User Manual

21
4. For Conventional batteries, check electrolyte level
and add distilled water if necessary. Don’t add acid—
only distilled water. Before any testing, charge the
battery so the water and acid mix.
5. If equipped, check the battery vent tube. Make sure
it’s not kinked, pinched or otherwise obstructed. On
a motorcycle, it should exit away from the drive chain and
from below the swing arm. Small cuts in the tube near the
battery vent are OK; they form an emergency escape for
trapped gas in case the vent tube becomes obstructed.
Battery Testing — Hydrometer
Because Conventional batteries have fi ller caps their state-
of-charge can be checked using a hydrometer by measuring
specifi c gravity. If after charging, the battery’s specifi c gravity
does not increase to indicate a full charge, the battery should
be replaced.
A hydrometer measures the ratio of sulfuric acid to water, or the
specifi c gravity (SG) of the electrolyte. The SG for pure water is
1.000 and sulfuric acid has an SG of 1.835. Combined, their SG is
between
1.265 to 1.280. In general, an SG reading between 1.265
to
1.280 indicates a fully charged battery. A reading of 1.230 to
1.260 indicates the battery should be charged before testing.
Yuasa YuMicron batteries use Sulfate Stop, a chemical additive
that increases battery life by reducing sulfate buildup. Sulfate
Stop may cause a slight increase in SG readings for these types
of batteries. A battery’s specifi c gravity changes with
temperature. Ideally, readings should be taken at
77° F. If the
temperature is much colder, or hotter a conversion factor can
be used to obtain an accurate reading. Add
.001 to the SG for
every
3° F above 77° F and subtract .001 from the SG for every
degree below
77° F. SG has a direct relationship to battery cell
voltage. By adding
.84 to the SG number, the cell voltage can
be calculated. For example, an SG of
1.265 + .84 = 2.105 volts.
Multiply
2.205 volts x 6 (six cells for a 12-volt battery) and the
result is
12.63 volts—indicating a fully charged battery.
There are two types of hydrometers used to measure SG:
calibrated fl oat and fl oating ball. The calibrated fl oat provides
an exact SG reading, however due to the amount of electrolyte
needed to cause the fl oat to rise inside the hydrometer they are
impractical for use on small powersports batteries. The fl oating
ball type hydrometer is much smaller in size and easy to use
on small batteries. Instead of reading specifi c gravity directly,
it uses colored balls to indicate state-of-charge. After drawing
in enough electrolyte to cover the balls inside the hydrometer,
the number that fl oat are counted. One fl oating ball equals
25% charge, two balls—50%, three balls—75% and four balls
indicate
100% state-of-charge (see chart page 19). Again, if
after charging, the battery’s specifi c gravity does not increase
to indicate a full charge, the battery should be replaced as it
may have an open/shorted cell or excessive sulfation.
Methods of Checking Battery Condition
State of
Charge
Syringe
Hydrometer
Digital
Voltmeter
5-Ball
Hydrometer
100% Charged
(w/Sulfate Stop)
100% Charged
75% Charged
50% Charged
25% Charged
0% Charged
1.280
1.265
1.210
1.160
1.120
< 1.100
12.80v
12.60v
12.40v
12.10v
11.90v
< 11.80v
5 Balls Floating
4 Balls Floating
3 Balls Floating
2 Balls Floating
1 Balls Floating
0 Balls Floating
Three methods of determining state-of-charge are shown; Syringe
Hydrometer, Digital Voltmeter and 5-Ball Hydrometer.
This hydrometer,
used to test
state-of-charge,
shows 5 balls
fl oating in the
electrolyte inside
the hydrometer
indicating that
the battery is
100% charged.