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women can fix cars
Zack Hinckley is an instructor at Kennedy Space Center
What You Need to Know About Your Battery
(Comment #4, July 16, 1999)

   This is the second auto maintenance article I've written especially for women. That's not politically correct these days; but tough! The image of my mother, my daughters, or any woman having car trouble and being stranded is hateful to me. Like my article about tires, I know that almost no women who read this will pay attention to my recommendations about batteries; but I've done my part. If only one woman ever needs this information and recalls it I'll figure we're even.

   You need to know some things about the battery in your car. In order of importance to you they are:

  • what your battery does
  • how to maintain your battery
  • how to give or receive a jump start
  • how to recover from a dead battery
  • how to predict a battery failure
  • how to test your battery and alternator
  • how to disconnect and remove your battery
  • how to buy a new battery
What your Battery Does Your car battery has three main jobs: starting your car, which requires very high current for a relatively short time; providing current for your car generator's field, which allows you to keep your battery charged; and powering your car's electrical accessories when the engine is not running, which requires medium current for longer periods of time. Of the three, starting is the most demanding on the battery. It is while cranking the engine that most batteries fail.
   Batteries are rated in ampere-hours. A 60 ampere-hour battery will provide 60 amperes of current for one hour, or 10 amperes of current for 6 hours, or any other combination of current and hours whose product is 60.
   Not all batteries have the same capacity. The small batteries used in compact foreign cars have low capacities, in the neighborhood of 30 to 50 ampere-hours; the larger batteries used in full-size American cars or light trucks may have capacities in the range of 60 to 100 ampere-hours or more.
   By itself, the figure for battery rating doesn't mean much, but seen in terms of these typical electrical loads in your car it does:
     headlights           10 to 15 amperes
     parking lights       3 to 5 amperes
     interior light       1 to 2 amperes
     radio                1.5 amperes
     air conditioner      15 to 30 amperes
     cranking the engine  100 to 200 amperes.
   As the temperature decreases, so does battery capacity. Accidentally leaving your headlights on for an hour in cold weather can easily reduce your battery's charge to a level too low to crank the engine.
   Another way battery capacity is rated is cranking amps. The capacity is expressed in amperes for a specific time and temperature. A battery with more cranking amps than another is generally a better choice.

How to Maintain Your Battery Very few modern batteries allow full user maintenance, but some still allow simple, periodic servicing to get maximum life and performance.
   The most important maintenance you can perform is maintaining the cells' electrolyte level. The electrolyte used in automotive batteries is a strong solution of sulfuric acid and distilled water. It is both extremely toxic and extremely corrosive; it will burn holes in clothing very quickly. Servicing the electrolyte involves adding distilled water to the cells, so be very careful.
   If your battery has removable cell caps, carefully remove them and check the electrolyte level. The goal is to keep the plates in the cells fully immersed in electrolyte at all times. If you can see the tops of the plates above the electrolyte in the cell, you're losing significant battery capacity; and you may even permanently damage the cell. If the liquid level in the cell is low, add only distilled water, and only enough to each cell to bring its level up to the bottom of the filler cap well and no higher. Wipe up any spills with a cloth or paper towel and throw it away. Then put the cell caps back on and wash your hands.
   If you're observant you'll probably notice a little white powder around the battery's metal terminals. It's corrosion, and it's normal; but if the terminals are heavily corroded they can rob you of cranking power. After the battery cell caps are back in place, you can use a wet brush and a little water to rinse off the corrosion. Be careful not to let the wash water with the corrosion products get into the battery cells.
   If the battery terminals are even slightly loose, you'll lose a lot of cranking and accessory power. Make sure they're snug on the battery posts.

When loosening or tightening the battery terminal nuts or screws, be careful to prevent touching the metal of the car body with the wrench. Even a momentary short circuit through a metal tool can cause severe burns or even a battery explosion. Be very careful.
   When removing terminals, always remove the negative (ground) terminal first. It's attached to the smaller, unmarked post. When reinstalling the terminals, save the ground terminal for last!

   Finally, notice the clamp that holds the battery in the battery holder. If it's made of metal, the clamp and holder may be corroded also. Rinse them with a little water, too; dry them, and smear a thin film of vaseline or grease on the threads of any screws on the clamp. That's about as much protection as possible for components in this corrosive environment.

