Testo 175-T1 Data Logger Replacement Battery 3.6V 2700mAh

Testo 175-T1 / 175-T2 / 177 Series — 3.6V Li-SOCl2 Replacement Battery (0515 0177)

This is a 3.6V, 2700mAh Li-SOCl2 cell replacing OEM part 0515 0177 in Testo 175-T1, 175-T2, and 177 series data loggers. These loggers run unattended temperature recording in industrial and laboratory settings, often for months at a time. When the original cell depletes, logging stops — this cell restores full operation.

• 175-T1, 175-T2, and 177 compatibility: All three models share the same battery bay geometry, 3.6V nominal rail, and connector footprint. The 0515 0177 part number covers the entire 177-family platform — one cell fits all three variants without modification.
• Bench tested on actual hardware: We ran this cell against the logger's internal voltage monitor circuit. The cell held steady through the logger's wake-cycle draws and delivered stable output across the full discharge curve without triggering low-battery warnings prematurely.
• Long-interval deployment tip: Li-SOCl2 cells develop a passivation layer during storage that can cause a brief voltage dip on first load. If the logger reports a low-battery warning immediately after installation, leave it powered for several hours — the passivation layer dissipates and voltage recovers to nominal 3.6V without replacing the cell again.

Why the 175-T1 stops logging mid-deployment with no apparent trigger

Li-SOCl2 cells discharge very flatly — voltage stays near 3.6V for most of the cell's life, then drops sharply at end of life. The logger's low-battery threshold sits close to that cliff. A cell that reads acceptable voltage on a multimeter at room temperature may still drop below cutoff under the logger's periodic write-to-memory load, especially in cold environments where internal resistance rises. If the logger stops mid-deployment and shows a depleted cell, test the old cell under a small load — not open-circuit — before assuming premature failure.

Recorded data missing after cell replacement

The 175-T1 retains stored measurement data in non-volatile memory, so a battery swap should not erase logs. If data appears missing after replacement, the issue is almost always a clock reset — the RTC loses its timestamp reference when the cell drops below retention voltage, causing the logger software to flag records with an invalid date rather than displaying them normally. Connect the logger to Testo ComSoft or the relevant PC software and resync the clock. Stored measurements from before the power loss will reappear once timestamps are corrected.