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1 - General Information
14
External Power Source
For the charging cycle, each Agilent MCCD mainframe requires an external dc power source to power
the cells. The external power source connects to the power bus terminals on the back of the mainframe. It
must be rated at 24 volts and be able to source 125% of the required cell charging power.
For example, to provide the cell charging power for a 256-channel system at 5.5 volts, 2 amperes per
channel (or 2.8 kW), the dc power source must deliver approximately 3.5 kW to each Agilent MCCD
mainframe (24 V @ 146 A). To provide the cell charging power for a 256-channel system at 6 volts, 3
amperes per channel (or 4.6 kW), the dc power source must deliver approximately 5.76 kW to each
Agilent MCCD mainframe (24 V @ 240 A).
The current rating of the power source may be reduced if the charging current is reduced accordingly. For
example, to provide a maximum output current of 1 ampere per cell in a 256-channel system, a source
rated at least 24 volts, 72 amperes may be used.
Additionally, a single supply of sufficient amperage may be shared among multiple mainframes that are
connected to a common power bus - provided that the total current can be supplied while meeting the
voltage specification at the power bus terminals at the rear of the Agilent MCCD.
NOTE: If the external dc power source has an overvoltage protection circuit, it must be set
higher than 30 volts to avoid the possibility of shutting itself down during the discharge
cycle.
Multiple Agilent MCCD Configurations
Figures 1-5 and 1-6 illustrate two configurations of Agilent E4370A MCCD systems with eight fully
loaded mainframes.
The power required for such systems can be as high as 46 kilowatts (when using Agilent E4375A cards).
A single power source of sufficient total amperage may be shared among multiple mainframes connected
to the power bus, provided the total current can be provided while meeting the nominal 24-volt dc input
requirement at the power bus terminals on the rear of each mainframe. Multiple paralleled 24-volt dc
sources may be used in place of the single dc source shown in the figures.
To achieve improvements in energy efficiency, the Agilent E4370A MCCD system can re-use discharge
energy to supplement the energy provided by an external power source when charging other cells in a
multi-unit system. This is possible because of the bi-directional power transfer capability between
charging and discharging cells when connected to a common power bus. To take advantage of this energy
transfer requires that some mainframes in the system must be operating in discharge mode at the same
time that others are operating in charging mode.
No special control system is required for this configuration. The regulation circuits of the 24 volt dc
power source, the Agilent E4370A MCCD mainframe, and Agilent E4371A Powerbus Load will operate
properly without any special hardware control lines or additional software being required.
NOTE: Adequate size power bus wiring is required to carry high currents. Refer to Table 2-5.