Batteries
Mr. Conrado
Batteries
• A battery stores electrical
energy in chemical form.
• Battery current is produced by a
chemical reaction between the
active materials of the battery
plates and the sulfuric acid in
the electrolyte.
• The battery is a voltage
stabilizer for the system and
acts as a reservoir of power.
Battery Basic Theory
• All Batteries operate on the
principle of dissimilar metals -
2 different metals (plates) in the
presence of a liquid
(electrolyte) make a voltage.
• Battery chemistry determines
cell capacity
• Battery size determines amp
capacity.
• Batteries contain voltage - not
Amperage.
For good operation a battery must...
• Supply current for starting.
• Supply current when demand exceeds the
charging system output.
• Stabilize the voltage in the system during
operation.
Battery Construction
• The basic parts consist of
positive and negative plates
encased in a plastic or hard
rubber case and submerged in
electrolyte.
– Negative plates have a lead
surface, which is gray in color.
– Positive plate have a lead
peroxide surface which is
brown in color.
– The negative and positive
plates are connected in plate
groups.
Battery Construction
• Each plate in the group is kept
apart by porous separators to
allow the flow of electrolyte
around the plates.
• The complete assembly is
called an element. Elements are
connected in series to increase
voltage.
• Cells are separated from each
other so there is no flow of
electrolyte between them.
• Each cell will produce about 2.1
- 2.2 volts.
Battery Electrolyte
• Electrolyte is a concentrated
solution of sulfuric acid in
water.
• It has a specific gravity of 1.270
at 80deg. F.
• The solution is about 36%
sulfuric acid and 64% water.
• Battery water - it is best to use
distilled water to prevent
impurities in the battery thus
reducing the life and
performance of the battery.
Battery Terminals and Caps
• Batteries have negative and
positive posts or terminals.
• The positive post is larger than
the negative to help prevent the
battery from being connected in
reverse polarity.
• Vent caps are located in each
cell cover.
• Vent caps cover access holes
through which the electrolyte
level can be checked and water
added. The vents provide an
escape of gasses during
charging.
Battery Potential
• Each cell in a battery has a
potential of about 2 volts. Six
volt batteries have three cells in
series, while 12 volt batteries
have 6 cells in series.
• For higher voltages,
combination of batteries are
used.
How a Battery Works
• The battery produces current by
a chemical reaction between the
active materials of the unlike
plates and the sulfuric acid.
During this process the battery
is discharging. After almost all
of the materials have reacted
the battery is discharged.
• Battery current depends on the
size and number of its plates.
Battery Cycles
• Batteries have two cycles
– Discharging
– Charging
• Discharging cycle - When a
battery discharges lead sulfate
forms on both plates making the
two plates similar. This
accounts for less cell voltage
because the process depends on
dissimilar metals. In addition
during the discharging process
more water is formed in the
electrolyte. The acid never
leaves the battery it forms in the
lead sulfite. Therefore never
add more acid to a battery
Battery Cycles
• Charging Cycle - in essence the
discharge process is reversed in
the charging process.
• The sulfuric acid leaves the
plates and goes back into
suspension in the electrolyte.
Variation of terminal voltage
• Battery voltage in not constant.
The main factors affecting
voltage is temperature and
operating cycle.
• Temperature affects the
chemical reactions. At lower
temps the reactions are slower
thus reducing voltage and
efficiency.
• A Battery is 100% efficient at
81 deg. F and 30% efficient at -
22 deg F.
Types of batteries
• There are two types of batteries
- conventional and maintenance
free.
• Conventional batteries can be
dry or wet charged. A dry
charged battery contains no
electrolyte but is fully charged.
Once activated with electrolyte
it becomes wet charged. Dry
charged batteries if maintianed
correctly will not loose charge
on the rack.
Types of batteries
• Wet charged batteries are fully
charged and contain electrolyte.
• During storage a slow reaction
between the plates and
electrolytes takes place
discharging the battery.
• A fully charged battery stored
at 103 deg. F will fully
discharge in 90 days.
Types of batteries
• Maintenance free batteries are
the same as conventional
batteries minus the vent caps so
the electrolyte is sealed inside
the battery.
• Often an indicator is built into
the battery. The indicator has a
small green ball that floats
when the specific gravity is
1.225 or higher.
Types of batteries
• Maintenance free batteries
produce the same gasses during
charging and discharging but
the gasses are contained in a
special chamber that condenses
them and returns them to the
electrolyte.
• Also M-F battery plates are
sealed in envelopes to contain
sediment during normal wear,
conventional batteries leave
room at the bottom of the case
for sediment to settle.
Types of batteries
• Deep cycle batteries - Also a • Batteries are rated in three areas
lead acid battery but is specially - Cold Cranking Amps,
constructed for applications Cranking performance, and
where there may not be a reserve capacity.
charging circuit in the system, – Cold Cranking Amps - the
or used when the charging basic job of the battery is to
system is not being used (ie a start the engine. Since it is
motor-home). The deep cycle harder to start a cold engine
has denser electrolyte and and a battery is less efficient
when cold this is a good rating
thicker plates. These type of
for batteries
batteries can be discharged and
– Definition - A fully charged
recharged several times without
battery can continually crank
harm. for 30 seconds and maintain
1.2 volts per cell.
