S-Box

The requirements for functional safety demand a safety level of at least ASIL C for the battery shutdown. The Futavis S-Box is developed according to international standards (including ISO 26262 or IEC 60730 as well as LV 123 and LV 124) and can therefore withstand the required safety requirements.

In addition, the modular Futavis S-Box as a series product is perfectly matched to our BMS and, thanks to its small and compact design, can be used in a wide range of applications. The modular development approach also allows the S-Box to be used for batteries of up to 1000 V DC. Whereby the number of modules and cells can be freely scaled.

When switched off, the battery is permanently and de-energized disconnected from the surrounding system. Only when the BMS gives the command, the contactor is closed and the battery is connected.

The BMS enables continuous monitoring of the temperature and voltage characteristics of the battery modules, which means that faults can be detected at an early stage, and thus the command can be given to the S-Box to open the contactor again. The special challenge here is that the contactors must permanently withstand the high currents and voltages when switched on. In addition, there are the requirements from the current standards that demand an ASIL C safety level. Therefore, we have installed a redundant current measurement with two different current sensors, a Hall and a Shunt sensor, in the S-Box.

Functions:

  • ASIL C current measurement (requires two different current sensors: shunt sensor and hall sensor)
  • Project-specific fuse design (short-circuit protection)
  • Main current path separation
  • All-pole disconnection via contactor
  • Voltage measurements for contactor monitoring
  • HV measurements
  • Contactor status monitoring
  • DC link precharge
  • Low impedance external short circuit Disconnection of the HV circuit
  • Fast disconnection of the HV circuit by means of a fuse
  • Temperature monitoring
  • Cooling by means of air circulation

Certifications:

  • ASIL C – Current measurement (Hall and shunt)
  • Internal contact fuse acc. DIN 40050-9
  • Personal protection during operation (cf. ECE R100, ISO 6469-3)
    • Protective caps for non-insulated interface
  • External contact protection acc. DIN 40050-9 (cf. ECE R100, ISO 6469-3)
  • Clearance and creepage distances acc. DIN EN 60664-1 and ISO 6469-1
  • 50g mech. Impact resistance

Flexibility:

  • Modular design
  • CAN interface
  • Up to 48V up to 800V
  • Backup selection

The S-Box provides the HV and LV interface between the battery modules and the surrounding system. It is directly linked to the BMS, which is the monitoring unit of the battery and thus gives the S-Box the appropriate connection and disconnection commands. The sensor system of the S-Box consists of 2 current sensors, a Hall and a shunt sensor, and 2 voltage measurements. The 3 contactors are designed for the high currents and voltages and ensure that disconnection of the battery is possible even under current.

The contactors as well as the included precharging circuit are controlled by the BMS, whereas current and voltage measurements are read in by the BMS via taps and current sensors.

Battery voltage in V Fuse IMD Board voltage Precharge resistor
48 V

400 V

EV25/EV30

100A -400 A

yes/

no

12V

24V

30 Ohm

90 Ohm

customer specific

800V Square Body 170M yes/

no

12V

24V

30 Ohm

90 Ohm

costumer specific