About this replacement
TDK Life on Record A28 / A28 Trek Flex — 3.6V Ni-MH Replacement Battery (3AA-HHC)
This is a 3.6V, 2000mAh Ni-MH replacement battery using OEM part number 3AA-HHC. It fits the TDK Life on Record A28 and the A28 Trek Flex portable Bluetooth speakers. The battery slides into the original housing with no modification and connects directly to the speaker's charging and protection circuitry.
- A28 and A28 Trek Flex compatibility: Both models share the same 3.6V cell architecture, physical footprint, and connector pinout — that is why a single part number covers both. Swapping between variants does not require any firmware or BMS reconfiguration.
- Bench tested on actual hardware: We ran this cell through charge and discharge cycles on a TDK A28 unit. The speaker's onboard charging circuit accepted the cell without fault flags, and the BMS held the cutoff voltage within expected Ni-MH termination thresholds throughout.
- Ni-MH discharge discipline for the A28: Ni-MH cells in compact speakers accumulate a memory effect faster than Li-ion. If the A28 is charged from 70–80% daily, capacity readings drift within weeks. Run the speaker until audio distortion starts — a sign the cell is near depletion — before plugging in, at least once per month.
Audio distorting before the battery indicator reaches empty on the A28
The A28 amplifier draws a surge of current at moderate-to-high volume. When the Ni-MH cell voltage sags under that load, the amplifier clips before the fuel gauge has registered empty. This happens because the gauge reads resting voltage, not loaded voltage — there is a gap between the two on aged or partially degraded cells. A fresh 3AA-HHC cell holds a flatter discharge curve under load, which closes that gap. If distortion persists on the new cell, confirm the cell reached full charge by checking the indicator shows 100% after a full uninterrupted charge cycle.
A28 shows a full charge bar but audio drops out after extended play
This is fuel gauge drift — a known Ni-MH behaviour when the cell is repeatedly topped off at high state of charge without a full discharge. The battery management circuit loses calibration and reports full capacity when the usable capacity has already fallen. Replacing the 3AA-HHC cell resets the physical baseline, but the gauge will redrift if shallow charging resumes. After fitting the new cell, do one full charge-from-empty cycle so the speaker's circuit can re-anchor its voltage reference points at the correct 3.6V floor.