Date: Sun, 14 Apr 96 23:04:13 CDT
Sender: Vanagon Mailing List <vanagon@vanagon.com>
From: Joel Walker <JWALKER@ua1vm.ua.edu>
Subject: Battery FAQ ...
i'm not sure any of this has been posted to the list, and not real sure
of the polite protocol, but i found this on another car list, and thought
it might be of some use to folks on ours. i don't know anything about the
folks who wrote it, but it seems to be pretty good.
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FROM THE BATTERY FAQs:
Here is the new and improved edition of the Car Battery FAQ.
CAR BATTERY FREQUENTLY ASKED QUESTIONS 1.1
August 19, 1995
A word of caution. Batteries contain a sulfuric acid electrolyte which
is a highly corrosive poison and produces gasses that will explode if
ignited. When working with batteries, you need to remove jewelry, wear
protective clothing and eye ware, and exercise caution. Follow the
manufacturer's instructions for testing, jumping, installing and
charging.
This FAQ assumes a 12 volt negatively ground system. For six volt
batteries, divide the voltages by two.
CONTENTS
1. WHAT IS THE BOTTOM LINE?
2. WHY BOTHER?
3. HOW DO I TEST A BATTERY?
4. HOW DO I KNOW IF THE CHARGING SYSTEM IS OK?
5. HOW DO I JUMP START MY CAR?
6. WHAT DO I LOOK FOR IN BUYING A NEW BATTERY?
7. HOW DO I INSTALL A NEW BATTERY?
8. HOW DO I RECHARGE MY BATTERY?
9. HOW CAN I INCREASE THE LIFE OF MY BATTERY?
10. WHAT ARE THE MOST COMMON CAUSES OF PREMATURE BATTERY FAILURES?
11. WHAT ARE THE MYTHS ABOUT BATTERIES?
1. WHAT IS THE BOTTOM LINE?
A. Check specific gravity in each cell and remove surface charge
before load testing,
B. Retest after deep discharges or jump starts,
C. Recharge slowly at 14.6 volts,
D. Buy the freshest and largest Reserve Capacity, non-sealed
car battery that will fit with a CCA rating for your climate
that meets or exceeds the car's OEM cranking amps requirements,
and
E. Perform preventative maintenance, especially during warm
weather.
2. WHY BOTHER?
Because only the rich can afford cheap batteries.....
A good quality car battery will cost between $50 and $100 and, if
properly maintained, will give you four to eight years of service. The
purpose of a battery is to start the car; to provide power for the
ignition, lighting and other accessories when their combined load
exceeds the capability of the alternator; and to filter the power. Dead
batteries almost always occur at the most inopportune times, e.g.,
returning home from a long trip, during bad weather, late at night in a
dark parking lot or when you are late for an appointment. You can
easily spend the cost of a new battery or more for an emergency jump
start or tow.
Most store employees do not know how to correctly test a battery. The
national average of "defective" batteries returned to the manufacturer
that are in fact good exceeds 50%.
3. HOW DO I TEST A BATTERY?
A. Visually inspect for obvious problems, e.g., damaged case,
corrosion, loose hold-down clamps or cable terminals, or low
electrolyte.
B. If you have just recharged you battery or driven your car,
eliminate any surface charge by one of the following methods;
otherwise, go to the next step:
1. Allow the battery to sit for two to three hours,
2. Turn the headlights on high beam for three minutes and
wait five minutes before further testing, or
3. With a battery load tester, apply a 150 amp load
for 10-15 seconds.
C. Using the following table, determine the battery's
state-of-charge. The BEST way to measure the state-of-charge is to check
the specific gravity in each cell with a hydrometer. A temperature
compensating hydrometer can be purchased at a auto parts store for
approximately five dollars. If the battery is sealed (maintenance
free), the correct procedure to test it is to measure the battery's
voltage WITHOUT the engine running with a good quality digital DC
voltmeter. Some sealed batteries have built-in hydrometers. They are
not good testing devices because they only measure the state-of-charge
in one of the six cells.
