22 | SAMLEX AMERICA INC.
SECTION 7 |
General Information on Lead Acid
Batteries
TABLE 7.4: STATE OF CHARGE VERSUS STANDING VOLTAGE
Percentage of
Full Charge
Standing Voltage
of Individual Cells
Standing Voltage of
12V Battery
Standing Voltage
of 24V Battery
100%
2.105V
7
7
2.10V
7
25.20V
80%
2.08V
12.5V
25.00V
70%
2.05V
7
7
7
12.2V
24.40V
50%
2.02V
12.1V
24.20V
7
11.8V
7
20%
7
11.7V
7
10%
7
7
7
0%
7
7
7
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more than a 0.2V, or the specifi c gravity difference is 0.015 or more, the cells will require
equalization.
Please note that only the non-sealed / vented / fl ooded / wet cell batteries
are equalized. Do not equalize sealed / VRLA type of AGM or Gel Cell Batteries.
7.10 STATE OF DISCHARGE OF A LOADED BATTERY – LOW BATTERY /
DC INPUT VOLTAGE ALARM AND SHUTDOWN IN INVERTERS
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Inverters are provided with a buzzer alarm to warn that the loaded battery has been
deeply discharged to around 80% of the rated capacity.
Normally, the buzzer alarm is
triggered when the voltage at the DC input terminals of the inverter has dropped to
around 10.5V for a 12V battery or 21V for 24V battery at C-Rate discharge current of
C/5 Amps and electrolyte temp. of 80°F.
The inverter is shut down if the terminal voltage
at C/5 discharge current falls further to 10V for 12V battery (20V for 24V battery).
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of the battery. The terminal voltage of the battery is dependent upon the following:
-
Temperature of the battery electrolyte:
Temperature of the electrolyte affects the
electrochemical reactions inside the battery and produces a Negative Voltage
Coeffi cient – during charging / discharging, the terminal voltage drops with rise in
temperature and rises with drop in temperature
-
The amount of discharging current or “C-Rate”:
A battery has non linear internal
resistance and hence, as the discharge current increases, the battery terminal voltage
decreases non-linearly
