CAN bus

Example

Use in Lemonergy

Make series/parallel architecture explicit.

This is a reference concept. No executable Lemonergy block has been verified for this term.

Connected concepts

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Battery management system

The electronics and software that keep a battery inside its safe window: measuring every cell voltage and many temperatures, estimating SOC and SOH, balancing cells, computing current limits, controlling the contactors and reporting over the vehicle network.

CAN FD

An extension of classical CAN that switches to a higher bit rate, up to 5–8 Mbit/s, for the data part of each frame and allows 64 data bytes instead of 8. BMS data-logging and over-the-air updates are its usual battery uses.

CAN high and CAN low

The two wires of a CAN bus, a twisted pair driven in opposite directions. Idle, or recessive, both sit near 2.5 V; for a dominant bit CAN_H is pulled up to about 3.5 V and CAN_L down to about 1.5 V, so the receiver reads the 2 V difference. Noise picked up by the pair adds equally to both wires and cancels in the difference.

FMS interface

The manufacturer-independent CAN data interface of trucks and buses, defined by the major European OEMs, that exposes vehicle data — including, for electric vehicles, battery state of charge, charging status and energy consumption — to fleet-management telematics.

LIN bus

A cheap single-wire serial bus at up to 20 kbit/s with one master and several slaves, used where CAN is overkill: a smart 12 V battery sensor, a cooling fan or a heater controller reporting to the BMS.

CAN termination

A 120 Ω resistor between CAN_H and CAN_L at each end of the bus, matching the cable impedance so signals do not reflect. A healthy bus measures about 60 Ω between the two wires when powered down; 120 Ω means one terminator is missing.

References & further reading

Technical references

1. 3rd generation of the CAN data link layer

   CAN in Automation, CAN Newsletter · 2020

   Technical reference · Classical CAN, CAN FD and CAN XL data-link concepts; publication describes the 2020 state.

Further reading on this topic

These sources provide broader context; they are not presented as citations for every statement in this entry.

2. Extended Kalman filtering for battery management systems of LiPB-based HEV battery packs: Part 2. Modeling and identification

   Gregory L. Plett · Journal of Power Sources · 2004

   Topic background · Battery charge balance, open-circuit voltage, ohmic loss, polarization dynamics and model identification; parameters require cell-specific data.

3. Getting Started with the BQ76925

   Texas Instruments · 2019

   Topic background · A concrete BMS analog front-end example: cell voltage, current, temperature measurement and MCU integration.