Overtemperature Detection System Seamlessly Integrates With EV BMS
Littelfuse has rolled out TTape, an innovative temperature monitoring and detection system that seamlessly integrates with electric vehicle battery management systems.
Thermal management is critical for the safety, efficiency, and longevity of lithium-ion (Li-ion) battery packs, which are growing in demand because of the electric vehicle (EV) market boom.
Littelfuse’s TTape thermal monitoring device. Image used courtesy of Littlefuse
Littelfuse, an industrial technology manufacturing company, has created an innovative solution for Li-ion temperature monitoring with their product TTape.
TTape Advantages and Product Dimensions
An important advantage of TTape is its hyper-localized temperature monitoring and ability to detect any problematic temperature increases in every cell within an Li-ion battery pack.
TTape illustration showing thermal indicators and attached circuitry. Image used courtesy of Littelfuse
The TTape is adaptable to different battery pack models and sizes. The TTape width can be 8 mm or 10 mm, depending on design needs and customer preferences. The number of printed thermal indicators (PTIs) is typically 50 or less. The distance between the PTIs can also be customized, but it is typically 10 mm or less.
TTape provides a two-wire interface to maximize thermal monitoring and simplify the installation process. TTape activates at 58±3°C and resets at a temperature of 42±3°C.
Thermal Runaway and Monitoring Challenges
While EV battery fires make headlines, they are not common. In fact, conventional internal combustion engine vehicles catch fire more frequently than EVs, with a rate of 1,529 fires per 100,000 vehicles compared to 25.1 fires for every group of 100,000 EVs.
Even if fires are unusual, thermal management remains integral to battery lifespan, performance, and efficiency.
Thermal runaway occurs when an exponential temperature increases inside any cell of an Li-ion and cannot be compensated for by heat removal. Due to the density of Li-ion battery packs, when one cell catches fire, it has a cascading effect on neighboring cells.
The short circuits and cascading effects leading to thermal runaway might be easy to understand, but implementing monitoring solutions is much more difficult.
Various causes of thermal runaway. Image used courtesy of ResearchGate
Voltage sensors are often affixed to battery cells to monitor conditions and performance, but fitting every cell with a voltage sensor is impractical. Too many voltage sensors overburden the battery management system (BMS) with inputs, thus compromising its resources and ability to manage charging and discharging processes.
Littelfuse’s TTape avoids this excessive resource depletion because it can monitor a large area and many cells with only a single microcontroller unit (MCU). Look-up tables and calibration are not necessary. TTape is simple to integrate with other BMS and doesn’t consume bandwidth with inputs. This ultrathin device can produce responses to temperature increases in less than a single second, so fast response times are not compromised by using only a single MCU input.
Electrical Specs and Applications
The most obvious application for TTape will be Li-ion batteries used in EVs. However, TTape can also be used for other battery packs or other large-area distributed temperature monitoring needs.
Ideal operating conditions for TTape. Image used courtesy of Littelfuse
Another possible application for this technology might be e-bikes and e-scooters, which are causing a significant share of fires because of Li-ion failures.
The simple, versatile, and localized temperature monitoring offered by TTape is an important addition to the rapidly growing Li-ion and EV markets.