Types of batteries
• Cranking performance - The • Reserve Capacity - The ability
discharge rate in amps which a of a battery to sustain a
new fully charge battery at 32 minimum machine electrical
deg. F can continuously deliver load in the case of a charging
for 30 seconds and maintain a system failure.
voltage of 1.2 volts per cell. • Group Size - This is the
physical dimension of the
batteries and is industry
standardized
Lab
Battery Lab 1
Battery Charging
• When a battery’s state of charge
is low, it should be recharged.
• There are two classifications of
battery chargers, constant
current and constant voltage.
– Constant current – Supplies a
constant or set amount of
current to the battery. Charge
at a rate of 1 amp per positive
plate per cell. (ie; if 5 positive
plates per cell charge at 5
amps.) Most batteries which
are charged with a constant
current charger will take 5 to 6
amps.
Battery Charging
– Constant voltage – Supplies
battery with a constant
voltage during charging.
(ie; 15 volts for a 12 volt
battery). When the battery
is low this type of charger
will supply a fairly large
amount of amperage but as
the battery builds up charge
the current supply gradually
tapers off until almost
nothing.
Charging Conventional Batteries
• If possible slow charging is
preferable because the battery is
more thoroughly charged.
However a proper slow charge
takes 24 to 48 hours. A slow
charge is defined as a rate of 10
amps or less.
• The batteries specific gravity
should be checked twice a day.
If the battery reaches a specific
gravity of 1.275 remove the
charger.
Fast Charging
• Fast chargers
– will give a battery a high
charge rate for a short time.
– are generally portable
allowing for easier in machine
charging.
– Usually can charge only one
battery at a time.
– Many modern fast charges can
also slow charge as well.
Precautions when fast charging
• Never allow the batteries
electrolyte to exceed 125 deg.
F.
• During fast charging the
sediment is stirred up in the
electrolyte and can lodge
between plates shorting them.
Sediment will be noticeable by
discoloration of the electrolyte.
If this happens reduce the
charge rate.
Correct Charging Practices
• Before connecting the charger • Charging time
be sure that the battery tops are – Maintenance free batteries are
clean and the electrolyte is at charged at lower rates for
the correct level (conventional). longer periods.
• Be sure charger is off before – Never fast charge for longer
connecting and disconnecting than one hour.
the charger leads to the battery.
• Be sure to connect charger
leads in the correct polarity.
• Check the charger settings
before tuning it on.
Jump Starting
• Before jump starting be sure all
electrical accessories are off.
• Observe proper battery voltage
when jump starting. (12v to
12v, 24v to 24v etc.) If you do
not the battery could spark and
explode.
• Be sure to observe proper
polarity when connecting
jumper cables.
Jump Starting
• Be sure to connect cable in the
proper order.
– Positive of dead battery first.
– Positive of booster battery
second.
– Negative terminal of booster
battery.
– Connect negative lead at dead
battery end to a good ground
on the equipment.
• Remove in reverse order.
Battery Testing
• In order to determine what is
wrong with a battery you must
perform two tests.
– Specific Gravity Test
– Load Test
• Specific Gravity Test – Specific
Gravity is the weight of the
battery electrolyte compared to
water. When performing this
test you are determining the
state of charge based on the
percentage of acid to water. The
state of electrolyte varies
directly with the state of
charge. Specific Gravity is done
using a Hydrometer.
Battery Testing
• Hydrometers are calibrated to
measure at 80°. F. You must
compensate for varying
temperatures.
– Add 0.004 hydrometer points
for each 10° F above 80°.
– Subtract 0.004 hydrometer
points for each. 10°
• Specific Gravity will not be
correct if water was recently
added. Charge the battery and
re-test.
Specific Gravity
• Electrolyte should be clear.
• If the battery tests below 1.250,
charge the battery and retest.
• The amount of variation
between cells should be
between 30 to 50 points.
Load Testing Batteries
• A load test is the best indication
of a batteries condition.
• A load test can be performed if
the batteries state of charge is
75% or better. If below charge
then test.
• If a battery maintains 9.6 volts
or more during a load test it is
considered good.
Load Testing Batteries
• Load Test Procedures
– Place control knob in off
position
– connect leads observing proper
polarity.
– Turn on the control knob until
the ammeter reads one half the
cold cranking rate of the
battery.
– Maintain the load for 15
seconds.
– Note the reading of the
voltmeter and turn off tester.
– If the battery maintained a
minimum of 9.6 volts the
battery is good.
Safety and Clean-up
• Lead Acid Batteries produce • To avoid arcing and melted
hydrogen and oxygen when tools always disconnect
over-charged. negative cable first and
• Hydrogen + Oxygen + Flame = reconnect last.
Explosion.
• Use 8 tablespoons of baking
soda in one gallon of water to
neutralize battery acid.
• Never add acid to cells -
distilled water only.
Video
Kubota Battery Pro
Demonstrations
• Battery voltage test
• Post leakage test
• battery draw test
• Hydrometer test
• Headlight test
• Load test
• Battery charging
Lab