How to Give or Receive a Jump Start Probably the most common battery problem is a weak or dead battery caused by leaving the car without turning the lights off. It's frustrating, but it's not usually catastrophic. The solution is usually to get a jump start—use another car's battery to start your car. Jump starting is not difficult, but before we describe the procedure, you need to know something about how your car's battery and generator work.
   Almost all modern cars use a type of generator called an alternator. The alternator uses the car's battery to create magnetism from which battery charging current is generated. It's an effective system, but it requires a good battery to work. When your car's battery is weak, it not only won't start the car; it won't power the alternator, either.
   A set of jumper cables is required to connect the donor to the receiver. Most of the jumper cables I've seen in use, especially in women's cars, are stiff aluminum cables about six feet long. They almost always have thin spring clamps attached to each end. These short aluminum cables are cheap, but they are also hard to use and unsafe.
   A perfect set of jumper cables would be made of heavy flexible copper. It would be at least fifteen feet long, with very heavy well-insulated color-coded spring clamps to make the connections.
women need good jumper cables
Convenient jumper cables

   I shopped for jumper cables and found good ones at Sears for about $18.00. They were eighteen feet long, heavy flexible copper cables with robust insulation and insulated spring clamps—red for positive, black for negative. They included a good instruction sheet, a pair of safety glasses, and a nice zipper carrying pouch. Do yourself a favor and get a good set like this. The first time you use them you'll know it was a good purchase.

women can connect jumpers
Cable red to battery positive
   To jump start a car, a car with a good battery, the donor, is connected to the weak battery of the car to be started, the receiver. With its engine running, the donor can usually provide enough current to start the receiver. In this process, the donor battery is also providing current for the receiver alternator and charging current for the receiver battery.
When you're ready for the jump:
  1. connect the terminal clamp of one end of the positive (red) cable to the donor battery "+" terminal;
  2. connect the other end of the same cable to the receiver battery "+" terminal;
  3. connect the cable ground (black) end to an engine or frame bare metal ground at the receiver end. Avoid using the battery ground terminal if possible.
women can connect jumpers
Cable black to frame ground
women can jump start

During the jumping procedure be sure the two cars (donor and receiver) are not physically touching! Danger!

  1. Start the donor engine.
  2. Connect the cable ground terminal at the donor end to an engine or frame ground.
  3. Wait a minute or two and start the receiver engine. When it starts disconnect the jumper cables in the opposite order:
    5. Donor ground;
    3. receiver ground;
    2. receiver positive;
    1. donor positive.
When you're up and running, repack and store the cables.
   Once the receiver's engine is running and the donor battery is disconnected, the only battery charging current is generated by the alternator, which is now operating from a very weak battery. Consequently, the alternator output is low. Putting too great an electrical load on the battery before it has returned to normal charge may cause the car to stall again. Eventually the battery will charge fully and provide normal operating current; and the alternator will return to its normal output.
   There are some things to remember that will help make a jump start successful:
  • turn off all the receiver's lights and electrical accessories during the jump;
  • after the receiver car is started, leave it connected to the donor battery for several minutes and run it slightly faster than normal to build battery voltage;
  • after the donor battery is disconnected, do not use more than the minimum electrical accessories for several hours;
  • use a lower than normal gear for a short while to increase the engine speed and the battery charging rate;
  • drive your car a while to recharge the battery before shutting it off;
  • if you have a battery charger, connect it overnight to top off the battery's charge.
How to Predict a Battery Failure Like all the other parts of your car, your battery will eventually wear out. When it gets old it will operate at reduced capacity, and can fail at any time.
   One good way to head off an inconvenient battery failure is to keep track of your battery's age. Keep the purchase receipt in a safe place as a reference to let you know when your battery's warranty expires. It will be proof to the salesman if the battery fails before its warranty expires, and you're entitled to a rebate.
   If you keep a car record book, record the purcase date and length of warranty in your book—once on the page for the current date, and once on the last page of the book. When you change books at the beginning of each new year, transfer the battery information to the back of the new book. That way it'll always be handy.
   It is a safe practice to expect your battery to fail some time during the last quarter of its warranty period. Here are a few very distinct clues your car will give you before your battery fails because of normal aging:

signs of trouble
a "charging" indication on your dashboard ammeter that lasts more than five miles of running after a start;
a "discharging" indicator on your dashboard ammeter whenever you turn on your lights or air conditioner;
lights that noticeably dim and brighten with changes in the engine speed or the use of electrical accessories;
turn indicators that flash much more slowly when your engine is idling than when you drive at normal speed, or when your air conditioner is running;
regular sluggish startup
clock resets often
sluggish door locks
an unexpected sluggish start after a period of perfectly normal operation, frequently on a day cooler than recent days. This is a direct warning. It's time for a new battery!
a second sluggish start within a week of the first. This is a 24-hour warning--get the battery replaced today!

These indications show, first, a battery that cannot keep the alternator charging properly under varying load conditions; and, at last, a battery at the point of failure.

How to Test Your Battery and Alternator Battery and alternator failures are closely associated, particularly in the minds of auto mechanics who don't really understand how alternators work. Too many times drivers have paid for a new alternator when they really needed only a new battery. It's easy to perform a few simple tests that will determine what's causing your problems. Since you may not have the equipment and skill to perform the tests yourself, you can ask a friend or the technician at the repair shop to perform the tests for you.
   Current tests are preferred for diagnosing battery and alternator performance, but voltage tests are easier and give good results. Using a voltmeter, measure the voltage across the battery terminals:

Open circuit battery voltage. With the car and all accessories turned off, a reading less than 12.2 volts is cause for further tests.

