About this replacement
IMX Free DOP Probe / Freedrop MB413 — 7.2V Ni-MH Replacement Battery (AVT1007V)
This is a 7.2V, 230mAh Ni-MH rechargeable battery for the IMX Free DOP Probe and Freedrop Foetal Doppler MB413. It replaces OEM part AVT1007V and restores portable power to the handheld Doppler unit used for vascular and foetal blood flow assessment. Capacity figure is 230mAh (1.66Wh) as listed in the product specification.
- Free DOP Probe and Freedrop MB413 fitment: Both devices share the AVT1007V cell format — same voltage rail, same physical envelope at 41.10 × 26.70 × 25.80mm, and the same BMS handshake protocol. One replacement covers both units.
- Bench tested on actual hardware: We cycled this cell through charge and load on the bench. The BMS completed its verification sequence without error flags, and the cell held voltage within the expected band across the discharge curve for Ni-MH at this capacity.
- Power-on self-test protocol: After fitting this battery, let the device complete its full startup self-test sequence without interruption. Medical Doppler units run a BMS verification check at boot — cutting power during that window logs a false battery fault that persists until a complete cold reboot clears it.
Why the Free DOP Probe alarms low battery immediately after a confirmed full charge
The device BMS compares cell behaviour against a stored reference profile calibrated for the original OEM cell. A new replacement cell has no charge history, so the BMS flags it as suspect during the first few cycles. This is not a fault in the replacement battery — it is a learn-cycle limitation in the charge IC. Run one complete charge-discharge-recharge cycle before clinical use. After that first full cycle, the BMS updates its reference and the alarm condition clears.
Free DOP Probe will not power on after the battery sat unused in storage
Ni-MH cells self-discharge during storage — typically losing 1–2% capacity per day under ambient conditions. If the cell drops below the BMS recovery threshold, the device will not boot even after placing it on charge. Connect the probe to its charger and leave it for a minimum of 30 minutes before attempting to power on. If the charge indicator shows no activity after that window, check that the charger output is delivering the correct voltage — the AVT1007V charges at 7.2V nominal.