An automobile battery produces electricity through chemical reaction. Two plates, made of different metals, are immersed in sulfuric acid (an electrolyte) which creates a flow of electrons to produce electrical power. Automobile batteries have several cells, each of which produces 2 volts of power. Most automobiles require 12V batteries consisting of six cells. Each cell has its own plates and electrolyte to produce a portion of the total output of the battery. These are wired in series to the positive and negative posts of the battery.
- BATTERY SAFETY TIPS
Batteries are filled with sulfuric acid and therefore can be dangerous if handled improperly. The acid can eat through clothing and burn flesh. Do not smoke or cause sparking near an auto battery. Wear outer garments including gloves and safety goggles when working on a battery. If battery acid comes in contact with skin or eyes, flush with water for 15 minutes and get medical attention.
- LEAD ACID BATTERY ALERT
As current is drawn from the battery, the acid is absorbed by the plates. When all the acid is absorbed, the electrolyte becomes essentially water and the battery can no longer produce a current. Charging the battery causes the acid to move from the plates back into the solution. Ampere-hour capacity or electrical size are terms referring to the number of plates per cell or the size of the plates. Increasing size or number means increased power capacity.Lead acid batteries are the major source of lead entering the municipal solid waste system. Disposals of batteries in landfills and incinerators can result in human exposure to lead via ground water, drinking water and ambient air. High levels of lead exposure can cause brain and nervous disorders, anemia, high blood pressure, kidney and reproductive problems and even death. Children are particularly sensitive to the effects of lead poisoning. Many states have enacted legislation which bans the disposal of batteries in municipal solid waste landfills and incinerators. Most of these laws are specific regarding how used batteries are handled. Retailers selling a new battery are required to accept and recycle the old battery. In addition, many states require that the secondary lead smelter or state-authorized collection and recycling facility by the retailer who accepts used batteries. Check to see if your state has such legislation and be sure your store has a copy of the law.
Wet/Dry Charge
The terms wet or dry charge refer to whether the electrolyte is in the battery when it is shipped. If batteries arrive dry, the electrolyte must be added and the battery given a “boost” charge. The following procedures are recommended:
- Fill each cell to the top of the separators with electrolyte (water cannot be used).
- Boost charge until warm to the touch. Electrolyte should be about 80°F.
- Check specific gravity with hydrometer. Should be minimum of 1.250.
- Add electrolyte to each cell to bring level to appropriate level indicated by manufacturer.
Shipping and storing dry batteries has the obvious advantage of eliminating spillage, etc. The disadvantage is the time, labor and materials necessary to convert dry batteries to wet. Maintenance-free batteries are permanently sealed; the unit contains fluid but provides no access to it. They are considerably more costly but require no additional water throughout the normal life of the battery. Special alloy grids reduce water loss, and a greater reservoir of electrolyte works with the grids to extend the normal life.
Cranking Amps
Cranking amps, or cranking performance, is a measurement of the power relationship between batteries and engine size. One cranking amp is recommended for each cubic-inch displacement of the engine.
A cranking amps value of 400, for example, is the minimum rating that should be used for an engine with a 400-cubic-inch displacement. High compression ratios, extreme weather conditions or high-power accessories would require an even higher cranking amps rating.
Battery Testing
The battery charge can be tested with a hydrometer, which measures the specific gravity of the electrolyte. A specific gravity of 1.000 means that the liquid is essentially water. A fully charged battery should have a specific gravity reading of approximately 1.265. A reading of 1.220 indicates a half charged battery and 1.180 means the battery is near total discharge.
Batteries must also be tested for variance between cells. A reading showing a difference of more than .050 between cells means the battery must be replaced; less indicates it can be recharged. Batteries stored wet should be periodically checked to ensure that the specific gravity reading remains above 1.250. Every battery should be checked prior to its sale.
Another test that should be made prior to selling the battery is the load test. A meter is connected between the negative and positive poles to check the actual load produced. A poor reading indicates that the battery is either not fully charged or that it is defective.
Maintenance Tips
Fluid levels should be checked once a month and cells filled to within 1/4” of the bottom of the filler neck. If it is necessary to add fluid, distilled water should be used and the engine run for a time if the temperature is below freezing. Dirt and water should be cleaned from the top of the battery and corrosion removed from the terminals and clamps.
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