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Essential Temperature Monitoring for Batteries

        In the e-vehicle battery market, battery system designers are under increasing pressure to maximise the conflicting requirements of size, weight, energy capacity, performance and cost, meaning that batteries are often required to perform at the very limits of their technology.  At these extremes, accurate and consistent temperature measurement (with minimal time lag) is crucial to maximise battery performance, minimise cell degradation and also to prevent catastrophic failures.

        To assist these battery engineers, ATC Semitec helps to design and develop bespoke temperature sensors, offering a wide range of connection methods to match customers’ requirements.  Many of these unique designs are rapidly becoming industry standards due to the high quality and performance of these sensors and the respect that ATC Semitec carries within the temperature sensor industry.

        As many as there are different types of battery cells (and associated cooling systems), our range of sensor designs cover bolt-on ring terminal sensors, thin flexible film NTCs/RTDs, epoxy-coated flexible lead thermistors/RTDs, insertion screw-thread sensors and integral T-piece coolant pipe designs.  Their system suitability is ultimately dependent on the engineers’ available space, preferred fixing system, operating temperature range and finally cost.  ATC’s range of sensors can be further detailed as follows;

STS2 Series Ring Sensors – This range of ring terminal temperature sensors are one of the most popular products for monitoring battery terminal temperatures.  Insert-moulded sensor housings offer a fast-responding metal sensing ring with an integrated, over-moulded plastic case which helps to minimise heat-loss.  These insert-moulded sensors are supplied with either M3 or M4 mounting holes as well as an M3 spade tongue version.  These sensors have a fast thermal response (Tc ≤ 5s) and can be fitted with NTC or RTD sensing elements.  NTCs with 1% R25 tolerance (or class B Pt100s/Pt1000s) ensure absolute temperature accuracies better than ±0.5deg.C.  Additionally this type of housing combines excellent electrical isolation up to 1.5KVAC.

Furthermore, various metal ring versions offer an even wider range of mounting options, lead-wire gauges up to 20AWG (to meet automotive standards) and higher dielectric ratings.

Flexible Film Sensors – Slim but strong, Semitec’s JT series NTC thermistor is only 0.5mm thick at its sensing tip making it the thinnest, flexible NTC available world-wide.  The slim fast-responding NTC element is laminated between two polymer layers making it flexible and resilient at the same time.  This flexibility allows the JT’s sensing tip to be placed much closer to the heat source it is measuring (i.e. between adjacent battery cells), helping to deliver optimum temperature control even in the tightest of spots. 

Semitec JT -Ultra thin flexible film NTC thermistor
UK Stock from ATC Semitec

With 1% R25 tolerances delivering accuracy better than ±0.5deg.C and various film lengths available including custom lengths, the JT thermistor is becoming increasingly ubiquitous.  Extending the lead-wires and adding integral connectors opens up even more sensing possibilities.

If the temperature range of the NTC is a limiting factor, Heraeus Nexensos SMD Pt100s or Pt1000s mounted on a high-temperature flexi-pcb material offers sensing options up to 200deg.C. 

Solder or sintered flip-chip solutions ensures optimal performance for IGBT and other power component monitoring or control.

Finally ATC Semitec offers various flexible lead-wire sensors where a more robust sensing solution is required.  The Semitec AT-4 series are small, fast-responding epoxy-coated NTC thermistor bead sensors with various lengths of 26AWG or 30AWG PVC insulated lead-wires, from 50mm up to 1000mm long.  The flexible PVC lead-wires provide a simple, easy to install sensor helping to save valuable battery assembly time.  In particular the 10kohm 103AT-4 version uses the industry standard 103AT-2 NTC thermistor which has long been used in rechargeable battery applications.  

If an even more robust sensor is required, the Semitec 103AT-11 is an IP67 over-moulded temperature sensor that uses 22AWG TPE wire.  The sensing head of these AT-11s is 6 x 5 x 15mm long giving a fast response whilst maintaining environmental and electrical integrity.

For high-temperature applications up to 200deg.C (or 250deg.C intermittent), the Heraeus Nexensos EC-3032 encapsulated sensor offers IP68 integrity whilst using a highly accurate Pt100 or Pt1000 sensing element.  Primarily designed for use in e-motor applications, these high integrity sensors offer extremely stable temperature monitoring in any application where a small, accurate and tough sensor is required.

Encapsulated high temperature Pt1000 RTD Temperature Sensor
Heraeus EC3032

 ATC Semitec has over 25 years’ expertise supporting engineers across the world with their temperature sensing and thermal management solutions. Our experience will ensure that the very best thermal protection solutions are available for your products. Off-the -shelf or bespoke solutions, we can provide full support from initial design to production.

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