plate). Insulator s or plat e separ ators ma de of a n on-
conductive ma terial are inser ted between t he positive
and negat ive plates t o prevent them from contacting
or shorting aga inst one another. Th ese dissimilar
meta l pla tes are submerged in a sulfu ric a cid and
water solution called an electr olyte.
Th e fa cto ry -in s t a lle d lo w -ma in te n a n c e ba t-
tery has removable battery cell caps. Wat er can
be a dded to t his batt ery. The chem ical com position of
the m etal coated pla tes wit hin th e low-m aintenance
batt ery redu ces bat tery gassin g and wa ter loss, a t
normal char ge and dischar ge rat es. Ther efore, the
batt ery should not require additional wa ter in nor-
mal ser vice. Rapid loss of electr olyte ca n be ca used
by a n overcharging condition . Be certa in to diagnose
the cha rging system before r eturning the vehicle to
service.
OPERATION
The batt ery is designed to store electrical energy in
a chem ical for m. When an electrical loa d is applied to
the term inals of th e bat tery, an electr ochemical reac-
tion occurs. This rea ction causes t he batt ery to dis-
charge elect rical curr ent from its termina ls. As th e
batt ery discharges, a gradual chemica l cha nge ta kes
place with in ea ch cell. The su lfuric a cid in the elec-
trolyte combines with the plat e ma terials, cau sing
both plat es to slowly change to lead sulfate. At t he
sa me time, oxygen fr om th e posit ive plat e ma terial
combin es wit h hydr ogen from the su lfuric acid, cau s-
ing th e electr olyte to become ma inly water. The
chemical chan ges wit hin th e battery are caused by
the movem ent of excess or free electrons bet ween t he
positive and negat ive plate groups. This movem ent of
electrons produces a flow of elect rical cur rent
through the load device attach ed to t he bat tery ter-
minals.
As the plate materials become mor e similar chem-
ically, and t he electr olyte becomes less acid, th e volt-
age pot ential of each cell is reduced. However, by
charging the ba ttery with a voltage high er than th at
of t he batt ery itself, the bat tery disch arging process
is r ever sed. Charging the bat tery gradually chan ges
the sulfa ted lead plates back into sponge lead an d
lead dioxide, and th e wat er back into su lfuric a cid.
This a ction restores the difference in the electron
charges deposited on the plates, and the voltage
pot ential of the bat tery cells. For a batt ery to remain
useful, it must be able to produce high-a mperage cur-
rent over a n ext ended period. A battery mu st also be
able to accept a charge, so tha t its voltage poten tia l
may be rest ored.
The ba tter y is vented t o release excess hydr ogen
gas that is creat ed when th e batt ery is being char ged
or discha rged. However, even with t hese vents,
hydrogen gas can collect in or arou nd the batt ery. If
hydrogen gas is exposed to flame or spar ks, it may
ign ite. If the electrolyte level is low, the battery m ay
arc inter nally a nd explode. If the bat tery is equipped
with remova ble cell ca ps, add distilled water wh en-
ever the electr olyt e level is below the top of the
plates. If t he battery cell ca ps ca nnot be r emoved, the
batt ery must be replaced if the electrolyt e l evel
becomes low.
DIAGNOSIS AND TESTING - BATTERY
The ba tter y mu st be complet ely charged and the
term inals should be proper ly cleaned and inspected
before diagn ostic procedu res are per formed. Refer to
Batt ery System Clea ning for the proper cleaning pro-
cedures, and Battery System Inspection for t he
pr oper batt ery inspection pr ocedu res. Refer to Sta n-
da rd P rocedures for the proper battery charging pro-
cedures.
MICRO 420 BATTERY TESTER
The Micro 420 au tomotive ba tter y t ester is
designed to help t he dealership techn icians dia gnose
the cause of a defect ive bat tery. Follow the in st ruc-
tion ma nua l supplied with th e tester to properly
diagnose a vehicle. If th e instruction ma nual is not
ava ila ble refer to the st andar d procedur e in this sec-
tion, which in cludes the direct ions for using t he
Micro 420 battery tester.
WARNING: IF THE BATTERY SHOWS SIGNS OF
FREEZING, LEAKING OR LOOSE POSTS, DO NOT
TEST, ASSIST-BOOST, OR CHARGE. THE BATTERY
MAY ARC INTERNALLY AND EXPLODE. PERSONAL
INJURY AND/OR VEHICLE DAMAGE MAY RESULT.
WARNING: EXPLOSIVE HYDROGEN GAS FORMS IN
AND AROUND THE BATTERY. DO NOT SMOKE,
USE FLAME, OR CREATE SPARKS NEAR THE BAT-
TERY. PERSONAL INJURY AND/OR VEHICLE DAM-
AGE MAY RESULT.
WARNING: THE BATTERY CONTAINS SULFURIC
ACID, WHICH IS POISONOUS AND CAUSTIC. AVOID
CONTACT WITH THE SKIN, EYES, OR CLOTHING.
IN THE EVENT OF CONTACT, FLUSH WITH WATER
AND CALL A PHYSICIAN IMMEDIATELY. KEEP OUT
OF THE REACH OF CHILDREN.
A bat tery that will not accept a charge is fa ulty,
and m ust be repla ced. Further testing is not
required. A fully-char ged bat tery must be t est ed to
determ ine its cr anking capacity. A battery that is ful-
ly-ch arged, but does not pa ss the Micro 420 or load
test, is faulty and must be replaced.
NOTE: Completely discharged batteries may take
several hours to accept a charge. Refer to Standard
Procedures for the proper battery charging proce-
dures.
VA BATTERY SYSTEM 8F - 7
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