162
House Electrical
SECTION NINE
If one cell in a particular battery bank being tested is
at a 50% state of charge and the other cells indicate a
full state of charge, charge only the low battery to see
if the low cell will come up and at the same time do not
over-charge the healthy cells .
If the low cell does not improve after charging, this battery
can damage the rest of the battery bank and should be
replaced . An accurate digital Volt meter + - .5% will also
give an indicator of the battery’s state of charge .
Temperature and recent
battery activity (charging
or discharging) affect the
hydrometer readings . It is
best to check the battery
when it has been at rest
for at least three hours,
although readings taken
at other times will give
a ballpark figure . When
using the hydrometer,
draw
the
electrolyte
solution up into the tube .
Allow the hydrometer
to
attain
the
same
temperature
as
the
electrolyte solution . Note
the reading for that cell .
Complete the same test
for the rest of the cells
on that battery bank . The
hydrometer is calibrated at
80° F . Temperature affects
the hydrometer readings .
The higher the electrolyte
temperature, the higher
the
specific
gravity
reading . The lower the
temperature, the lower the
specific gravity reading .
Add or subtract four points for each 10° variance from
the 80° F . chart . Readings between cells should not
vary more than 50 points .
Periodically check the batteries for corrosion and
cracks . Replace vent plugs that are cracked or missing .
Keep the top of the batteries clean . The accumulation
of electrolyte and dirt may permit small amounts of
current to flow between the terminals that can drain
the battery .
Check the battery connections for tightness and
corrosion . Battery cables will occasionally need the
corrosion removed to clean the cable ends and battery
terminals . The batteries and trays will also need to be
cleaned .
NOTE:
See the chart for temperature compensation .
Liquid levels should be even between the cells
of the battery being tested as it will affect the
accuracy of the test .
Temperature Correction Chart
030815
WARNING:
Liquid lead acid batteries produce hydrogen gas
while charging . Do Not smoke around batteries
and keep all sources of ignition or flames away from
batteries . Hydrogen is an extremely flammable gas
and can explode resulting in fire, personal injury,
property damage or death .
WARNING:
Sulfuric acid in the batteries can cause severe
injury or death . Sulfuric acid can cause permanent
damage to eyes, burn skin, and eat holes in
clothing . Always wear splash-proof safety goggles
when working around the battery . If the battery
electrolyte is splashed in the eyes, or on skin,
immediately flush the affected area for 15 minutes
with large quantities of clean water . In case of
eye contact, seek immediate medical aid . Never
add acid to a battery once the battery has been
placed in service . Doing so may result in hazardous
splattering of electrolyte .
Summary of Contents for Class A Gas 2020
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