About this replacement
Endress+Hauser Prosonic Flow 91W / 92F / 93T — 7.2V Ni-MH Replacement Battery (93TA1-AABEAG)
This is a 7.2V 4000mAh Ni-MH replacement battery for the Endress+Hauser Prosonic Flow 91W portable ultrasonic flow meter and its close variants. It fits the Prosonic Flow 91W, 92F, 93T, and 93C series — portable instruments used for non-invasive flow measurement in water, wastewater, and industrial process applications. Voltage and capacity match the OEM specification (93TA1-AABEAG).
- Prosonic Flow 91W / 92F / 93T / 93C compatibility: These models share a common battery bay, connector pinout, and BMS handshake voltage window. The 7.2V rail feeds the transducer drive circuit and the display simultaneously — any pack outside the accepted voltage range trips a protection fault and prevents startup.
- Bench tested on actual hardware: We ran this pack through charge and discharge cycles on a Ni-MH conditioning unit, then monitored BMS response under a simulated transducer initialisation load spike. The protection circuit held across all test cycles with no false cutoffs.
- Post-install calibration cycle: After fitting this battery, run a full calibration sequence through the Prosonic Flow instrument menu before going to site. The instrument maps battery state during calibration — skipping this step causes premature low-battery warnings during the first measurement session, even with a fully charged pack.
BMS lockout after the Prosonic Flow 91W sat unused in a carry case for months
Ni-MH cells self-discharge at roughly 1–3% per day at room temperature. A pack stored for three to six months in a case can drop below the BMS recovery threshold — typically around 5.4V for a 7.2V pack. When the instrument sees voltage this low, it either shows a battery error or refuses to power on, even after you connect the charger. The fix is a slow recovery charge at a low rate (0.1C or less) using a Ni-MH compatible charger until the pack climbs above 6.0V, at which point the BMS re-initialises and normal charging resumes.
Prosonic Flow 91W shuts down mid-measurement during active logging
During a sustained logging session, the transducer drive and onboard processor draw current continuously — a higher sustained load than standby or menu navigation. If cell internal resistance has risen with age, voltage sags under this load and crosses the BMS undervoltage cutoff, triggering an abrupt shutdown. This is not a charge state problem — the battery may show 50% or more before the shutdown occurs. Check resting voltage immediately after a dropout: if it recovers quickly above 7.0V with no load, rising internal resistance is the cause and the pack needs replacement.