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Theory of Operation
A8 Rechargeable Battery Assembly
4-12 Agilent E4418B/E4419B Service Guide
A8 Rechargeable Battery Assembly
The A8 Rechargeable Battery Assembly allows the EPM power meter with
option 001 fitted to operate when no AC power input is available. The
battery pack contains a health monitoring circuit which the A2 processor
assembly can interrogate. The A8 battery assembly connects to the A2
processor assembly and the PSU/battery charger circuit via the A5
Daughter Assembly.
There are three connections from the rechargeable battery assembly to the
A1 psu/charger assembly, +12V, 0V, and Signal 1. The Signal 1 line is an
indicator line which signals when the battery is below a threshold limit.
When this line goes low, indicating there is insufficient charge left in the
Battery Assembly to continue operating the power meter, it will cause the
A1 psu/charger assembly to shut down.
There is one connection, the communications line, from the A8 Battery
Module to the A2 processor assembly. This line provides serial
communications with the processor assembly on battery pack status
information, such as amount of charge remaining. When there is less than
10 minutes run time charge remaining in the battery an error message
"Battery Power Low’" is displayed on the power meter front panel display.
The battery assembly can only be recharged when fitted to a power meter
with the battery option fitted. The charge current from the charging
circuit is controlled by a module contained within the Battery assembly.
When the ac power is connected the battery assembly regulates the
charging current based on the discharge state of the battery.
The battery should fully charge from empty within 2 hours. At 25 degrees
C this will give the meter 2 hours operational time. The A8 Battery
module has a lifetime of approximately 450 charge/discharge cycles after
which the battery can still be used, but will only have approximately 70%
of its original capacity. The battery capacity may be reduced whilst
charging at temperatures above 35 degrees C.
Note:- partially discharging and recharging the battery module will
reduce its lifetime. It is advised that periodically the battery assembly
should have its charge fully cycled i.e. fully discharged and then fully
recharged.