Bosch GWS 18V-LI Replacement Battery 4000mAh BAT609

Bosch GWS 18 V-LI / GSR 18 Series — 18V Li-ion 4.0Ah Replacement Battery (BAT618)

This is an 18V 4000mAh lithium-ion replacement battery for the Bosch GWS 18 V-LI cordless angle grinder and the broader Bosch 18V tool family. It replaces OEM part numbers including BAT609, BAT610G, BAT618, BAT618G, BAT622, and 2 607 336 091 among others. Voltage is 18V nominal; capacity is 4000mAh (72Wh).

• Bosch 18V platform fit: These tools share the same 18V slide-pack rail, connector pinout, and BMS communication protocol. The GWS 18 V-LI angle grinder, GSR 18-2-LI, GSR 18 VE-2-LI, and over 30 other Bosch 18V tools draw from the same battery interface — one pack works across the platform without adapters.
• Bench tested on actual hardware: We ran this pack on a GWS 18 V-LI under repeated load cycles. The BMS held a steady rail voltage through motor-start inrush, maintained overcurrent thresholds correctly, and the charger handshake completed without faults on a genuine Bosch AL 1814 CV charger.
• Break-in procedure for angle grinder use: On first use, run the grinder at light load for two full cycles before tackling heavy grinding or cutting. This allows the BMS to register the motor's inrush current signature and calibrate overcurrent trip thresholds — reducing nuisance cutoffs on aggressive trigger pulls later.

BMS overcurrent trip on GWS 18 V-LI trigger pull

The GWS 18 V-LI draws a sharp current spike the instant the trigger engages — the 9,000 rpm no-load speed is reached in under a second. A freshly installed or storage-rested pack can trip the BMS overcurrent protection at that inrush spike before the cells have delivered any meaningful run time. The BMS interprets the spike as a fault, latches off, and the tool dies immediately. Two or three short trigger pulls at low load re-establish the BMS current profile and clear the latch — after that, normal use resumes.

Charger not recognising pack after storage — red blink, no charge

Bosch 18V chargers reject packs where cell voltage has dropped below the acceptance threshold — typically around 2.5V per cell. A pack stored for several months can sit below that floor, causing the charger to blink red and refuse to start a charge cycle. The fix is a short manual recovery: connect the pack to the charger, press and hold the charger's mode button if available, or place the pack in the charger for 10–15 minutes — most Bosch AL-series chargers will attempt a trickle recovery pulse at voltages above 2.0V per cell. If recovery starts, the LED shifts to amber within a few minutes and the normal charge cycle follows.