Defelsko PosiTest AT-A Replacement Battery HHR-17670 7.2V

Defelsko PosiTest AT-A / ATA20 — 7.2V Ni-MH Replacement Battery (HHR-17670)

This 7.2V 3600mAh Ni-MH battery replaces part number HHR-17670 in the Defelsko PosiTest AT-A and ATA20 adhesion testers. These are handheld pull-off adhesion instruments used in coating inspection and quality control work. The battery slots into the grip housing and powers the motorised actuator, display, and onboard data logging.

• PosiTest AT-A and ATA20 compatibility: Both units run the same 7.2V battery rail and use the same connector orientation and BMS handshake protocol — one pack covers both variants without modification.
• Bench tested on actual hardware: We ran this pack through repeated actuator cycles on the AT-A. The BMS held voltage steady through the motor-start surge at pull-off initiation and did not trip under the combined actuator and display draw during multi-point logging sessions.
• Post-install calibration before field use: After fitting this battery, run a full calibration cycle through the PosiTest AT-A instrument menu before taking it to site. The instrument maps battery state during that calibration sequence — skipping it causes premature low-battery warnings during your first measurement session in the field.

BMS lockout after the PosiTest AT-A sat unused in a carry case for months

Ni-MH cells self-discharge continuously, even in storage. If the PosiTest AT-A sat in a case long enough, the pack voltage can drop below the BMS recovery threshold — typically around 5.0V for a 7.2V Ni-MH pack. At that point the BMS locks the output circuit and the instrument will not power on, even on charge. A slow pre-charge at low current (0.1C or lower) for 30–60 minutes usually recovers the cells enough for the BMS to release and allow normal charging to resume.

Instrument shuts down mid-pull during adhesion testing

The motorised actuator in the AT-A draws a sharp current spike at the moment of pull-off initiation. On a depleted or degraded cell, this spike causes a voltage sag that crosses the BMS undervoltage cutoff threshold — the instrument shuts off mid-test and logs an incomplete data point. This is not a firmware fault. Charge the battery fully before a test session and check resting voltage: a healthy pack should read at or above 7.2V at rest before use.