If the state-of-charge is BELOW 75% using either test, then the battery
needs to be recharged BEFORE proceeding. If there is a .050 or more
difference in the specific gravity reading between the highest and
lowest cell or the battery will not recharge to 75% or higher, then the
battery should be replaced.
Battery Approximate Average Cell
Voltage State-of-charge Specific Gravity
12.66 100% 1.265
12.45 75% 1.225
12.24 50% 1.190
12.06 25% 1.155
11.89 0% 1.120
Note: If the temperature of the electrolyte is below 70 degrees F, then
add .012 volts (12 millivolts) per degree below 70 degrees F.
D. If the battery's state-of-charge is at 75% or higher, then load
test the battery by one of the following methods:
1. Turn the headlights on high beam for six minutes,
2. Disable the ignition and turn the engine over for 15
seconds with the starter motor,
3. With a battery load tester, apply a load equal to one half
of the Cold Cranking Amp (CCA) rating of the battery, or
4. With a battery load tester, apply a load equal to one half
the Original Equipment Manufacturer (OEM) cranking amp
specification.
DURING the load test, the voltage on a good battery will NOT drop below
9.7 volts with the electrolyte at 80 degrees F. (If the electrolyte
is above 80 degrees, add .1 volt for every 10 degrees above 80 until you
reach 100 degrees. If below 80 degrees, subtract .1 volt for every 10
degrees until 40 degrees.) After the load is removed, the battery
should "bounce back" to the 50% state-of-charge level or above. If the
battery drops below minimum test voltage, does not bounce back or will
not start the engine, then you should replace it. If it passes this
test, you should recharge your battery to restore it to peak
performance.
4. HOW DO I KNOW IF MY CHARGING SYSTEM IS OK?
When the charging system fails, usually the alternator light will come
on. With a good battery and the engine running at 2000 RPM or more for
two minutes, depending on the load and ambient temperature, the voltage
will increase to between 13.0 and 15.1 volts. Other factors affecting
the charging voltage are the battery's age, state of charge, and
electrolyte level and purity. A loose alternator belt or bad diode will
significantly reduce the alternator's current output. If the battery
tests good after being externally recharged and you are still having
problems keeping it charged, then have the alternator's output voltage
and current and car's parasitic (key off) load tested.
5. HOW DO I JUMP START MY CAR?
A. Determine that the electrolyte is NOT frozen. If frozen, allow
to thaw.
B. Turn off all unnecessary accessories and lights on both cars.
C. Start the car with the good battery and let it run for at least
two or three minutes at fast idle BEFORE attempting to start
the disabled car to recharge it's battery.
D. Connect the POSITIVE terminal on the disabled battery to the
POSITIVE terminal on the good battery.
E. Connect the NEGATIVE terminal on the good battery to a clean,
unpainted area on the ENGINE BLOCK on the disabled car.
F. Let the good car to continue to run for five minutes or more.
This will allow the dead battery to receive some charge and to
warm it's electrolyte.
G. Start the disabled car and allow to run at fast idle.
[Starting the disabled car with the good car running will
prevent having two disabled cars.]
H. Disconnect the jumper cables in the reverse order, starting
with the ENGINE BLOCK on the disable car.
