Low-Power Cellular Telemetry Solution for Electric Vehicles

This paper investigates a novel way to collect electric vehicle telemetry data over a cellular network. The goal is to acquire vehicle internal states and store them in a remote location. The states of the vehicle could be values, either measured or calculated by one of the vehicle’s electronic control unit (ECU). A telemetry system for the solar powered electric vehicle was designed for the iLumen European Solar Challenge 2024. The competition vehicle was equipped with a battery management system (BMS), two maximum power point tracking devices (MPPTs), a power inverter, a dashboard, and an auxiliary power system. Every ECU communicates over a classical controller area network (CAN) with a bus topology. The typical information encoded in the CAN messages includes voltages, amperages, temperatures, velocity, odometer information, fault states, driving modes, and serial information. The performance of the proposed telemetry solution was evaluated by monitoring the power consumption, network latency, bandwidth, and error rate of the system. This paper separates the system architecture into hardware and software sections. The hardware design includes an ARM Cortex-M3 processor integrated in a STM32 Nucleo development board and a DIGI XBee XR 868 LTE module. Both modules were selected because of their low power design with the possibility to enter into "standby" mode. To secure communication over the cellular network, each outgoing data packet is encrypted using the transport layer security (TLS) protocol. The software component was developed with an interrupt-based design that leverages Cortex-M nested vector interrupt controller (NVIC) to maintain real-time code execution. In order to increase the system’s bandwidth and to reduce error rate techniques such as direct memory-to-peripheral writing and cyclic redundancy check (CRC) were used. The final telemetry solution continuously monitored the solar vehicle for 24 hours during the aforementioned competition.