About this replacement
Festool Quadrive T18 Series — 18V Li-ion Replacement Battery (BPC 18 Li)
This is an 18V 4000mAh Li-ion replacement battery for Festool's Quadrive T18 platform. It fits the Quadrive T18, Quadrive TSC55, T18+3, and PSC/PSBC 400/420 series, along with four additional compatible models. OEM part numbers covered: BPC 18 Li, 498343, and 499849.
- Quadrive platform compatibility: These models share Festool's 18V slide-rail form factor and the same BMS communication handshake. The connector pinout and cell voltage profile match across the T18, TSC55, T18+3, and PSC/PSBC 400/420 lines — the charger and tool ECU recognise this pack the same way they recognise the original.
- Bench tested on actual hardware: We cycled this pack on a T18+3 driver under repeated fastening loads. The BMS handled motor-start inrush current without nuisance tripping, and cell voltage held within spec across all five cells at peak draw.
- Motor-start break-in on first use: Run the drill at half-load torque settings for two full charge cycles before heavy fastening or driving applications. This lets the BMS log the motor's inrush current signature and set overcurrent thresholds accurately before you push maximum torque.
BMS overcurrent trip on trigger-pull inrush with the Festool T18
The T18 motor draws a sharp current spike the instant the trigger is pulled — often three to four times the steady running current. On a new or storage-discharged pack, the BMS overcurrent threshold may not yet be calibrated to the motor's inrush profile, causing the pack to cut out immediately on trigger pull. This is not a faulty battery. Running two or three partial cycles at reduced torque gives the BMS enough data to widen the inrush window appropriately. After that, full-torque trigger pulls clear without cutoff.
Charger stays on red and never transitions to green
Festool chargers perform a cell-voltage check before entering the main charge cycle. If the pack has been in storage, individual cells can drop below 2.5V — the charger's acceptance threshold. The charger blinks red and halts instead of charging. Leave the pack on the charger for 20–30 minutes; most Festool chargers will attempt a slow recovery trickle below the main charge threshold. If cells recover to 3.0V per cell, the charger transitions to normal green charge mode automatically.