6. WHAT DO I LOOK FOR IN BUYING A NEW BATTERY?
A. Cold Cranking Amps (CCA)
The most important consideration is the battery's CCA rating. CCAs are
the discharge load measured in amps that a fully charged battery at 0
degrees F can deliver for 30 seconds and while maintaining the voltage
above 7.2 volts. Batteries are sometimes advertised by their Cranking
Amps (CA) measured at 32 degrees F or Hot Cranking Amps (HCA) measured
at 80 degrees F, which are not the same as CCA. Do not be mislead by
CAs or HCAs. To convert CAs to CCAs, multiply the CAs by .8. To
convert HCAs to CCAs, multiply HCAs by .69. In hot climates, buying
batteries with double or triple the CCA ratings that exceed the OEM
requirement is a WASTE of money. However, in colder climates the higher
CCA rating the better, due to increased power required to crank a
sluggish engine and the inefficiency of the cold battery. One of the
major manufacturers, Exide, publishes the following table:
Available Power Temperature Power Required
From Battery degrees F To Crank Engine
100% 80 100%
65% 32 155%
40% 0 210%
25% -32 350%
If more CCA capacity is required, two 12 volt batteries can be connected
in parallel.
B. Reserve Capacity (RC)
The next most important consideration in buying a battery is the Reserve
Capacity rating because of the effects of an increased parasitic or "key
off" load produced by electrical devices, e.g., fans, clocks, computers,
etc., that operate after the engine is stopped. RC is the number of
minutes a fully charged battery at 80 degrees F can be discharged at 25
amps until the voltage falls below 10.5 volts. More RC is better in
every case. For example, if your car has a 360 OEM cranking amp
requirement, then a 450 to 500 CCA rated battery with 120 minute RC
would be more desirable in a warm climate than one with 700 to 800 CCA
with 90 minutes of RC. If more RC is requires, two six volt batteries
can be connected in series or two 12 volt batteries can be connected in
parallel.
C. Type
The two most common types of car batteries are non-sealed (low
maintenance) and sealed (maintenance free). A sealed (maintenance free)
battery will NOT allow you to test the specific gravity with a
hydrometer or add DISTILLED water when required. Sealed batteries are
more prone to deep discharge failures, but require less preventative
maintenance. Some manufactures have introduced a "dual" car battery
that combines a standard battery with switchable emergency backup cells.
For about the same cost a better approach is to buy two batteries and
isolate them.
Car batteries are specially designed for high initial cranking amps
(usually for five seconds) to start a car; whereas, deep cycle or
"marine" batteries are designed for prolonged discharges at lower
amperage. A "dual marine" battery is a compromise between a car and
deep cycle battery. However, a CAR battery will give you the best
performance in a CAR. For RV's, a car battery is used to start the
engine and a deep cycle battery is used to power the accessories. The
batteries are connected to a diode isolator and recharged by the RV's
alternator.
D. Size
Manufacturers build their batteries to an internationally adopted BCI
group number (24F, 35, etc.) specification, which is based on the
physical case size, terminal placement and terminal polarity. The OEM
battery group number is a good starting place to determine the
replacement group. Within a group, the CCA and RC ratings, warranty and
battery type will vary in models of the same brand or from brand to
brand. Batteries are generally sold by model, so the group numbers will
vary for the same price. This means that for the SAME price you can
potentially buy a physically larger battery with more RC than the
battery you are replacing. Be sure that the replacement battery will
fit, the cables will correct to the correct terminal, and that the
terminals will NOT touch the hood when closed.
The battery manufacturers publish application guides that will contain
the OEM cranking amp and group number replacement recommendations by
make, model and year of car, and battery size, CCA and RC
specifications. Manufacturers might not build or the store might not
carry all the group numbers. To reduce inventory costs, dual terminal
"universal" batteries that will replace several group sizes are becoming
more popular. The four largest domestic battery manufacturers are
Johnson Controls (Interstate, Motorcraft, Energizer, older Diehards),
Delco (Sears, newer Diehards), GNB (Champion) and Exide (NAPA).
E. Freshness
Determining the "freshness" of a battery is sometimes difficult. NEVER
buy a battery that is MORE than SIX months old. The date of manufacture
is stamped on the case or printed on a sticker. It is usually a
combination of alpha and numeric characters with letters for the months
starting with "A" for January (skipping "I") and digit for the year,
e.g., "F5" for June, 1995. Like bread, fresher is definitely better.
