Subaru IMPREZA 2002 Service Manual page 323

BATTERY
START1 NG/CHARG I NG
SYSTEMS
3. SPECIFIC GRAVITY OF ELECTROLYTE:
1) Measure specific gravity of electrolyte using a
hydrometer and a thermometer.
Specific gravity varies with temperature of electro-
lyte so that it must be corrected at 20°C (68°F) us-
ing the following equation:
s , ,
=
St
+
0.0007 x (t
-
20)
S 2 ~ Specific gravity corrected at electrolyte
temperature of 20°C
St : Measured specific gravity
t : Measured temperature ("C)
Determine whether or not battery must be
charged, according to corrected specific
gravity.
Standard specific gravity: 1.220
-
1.290 [at
20°C (SSOF)]
I
1.28
i ,
I
~-
! E l
100%
75% 50% 22%
0%
1
Complete charge Charging condition ( I )
Specific gravity and state of charge
G6M01
I
2) Measuring the specific gravity of the electrolyte
in the battery will disclose the state of charge of the
battery. The relation between the specific gravity
and the state of charge is as shown in the figure.
D: MEASUREMENT
WARNING:
Do not bring an open flame close to the bat-
tery at this time.
CAUTION:
Prior to charging, corroded terminals should
be cleaned with a brush and common baking
soda solution.
Be careful since battery electrolyte overflows
while charging the battery.
Observe instructions when handling the bat-
tery charger.
Before charging the battery on vehicle, dis-
connect the battery ground terminal. Failure to
follow this rule may damage the generator's di-
odes or other electrical units.
1. JUDGMENT OF BATTERY IN CHARGED
CONDITION
1) Specific gravity of electrolyte is held at a specific
value in a range from 1.250 to 1.290 for more than
one hour.
2) Voltage per battery cell is held at a specific value
in a range from 2.5 to 2.8 volts for more than one
hour.
2. CHECK HYDROMETER FOR STATE OF
CHARGE
1
State of charge
I
Required action
Hydrometer
I
indicator
I
Greendot
1
Above65%
I
Load test
Dark dot
1
Below65%
1
Charge battery 1
Replace battery*
I
'Iear dot
1
electrolyte
(If cranking complaint)
I
*: Check electrical system before replacement.
3. NORMAL CHARGING
Charge the battery at current value specified by
manufacturer or at approximately 1/10 of battery's
ampere-hour rating.
4. QUICK CHARGING
Quick charging is a method in which the battery is
charged in a short period of time with a relatively
large current by using a quick charger.
Since a large current flow raises electrolyte temper-
ature, the battery is subject to damage if the large
current is used for prolonged time. For this reason,
the quick charging must be carried out within a cur-
rent range that will not increase the electrolyte tem-
perature above 40°C (1 04°F).
It should be also remembered that the quick charg-
ing is a temporary means to bring battery voltage
up to a fair value and, as a rule, a battery should be
charged slowly with a low current.
CAUTION:
Observe the items in 1. NORMAL CHARGING.
Never use more than 10 amperes when
charging the battery because it will shorten bat-
tery life.
sc-19