Testo 350 Control Replacement Battery 4.8V 2000mAh

Testo 350 Control / 454 Control — 4.8V Ni-MH Replacement Battery (0515 0097)

This is a 4.8V, 2000mAh Ni-MH battery pack that fits the Testo 350 Control and 454 Control combustion analyzers. These are portable flue gas and emissions testing instruments used by HVAC technicians, boiler engineers, and environmental surveyors. This pack replaces OEM part 0515 0097 when the original cells lose capacity or fail to hold charge.

• 350 Control and 454 Control platform fit: Both instruments share the same 4.8V four-cell NiMH pack with identical connector pinout and physical envelope. The BMS in each unit expects the same charge termination voltage and delta-V cutoff signature, so one pack serves both.
• Bench tested on actual hardware: We ran charge and discharge cycles through a Testo 350 Control unit. The BMS accepted the pack, completed charge termination correctly, and sustained voltage under probe-module initialisation current spikes without tripping the protection circuit.
• Post-install calibration cycle: After fitting this pack, run a full calibration sequence through the instrument menu before your first field deployment. The 350 Control maps battery state during calibration — skipping this step causes premature low-battery warnings on the first measurement session, even with a fully charged pack.

BMS lockout after the 350 Control sat unused in a carry case for months

NiMH cells self-discharge at roughly 1–2% per day at room temperature. After several months in storage, the pack voltage can drop below the threshold the instrument's BMS will attempt to charge from — the charger sees a voltage too low to identify as a valid pack and refuses to start. The fix is to apply a slow, low-current trickle charge externally using a compatible NiMH charger until the pack reaches approximately 5.0V, then return it to the instrument. At that voltage, the 350 Control's onboard charger will recognise the pack and resume normal charge termination.

Readings resetting or dropping out during a continuous logging session

Sustained sensor load — particularly when the O₂, CO, and NOx sensors are all active simultaneously — draws more current than standby mode. If the cells have aged or are partially discharged, voltage sags under this combined load and the instrument briefly loses the minimum operating voltage, causing a mid-session reset. This is a cell capacity issue, not a BMS fault. A freshly charged, full-capacity pack holds voltage flat under sensor load — charge fully before any extended logging run and confirm the instrument reports a full charge state before connecting probes.