F. Warranty
As with tire warranties, battery warranties are not necessarily
indicative of the quality or cost over the life of the car.
Manufacturers will prorate warranties based on the LIST price, so if a
battery failed half way or more through its warranty period, buying a
NEW replacement might cost you less. The exception is the free
replacement warranty period. This represents the risk that the
manufacturer is willing to assume. A longer free replacement warranty
period is better.
7. HOW DO I INSTALL A BATTERY?
A. Thoroughly wash and clean the old battery, battery terminals
and case or tray with water to minimize problems from acid or corrosion.
Heavy corrosion can be neutralized with a mixture of baking soda and
water. Auto parts stores sell a cheap wire brush that will allow you to
clean the inside of a terminal clamps. Mark the positive cable so you
do not forget which one it is when you reconnect.
B. Remove the NEGATIVE cable first, the POSITIVE cable and then
the hold-down bracket or clamp. Dispose the old battery by exchanging
it when you buy your new one or at a recycling center. Batteries
contain large amounts of lead and acid.
C. After removing the old battery, be sure that the battery tray
and cable connectors are clean. If the cables are corroded or damaged,
replace them; otherwise, they will significantly reduce starting
capability.
D. Place the replacement battery so that the NEGATIVE cable will
connect to the NEGATIVE terminal. Reversing the polarity of the
electrical system WILL severely damage it.
E. After replacing the hold-down bracket, reconnect the POSITIVE
cable first and then the NEGATIVE cable.
F. Before starting the engine, check the electrolyte levels and
state-of-charge and refill or recharge as required.
F(b). Turn off the good car's ignition. Its battery is
presumably ok, so it should easily be able to start
the disabled car, even through the long jumper cables.
Failure to do this, especially if the well-meaning owner
of the good car tries to "help" start the disabled car by
revving his engine as the disabled car's starter is
cranked, can destroy the good car's alternator.
G. Coat the terminals with a high temperature grease to prevent
corrosion.
If you do not want to lose your car's computer memory, security codes or
radio settings, a second battery can be temporarily connected to the
electrical system in parallel before disconnecting the first one. A
cigarette lighter plug can easily connect a parallel battery.
8. HOW DO I RECHARGE MY BATTERY?
Some more words of caution. Do NOT ever disconnect a battery cable from
car with the engine running because the battery acts like a filter for
the electrical system. Unfiltered electricity can damage the electrical
components, for example, computer, radio, etc. Check the electrolyte
level before recharging. Do NOT add water if the electrolyte is
covering the top of the plates because during the recharging process, it
will warm up and expand. After recharging has been completed and the
electrolyte has cooled, RECHECK the level and add DISTILLED water to
1/8" BELOW the bottom of the filler tube (vent wells) or to the level
indicated by the battery manufacturer. Reinstall the vent caps before
recharging and recharge ONLY in well ventilated areas. NO smoking,
sparks or open flames because while being recharged, batteries give off
explosive gasses. If your battery is the sealed, do NOT recharge with
high current.
Usually, a car is jump started and run to recharge or "equalize" the
battery, which might NOT fully charge it. The length of time to fully
recharge the battery depends on the amount of discharge, the amount of
surplus current that is diverted to the battery, how long the engine is
run, RPM, and temperature. That is, an alternator is sized by the car
manufacturer to carry the maximum accessory load and maintain a battery,
NOT recharge a dead one. If you have added audio amplifiers, alarms,
cellular telephones or other accessories, the alternator might not
produce enough current to keep your battery fully charged. If you jump
start your car, test your battery after you have finished driving it,
and recharge if the state-of-charge is below 75%.
A better method to recharge batteries is to use an external constant
current charger which is set not to deliver more than 1% of the CCA
rating of the battery.
