Ryobi 18V Hedge Trimmer Replacement Battery 3300mAh

Ryobi CTH1802 Series — 18V Ni-MH Replacement Battery (B-8288)

This is an 18V 3300mAh Ni-MH replacement battery for the Ryobi CTH1802 cordless hedge trimmer and related 18V Ryobi tools. It fits the CTH1802, CTH1802K, HD1800M, HP1802M, and 17 additional models sharing the same 18V Ni-MH platform. Dimensions are 132.95 x 73.00 x 104.90mm — check your housing clearance before ordering.

• CTH1802 platform compatibility: The CTH1802 series and its sibling models share the same 18V Ni-MH voltage rail and battery connector footprint. OEM part numbers B-8288, BCHI-18, BPT1027, 130224007, and 130256001 all map to this same pack — Ryobi used multiple part numbers across production runs, but the cell format and BMS handshake remain consistent across the platform.
• Bench tested on actual hardware: We cycled this pack through full charge and load discharge sequences on an 18V Ni-MH compatible charger. The BMS held steady through the dual-action blade motor's start inrush current without tripping overcurrent protection. Cell temperature stabilised within the expected range under sustained trimming load.
• First two cycles on the CTH1802: Run the trimmer at partial blade load — light hedge passes, not dense branch work — for the first two charge cycles. This lets the BMS log the motor's actual inrush draw before it locks overcurrent protection thresholds. Skipping this on Ni-MH packs can cause premature BMS cutoff during the first heavy trimming session.

BMS cutoff on CTH1802 motor-start inrush surge

The CTH1802's dual-action blade motor draws a sharp current spike the instant the trigger is pulled. On a fresh or storage-rested Ni-MH pack, the BMS may read this spike as an overcurrent event and cut power before the blades reach speed. This is not a faulty battery — it is the BMS protecting cells that have not yet been profiled under load. Two partial-load break-in cycles give the BMS enough data to distinguish a normal motor-start surge from a genuine fault. After break-in, trigger-pull cutoffs on this pack stop occurring under normal trimming conditions.

CTH1802 runs weak and bogs mid-cut

Bogging under load on the CTH1802 is almost always voltage sag — the battery's output voltage drops under sustained blade load rather than holding steady. On Ni-MH chemistry, this gets worse when the rail contacts in the tool's battery slot have oxidation or debris build-up, because added contact resistance compounds the sag. Clean the battery terminals and the tool's contact rails with isopropyl alcohol before dismissing a weak-running pack as a capacity problem. If the pack reads below 15.5V under load on a multimeter, the cells are genuinely fatigued and the pack needs replacement.