Black & Decker 499055-04 Cordless Drill Replacement Battery 3.6V

Black & Decker KC9039 / KC9036 — 3.6V Ni-MH Replacement Battery (499055-04)

This is a 3.6V, 2000mAh Ni-MH battery pack for the Black & Decker KC9039 and KC9036 cordless drill/drivers. It replaces OEM part numbers 499055-04 and 3HR-4/5SC. Fits directly into the battery bay of both models with no modification.

• KC9039 and KC9036 compatibility: Both models run the same 3.6V power rail and use an identical battery housing geometry with the same terminal layout. The sub-C Ni-MH cell format and connector match across both platforms, so one part number covers both drills.
• Bench tested on actual hardware: We cycled this pack through charge and discharge on a KC9039 drill and monitored cell voltage across three full cycles. The pack accepted charge correctly from the standard Black & Decker charger and held voltage under torque load without mid-cycle dropout.
• Ni-MH break-in on this drill: On first use, run the drill at half load — light fastening work, not max-torque driving — for the first two cycles. Ni-MH cells at this voltage have a memory-sensitive charge profile, and shallow full-load cycling early on can reduce total usable capacity from the start.

Inrush spike tripping the protection circuit on trigger pull

When you pull the trigger on a cordless drill, the motor draws a short surge of current well above its running draw. On a 3.6V Ni-MH pack, this inrush spike can exceed the overcurrent threshold of the protection circuit if the cells are cold or not yet fully charged. The drill cuts out immediately at trigger pull — not under sustained load, but right at the start. Let the pack warm to room temperature and ensure it is fully charged before heavy use. A full charge brings cell impedance down and allows the pack to deliver the burst current the motor demands at startup.

Drill bogs down and loses torque partway through a fastening job

This happens when the battery voltage sags under sustained motor load — the cells can't maintain rail voltage as current draw climbs, so the drill slows or stalls mid-screw. On Ni-MH packs, this is often caused by high contact resistance at the battery terminals rather than a failing cell. Clean the battery contacts and the drill's terminal bay with a dry cloth or fine abrasive. If the sag continues after cleaning, check resting voltage with a multimeter — a healthy 3.6V Ni-MH pack should read 4.1–4.3V immediately after a full charge.