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Manual Number 9019286 • Revision E, January 06, 2022
Switch Board
The Switch board incorporates high-power transistors used to enable and disable
charging or discharging of the unit. This allows for the unit to take action based on its own
monitoring and protections to prevent damage to the product. The Switch board also
contains the current limiting functionality. This important feature allows the battery to
control the amount of current it will accept from aircraft. Although the very low internal
impedance of lithium-ion cells produces benefits of fast charging and high power, it also
can accept as much or more than many aircraft power generation systems can supply.
The current limiting feature prevents the unit from utilizing the full available power of the
aircraft so that other key systems can remain active. The Switch board also includes the
unit’s ability to measure current flow of the battery as a protective input.
Control Board
The Control board contains the logic to collect cell parameters and report to the Battery
Management System (BMS). It also receives decisions back from the BMS and sends
information to the Switch board to enable, limit, or disable charging and discharging.
Battery Management System (BMS)
The BMS board is independent of the modules and manages the power control and external
data interface of the battery. Using cell and battery conditions passed to it by the Control
boards, the BMS microcontroller and software provide instructions back to the Control
boards, and through it, the Switch boards, to control the battery. The software logic monitors
the battery functions and provides protections for conditions such as short circuit, over-
temperature, over-discharge and others. It also controls the internal heaters. The BMS
generates battery status and data that is provided to the aircraft through the 18-pin
communication connector for cockpit monitoring. Data is provided in serial (ARINC 429),
discrete, and analog formats. The BMS provides the logic that operates the built-in/on-board
visual status indicator on the outside of the case as well.
The software is qualified to RTCA/DO-178C, Design Assurance Level A (DAL A). The battery
contains no airborne electronic hardware, known as AEH or complex hardware.
Resistance Temperature Detectors
There are two Resistance Temperature Detectors (RTDs) in the unit that supply direct analog
resistance through four pins on the 18-pin connector for independent temperature monitoring.
Each RTD uses two pins of the connector (see Figure 3.2 and Table 3.2) and are
characterized with a resistive output. See Section 4.4.1 for details.
Summary of Contents for True Blue Power TB20 Series
Page 1: ...Revision E January 6 2022...
