Detecting high voltage battery isolation failures in electric vehicles
The SIM100 module is presented as unique in that it can be used while the car is in operation; specifically, it is claimed to be a new type of automotive rated isolation monitoring safety device that is capable of detecting potential electrical hazards during the dynamic operation of high voltage unearthed systems, such as electric and hybrid vehicles.
The module, Sendyne continues, is the first device of its kind capable of unambiguously detecting the electrical isolation state of a high voltage system while the system is active and operating, and experiencing large voltage variations. Alternative monitoring detects only resistive leakages and only when the system voltage does not vary significantly. SIM100 detects both resistive leakages and capacitively stored energy that could be harmful to human operators.
High voltage battery systems, such as the ones used in electric vehicles, are typically electrically isolated from the chassis, to protect human operators. However, this isolation may deteriorate either gradually or suddenly, exposing those who come in contact with chassis to potential hazardous shocks. In addition, capacitances from the power system to the chassis may inadvertently change, accumulating hazardous charges. If either condition is detected, the operator should be notified in order to immediately service the vehicle. In case of an accident, the emergency first respondents will also rely on this information so they may approach the vehicle safely.
Sendyne’s SIM100 can detect these types of potential hazards while the system is operating and voltages are fluctuating as much as 100 V. Commercial devices so far are only able to detect resistive leakages when there are no dynamic fluctuations in the electrical system. For industrial and commercial systems that have to be in operation most of the time, this limitation can be dangerous.
Sendyne was able to achieve this performance with its proprietary modelling and embedded computing techniques. A custom IC models the supervised unearthed system, and through stochastic optimization methods, determines the condition of all types of electrical paths from the high voltage system to the chassis. The SIM100 can detect the values of each resistance or capacitance, as well as the location of the potential hazard, whether on the positive or the negative path. In addition, the SIM100 calculates and provides uncertainty values for each estimate.
Communications are achieved with the host ECU via an isolated CAN 2.0B interface (500 kbit/sec). The module has a wide input voltage of 5V to 53V, thereby accommodating most vehicle systems. It provides a wide temperature range of –40 °C to +105 °C. The module was designed to ISO 6469-3:2011-12 / FMVSS 305. An evaluation kit, with cables, CAN to USB dongle and software is available. Sendyne’s SIM100 IC is also obtainable as a separate component.
“It’s a new type of electronic device that takes advantage of the modern stochastic process theory in order to solve a safety problem with very few known parameters. We are very pleased with the results. We were able to achieve them utilizing modelling and computing tools which we have developed for a wide area of IoT analytics applications,” said Sendyne’s CEO John Milios.