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Lead Acid Batteries and Jump Starts
 This
topic will cover basic battery operation, maintenance and testing.
Batteries are very dangerous devices for several reasons. If you
are not qualified to work with batteries, then we suggest you
have a professional do it for you.
Battery Safety Issues
Safety is always an important consideration while working with
batteries. Remove all of your jewelry, so that you won't melt
your watch band or ring while you are working. It is one thing
to ruin your ring, but quite another thing to try and remove a
red hot ring from your burning finger. Because gold is a perfect
conductor, that innocent ring or watch band will heat up much
faster than you ever thought possible.
The hydrogen gas produced by charging or discharging batteries
is very explosive. I have seen three batteries blow up and trust
me, it is not a pretty sight. This is a good time to use those
safety goggles that are hanging on the wall. Sulfuric acid eats
up clothing, so you may want to consider wearing junk clothing
while working with batteries.
When doing work on electrical circuits in vehicles, it is best
to disconnect the ground cable. Just remember you are playing
around with corrosive acid, explosive gases and hundreds of amps
of electrical current capacity which has welding capabilities.
Battery
Stored Energy
Batteries
provide a way to store electrical energy in chemical form. When
electrical energy is required, the battery converts chemical energy
into electrical energy as needed. The lead acid battery, is composed
of lead plates and acid electrolyte, and is used for all truck
applications.
Each truck
battery cell produces 2 volts; therefore 12-volt batteries have
6 cells. The two plates of the battery cell are labeled plus (+)
and minus (-). As the lead acid battery is charged, the charging
energy is stored  within
the electrolyte (acid) of the battery, and a 2-volt potential
difference exists between the two battery plates. When the battery
is in use (or discharged), the electrolyte and the battery plates
work together to provide free electrons to do the battery's work.
In other words, the energy stored within the battery is converted
chemically into electron potential difference between the two
plates, which performs electrical work outside of the battery.
Battery Ratings
Battery rating is based upon the number of plates per cell and
the total surface area of each plate. Given the number of plates
and surface area, then the strength and volume of electrolyte
also determine the battery output. The temperature of the battery
also dictates the battery output. During extreme cold weather,
the battery has less output capability.
The battery reserve capacity represents the number of minutes
that the battery can produce 25 amps. This is an approximation
of night driving without a working alternator.
The cold cranking test measures the minimum cranking amps available
at zero degrees. This measurement specifies the number of cranking
amps maintained for 30 seconds while the battery terminal voltage
remains above 7.2 volts (12 volt battery). The cold cranking power
for a truck starter is about 1 amp for each cubic-inch of engine
displacement. As an example, the Caterpillar 3406E has 893 cu-in
displacement. Therefore the cold cranking rating of the battery
should be about 900 amps.
A battery at -20 degrees will produce about 20% of its rated
cranking current, and a battery at 32 degrees will produce about
50% of the output that the same battery would produce at 80 degrees.
It is also important to note that a very cold engine requires
about 2.5 times the cranking power of a warm engine.
Battery Maintenance
Battery Maintenance is an important issue. The battery
should be clean. Use a baking soda and water mix to clean the
battery. Cable connections need to be clean and tight. Many battery
problems are caused by dirty and loose connections. Serviceable
batteries need to have their fluid levels checked. Use only mineral
free water, distilled water is best. Don't overfill the battery
cells especially in warmer weather. The natural fluid expansion
in hot weather will push excess electrolytes from the battery.
Add distilled water to the level indicated by the battery manufacturer
or to 1/8" BELOW the bottom of the filler tube (vent wells).
To prevent corrosion of cables on top post batteries,
use a small bead of silicon sealer at the base of the post and
place a felt battery washer over it. Coat the washer with high
temperature grease or petroleum jelly (Vaseline). Then place the
cable on the post and tighten. Coat the exposed cable end with
the same grease. Most truckers don't realize that just the gases
from the battery condensing on the metal parts is what causes
most cable corrosion.
Battery Operation
Battery current is produced by a chemical reaction between the
positive and negative plates, that are submerged in the electrolyte
(diluted sulfuric acid). This chemical reaction will cause the
battery to self discharge if it is stored unused for a long period
of time.
All batteries produce oxygen and hydrogen during charge and discharge.
These gases are produced by the breaking apart of water molecules
in the electrolyte. As these gases escape, the water level of
the battery goes down.
 The
electrolyte specific gravity of a fully charged battery is 1.260
- 1.270 at 80 degrees. This means that the electrolyte is heavier
than water which has 1.000 specific gravity. The electrolyte consists
of about 64% water and 36% acid.
During discharge of the battery, oxygen in the positive plate
combines with hydrogen in the electrolyte solution, to form water.
At the negative plate, lead combines with the sulfate radical
to form lead sulfate. Upon complete discharge of the battery,
the electrolyte consists of 17% sulfuric acid and 83% water. Since
there is now more water and less sulfuric acid, the specific gravity
of the electrolyte has decreased to about 1.100
When using a hydrometer, the temperature determines an offset
to add to the hydrometer float reading. The hydrometer shown above,
incorporates a thermometer chart at the bottom. This consists
of a chart which shows the amount to add or subtract from the
hydrometer float reading. For example, if the hydrometer reads
1.230 and the temperature is 90 degrees, then add .004 to the
reading for a final reading of 1.234. The temperature offset to
add or subtract always consists of 0.0xx, not just xx.
Battery Testing
Slow cranking, especially on a cold day, is a good indication
that your battery may be going bad and should be tested. An easy
way to test a battery is by measurement of the specific gravity,
or measurement of the battery voltage. To measure specific gravity,
use a temperature compensating hydrometer, which can be found
at most auto parts stores for around $5.00. Or you can measure
the battery voltage, using a digital D.C. Voltmeter.
