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Installation - 2
31
1. Multiply the power used by one cell times the number of cells in the Agilent MCCD. Divide the
result by the efficiency of the unit to determine the total input power required for that mainframe.
The efficiency of the unit in charging mode is assumed to be 80%, which is a worst-case value as far
as calculating the total power required by the mainframe.
#_of_cells × power_per_cell
0.8
= Max_power_in
2. Divide the input power requirements of the Agilent MCCD by the minimum voltage required at the
input terminals of the Agilent MCCD (22.8 volts). The result will be the maximum charging current
required by the Agilent MCCD. (Double this current if you are simultaneously charging two Agilent
MCCD mainframes as illustrated in Figures 2-1 and 2-2.)
Max_ power_in
Power_source_voltage
= Max_powerbus_current
3. Determine the voltage drop that the maximum current will produce in the power bus leads using the
resistance values in Table 2-6.
4. Add this voltage drop to the minimum voltage required at the input terminals of the Agilent MCCD
to determine the output voltage setting of the dc power supply.
5. The voltage at the input terminals of the Agilent MCCD during charging mode must be between 25.2
and 22.8 volts. If the sum of the voltage drops in both the + and − power bus leads causes the voltage
at the mainframe power terminals to drop below 22.8 volts, the Agilent E4370A MCCD will shut
down due to an undervoltage condition. Use a larger size wire to reduce the voltage drop.
Discharging Mode Guidelines:
Power bus wires must also capable of handing the full discharging current requirements of all Agilent
E4370A MCCD units connected to the power bus. In the example that follows, the calculations are also
for worst case current requirements. Calculate the output current of one fully loaded Agilent E4370A
MCCD as follows:
1. Multiply the power generated by one cell times the number of cells in the Agilent MCCD. Multiply
the result by the efficiency of the unit to determine the total output power produced by that
mainframe. The efficiency of the unit in discharging mode is approximately 80% with Agilent
E4374A cards and 75% with Agilent E4375A cards. This percentage represents the highest
efficiency possible for calculating the total power that is generated by the mainframe in discharge
mode.
(#_of_cells × power_per_cell) × Efficiency
= Max_power_out
2. Divide the power generated by the Agilent MCCD by the input voltage of the Agilent Powerbus
Load. At an input voltage of 26.5 volts, the result will be the maximum discharging current that will
be absorbed by the Agilent Powerbus Load. (Double this current if you are simultaneously
discharging two Agilent MCCD mainframes as illustrated in Figure 2-5.)
Max_ power_out
26.5
= Max_powerbus_current
3. Determine the voltage drop that the maximum current will produce in the power bus leads using the
resistance values in Table 2-6.
4. The sum of the voltage drops in both the + and
−
−−
−
power bus leads cannot exceed 1.5V. If the
voltage drop exceeds 1.5 volts in discharging mode, the Agilent MCCD will shut down due to an
overvoltage condition at the mainframe terminals. Use a larger size wire to reduce the voltage drop.