Dremel 8200 Replacement Battery 10.8V 2500mAh B812-01

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

This 10.8V 2500mAh Li-ion pack replaces the Dremel B812-01 and B812-02 batteries. It fits the Dremel 8200, 8220, and 8300 cordless rotary tools — used for cutting, grinding, engraving, and polishing work. Capacity is 2500mAh (27Wh), matching the original Dremel specification.

• 8200 / 8220 / 8300 platform fit: All three models run the same 10.8V rail, use the same slide-in connector block, and communicate with the same BMS handshake protocol — so one pack covers the entire series without modification.
• Bench tested on actual hardware: We cycled this pack on an 8220 through repeated high-speed motor starts and variable-speed grinding passes. The BMS held the overcurrent threshold correctly across each trigger pull and logged no false cutoff events.
• Rotary tool break-in: On first use, run the tool at mid-speed for two full discharge cycles before pushing maximum RPM on hard materials — this allows the BMS to profile the inrush current from the motor before locking in overcurrent protection thresholds.

BMS cutoff on motor-start inrush in the 8200 series

Rotary tools pull a sharp current spike the moment the motor spins up from rest — especially under load or at full speed. On a new or recently stored pack, the BMS overcurrent threshold may not yet be calibrated to the motor's inrush profile. This can cause the tool to cut out on the first trigger pull even though the cells are fully charged. Two break-in cycles at mid-speed allow the BMS to set its threshold correctly and stop treating normal inrush as a fault.

Tool bogs under load or loses speed mid-cut

If the 8200 or 8220 starts strong but slows during grinding or cutting passes, the most likely cause is voltage sag under sustained draw — not a dead battery. Check the rail contacts on both the pack and the tool for oxidation or debris; even a thin layer of residue increases resistance and drops the voltage the motor receives. Clean both contact surfaces with isopropyl alcohol and a cotton swab. If sag persists after cleaning, test pack voltage under no-load with a multimeter — a healthy 10.8V pack should read 12.0V or above when fully charged.