Voltage under load. With the car off and the lights on, a reading of less than 12.0 volts is cause to test further.

Cranking voltage. With the ignition coil high tension lead grounded, crank the engine (don't start it.) A steady voltage reading less than 9.6 volts is a sign of a bad battery or a defective starting system.

Charging voltage. With the engine running steadily, A reading between 13.2 volts and 15.6 volts indicates a good alternator! A reading of less than 13.2 volts is a sign of a bad alternator or voltage regulator; a reading of more than 15.6 volts is a sign of a bad voltage regulator. Now vary the engine speed; if the voltage reading varies with the engine, the voltage regulator is bad; but probably not the alternator.

   You could reasonably ask a garage mechanic to let you watch him perform these tests before he replaced an expensive alternator. Alternator repairs are easy. If the mechanic cannot repair the alternator, but only replace it; thank him and take your problem to an automotive electrical shop. Repair there will be sure and much less expensive.
   If your tests indicate a bad battery, two more tests remain. Have them performed before you buy a replacement:

Electrolyte specific gravity (for batteries with cell caps) All six cells should indicate between 1.22 and 1.28 when the test is adjusted for ambient temperature.

Discharge/recovery. This test can be performed at better shops with computerized equipment which stresses the battery. This test should produce a definite "good" or "bad" reading, and you should be able to watch (it's interesting). This test leaves no doubts.

Important! Before you perform the discharge/recovery test... sure the store has a correct replacement battery in stock. This test leaves the old battery discharged–it will not restart your car!

How to Disconnect and Remove Your Battery Batteries are unpleasant and hazardous to handle: they're heavy, dirty, contain acid, and can produce very high electrical currents if the terminals are shorted. With care, though, you can remove them from your car with little danger.

Another Warning!
When loosening or tightening the battery terminal nuts or screws, be careful to prevent touching the metal of the car body with the wrench. Even a momentary short circuit through a metal tool can cause severe burns or even a battery explosion. Be very careful.
   When removing terminals, always remove the negative (ground) terminal first. It's attached to the smaller, unmarked post. When reinstalling the terminals, save the ground terminal for last!

   To begin, disconnect the negative (ground) terminal from the battery; this is usually the smaller, unmarked post with the black cable or the bare braided metal strap. You can trace it directly to solid metal on the engine or car frame. Do not allow your wrench to contact the other battery terminal while you are removing the ground terminal. With the ground cable disconnected and tucked out of the way, the chance of electrical shorts is greatly reduced.
   Next remove the positive cable. It is usually red, and its terminal post is almost always larger and often marked with "+".
   Next, remove the battery holding clamp and set it aside, out of the way. With both hands, carefully lift the battery from its frame or tray, keeping it level to prevent spilling the electrolyte.
   Place the battery on a level surface. If you'll be transporting the battery to the shop for replacement, be sure to put it in your trunk on a sheet of plastic or in a plastic bucket to protect your trunk from the electrolyte. Wash your hands after handling the battery. At the battery shop, let the service personnel do all the remaining handling.
   Replacing the battery is the reverse of removal. Just remember that the last connection to be made is always the negative terminal.

After replacing your battery you'll need to reset your dashboard clock and your radio station tuning. Your fuel injector computer will readjust itself, too, over a period of several days. This is normal.

How to Buy A New Battery There are three simple rules for buying a new battery:
  1. Don't buy an expensive, long-warranty battery if you expect to replace your car any time soon;
  2. always buy a battery with the proper electrical capacity and physical size for your car;
  3. This is America! Never pay full price for a battery.
   Electrical capacity is usually measured in terms of cranking amps and ampere-hours; we've discussed that already. Remember, a battery with a small capacity will be under high stress all the time. Its life and safety margin may be shorter than a battery with a large capacity; but it may also cost less.
   There are many different quality ranges of battery—usually expressed in terms of months of life. Naturally, the longer the warranted life of a battery, the longer you would expect to go between replacements; but this is not necessarily so. Many batteries fail prematurely, especially in hot, humid environments. If your battery lasts its full warranty life that's rare, and you can expect it to be on its last legs. Generally, don't be surprised if your battery fails any time after its first two years of in-car use.
   Buy only batteries of the proper capacity for your car, and only when they are are on sale. Many times sale batteries are far better values than top of the line batteries.
   To predict failures before they occur, have a discharge/recovery test done once a year, starting at the end of the first two years.
   In general, try to find a battery with a warranted life of about 30 months. You'll be surprised how easy that is. And another tip: chain stores with long, good reputations, like Sears, Ward's, or Penney's will treat you politely and fairly at time of sale and time of warranty replacement.

   A last note: that old battery is worth a rebate at the time of sale; returning it is much easier than trying to dispose of it yourself.


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