control functions of the BMS in conjunction with some other equipment (such as an inverter). This
controller requires periodic and rapid responses of MESA point reads as well as some control over
the operation of the BMS (such as stack connectivity). If there is a loss of communication between
this controller and the BMS, the BMS will disconnect the stack(s) as a safety precaution.
2. An owner/operator of a battery system requires control of the BMS to monitor the activity of the
batteries and track battery usage and its charge/discharge activities. This information can then be
used to characterize the usage of the battery management system and to validate battery
warranties of a vendor.
Read and write Modbus TCP operations can be performed over the standard Modbus port
502
(only a
single connection is supported on this port).
These two operational cases will be discussed in detail in the following sections.
7.1.4.1. External Controller Communicating Over MESA Interface
An external controller typically polls Nuvation Energy BMS battery control points at a rate of 2–4 Hz.
This controller reads data points required to manage current flow in the system. The following table
summarizes the most important points an external controller may want to read from the BMS.
Table 10. MESA Points Read by an External Controller
Model
Block
Point Name
Address
Scale
Factor
Purpose
801
Fixed
DERHb
40086
No
BMS Heartbeat counter incremented every second
802
Fixed
Evt1
40101
No
Bit field of all faults/warnings of a the BMS
802
Fixed
Vol
40105
Yes
External DC voltage of the battery system
802
Fixed
MaxBatACha
40106
Yes
Charge current limit calculated by the BMS
802
Fixed
MaxBatADischa
40107
Yes
Discharge current limit calculated by the BMS
803
Fixed
BTotDCCur
40127
Yes
Total DC current of the battery system
A controller may also want to command Nuvation Energy BMS to perform certain actions, such as
connecting/disconnecting the battery. The following table provides the different writeable points in
the MESA interface for different control functions:
Table 11. MESA Points Written to by an External Controller
Model
Block
Point Name
Address
Purpose
801
Fixed
ControllerHb
40087
Heartbeat register for external controller
801
Fixed
DERAlarmReset
40088
Clears all latched alarms in the BMS
802
Fixed
BSetOperation
40110
Commands Nuvation Energy BMS to connect/disconnect the
battery
When configured, the heartbeat controller can be used to update the watchdog timer of Nuvation
Energy BMS on single-stack and multi-stack implementations. If the heartbeat point is not updated
within the watchdog timer period, a fault will be generated on the BMS stack and its corresponding
contactors will be opened. The value written to the heartbeat point must increase in value and roll
over to zero when the 16 bit range limit is reached.
The clearing of alarms of Nuvation Energy BMS is accomplished by writing a value of
1
to the
DERAlarmReset
point. This point is erroneously identified as read-only in the Mesa Draft 3 spreadsheet
Nuvation Energy High-Voltage BMS - Product Manual
Document ID: NE-PM-003
66
Rev 1.2, 2021-03-03
Curie Update 1
