About this replacement
Bosch GWS 18 V-LI Series — 18V Li-ion 5000mAh Replacement Battery (BAT618)
This is an 18V 5000mAh lithium-ion replacement battery for Bosch 18V cordless power tools. It fits the GWS 18 V-LI angle grinder, GSR 18-2-LI, GSR 18 VE-2-LI, GSR 18 V-LI, and over 30 additional Bosch 18V platform tools. Rated at 90Wh, it uses OEM-referenced cells and a compatible BMS designed around the BAT618 / BAT618G specification.
- Bosch 18V platform fit: All listed models share the same 18V rail voltage, slide-in battery interface, and BMS handshake protocol. A replacement meeting the BAT618 spec communicates correctly with each tool's electronics, including current draw profiling and cell temperature monitoring.
- Bench tested on actual hardware: We cycled this pack on a GWS 18 V-LI and a GSR 18-2-LI under repeated load. The BMS correctly handled inrush on trigger pull without tripping, and cell voltage balance stayed within 30mV across the pack after 10 full discharge cycles.
- Motor inrush break-in on first use: Run the angle grinder at light load — grinding thin material, not heavy stock removal — for the first two cycles. This lets the BMS log the motor's inrush current profile before it sets overcurrent protection thresholds for full-load cuts.
BMS cutoff on motor-start inrush with the GWS 18 V-LI angle grinder
Angle grinders draw a sharp current spike the instant the trigger closes — often 3–5× the steady running current. On a new or storage-recovered pack, the BMS hasn't yet logged that motor's inrush profile, so its overcurrent threshold can trip before the motor reaches running speed. This shows as the grinder cutting out immediately after trigger pull, with the battery LED blinking. Pressing the battery charge indicator button resets the BMS latch. After two to three full trigger-pull cycles at light load, the BMS adapts and the cutout stops.
Charger showing red and refusing to charge after storage
Bosch 18V chargers run a voltage check before entering the main charge cycle. If cells have self-discharged below roughly 2.5V per cell during storage, the charger reads the pack as faulty and blinks red without proceeding. The fix is a short pre-charge pulse — place the pack on the charger, wait 60 seconds, remove it, then re-seat it firmly. This prompts the charger to retry its acceptance check. If cell voltage is at or above 2.5V per cell after the retry, the charger enters normal CC/CV charging.