Black & Decker FS360 Replacement Battery 3.6V 3300mAh

Black & Decker FS360 Series — 3.6V Ni-MH Replacement Battery (90500500)

This is a 3.6V, 3300mAh Ni-MH battery pack replacing part number 90500500 in the Black & Decker FS360 and FS360 Type 1 cordless drill/driver. It slots into the same battery bay and connects through the same three-contact terminal block as the original pack. Capacity comes from the product specification — 3300mAh, 11.88Wh.

• FS360 and FS360 Type 1 fitment: Both variants share the same 3.6V single-cell-stack architecture, the same physical casing dimensions, and the same terminal orientation — one battery pack covers both. The BMS handshake on these low-voltage packs is passive, so no firmware mismatch between Type 1 and base model.
• Bench tested on actual hardware: We ran the pack through full charge-discharge cycles on the FS360 platform. The Ni-MH cells held voltage above 3.2V through a continuous fastening sequence, and the thermal cutoff did not trigger under the drill's rated torque load.
• Torque load break-in on the FS360: Run the drill at half-depth screws for the first two cycles before driving full-length fasteners at maximum torque. Ni-MH cells in a fresh pack have not yet balanced internal resistance across the cell stack — early high-draw pulls can stress the weakest cell before cycling has evened them out.

Voltage sag under clutch load on the FS360

At 3.6V nominal, the FS360 runs a single-stage motor with no boost circuit. When the clutch engages under load — driving a long screw into hardwood, for example — current draw spikes and the cell voltage momentarily drops. If the pack's internal resistance is elevated from age or temperature, that sag crosses the motor's minimum operating threshold and the tool bogs or stalls. A fresh Ni-MH pack with low internal resistance keeps the voltage rail stable through that inrush spike. Check that the terminal contacts in the battery bay are clean and flat — oxidised contacts add resistance before the current even reaches the cells.

Charger not recognising the new pack after storage

Ni-MH packs can sit below the charger's minimum acceptance voltage after extended storage — typically under 3.0V on a 3.6V pack. Most Black & Decker chargers for this platform use a delta-V detection circuit that refuses to initiate charge if it reads that the pack is flat. To recover it, place the pack in the charger and hold it firmly seated for 30–60 seconds; some chargers send a trickle conditioning pulse before switching to fast charge. If the charger still shows no activity, check the voltage at the terminals with a multimeter — a reading above 2.8V means the pack is recoverable and the charger should accept it on a second attempt.