About this replacement
Festool BPH9.6C Series — 9.6V Ni-MH Replacement Battery (CDD9.6)
This is a 9.6V Ni-MH battery rated at 3300mAh (31.68Wh), built to replace the original pack in Festool cordless drills and drivers. It fits the BPH9.6C platform along with FSP-487512, FSP-488437, and FSP-490355 among others. OEM part numbers CDD9.6, CCD9.6, CCD9.6ES, and CCD9.6FX all cross to this replacement.
- BPH9.6C platform fit: These models share the same 9.6V rail, battery connector format, and cell count. The BMS on each communicates the same charge termination signal, so this pack charges and discharges without modification.
- Bench tested on actual hardware: We ran this pack through charge and discharge cycles on the BPH9.6C platform. The BMS registered correct delta-V cutoff at end of charge and held voltage under motor-start inrush without tripping overcurrent protection.
- Motor break-in on first use: On the first two cycles, run the drill at half load — moderate torque applications only. This lets the BMS sample the motor's inrush current draw and set its overcurrent threshold accurately before you push the tool to full torque.
BMS overcurrent trip on trigger pull in Festool 9.6V drills
The BPH9.6C motor pulls a spike of current the instant the trigger engages — often two to three times the running current. A new or freshly stored Ni-MH pack has slightly elevated internal resistance, which amplifies the voltage dip at that spike. If the BMS reads the dip as an overcurrent fault, it cuts power immediately and the tool stops before the motor reaches speed. Two break-in cycles at moderate load bring cell resistance down and allow the BMS to calibrate its trip threshold correctly.
Pack gets warm and drill bogs under sustained load
Ni-MH cells generate more heat than Li-ion during high-current discharge, and the BPH9.6C housing gives that heat nowhere to go quickly. Under sustained heavy load — driving long screws or boring large-diameter holes repeatedly — cell temperature climbs and internal resistance rises, which causes voltage sag and the bogging sensation. The thermal cutoff trips if the pack reaches its limit, and the drill stops entirely. Let the pack rest for at least 10 minutes after a thermal cutoff before resuming work, and check that the battery contacts are clean and seating fully to rule out contact resistance adding to the load.