Wireline electromechanical release devices are critical and imperative for wireline operations. New-technology intervention and tractor tools cannot be deployed in oil wells without a reliable release device. For the intrinsic challenges of high temperature and longer horizontal wells, the reliability of these electromechanical release devices in the event a toolstring gets stuck downhole becomes even more important. The ability to operate an electromechanical release device on battery at high temperature reduces the overall risk of the intervention because it provides a secondary release option in case there is a damage to the wireline cable or toolstring that prevents communication with the release device downhole. A battery-operated release device activates on the expiration of a programmed timer, even in the absence of wireline power or the presence of a short circuit. The programmed timer can be updated only if communication with the toolstring is feasible, otherwise it reliably releases as originally programmed. Battery-operated electromechanical release devices for 175°C-rated tools, require the battery and associated control and power management electronics to function reliably at 175°C. Due to the chemical composition of this high-temperature battery, its capacity at low temperature is a small fraction of its capacity at high temperature. This presents a challenge in deploying these batteries, because some are installed and activated at surface ambient temperature of –10°C, for deployment in 175°C wells. Now the solution exists as a result of the combination of the development of a high-temperature battery and sophisticated battery management to maximize battery capacity for high-temperature operations. Through thorough qualification, this high-temperature battery was developed and validated. Test results show that the battery works optimally above 120°C. Below 120°C, the battery depletes exponentially, as the temperature decreases. The release device has been designed to intelligently manage battery capacity by switching to wireline power when it is present. The reliable low-bandwidth telemetry makes it possible to update the timer as desired during the wireline operation. The passivation prevention circuit helps prevent battery chemical passivation, maintaining its maximum capacity during the operation. All these technology components combined enable reliable and repeatable battery activation of the electromechanical release device at 175°C.