About this replacement
Black & Decker BDCS40G Type 1 — 3.6V Li-ion Replacement Battery (NCR18650-8)
This is a 3.6V, 2500mAh Li-ion replacement battery for the Black & Decker BDCS40G Type 1 cordless screwdriver. It also fits the CS3652LC, CS3652LC Type 2, and CS3652LC-GB series. Capacity is 9Wh — matching the original pack specification exactly.
- BDCS40G and CS3652LC series fit: These models share the same 3.6V single-cell architecture, NCR18650-8 cell format, and BMS connector pinout. The voltage rail and handshake logic are identical across the range, so one cell replacement covers the full group.
- Bench tested on actual hardware: We ran this cell through charge and discharge cycles on a BDCS40G Type 1 unit. The BMS accepted the cell without fault flags, held the protection threshold correctly, and the charger moved through its stages without interruption.
- Motor inrush break-in on first use: On first use, run the screwdriver at light load for two cycles before tackling full-torque fastening. This lets the BMS log the motor's inrush current signature and set its overcurrent threshold accurately before you drive into hardwood or dense substrate.
BMS cutoff on trigger pull during high-torque fastening
At the moment of trigger engagement, the BDCS40G motor draws a short inrush spike that can exceed the BMS overcurrent threshold — especially on a new or recently stored cell. The BMS reads that spike as a fault and cuts output instantly, which feels like the tool is dead. This is not a cell failure. Let the pack rest for 60 seconds, then re-engage at a lower torque setting to allow the BMS to re-initialise and profile the load correctly.
Charger not recognising the new pack after storage
Li-ion cells shipped or stored for several months can drop below the charger's minimum acceptance voltage — typically around 2.5V per cell. When the charger sees a voltage below its threshold, it either blinks an error or sits idle rather than beginning the charge cycle. Some Black & Decker chargers include a recovery or trickle mode — check the charger indicator sequence in the manual to confirm it has entered that mode. If the charger does not recover the pack after 30 minutes, measure the cell voltage directly; anything above 2.0V is recoverable with a compatible lithium recovery charger set to 3.0V pre-charge.