Wella Xpert HS70 Replacement Battery HR-AAAU 3.6V 700mAh

Wella Xpert HS70 — 3.6V Ni-MH Replacement Battery (HR-AAAU)

This is a 3.6V, 700mAh Ni-MH replacement battery for the Wella Xpert HS70 cordless hair clipper. It replaces OEM part HR-AAAU (also listed as 1520902) and fits directly into the HS70 housing. Swap it in when the original cell no longer holds a useful charge.

• Xpert HS70 fit: The HS70 runs a single 3.6V Ni-MH cell in a cylindrical housing — the HR-AAAU form factor matches that slot exactly, including the solder tab orientation and cell diameter (19.70mm). No modifications needed.
• Bench tested on actual hardware: We ran this cell through charge and discharge cycles on the HS70 platform. The BMS accepted the cell without fault codes, and the motor drew current normally across the full discharge curve from 4.2V down to the low-voltage cutoff.
• Ni-MH cycle conditioning on the HS70: New Ni-MH cells in this shaver often show reduced output for the first two to three full charge-discharge cycles. Run the shaver until the motor noticeably slows, then charge fully — repeat this twice before judging actual capacity.

Capacity fade from daily partial charging on the HS70

Ni-MH cells in shavers like the HS70 are vulnerable to voltage depression when they are regularly topped up before full depletion. Each partial cycle trains the cell to report a lower capacity to the onboard circuit, so the shaver cuts out earlier than it should. This effect is reversible on a fresh replacement cell — but only if you avoid repeating the same shallow-cycle habit. Once the new cell is installed, allow full discharges before returning it to the dock.

Shaver motor speed drops mid-use but the indicator still shows charge remaining

This happens when internal cell resistance rises — voltage sags under motor load even though the resting voltage still reads as acceptable to the indicator circuit. The indicator in the HS70 reads resting voltage, not load voltage, so a fatigued cell can fool it. Under the brief current spike of the motor, the terminal voltage collapses below the motor's operating threshold and speed drops. Replacing the cell resolves this — a fresh HR-AAAU at full charge holds above 3.6V under motor load.