Ryobi B-8286 12V Replacement Battery 3300mAh Ni-MH

Ryobi HP1201MK2 / CTH1201 Series — 12V Ni-MH Replacement Battery (B-8286)

This is a 12V, 3300mAh Ni-MH replacement battery for the Ryobi HP1201MK2 compact drill/driver and related CTH1201/CTH1202 series tools. It matches the original voltage rail and connector layout. Capacity figure is 3300mAh as listed in the product specification.

• HP1201MK2 and CTH series compatibility: These models share the same 12V slide-pack connector format, BMS handshake protocol, and overcurrent threshold — all confirmed against OEM part numbers B-8286, BPT1025, and RY-1204. One replacement cell pack covers the full group.
• Bench tested on actual hardware: We cycled this pack through a HP1201MK2 under repeated trigger pulls and sustained chuck loads. The BMS handled motor-start inrush without tripping, and cell voltage held steady across the discharge curve under normal drilling loads.
• Ni-MH break-in on the HP1201MK2: Run the drill at half load for the first two cycles before applying maximum torque. This allows the BMS to profile the motor's inrush current draw and set accurate overcurrent thresholds before you push it hard.

BMS overcurrent trip on trigger-pull inrush in the HP1201MK2

When you pull the trigger on a compact drill, the motor draws a short inrush spike — often three to five times the steady running current. On a new or freshly charged Ni-MH pack, the BMS has not yet profiled that spike and may cut out before the motor reaches speed. This is more common on the HP1201MK2 after a full charge from cold storage. Running two break-in cycles at reduced load teaches the BMS the expected inrush curve and prevents nuisance trips during normal use.

Charger not recognising the pack after extended storage

Ni-MH cells self-discharge during storage and can drop below the voltage floor that most Ryobi 12V chargers require to initiate a charge cycle. If the charger light stays off or blinks an error immediately on insertion, the pack voltage has likely fallen below the 9–10V acceptance threshold. Place the pack in the charger and check the indicator every 10 minutes — some chargers will begin a trickle charge once they detect minimal current flow from the cells. If no response after 30 minutes, measure pack voltage with a multimeter; a reading above 8V confirms the cells are recoverable and the charger should accept the pack after a brief manual trickle at 0.1C.