Type
Width
(bits)
Unimplemented Value
(hexadecimal)
signed int
16
0x8000
unsigned int
16
0xFFFF
signed int
32
0x80000000
unsigned int
32
0xFFFFFFFF
enumeration
16
0xFFFF
enumeration
32
0xFFFFFFFF
A write to a writeable MESA point that is unimplemented will generate a Modbus write error.
The MESA implementation on Nuvation Energy BMS has unimplemented points as follows:
Table 9. Unimplemented MESA Points
Model
Point Name
Description
801
Evt
Event status bit field
801
DisChaRate
Self Discharge Rate
801
MaxRsvPct
Maximum Reserve Percent
801
MinRsvPct
Minimum Reserve Percent
801
ChaSt
Charge Status
801
DerAlarmReset
Alarm Reset (read is unimplemented)
802
CycleCt
Cycle Count
802
WMaxDisChaRte
NamePlate Max Discharge Rate
802
SoH
State of Health (reported in 803 model per string)
802
BatReqPCSSt
PCS State Request
802
BatReqW
Battery Power Request
802
SoH_SF
State of Health Scale Factor
802
BatReqW_SF
Battery Power Request Scale Factor
803
StrEvt2
String Event 2
803
StrConFail
String Connection Fail
7.1.3.4. Scale Factors
All MESA points are integer values (signed or unsigned). To account for different range values beyond
the data size (i.e. greater than 65535 for an unsigned 16 bit value) or some fractional value (i.e.
1.1), some MESA points have scale factors associated with them. The scale factor is another point
within the model which contains a signed integer exponent of base 10 that scales a corresponding
point value. For example, a scale factor of 2 would result in multiplying the corresponding point by
100. Likewise a scale factor of -3 would result in a scale factor of 0.001. Refer to the prior MESA Draft
3 spreadsheet for the relationship between MESA points and their scale factors. All scale factors are
fixed for a model and do not change in value.
7.1.4. Operational Cases for MESA
There are two main operational cases for the control of Nuvation Energy BMS over its MESA interface:
1. An external controller (sometimes called "Energy Storage Controller") is used to coordinate power
Nuvation Energy High-Voltage BMS - Product Manual
Document ID: NE-PM-003
65
Rev 1.2, 2021-03-03
Curie Update 1
