About this replacement
AEG BS 18C / BS 18G Series — 18V Li-ion Replacement Battery (L1815R / L1830R)
This is an 18V, 1500mAh Li-ion replacement battery for the AEG BS 18C and BS 18G cordless drills, plus the BKS 18, BFL 18, and eleven additional AEG 18V platform tools. It replaces OEM part numbers L1815R and L1830R directly. Voltage and connector pinout match the original pack.
- AEG 18V platform fit: The BS 18C, BS 18G, BKS 18, and BFL 18 share the same 18V slide-rail connector and BMS handshake protocol. Any battery meeting the voltage rail and communication spec fits the full group — no adapters needed.
- Bench tested on actual hardware: We ran this pack through repeated motor-start cycles on an AEG 18V drill platform. The BMS handled inrush current spikes at trigger pull without nuisance tripping and held cell balance within spec across the test sequence.
- Motor inrush break-in: On first use, run the drill at half load for two full charge-discharge cycles before driving at maximum torque. This allows the BMS to profile the motor's inrush current draw and calibrate overcurrent thresholds before heavy fastening work begins.
BMS Cutoff on Trigger-Pull Inrush Surge in the BS 18C
The BS 18C motor draws a sharp current spike the instant the trigger closes — far above steady-state running current. If the BMS overcurrent threshold is set conservatively on a new or cold pack, it can interpret that spike as a fault and cut power immediately. This is not a defective battery; it is the protection circuit doing its job before it has profiled the load. Running two break-in cycles at half load teaches the BMS the motor's inrush signature and raises the effective trip threshold to match real-world use.
Pack Drops to 16V Under Load but Reads Full on the Charger
This is voltage sag — internal resistance in aged or cold cells causes the rail voltage to collapse under load even when the resting voltage looks normal. On the BS 18C, it shows up as sluggish chuck speed or the drill bogging mid-screw. Check the slide-rail contacts for oxidation first — dirty contacts add resistance and worsen sag. If contacts are clean, measure cell voltage under load with a multimeter; anything dropping below 15V at the rail under drilling load points to cell degradation rather than a contact issue.