If you have a maintenance free wet cell battery, the best way
to test is with the voltmeter. Most of the maintenance free batteries
have a built in hydrometer that tells you the condition of 1 of
the 6 cells. You may get a good reading from 1 cell but have a
problem with any one of the other 5 cells in the battery. Therefore
the built in one cell hydrometer is not very good indicator of
battery condition.
If you have just recharged you battery or driven your truck,
eliminate any surface charge before testing, by using one of the
following methods;
- Allow the battery to sit for two to three hours
- Turn the headlights on high beam for five minutes and then
wait five minutes
- With a battery load tester, apply a load at one half the
battery's CCA rating for 15 seconds and then wait five minutes.
After the surface charge has been removed, the following table
demonstrates the relationships of battery charge:
Battery Voltage
11.70
12.12
12.30
12.48
12.66 |
Specific Gravity
1.100
1.170
1.200
1.230
1.265 |
Battery Charge (%)
00% charged
25% charged
50% charged
75% charged
100% charged |
Extending Battery Life
Battery life and performance have become shorter
as energy requirements increase with the increased electrical
load of trucks. It is interesting to note that 80% of all battery
failures are related to battery plate sulfation build-up.
This build up occurs when the sulfur molecules
in the electrolyte (battery acid) becomes so deeply discharged
that they begin to coat the battery lead plates. After time
the plates become coated and the battery fails. Here is a list
of typical causes of sulfation build-up:
-
Batteries sitting too long between charges.
As little as 24 hours in hot weather and several days in
cold weather.
-
Battery storage, leaving a battery sit without
some type of energy input.
-
Deep cycling the engine start battery, remember
these batteries can't handle deep discharge.
-
Undercharging of the battery.
-
Tempertures of 100 plus F. increases battery
internal discharge. As the temperature increases, so does
the internal discharge. A new and fully charged battery
left in 110 degrees F. for 30 days, would not crank over
an engine.
-
Low electrolyte level exposes battery plates
to air, which will immediately sulfate.
-
Cold weather is hard on the battery because
the chemistry does not work well, leaving the battery partially
charged, resulting in sulfation.
As a normally battery ages, the active plate material
sheds (or flakes off) due to the expansion and contraction that
occurs during the discharge and recharge cycles. Deep discharges,
heat and vibration, accelerate this aging process. Eventually,
the sediment which builds up in the bottom of the cell, can
short out that cell.
Parasitic Battery Drain
Parasitic drain is a load put on a battery with
the key off. Many vehicles have clock radios, alarm systems,
and other electrical loads with the key switched off. You may
also have parasitic loads caused by a short in the electrical
system. If you are always having dead battery problems most
likely the parasitic drain is excessive. The constant low or
dead battery caused by excessive parasitic energy drain, will
dramatically shorten the battery life. Find the source of excessive
parasitic drain and get rid of it if you want prolonged battery
life.
Emergency Jump Starting
The following considerations are necessary for
safe and successful jump starts. This list of requirements may
appear quite lengthy, but failure to recognize these requirements
usually results in damage to vehicles and/or people, or failed
success. First we will show the usual battery configurations
and where the boost cables should be connected. Then we will
list the requirements that you should heed for safety's sake.
Emergency Jump Starting Continued
1. In cold weather, a good quality booster cable
with four to six gauge wire is necessary to provide enough charging
current to the disabled truck. (The smaller the wire gauge number,
i.e., the larger the wire diameter, the better.)
2. Ensure that both vehicles are negative ground
or positive ground systems. Do not mix system polarities. Mixed
polarity systems can cause damage to both trucks.
3. Do not allow the booster cable clamps to touch
each other.
4. Do not allow the positive clamp to touch the
frame or engine block for negative ground systems.
5. Do not allow the negative clamp to touch the
frame or engine block for positive ground systems.
6. If below freezing, look at the electrolyte to
determine that the electrolyte is not frozen in the dead battery.
If frozen, thaw out the battery before proceeding. A discharged
battery, battery voltage or 12.0 volts or less and/or a specific
gravity of 1.140 or less, will freeze at approximately 8 degrees
F.
7. Without the trucks touching each other, turn
off all unnecessary accessories and lights on both trucks, and
ensure plenty of ventilation around the batteries, and use protective
eye ware.
8. Start the truck with the good battery and let
it run for at least two or three minutes at fast idle to recharge
it's own battery before proceeding.
9. Connect the positive booster cable clamp (usually
RED) to the positive terminal on the dead battery. Connect the
positive booster cable clamp on the other end of the booster cable
to the positive terminal on the good battery.
10. Connect the negative booster cable clamp (usually
BLACK) to the negative terminal on the good battery and the negative
booster cable clamp on the other end to a clean, unpainted area
on the engine block or frame on the disabled truck, and away from
the battery.
11. Let the good truck continue to run at high
idle for five minutes or more to allow the dead battery to receive
some recharge and to warm it's electrolyte.
12. If the bad truck has two battery banks, which
are not in parallel during normal charging, then charge each bank,
one at a time, for ten minutes or more. This will also warm up
both batteries which makes them more powerful.
13. Start the disabled truck and allow to run at
high idle. If the truck does not start the first time, recharge
the batteries for another ten minutes (each bank) and try again.
14. Disconnect the booster cables in the reverse
order, starting with the negative clamp on the block or frame
of the disabled truck to minimize the possibility of a spark near
the batteries which could cause a hydrogen gas explosion.
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