The first prototype of the Li-ion battery system that was specially developed for the UrbANT is going through its initial commissioning with the corresponding tests.
The highlights of the system are:
- 24 V / 70 Ah produce an energy content of 1.7 kWh, which are accommodated in a space of only 5.7 litres (volumetric energy density thus results to 310 Whl-1); that became possible by using the high-performance cell INR-21700M50A from the manufacturer and Li-ion pioneer E-One Moli in the new 21700 design and by the clever use of the available space.
- Cutting-edge BMS (battery management system) in a decentralized design, consisting of an analog front end, high-performance controller and semiconductor switchgear.
- Industrial standard CANopen interface for secure communication and transmission of all relevant battery data with and to the vehicle control computer.
Besides the configuration of the cell stack with optimized energy content for maximum operating time of the UrbANT, the main focus was on developing an 1st tier BMS with all currently required features of such a system (e.g. RTC, operating data storage, bootloader, cycle-counter, SafeEnergyManagement, ServiceTool software etc.).
The administration of an unlimited series connection of battery cells is a spin-off of the created topology in a decentralized form. In this way batteries can theoretically be implemented in any voltage level (currently up to 360S, corresponds to approx. 1.300 V). The use of the semiconductor switching mechanism eliminates the holding currents of conventional relays, and more and above this, the current directions for charging and discharging can be switched selectively. A pre-charging circuit avoiding switch-on peaks, the current measurement, short-circuit current detection and safety monitoring for disconnection in the event of overload are also integrated into this module .
The pictures show the battery in the closed and open state of the stainless steel housing, connection side with Stäubli multifunctional plug and the user interface of the BE-Power Service Tool.