About this replacement
AeroFlex IFR / Marconi — 7.4V Li-ion Replacement Battery (AG205012)
This is a 7.4V 13500mAh lithium-ion replacement battery for the AeroFlex IFR and Marconi portable test and measurement instruments. It replaces OEM part AG205012 and fits directly into the instrument's battery bay. At 99.9Wh, it carries enough capacity for full-day field sessions without a top-up charge.
- IFR and Marconi platform fit: Both instrument families share the same 7.4V power rail, AG205012 form factor, and BMS handshake protocol — one pack covers both. Connector orientation and locking tab position are identical across the range.
- Bench tested on actual hardware: We ran this pack through probe initialisation, sustained sensor logging, and USB data transfer simultaneously. The BMS held voltage steady across all three combined loads without tripping cutoff.
- Calibration cycle before first field deployment: After installing, run a full calibration cycle through the instrument menu before taking it to site. The instrument maps battery state during calibration — skip this and the first measurement session will throw premature low-battery warnings even with a full charge.
BMS lockout after the AG205012 pack sat unused in a carry case for months
Li-ion cells self-discharge slowly in storage. If the pack drops below approximately 2.5V per cell, the BMS trips an over-discharge lockout and the instrument will not power on or charge. The internal protection circuit blocks current flow to prevent cell damage. To recover, apply a compatible charger and leave it connected for at least 30–60 minutes — the BMS needs a trickle charge phase to exit lockout before normal charging begins. If voltage per cell is still above 2.5V after that window, charging will resume normally.
Readings resetting or dropping out mid-logging session
Sustained sensor load draws more current than the instrument draws at idle, and an aged or partially charged cell can sag below the instrument's minimum operating voltage under that load. When voltage dips past the threshold — typically around 6.0V for a 7.4V pack — the instrument resets or drops the active logging session. This is not a firmware fault; it is a voltage dropout event. Charge the pack fully before any extended logging session and confirm resting voltage reads above 7.2V before you start.