HILTI TCD12 Ni-MH Replacement Battery 12V 2100mAh

HILTI TCD12 / SF121 Series — 12V Ni-MH Replacement Battery (00315082)

This 12V Ni-MH battery replaces the original pack on the HILTI TCD12, SID121, SF121, and SF121-A cordless drill/drivers. Capacity is 2100mAh (25.2Wh), matching the original specification. It uses the same slide-rail connector and cell count as the factory pack, so no adapter or modification is needed.

• TCD12 / SF121 platform fit: These four models share the same 12V cell stack, slide-rail contact geometry, and BMS handshake protocol. One battery pack covers all of them without any electrical mismatch.
• Bench tested on actual hardware: We cycled this pack on a TCD12 under repeated motor-start loads. The BMS held the overcurrent threshold without nuisance trips, and cell voltage balanced across all sticks after three full discharge-charge cycles.
• Ni-MH memory management on the TCD12: Ni-MH chemistry is more sensitive to partial-cycle memory than Li-ion. On the TCD12, run the pack to the tool's low-voltage cutoff — when the chuck noticeably slows — before recharging. Topping up from 50% repeatedly compresses usable capacity over time.

BMS overcurrent trip on trigger-pull inrush with the TCD12

When you pull the trigger on the TCD12, the motor draws a spike of current — often three to five times the running draw — before the chuck starts turning. A new Ni-MH pack from storage has slightly elevated internal resistance, which amplifies the voltage dip at that moment. If the BMS reads that dip as an overcurrent fault, it shuts the pack down before the drill fires. Run two light-load cycles first to let the cells warm up and internal resistance drop. After conditioning, the BMS inrush threshold sits comfortably above normal trigger-pull spikes.

Pack not recognised by the HILTI charger after sitting unused

Ni-MH packs self-discharge during storage — faster than Li-ion — and the HILTI charger's detection circuit requires a minimum cell voltage before it begins a charge cycle. If the pack has been sitting for several months, the resting voltage may fall below that threshold and the charger will not respond or will show a fault LED. To recover, use a compatible Ni-MH charger set to a trickle or recovery mode at around 100mA for 15–20 minutes to bring cell voltage above 10.8V. Once the charger detects that minimum, it will accept the pack and continue the full charge cycle normally.