The best method is to use an external constant voltage or tapered
current charger. A constant voltage "automatic" charger applies
regulated voltage at approximately 14.6 volts. A 10 amp automatic
charger will cost between $30 and $50 at an auto parts store. To
prevent damage to the battery, the current should be less than 1% of the
CCA rating during the first 30 minutes. With a taper charger, a high
current, up to 30 amps, is applied to the battery for a short period up
to 30 minutes maximum and then is regulated downward until the charge
state reaches 100%. A 15 volt regulated power supply adjusted to 14.6
volts makes an excellent automatic battery charger.
For batteries with a state-of-charge of 25%, the following table,
published by Interstate Batteries, lists the recommended battery
charging rates and times:
Reserve Capacity Slow Charge Fast Charge
(RC) Rating @ 5 Amps @ 20 Amps
80 Minutes or less 10 Hours 2.5 Hours
80 to 125 Minutes 15 Hours 4 Hours
125 to 170 Minutes 22 Hours 5 Hours
If left unattended, cheap, unregulated trickle battery chargers can
overcharge your battery, because they can "boil off" the electrolyte.
Do NOT use fast, high rate, or boost chargers on any battery that is
sulfated or deeply discharged. This condition requires a constant
current from one to two amps for 60 to 100 hours. The electrolyte
should NEVER bubble violently while recharging. High currents only
create heat and excess gas.
9. CAN I INCREASE THE LIFE OF MY BATTERY?
Keeping your battery well maintained is the BEST way to extend the life
of your battery. For cold climates, keeping the battery fully charged
and warm will help. In the warmer climates and during the summer, the
electrolyte levels need to be checked more frequently and DISTILLED
water added, if required, due to the high under hood temperatures.
Batteries last approximately two thirds as long in hot climates as cold
ones. The parasitic load will determine how long a car can sit and
still be started. Disconnecting the NEGATIVE cable will extend the
"life" of the battery. Turning off unnecessary accessories and lights
BEFORE starting your car will decrease the load on the battery while
cranking. Leaving your lights or other accessories on and fully
discharging the battery can ruin it, especially if it is the sealed or
maintenance free type. Should this occur, you should test the battery
after it has been recharged to determine if there is permanent damage.
NEVER add acid--just distilled water.
Maintaining the correct electrolyte levels, tightening loose hold-down
clamps and terminals, and removing corrosion is normally the ONLY
preventative maintenance required for a battery.
10. WHAT ARE THE MOST COMMON CAUSES OF PREMATURE BATTERY FAILURES?
A. Loss of electrolyte due to underhood heat or overcharging,
B. Deep discharges (leaving your lights on),
C. Using an undersized battery,
D. Undercharging,
E. Vibration,
F. Using tap water,
G. Corrosion, and
H. Freezing.
11. WHAT ARE SOME OF THE MYTHS ABOUT BATTERIES?
A. Storing a battery on a concrete floor will discharge them.
Modern lead acid battery cases are better sealed, so external leakage
causing discharge is no longer a problem.
B. Driving a car will fully recharge a battery.
There are a number of factors affecting 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 temperature. Generally, short trips during bad weather
will not recharge the battery; whereas, a long daytime drive in good
weather will.
C. A battery will not explode.
While recharging, a battery produces hydrogen and oxygen gasses. If a
spark occurs, an explosion can occur. Remember the "Hindenburg"!
D. A battery will not lose it's charge sitting in storage.
A battery has internal electrical leakage that will cause it to become
fully discharged and sulfated over time. Prior to storing a battery, it
should be fully charged and recharged when it reaches the 50%
state-of-charge level. Batteries on store shelves should be checked
periodically and recharged if necessary. A regulated power supply
adjusted to 13.8 volts will maintain or "float" a battery at 100%
state-of-charge.
E. Maintenance free battery never requires electrolyte.
In hot climates, the electrolyte could be "boiled off" due to the high
underhood temperatures. It could also be lost due to excessive charging
voltage or using high charging currents.
Comments are always welcomed by Bill Darden at wdarden@mcimail.com.
------- FAQ END -------
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