Eagle Eye Power Solutions

BTM-Series Battery Temperature & Thermal Runaway Monitor

The BTM-Series is a dependable low-cost scalable solution for protecting your batteries against over-temperature and thermal runaway conditions. Meet IFC and NFPA code compliance (see Product Features). Individual sensors are quickly and securely attached to each battery and connected in series from the main unit. Each thermal runaway sensor is sealed to IP68 (water, gas and dustproof), and the provided special gel-filled connectors are also sealed against acid ingress, dust, and gases.


  • Monitor individual unit battery temperatures for thermal runaway conditions
  • Simple fail-safe change-over relay alarm interfaces
  • Bright LEDs pinpoint individual overtemperature cells
  • No special tools required for installation
  • Sensor circuit break detection
  • Alarm on power supply failure (fail-safe)

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Alarm RangeActivation at 35 °C (95 °F), ± 3 °C (5 °F)
Reinstatement Temp2 °C (3.5 °F) below activation temperature
Input VoltageDC 12V 2-pin connectors or 12V AC/DC wall adapter
Output Relays(2) SPDT volt-free contact relays
Output relay contact ratings: 7A at 240 VAC, 10A at 120 VAC
(L x W x D)
Monitor: 84 x 40 x 77 mm (3.3 x 1.6 x 3 in.)
Sensor: 38 x 20 x 10 mm (1.5 x 0.8 x 0.4 in.)
Cables: 300 mm (11.8 in.)
ComplianceIFC 2015 – 608.3, NFPA 1 – Article 53.3.2



What is the maximum number of sensors that can be connected to a single monitor?
The maximum number of sensors for each monitor is approximately 200. If there are more than 14 sensors in over-temperature then the LED’s on the sensors become so dim that they are not visible, however the 1+ and 4+ indicators and relays on the monitor are still active.

Why is the temperature threshold for alarming set to 95ºF (35ºC)?
The nominal operating temperature for batteries is generally considered to be 77ºF (25ºC). If the battery is operating at 18ºF (10ºC) above that, it is a candidate for thermal runaway. The BTM is a fixed temperature device, so the temperature selected is above the normal swings in operating temperature but low enough to ensure that a battery that is overheating can be identified before thermal runaway occurs.

What are the maximum cable lengths for the BTM system?
At this time there is not a concrete limit on the total cable loop length or the length of cable between sensors. From an electronic point of view there is no reason why the length cannot be greater than 30 m (100 ft.). If the lengths become to excessive then there may be a possibility that the 4+ warning may activate with 3+ over-temperature faults. The system has been tested with a total loop length of 122 m (400 ft.) and the system operated normally.

What are the communication options for the BTM?
The BTM has (2) SPDT volt-free contact relays. Ratings are 7A at 240VAC and 10A at 120VAC.

What is the power consumption of the BTM?
The power consumption is 1.2W regardless of how many sensors are connected.

What kind of adhesive is used on the BTM sensor?
The sensors use 3M type 93020LE adhesive. If a sensor needs to be re-installed it is recommended to use this type of adhesive.


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