Battery Bank
42
PCMS Operations, Safety & Maintenance V3.0
Ver-Mac 2018
State of Charge (SOC) Chart
% of Charge
Charging
At Rest*
Discharging
100
1
4.75
12.70
12.50
90
13.75
12.58
12.40
80
13.45
12.46
12.30
70
13.30
12.36
12.25
60
13.20
12.28
12.15
50
13.10
12.20
12.00
40
12.95
12.12
11.90
30
12.75
12.02
11.70
20
12.55
11.88
11.50
10
12.25
11.72
11.25
NOTE
Voltage and state of charge is an approximate, not a specific number. It can vary
depending on battery type, manufacturer, battery quality, current temp and the
age of the battery. The voltages shown are taken at 25°C (77° F).
Immediately after either charging or discharging the battery voltage may not have
stabilized. Because the battery is chemical in nature, the voltage normally settles
down about 30 minutes after charging or discharging has discontinued.
12.2.2.2 Hydrometer Test
A hydrometer measures the specific gravity (or relative density) of liquids. In a
battery it measures the proportion of the
battery electrolyte (sulphuric acid) to the
density of water.
Using a glass-float Hydrometer:
1. Check the electrolyte level, to be sure
that it is above the plates in all cells. If
it is below the plates, you cannot do
the test
2. Draw the acid into the hydrometer, so
that the float is lifted free and not
touching the top or the bottom. Hold the barrel upright and your eye level
with the surface of the liquid. Disregard the curvature of the liquid against
the glass and take your reading from the bottom of the curve
3. For accurate readings apply cell temperature corrections; add or subtract
0.004 points for each 5°C (9°F) +/- variation from 25°C (77°F)
