Stanley FMC687L 20V Replacement Battery 1500mAh Li-ion

Stanley FMC625D2 Series — 20V Li-ion Replacement Battery (FMC687L)

This is a 20V Li-ion replacement battery for the Stanley FMC625D2 compact drill-driver and related 20V platform tools including the FMC645D2, FMC675B, and FMC675B-XE. Capacity is 1500mAh (30Wh). It uses the OEM part number FMC687L and connects via the standard Stanley 20V slide-mount contact rail.

• FMC625D2 platform compatibility: These models share the same 20V rail voltage, slide-mount connector geometry, and BMS handshake protocol — any charger or tool in this family will accept this pack without modification.
• Bench tested on actual hardware: We ran this pack through charge-discharge cycles on a 20V Stanley charger. The BMS accepted charge without fault flags, balanced cells correctly, and held rail voltage within spec under simulated load cycles.
• Motor inrush break-in: On first use, run the drill at half load for two cycles before applying maximum torque. This lets the BMS profile the motor's inrush current spike and set overcurrent thresholds before you put the tool under real load.

BMS cutoff on motor-start inrush in the FMC625D2

The FMC625D2 motor draws a sharp current spike the moment the trigger pulls — this inrush can be three to five times the steady running current. If the BMS hasn't yet profiled the motor, it may read that spike as a fault and cut output. A new or storage-rested pack is more likely to trip here because the BMS protection thresholds default to conservative values. Two half-load warm-up cycles let the BMS log real inrush data and widen its cutoff window accordingly.

Charger blinking red on a new 20V pack after storage

Li-ion cells self-discharge during storage, and if the pack voltage drops below the charger's acceptance floor — typically around 10V for a 20V pack — the charger rejects it and blinks red rather than beginning a charge cycle. This isn't a faulty battery; it's a low-voltage lockout. Place the pack in the charger, wait 60 seconds, then remove and reinsert — some Stanley chargers will attempt a recovery trickle on the second handshake. If the pack voltage reads above 10V on a multimeter and the charger still rejects it, check the rail contacts for oxidation and clean with isopropyl alcohol before retesting.