Samlexpower PSE-12125A, Owner'S Manual

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18 | SAMLEX AMERICA INC. SAMLEX AMERICA INC. | 19
Table 6.3 (page 18) shows that a 100 Ah capacity battery will deliver 100% (i.e. full 100
Ah) capacity if it is slowly discharged over 20 hours at the rate of 5 Amperes (50w out-
put for a 12V inverter and 100w output for a 24V inverter). however, if it is discharged
at a rate of 50 Amperes (500w output for a 12V inverter and 1000w output for a 24V
inverter) then theoretically, it should provide 100 Ah ÷ 50 = 2 hours. however, the Table
above shows that for 2 hours discharge rate, the capacity is reduced to 50% i.e.
50 Ah. Therefore, at 50 Ampere discharge rate (500w output for a 12V inverter and
1000w output for a 24V inverter) the battery will actually last for 50 Ah ÷ 50 Amperes =
1 hour.
State of charge (Soc) of a Battery – Based on “Standing Voltage”
The “Standing Voltage” of a battery under open circuit conditions (no load connected
to it) can approximately indicate the State of charge (Soc) of the battery. The “Standing
Voltage” is measured after disconnecting any charging device(s) and the battery load(s)
and letting the battery “stand” idle for 3 to 8 hours before the voltage measurement is
taken. Table 6.4 below shows the State of charge versus Standing Voltage for a typical
12V/24V battery system at 80°f (26.7ºc).
tABle 6.4: 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 12.63V 25.26V
90% 2.10V 12.6V 25.20V
80% 2.08V 12.5V 25.00V
70% 2.05V 12.3V 24.60V
60% 2.03V 12.2V 24.40V
50% 2.02V 12.1V 24.20V
40% 2.00V 12.0V 24.00V
30% 1.97V 11.8V 23.60V
20% 1.95V 11.7V 23.40V
10% 1.93V 11.6V 23.20V
0% = / < 1.93V = / < 11.6V = / < 23.20V
check the individual cell voltages / specific gravity. If the inter cell voltage difference is
more than a 0.2V, or the specific gravity difference is 0.015 or more, the cells will require
equalization. Please note that only the non-sealed / vented / flooded / wet cell batteries
are equalized. Do not equalize sealed / VRLA type of AGM or Gel Cell Batteries.
State of Discharge of a loaded battery – low Battery /
Dc input Voltage Alarm and Shutdown in inverters
Most inverter hardware estimate the State of discharge of the loaded battery by meas-
uring the voltage at the inverter’s dc input terminals (considering that the dc input
cables are thick enough to allow a negligible voltage drop between the battery and
the inverter) .
seCtIOn 6 | General Information on
lead Acid Batteries