Testo 0515 0046 Compatible Battery 3.7V 2200mAh Li-ion

Testo 320 / 327 Gas Analyser — 3.7V Li-ion Replacement Battery (0515 0046)

This 3.7V 2200mAh Li-ion battery replaces the original pack in the Testo 320 and 327 combustion analysers, as well as the Testo 870-1 thermal imager and compatible 870 series units. It carries OEM part numbers 0515 0046, 0554 1087, 0515 0100, and 0515 0114. Dimensions are 74.50 × 20.80 × 28.50mm — confirm yours before ordering if your unit has been serviced previously.

• Cross-model fit — 320, 327, and 870 series: These models share a common battery bay geometry, connector pinout, and BMS communication protocol. The same cell format handles both the sensor-heavy draw of the combustion analysers and the display and IR sensor load of the 870-1 imager.
• Bench tested on actual hardware: We cycled this pack through the Testo 320's full probe initialisation sequence, which pulls a short current spike as the CO and O2 sensors power up. The BMS held the rail cleanly through that spike without triggering a cutoff event.
• Calibration cycle after installation: After fitting this pack, run a full calibration cycle through the instrument menu before heading to site. The 320 maps battery state during calibration — skipping this step causes the low-battery warning to fire early on your first measurement session, even with a fully charged pack.

BMS lockout after the Testo 320 sat unused in a carry case for months

Li-ion cells self-discharge at roughly 2–3% per month. Left in a case over a long off-season, the pack can drop below the BMS recovery threshold — typically around 2.5V per cell — and the protection circuit latches off. At that point the instrument shows no response and the charger may not register the pack at all. Connect the battery to the Testo docking charger and leave it for 30–45 minutes without interruption; most BMS circuits include a trickle pre-charge stage that recovers cells down to approximately 2.0V. If the charger LED never transitions from red to green after an hour, the cell voltage has dropped below recoverable range.

Testo 320 shutting down mid-measurement during a logging session

Sustained sensor load — CO, CO2, and O2 sensors running simultaneously during a timed log — draws more current than the standby or single-reading state. An aged or partially discharged pack can sag below the instrument's minimum operating voltage under that combined load, triggering an abrupt shutdown even though the battery indicator showed charge before the session started. This is a voltage-sag failure, not a capacity failure — the cell still holds energy but cannot deliver it fast enough under load. Fully charge the pack before any logging session and check that resting voltage at the battery terminals reads at or above 3.9V before starting.