Subaru LEGACY 2006 Manual page 899

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STARTING/CHARGING 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 × (t – 20)
20
S : Specific gravity corrected at electrolyte
20
temperature of 20°C (68°F)
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
[20°C (68°F)]
2) Measuring the specific gravity of the electrolyte
in the battery will disclose the state of charge of the
battery. The relation between specific gravity and
state of charge is as shown in the figure.
Battery with standard specific gravity 1,280 (20 C)
1.28
1.24
1.22
1.20
1.16
1.12
1.08
1.04
10 20 30 40
0
Amount of discharge (%)
D: MEASUREMENT
WARNING:
Do not bring an open flame close to the battery
at this time.
CAUTION:
• Prior to charging, corroded terminals should
be cleaned with a brush and common caustic
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 the vehicle,
disconnect the battery ground terminal to pre-
vent damage of generator diodes or other elec-
trical units.
Battery
50 60 70 80 90 100
SC-00054
SC(H4SO)-28
1. JUDGMENT OF BATTERY IN CHARGED
CONDITION
1) Specific gravity of electrolyte should be held
within the specific range from 1.250 to 1.290 for
more than one hour.
2) Voltage per battery cell should be held at a spe-
cific value in a range from 2.5 to 2.8 V for more than
one hour.
2. CHECK CONDITION OF CHARGE WITH
HYDROMETER
Hydrometer State of
indicator charge
Green dot 65% or more
Dark dot 65% or less
Low electro-
Clear dot
lyte
* Check electrical system before replacement.
3. NORMAL CHARGING
Charge the battery at the current value specified by
manufacturer or at approximately 1/10 of battery's
ampere-hour rating.
4. QUICK CHARGING
Quick charging is a method that 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 (104°F).
Also the quick charging is a temporary mean to
bring battery voltage up to some level, and battery
should be charged slowly with low current as a rule.
CAUTION:
• Observe the items in 3. NORMAL CHARGING.
• Never use more than 10 A when charging the
battery because it will shorten the battery life.
Corrective action
Load test
Charge battery
Replace the battery.*
(If cranking is difficult)