BTM-Series Battery Temp Sensor / Battery Thermal Runaway Monitor

Model # BTM-Series

The Eagle Eye BTM-Series Battery Temperature Sensor/ Thermal Runaway Monitor is a dependable low-cost solution to protecting stationary batteries against over-temperature and thermal runaway conditions. Individual sensors are quickly and securely attached to each battery jar and connected in series from the main unit. Each thermal runaway sensor is sealed to an IP68 rated-enclosure (water, gas and dustproof) and the provided special gel-filled connectors are also sealed against acid ingress, dust, and gasses.

The alarm relays are 'fail-safe', meaning the user will always get an indication of supply failure. Several batteries in the vicinity of each other may be connected in series to the same monitor. In the event of one or more jars exceeding critical temperature, or a break in sensor circuit, the monitor warning relay activates and the warning LED on the monitor is illuminated. Also, at the same time, an LED flashes on the battery temperature sensor attached to the over-temperature battery jar, indicating the source of the fault. Should more than 6 jars exceed critical temperature, the system critical alarm relay activates - warning of a serious situation in the battery as a whole. The microprocessor utilized by the BTM-Series Thermal Temperature Monitor updates changes in conditions every four seconds.

Longer interconnections, such as shelf-to-shelf and rack-to-rack are simple to accommodate with standard 20SWG cable, and the IDC connectors provided; cable lengths are not sensitive. Battery temperature sensor installation for a 40-jar battery will typically take less than an hour.

LED Indicators For:

  • 1+ Jars Critical Temperature
  • 4+ Jars Critical Temperature
  • Power Failure
  • Sensor Circuit Break

Over-temperature in a standby battery is a potentially serious condition, which is often caused by either a fault condition within the battery cells leading to higher cell temperature or a higher than recommended ambient temperature promoting a fault within the cell which leads to a higher current draw and so on. It is a ‘positive feedback’ progression of exponentially increasing temperature often leading to an explosion. The International Fire Code (US IFC 608.3) requires that if a sealed battery (or batteries) operated in a single premise contains over 50 gallons of acid the proprietor must install measures for thermal runaway prevention. The National Fire Protection Association also requires protective measures against thermal runaway in NFPA 1. Article 52.

While IFC 608.3 is intended to prevent a catastrophic explosion damaging the surrounding environment, batteries with smaller total amounts of acid should also be protected as they are just as vulnerable to thermal runaway as larger installations. Additionally, operating a standby battery in higher temperatures than specified can seriously shorten its life. Every 10°C above 25°C (77°F) reduces the service life of the battery by 50%.

The only way to prevent the damaging and costly effects of thermal runaway is to have a real-time battery monitoring system in place. The BTM-Series Battery Thermal Runaway Monitor is a cost-effective system that is easy-to-install, scalable, and protects against permanent battery damage in UPS cabinets, substation battery rooms, outside plant cabinets and other stationary battery applications. Contact us for more information about thermal runaway prevention and to request a quote.

  • Specifications
  • FAQs
  • Benefits

Technical Specs

Alarm Range:Activation at 35 °C (95 °F), ± 3 °C (5 °F)
Reinstatement Temp:2 °C (3.5 °F) below activation temperature
Input Voltage:DC 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.)
Compliance:IFC 2015 - 608.3, NFPA 1 - Article 53.3.2


What are some common applications areas for this product?
Common applications include but are not limited to:

  • Telecommunications
  • CATV / Broadband
  • Power Utilities
  • Mission Critical Facilities
  • UPS Systems
  • Generation & Distribution
  • Financial Institutions
  • Oil, Gas & Fuel
  • Mining
  • Government/Defense
  • Transportation Operations
  • Hospitals
  • Emergency Lighting
  • Green Energy
  • Call Centers
  • Battery Suppliers and Manufacturers
  • Medical/Biotechnology
  • Generators

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.

What are the listings on the BTM system?
Within the system the following parts are approved as:

  • The temperature sensor is UL
  • The monitor box is molded from flame retardant ABS UL94-V0 plastic
  • The warning relays have UL/CUL and VDE approvals with an isolation voltage between coil and contacts of 2KV.
  • 12 Volt power source has UL, CUL, and TUV
  • 2 and 3 way connectors (green) have CUL and VDE
  • PCB FR4-standard TD 140°C (284°F) to UL standard

What are the communication options for the BTM?
The BTM has (2) SPDT volt-free contact relays.

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. We have tried it with a total loop length of 122 m (400 ft.) and the system worked fine.

What is the power consumption of the Battery Thermal Runaway monitor?
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.


  • Low cost monitor for thermal runaway detection
  • Customized for any battery bank
  • Monitors individual unit temperatures for thermal runaway conditions
  • Ensures compliance with US IFC608.3
  • Simple fail-safe change-over relay alarm interfaces (2)
  • Bright LEDs pinpoint individual over-temperature jars
  • Fast one-wire acid and gas tight IDC connections
  • Sensor circuit break detection
  • Alarm on power supply failure (fail-safe)
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Request Information
  • Model #

    Battery Temperature Monitor includes (1) Monitor and number of sensors per jar / cells

    Model number varies per number of jars (Ex. BTM-60C for system with 60 jars)

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Companies We Serve
  • ATT: Telecom Battery Thermal Runaway Prevention Century Link: Telecom Battery Thermal Runaway Prevention
  • Duke Energy: Substation Battery MonitoringOG&E: Substation Battery Maintenance
  • Exxon Mobil: Battery Maintenance Cummins: Energy and Battery Testing