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 tar-lined wood boxes, so storing batteries on concrete floor would accelerate their 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 very large batteries could accelerate their internal "leakage" or self-discharge if the battery is sitting on an extremely 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, such as 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 or at night might not fully recharge the battery.  Please see Section 5.

14.3.  A battery will not explode.

There two types of battery explosions are external and internal. Recharging a wet lead-acid battery produces hydrogen and oxygen gasses. While spark retarding vent caps help prevent external battery explosions, sparks occur when jumping, connecting or disconnecting charger, or battery cables and ignite the gas.  Internal explosions usually occur while starting the engine and normally blow the filler caps or cover off and splatter electrolyte all over the engine compartment. The most probable cause is from a combination of low electrolyte levels in the battery and a low resistance bridge formed between or across the top of the plates called "treeing" between a positive and negative plate. When heavy current flows in the battery such as starting an engine, a spark occurs and ignites the residual gas in one or more of the cells. A second possible cause is a defect in the weld of one of the plate connecting straps.

[Source: Popular Mechanics]

Periodic preventive maintenance (Please see Section 3.), working on batteries in well-ventilated areas, or using sealed AGM or gel cell type batteries can significantly reduce the possibility of battery explosions. To neutralize the residual battery acid, be sure to thoroughly wash the engine compartment and the back of the hood with a solution of one-pound baking soda to one gallon of warm water and rinse with water. The largest number of battery explosions, while starting an engine, occurs in hot climates. While not fatal, battery explosions cause thousands of eye and burn injuries each year. Should a battery explosion occur and battery electrolyte (or battery acid) get in someones' eyes, flush them out with any drinkable liquid immediately because seconds count.

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 electro chemical "leakage" at a 1% to 25% rate per month. Over time the battery will become sulfated and fully discharged. Higher temperatures accelerate this process. A battery stored at 95° F (35° C) will self-discharge twice as fast than one stored at 75° F (23.9° C). (Please see Section 15. and Section 16.)

14.5. "Maintenance free" batteries never require maintenance.

In hot climates, the water in the electrolyte is lost 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 electrical system such as the emission computer, audio system, cell phone, alarm system, etc., or the charging system 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.

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 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. Short term gains are achieved by increasing the acidity of the battery.

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 cold temperatures, externally powered battery warmers or blankets and engine block heaters are highly recommended if the vehicle can not be parked in a heated garage.  AGM and Ni-Cad batteries will perform better than other types of wet Lead-acid 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 maintenance free batteries and cold reduces the battery's starting capacity. (Please see Section 11.)

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."  There is little doubt that 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 3% of the battery's capacity to start the engine from a 40 ampere-hour battery. This means you will need at least 7.5 amps for 10 minutes to flow from the good battery to the bad one.  Now let's also assume that it is below freezing and you have left your lights on.  You will need at least 50% capacity or 20 amp hours to start the vehicle. This will take over two hours to partially charge the dead battery.

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 its load.  A larger current capacity battery supplies only what is required. It will not damage your vehicle.  Using batteries with higher or lower voltage or physically too tall could potentially damage your vehicle.

14.12.  Lead-acid batteries have memories.

Lead-acid batteries do not have the "memory effect" found with first generation Ni-Cad batteries; however, continuous under charging will lower the capacity of the battery.  Deep discharges can also damage starting batteries or can 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.

14.14.  Once formed, batteries will not charge polarity.

If a battery is fully discharged and continues to have load, for example leaving the headlights on, it is possible for one or more cells to reverse polarity. This is referred to as "cell reversal". To change polarity, fully discharge the battery and charge it with the correct polarity.

<<<Previous        [Top]       Next>>>