Dremel B812-01 10.8V Replacement Battery 1500mAh

Dremel 8200 / 8220 / 8300 Series — 10.8V Li-ion Replacement Battery (B812-01, B812-02)

This is a 10.8V, 1500mAh (16.2Wh) lithium-ion replacement battery for the Dremel 8200, 8220, 8300, and 8200 Multi Max rotary tools. It slots into the same battery bay as the original and communicates with the same BMS handshake protocol. Fits the full range of Dremel cordless rotary platforms that use the B812-01 or B812-02 pack.

• 8200 / 8220 / 8300 platform compatibility: These models share the same 10.8V battery bay, connector pinout, and BMS communication line. One pack works across all three platforms without modification.
• Bench tested on actual hardware: We ran this pack on the 8220 under repeated grinding and cutting cycles. The BMS held overcurrent protection thresholds correctly and maintained stable cell balancing across all discharge curves.
• Motor inrush break-in: On first use, run the tool at half load for two cycles before pushing maximum torque. This lets the BMS profile the motor's inrush current draw and set accurate overcurrent thresholds before sustained heavy use.

BMS cutoff on rotary tool motor-start inrush surge

The Dremel 8200-series motor pulls a short but sharp current spike at trigger pull — far above its running draw. On a new or cold pack, the BMS may read that spike as an overcurrent fault and cut output before the motor reaches speed. This trips faster on cold cells because internal resistance is higher at low temperatures, amplifying the voltage drop across the spike. If the tool cuts out immediately on trigger pull, let the pack warm to room temperature and retry before assuming a fault.

Tool bogs or loses speed under sustained grinding load

Voltage sag under sustained load is the most common complaint on rotary tools used for prolonged grinding or cutting passes. When cell impedance rises — from age, cold, or a high-resistance contact at the rail — the pack voltage drops under load even if the resting voltage reads 10.8V. Check the battery bay contacts for oxidation or debris first; a dirty contact adds resistance and worsens sag significantly. If contacts are clean and sag persists, check resting cell voltage — a healthy pack should hold above 10.0V under moderate continuous load.