Mitsubishi 2CR17335A: The "Data Guardian" Hidden Deep Within Devices

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Mitsubishi 2CR17335A: The "Data Guardian" Hidden Deep Within Devices

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◇登録日: 2026年8月6日

: machii-little; 道場主

Lv.30

Tucked away on the circuit boards of electronic devices, one often finds unassuming yet vital coin or cylindrical batteries. While they do not perform calculations or power the display, they shoulder a mission-critical task: maintaining the real-time clock and protecting data stored on memory chips during power outages. The Mitsubishi 2CR17335A is a classic example of such an industrial-grade backup battery. Frequently found on the motherboards of PLCs, medical instruments, security alarms, and field monitoring equipment, it silently safeguards the system's "memory" thanks to its ultra-low self-discharge rate and exceptionally wide operating temperature range.

Meet the 2CR17335A: A Compact 6V Power Pack

The Mitsubishi 2CR17335A is no ordinary single-cell battery. Based on its designation and internal structure, it is a battery pack formed by connecting two high-performance CR17335A lithium-manganese dioxide (Li-MnO₂) cylindrical cells in series. It boasts the following core specifications:

Nominal Voltage: 6V (a single CR17335A is 3V; the voltage doubles when connected in series)

Nominal Capacity: Approximately 1800mAh—an energy density sufficient to support the long-term operation of low-power devices

Dimensions: Typically a compact, combined package (parallel or series configuration) featuring pins or solder tabs for direct PCB mounting

Operating Temperature Range: -40°C to +85°C; ensures stable output in both freezing cold and scorching heat

Annual Self-Discharge Rate: <1%; retains usable voltage levels even after 10 years of storage at room temperature

Chemical Characteristics: Contains no hazardous heavy metals; features an exceptionally flat discharge curve, providing a stable 6V output until the battery is nearly depleted

Unlike standard alkaline or rechargeable batteries, the 2CR17335A is a primary (non-rechargeable) lithium battery designed specifically for long-term, maintenance-free applications. It is typically soldered directly onto the circuit board and tied to the device's entire lifecycle; once depleted, it requires replacement by a professional engineer.

A Real-World Case: Hydrological Data That Nearly "Reset to Zero"

Late last autumn, Engineer Lao Zhou from a provincial hydrological bureau in the south took his apprentice to a large reservoir within their jurisdiction to conduct a quarterly inspection of an automated water quality monitoring station. This buoy-based station had been operating unattended for seven years, transmitting data—such as water temperature, pH levels, and dissolved oxygen—along with timestamps back to the data center via a wireless module every hour.

However, that morning, the data center detected that the data from this site had suddenly become unparseable; the generation timestamp for every record had reverted to "January 1, 2000, 00:00." This was a classic sign of a Real-Time Clock (RTC) reset. Lao Zhou surmised that the problem likely lay with the backup battery on the motherboard.

After boarding the buoy and opening the sealed equipment cabinet, Lao Zhou removed the controller motherboard from the multi-parameter water quality analyzer. By the light of his flashlight, he spotted a battery pack soldered in a corner—slightly shorter than a standard AA battery and featuring two leads—with "Mitsubishi 2CR17335A" clearly printed on its casing.

A multimeter reading revealed an open-circuit voltage of just 2.1V, far below the nominal 6V rating. This battery was responsible for powering the clock chip and the SRAM (which stored calibration parameters) during periods of unstable solar power, the momentary switchover between power sources on overcast or rainy days, and the annual equipment maintenance shutdowns. Once the battery was completely depleted, the clock reset to zero, causing all time-stamped cached data to lose its temporal reference.

Lao Zhou retrieved a brand-new Mitsubishi 2CR17335A of the same model from the spare parts kit. He carefully desoldered the old battery, installed the new one, and restored power. Instantly, the motherboard's clock chip retrieved the time from its preset baseline; after Lao Zhou used a laptop to calibrate it to the exact current time via the serial port, the instrument immediately resumed normal data transmission. Back at the data center, the data stream from the site—which had been interrupted for three hours—resumed, pulsing once again with the correct timestamps.

Afterward, Lao Zhou noted the following in his maintenance report:

"The 2CR17335A battery at site 2CR17335A was installed alongside the main unit in 2018 and has operated continuously for over six years. Throughout this period, it endured sweltering summer cabinet temperatures exceeding 70°C and freezing winter lows of -10°C. The battery casing showed no signs of leakage or swelling; it maintained stable output down to 2.1V right up until the end of its service life. The reliability and longevity of this battery model in extreme field environments far exceed standard specifications."

Lao Zhou kept the old battery as a teaching aid for his apprentices to learn about industrial electronics maintenance. Meanwhile, the newly installed 2CR17335A is expected to power the monitoring station through the next decade.

What relies on it?

Typical applications for the Mitsubishi 2CR17335A are almost exclusively found in systems that cannot simply be "rebooted":

Programmable Logic Controllers (PLCs) and industrial PCs: Preserving the integrity of user programs and data even after factory power outages lasting days or weeks.

Medical equipment: Such as infusion pumps and patient monitors, where parameter storage—and specifically calibration data—must not be lost due to battery depletion.

Security alarm control panels: Preventing the tampering of timestamps and event logs following unauthorized power disconnection.

Geological and environmental monitoring instruments: Sensor nodes buried underground or suspended from bridges often require batteries to independently power their internal clocks for 5 to 10 years.

High-end multimeters and measuring instruments: Providing uninterrupted backup power for high-precision reference sources or memory chips.

Conclusion

In an era where consumer electronics prioritize fast charging and wireless flash charging, industrial primary batteries like the Mitsubishi 2CR17335A maintain a remarkably low profile. It never connects to the internet and sends no "low battery" notifications; it simply rests quietly in the corner of a circuit board, measuring time in decades as it gradually exhausts itself to safeguard strings of critical data. For the veteran technicians at the reservoir monitoring station, replacing this battery takes just ten minutes—yet what is saved in the process is years of continuous monitoring records and invaluable environmental data.

If you, too, are grappling with RTC resets or parameter loss during equipment maintenance, try checking that long-overlooked 2CR17335A battery with a multimeter; that silent guardian may well have already stood its final watch.