Fellten Morgan XP-1 | Dossier 25 Condition-monitoring sensors A plethora of safety-critical sensing components operate in tandem with the BMS. An isolation monitoring system keeps track of high-voltage (HV) grounding. Hazell says this system in the Orion BMS has been programmed to deliberately output a 5 V AC signal into the DC bus in order to continually monitor the ground for signs of that signal and enable the rapid opening of all contactors upon sensing a cable being cut, or a similar HV fault of that nature. He explains: “There’s other isolation monitoring arrangements that swap between the positive and negative terminals for linked HV referencing, but that can build up a capacitive load. The Orion’s way of doing it is very clever, because it’s never trying to read the DC ground; doing that can create a HV ground scenario by creating the pertinent link, but doing it with AC means it is never putting DC to ground, and it is hence never conflicting with the motor inverters or the CCS.” The BMS also runs a high-voltage isolation loop (HVIL), so if someone unplugs a connector, the contactors simultaneously open, ensuring no one can gain access to the HV bus without opening the entire pack. Such features are compliant with UN ECE R100/01 and R100/02 regulations on battery safety. While UK retrofitting companies are not legally required to oblige by R100, Fellten is determined to stay ahead of the requirements laid out in such standards, so if they should ever come into force for converted EVs in Britain, Fellten-powered, converted-toelectric vehicles will pass. For detailed battery health monitoring, the XP-1’s BMS integrates Metis Engineering’s Cell Guard multisensor device, which internally monitors at the module and pack levels for humidity, gases with volatile organic compounds, absolute pressure and temperature as standard. “It senses moisture on a parts-permillion basis, thereby tracking not just the presence but build-ups of moisture, including setting a maximum level above which it is safe to assume water is leaking into the pack and risking a short across what used to be air gaps between the cell groups,” Hazell adds. “People tend to take our retrofitted vehicles into pretty poor weather, often wading into flooded roads with them, or even jet-washing them, all while assuming it is going to be waterproof forever. So, if we detect too much moisture, or a certain limit value for gases or venting from cells, the BMS can open the contactors to keep it from turning into a thermal event.” The Metis Cell Guard has a G-sensor for impact and crash detection, enabling Fellten to set a target number specific to the crash levels of G-force for each EV and pack. Upon sensing anything at or above that value, the Cell Guard triggers the BMS to open its contactors and stop the battery pack operating. Charge management Considerable effort has been made to install safe and precise control of the CCS rapid charging system into the battery pack. Principle governance of charging, and the associated communications between vehicle and grid are handled by a control module from US-based IoTecha. “Handling comms between the charger and grid is quite an in-depth E-Mobility Engineering | July/August 2024 Orion’s BMS and Metis’ Cell Guard are among the battery management and condition-monitoring tools integrated for pack health and safe running
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