little petroleum jelly onto the terminal before fastening the cable clamps to the posts. The grease will help slow corrosion. Most batteries are at least 75 percent charged when you buy them and should be ready for you to start your car and drive. Check with your supplier to see if your new battery needs charging before you use it.
Telltale Signs of a Low or Failing Battery
- Your headlights look dim at idle and then brighten when you rev the engine.
- The starter turns slowly, barely starting the car. But you may have alternator wiring problems that prevent the battery from fully charging. If that’s the case, schedule a service appointment. Check your fan belt. If it’s loose, frayed, cracked or glazed, have it serviced or replaced.
A low battery can also be caused by:
- Frequent short trips.
- Too many accessories left on or added.
- Look for a purchase date chart on the battery (it may be handwritten). The battery case will also have a decal stating its expected life, such as 60 or 84 months. If it’s near the end of this expected service life, replace it.
Battery Storage: Use a Battery Maintainer
You’ve emptied the gas, sealed the exhaust and prepared the engine for seasonal storage. But before you throw the tarp over your boat or roadster for the long winter sleep, think about how you’re going to care for the battery.
Batteries lose their charge when they sit idle, and when that happens, you could wind up with a worthless battery in the spring. To keep batteries healthy, they should be charged every six weeks. But leaving a standard battery charger connected for the whole season isn’t a good idea—that will overcharge the battery and shorten its life. Instead, invest in a “battery maintainer.”
Battery maintainers are designed to be left on for the entire off-season. They monitor battery voltage and automatically adjust the charge to avoid under- and overcharging.
Battery charger/maintainers and quick-release terminals are available at most auto parts stores or online.
Required Tools for this Project
Have the necessary tools for this DIY project lined up before you start—you’ll save time and frustration.
- Safety glasses
- Wrench set
Required Materials for this Project
Avoid last-minute shopping trips by having all your materials ready ahead of time. Here’s a list.
- petroleum jelly