Pelican 3750 Replacement Battery 4.8V 4000mAh Ni-MH

Pelican 3750 / 3759 — 4.8V Ni-MH Replacement Battery (3750-301-000)

This is a 4.8V, 4000mAh Ni-MH battery pack built to replace part number 3750-301-000 in the Pelican 3750 and 3759 rechargeable flashlights. These are four-cell sub-C Ni-MH packs wired in series to hit the 4.8V rail the driver circuit expects. Capacity is rated at 4000mAh / 19.2Wh.

• 3750 and 3759 compatibility: Both models share the same battery bay dimensions, connector pinout, and 4.8V driver voltage rail. The pack slots into either unit without modification — the same BMS and charge termination logic applies to both.
• Bench tested on actual hardware: We cycled this pack through the Pelican 3750's onboard charger and confirmed delta-V cutoff triggered correctly at full charge. Current draw under full-beam load matched the OEM spec, and the driver stepped down without fault codes.
• Multi-cell replacement rule: This pack contains four matched sub-C cells. If you're running two packs in rotation, do not mix cells from different batches or age groups. A weaker cell in series draws the rest of the pack down unevenly under high-current draw, accelerating failure in the weakest cell first.

Why the Pelican 3750 steps down to low mode before the battery indicator trips

The 3750's driver circuit monitors pack voltage continuously, not just at the indicator threshold. When voltage sags under high-beam current draw, the driver reduces output to protect the cells before the low-battery indicator has time to register. This is brownout protection — the driver steps the LED down rather than cutting power entirely. It's more visible on older packs because internal resistance rises with cycle count, causing a sharper voltage sag under load. A fresh pack at 4000mAh holds voltage flatter across the discharge curve.

Pack won't hold charge after sitting unused for several months

Ni-MH cells self-discharge at roughly 1–2% per day at room temperature. A pack left unused for three to six months can drop below 1.0V per cell — the point where the charger's delta-V detection may not see enough voltage rise to initiate a full charge cycle. Measure each cell individually with a multimeter. Any cell reading below 0.9V needs a slow conditioning charge at 0.1C before returning to normal charge. On the 3750's OEM charger, that means using the trickle mode if available, or an external Ni-MH charger set to 400mA to recover the pack first.