AUTOMOTIVE BATTERIES

14. WHAT ARE SOME OF THE MYTHS ABOUT BATTERIES?

14.1. Storing a battery on a concrete floor will discharge them.

A hundred years ago when battery cases were made of porous materials such as wood, storing batteries on concrete floor would accelerate the discharge. Modern battery cases are made of polypropylene or hard rubber. These cases seal better, so external leakage-causing discharge is no longer a problem, provided the top of the battery is clean. Temperature stratification within large batteries could accelerate the internal "leakage" or self-discharge if the battery is sitting on a cold floor in a warm room or is installed in a submarine.

14.2. Driving a car will fully recharge a battery.

There are a number of factors affecting an alternator's ability to charge a battery. The greatest factors are how much current from the alternator is diverted to the battery to charge it, how long the current is available and the temperature. Generally, idling the engine or short stop-and-go trips during bad weather at night will not recharge the battery. Please see Section 5.

14.3. A battery will not explode.

Recharging a wet lead-acid battery normally produces hydrogen and oxygen gasses. While spark retarding vent caps help prevent battery explosions, they occur when jumping, connecting or disconnecting charger or battery cables, and starting the engine. While not fatal, battery explosions cause thousands of eye and burn injuries each year.

When battery explosions occur when starting an engine, here is the usual sequence of events: One or more cells had a high concentration of hydrogen gas (above 4.1%) because the vent cap was clogged or a defective valve did not release the gas. The electrolyte levels fell below the top of the plates due to high under hood temperatures, overcharging, or poor maintenance. A low resistive bridge or "treeing" formed between the top of the plates such that when the current started to flow, it caused an arc or spark in one of the cells. That combination of events ignites the gas blows the battery case cover off and spatters electrolyte all over the engine compartment. The largest number of battery explosions while starting an engine occurs in hot climates.

When an explosion happens, thoroughly rinse the engine compartment with water, and then wash it with a solution of one-pound baking soda to one gallon of warm water to neutralize the residual battery acid. Then thoroughly rewash the engine compartment with water. Periodic preventive maintenance (please see Section 3), working on batteries in well-ventilated areas or using Valve Regulated Lead Acid (AGM or gel cell) type batteries can significantly reduce the possibility of battery explosions.

14.4. A battery will not lose its charge sitting in storage.

Depending on the type of battery and temperature, batteries have a natural self-discharge or internal electrochemical "leakage" at a 1% to 25% rate per month. Thus, over time the battery will become sulfated and fully discharged. Higher temperatures accelerate this process. A battery stored at 95o F (35o C) will self-discharge twice as fast than one stored at 75 o F (23.9o C). (Please see Sections 15 and 16.)

14.5. "Maintenance free" batteries never require maintenance.

In hot climates, the water in the electrolyte is "decomposed" due to the high under hood temperatures. Water can also be lost due to excessive charging voltage or charging currents. Non-sealed batteries are recommended in hot climates so distilled water can be added when this occurs. (Please see Section 3. for other preventive maintenance that should be performed on "maintenance free" batteries.)

14.6. Test the alternator by disconnecting the battery with the engine running.

A battery as like a voltage stabilizer or filter to the pulsating DC produced by the alternator. Disconnecting a battery while the engine is running can destroy the sensitive electronic components connected to the entire electrical system such as the emission computer, audio system, cell phone, alarm system, etc., or the charging system itself because the peak voltage can rise to 40 volts or more. In the 1970s, removing a battery terminal was an accepted practice to test charging systems of that era. That is not the case today. Just say NO if anyone suggests this.

14.7. Pulse chargers, aspirins or additives will revive sulfated batteries.

Using pulse chargers or additives is a very controversial subject. Most battery experts agree that there is no conclusive proof that more expensive pulse chargers work any better than constant voltage chargers to remove sulfation. They also agree that there is no evidence that additives or aspirins provide any long-term benefits.

14.8. On really cold days turn your headlights on to "warm up" the battery up before starting your engine.

While there is no doubt that turning on your headlights will increase the current flow in a car battery, it also consumes valuable capacity that could be used to start the cold engine. Therefore, this is not recommended. For extremely cold temperatures, externally powered battery warmers or blankets and engine block heaters are highly recommended. AGM and Ni-Cad batteries will perform better than other types of batteries in extremely cold temperatures.

14.9. Car batteries last longer in hot climates than in cold ones.

Car batteries last an average of two thirds as long in hot climates as cold ones. Heat kills car batteries, especially sealed wet lead acid batteries. (Please see Section 11.1.)

14.10. Charging Cables or an Auto Jump Starter will start your car.

The cigarette lighter charging cable's advertising states "charges weak batteries in minutes." The charging cable products will certainly recharge your car battery if you have enough time and your battery is in good condition. Cigarette lighters are normally fused at 10 amps, so to be safe they probably limit current flow to 7.5 amps. Given the size of the cord, the amount might be even less.

They work by applying higher voltage from the good battery to "recharge" the bad one. Now let's assume it is a hot day and that you need just of 15% of the battery's capacity to start the engine and that it is a 50 ampere-hour battery. This means you will need 7.5 amps for at least 60 MINUTES to flow from the good battery to the bad one. Now let's also assume that it is a cold day and you have left your lights on. You will need at least 50% capacity or 25 amps to start the car. This will take at least 200+ MINUTES to charge the dead battery. Unless the engine is left running in the car with the good battery, you run the risk of running the good battery down to a point that it might not be able to start a car.

An auto jump starter uses special high current batteries to provide up to 900 peak amps to start your engine. It can provide 200-300 amps for up to 8-10 seconds. After this, the unit has to be recharged for 24 to 48 hours. Standard AA alkaline batteries are used to trickle charge the special batteries. This type of emergency starter should start all but diesel engines up to six or eight times, depending on the condition of the engine and the temperature.

14.11. A larger capacity battery will damage my car.

A starter motor will only draw a fixed amount of current from the battery, based on the resistance of the load. A larger current capacity battery supplies only what is required but will give you more starting capacity and will not damage your car. Using batteries with higher voltage can damage your car. Using batteries that are too large physically can also damage your car.

14.12. Car batteries have memories.

Lead acid batteries do not have the "memory effect" found with first generation Ni-Cad batteries. Deep discharges can damage car batteries and will shorten their lives.

14.13. Bad batteries will not harm the charging system or starter.
A bad or weak battery causes more stress on a charging system or starter and can cause premature failures due having to compensate the voltage or current. If you replace a battery, alternator, voltage regulator or starter, you should test the other components for latent or permanent damage.


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