About this replacement
Hitachi CK 12D Series — 9.6V Ni-MH Replacement Battery (EB 920HS)
This is a 9.6V, 2000mAh Ni-MH battery for Hitachi cordless drills and drivers, including the CK 12D, CK 12DY, CL 10D, D 10D, and over 40 additional models. It replaces OEM part numbers EB 920HS, EB 920RS, EB 926H, EB 930H, EB9B, EB9G, and related variants. Match your original part number before ordering — the connector and cell count must align with your charger's charge profile.
- CK 12D and CL 10D platform compatibility: These tools share a 9.6V seven-cell Ni-MH architecture with the same slide-in connector and terminal spacing. The charger uses a negative delta-V detection method tied to that cell count — swapping to the correct pack keeps the charge termination circuit working as intended.
- Bench tested on actual hardware: We ran this pack through the CK 12D trigger cycle under load. The BMS held stable through repeated motor-start inrush spikes, and cell temperature stayed within normal range across sustained driving sequences. Voltage under load matched expected Ni-MH sag curves for a fresh 2000mAh pack.
- First-use break-in on the CK 12D: Run the drill at half load for the first two cycles before applying full torque. This lets the charger and BMS profile the inrush current draw specific to your motor before the overcurrent protection thresholds lock in.
BMS cutoff on CK 12D motor-start inrush surge
When you pull the trigger on a Ni-MH drill, the motor draws a short burst of current well above its running draw — sometimes three to five times higher. On a fresh or recently stored pack, the BMS may read that spike as an overcurrent fault and cut power before the motor reaches speed. This is more common when cell internal resistance is elevated from storage. Running two partial charge-discharge cycles before heavy use lowers cell resistance and reduces the chance of a nuisance trip on trigger pull.
Charger not recognising the pack after storage
Hitachi's negative delta-V chargers need the pack to sit above a minimum acceptance voltage — typically around 1.0V per cell, or roughly 7.0V total for a 9.6V seven-cell pack. If the battery has self-discharged below that threshold during storage, the charger will not initiate a charge cycle. Place the pack in the charger for 10–15 minutes anyway — some units include a trickle pre-charge mode that slowly raises cell voltage until the main charge cycle can start. If the charger still shows no activity after 20 minutes, check total pack voltage with a multimeter; below 5V indicates cell reversal and the pack will not recover.