The Wattius wBMS-MX is a distributed Battery Management System developed to work with high-voltage batteries up to 800V. The system has been designed to meet all relevant industry requirements such as ISO26262 / IEC61508 and provides reinforced isolation according to EN50178.

This system is composed by the BMU (Battery Monitoring Unit) and CMU12s (Cell Monitoring Units, each for up to 12 cells). Each BMU supports up to 24 CMU12s for a total of 288 cells in series. Multiple BMUs can be connected in parallel without additional hardware. The system automatically handles multiple string connection and provides a single control interface with the inverter / charger.

  • Each CMU12: up to 12 cell measurements with ± 1,5 mV max. error.
  • Up to 24 CMU12s for a single BMU.
  • Autonomous parallelization of multiple battery strings without additional hardware.
  • Ultra low power mode (< 15 mW).
  • High-precision SoC algorithm.
  • Up to 300mA autonomous balancing.
  • EMC CE Class A & B compatible.
  • CANbus, USB & Bluetooth Low Energy.
  • Real-time logging of events, alarms and data to micoSD card.
  • Monitoring, configuration & analysis with free wBMS-Toolkit PC software.
  • ISO26262 & EN50178 compatible design and components.
  • Internal extended diagnostics and safety-critical redundant systems.
  • Cell and relay open-wire detection.
Electric mobility & industrial traction
Large-scale ESS
Power Supply

10 – 36 Vdc

< 5 mW in deep sleep mode

Independent input for output supply

Maximum system voltage

800 Vdc (EN50178, reinforced isolation)

Compatible with transformerless stationary ESS use cases.

Supported CMUs24 CMU12s per each BMU (288 series max.)
Current sensingExternal 0 – 5 Vdc hall current sensor. < ± 0,1 mV.
CAN Interface

CAN bus 2.0 A/B (Up to 1Mb/s). Referenced to external power supply.

Configurable termination resistor with switch.

CANopen compatibility.

Other interfaces

Mini USB 2.0

Bluetooth 5.0 Low Energy.

General Input

2x analog / digital (configurable) signal up to 36 Vdc.

4x dry contact digital input.

Configurable to multiple functions (ignition key, HVIL, relay feedback etc.).

General Output

6x independent channels.
External supply voltage. Maximum total output 4 A. External fuse recommended.

Channel 1-4: 2 A nominal, 4 A peak per channel.

Channel 5-6: 1 A nominal, 2 A peak per channel.

Adjustable PWM @ 1 kHz max.

Open circuit, short-to-battery and short-to-ground detection.


Integrated redundant EEPROM to store system configuration and maximeter.

microSD support (up to 16 GB).

Data loggingContinuous logging of cell data. Event / error / alarm log.

Up to 16 devices in parallel without external hardware.

Dimensions80 x 70 mm

Cell measurements

(voltage & temperature)

Multiple cell chemistry and supercapacitors.

Extended internal redundancy and hardware integrity diagnostics.

Open wire detection.

Cell voltage

5 – 24 cells. 0 – 5 Vdc.

± 1,5 mV cell voltage max total error.

Cell temperature

Up to 6 channels. Configurable NTC 10 kΩ.

± 1 ºC cell temperature max total error.

BalancingAutonomous. Configurable. Up to 300 mA per channel.
Dimensions54 x 92 mm

With the wBMS-Toolkit PC software multiple configuration parameters can be tuned to work with different types of cells, architectures and use cases, as well as providing an excellent tool to monitor the system and access diagnostic and debug information.