Contactors with auxiliary switch feedback are used so the BMS can raise a fault when it detects
contactor failure during opening or closing. Note that the expected lifespan of a contactor is impacted
significantly each time it connects or disconnects under load.
3.2.4. Pre-Charge Circuit
The Stack Switchgear has a pre-charge circuit to ensure safe connection of its battery stack to the DC
bus. The pre-charge circuit temporarily connects the stack to the DC bus through a power resistor.
This resistor allows a smaller current (proportional to the difference in voltage between the stack and
the DC bus) to flow between the stack and the DC bus. After a 5-second pre-charge timeout, if the
measured current is below a safe threshold, the BMS bypasses the pre-charge circuit by connecting
the stack directly to the DC bus.
This ensures the battery stack will not connect to the DC bus when an unsafe voltage mismatch is
present. By default, the Stack Switchgear is configured with a 150 Ω, 300 W power resistor, suitable
for a DC bus capacitance of 15 mF at 1000 V and 10 mF at 1250 V. As a custom request, the pre-
charge resistor can be sized specific to the end application.
3.2.5. Fuses
Inline fuses are used on both the positive and negative connections and are sized according to the
Stack Switchgear variant. See
for the fuse ratings for each Stack Switchgear variant.
The fuses interrupt a short circuit event; two of them are used to provide redundancy and to permit
use of the Stack Switchgear with an ungrounded battery stack. A microswitch is used on each fuse so
that the BMS can recognize blown fuses and issue a fault alert.
Table 2. Internal fuse ratings
Stack Switchgear Variant
Fuse Rating
Interrupt Current Rating
1250 V DC, 100 A
200 A
100 kA
1250 V DC, 200 A
315 A
100 kA
1250 V DC, 300 A
450 A
100 kA
3.2.6. Safety Relay (for E-Stop)
The Stack Switchgear has an internal safety relay for monitoring an external E-Stop signal. A safety
relay is used to ensure the relay cannot fail shorted.
This relay meets the requirements of the following standards: EN 954-1, EN 60204-1, VDE 0113-1
and IEC 60204-1. It also has approvals from UL, cUL, CCC and TUV. For more information about the
E-Stop functionality, see
.
Nuvation Energy High-Voltage BMS - Product Manual
Document ID: NE-PM-003
9
Rev 1.2, 2021-03-03
Curie Update 1
