Remington R9 Replacement Battery 3.7V 700mAh Li-ion

Remington R9 — 3.7V Li-ion Replacement Battery

This is a 3.7V, 700mAh lithium-ion cell that replaces the original battery in the Remington R9 electric shaver. It restores cordless operation when the existing cell no longer holds a charge. Fits the R9 rotary shaver platform specifically.

• R9 platform fit: The R9 uses a single cylindrical Li-ion cell at 3.7V nominal. The BMS in the shaver monitors cell voltage directly — swapping in a cell outside that voltage window triggers a protection fault. This replacement matches the original voltage and physical dimensions (49.60 × 15.00 × 14.10mm) so the BMS handshake completes correctly.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on the R9 shaver platform. The BMS accepted the cell without triggering low-voltage lockout. Charge acceptance was clean across the full 700mAh capacity with no thermal anomalies at the housing.
• Charging port care for the R9: The R9 is used near water. Dry the charging port completely before connecting the charger — moisture bridging the contacts causes a BMS protection trip the device reports as a dead battery, not a charging error. A few seconds with a dry cloth before docking prevents this entirely.

Capacity fade from daily partial charging on the R9

Most R9 users charge the shaver overnight after a single daily use — often before the cell is meaningfully depleted. Li-ion cells cycled repeatedly through shallow charge windows develop a narrowed effective capacity over time. The cell's state-of-charge tracking drifts, so the indicator reads full while actual delivered capacity is lower. Replacing the cell resets this — but resuming daily partial-charge habits will repeat the pattern within 12–18 months.

Shaver motor speed dropping before the indicator shows low

The R9 motor draws a spike of current at startup and again when cutting through thicker hair. A degraded cell cannot hold voltage under that load — it sags below the motor's operating threshold before the BMS would normally trigger a low-battery cutoff. The indicator still shows partial charge because resting voltage recovers between cuts. If the motor audibly slows mid-use while the indicator reads above empty, the cell's internal resistance has risen and replacement is the fix.