Esotec 901021 Solar Replacement Battery 3.6V 2000mAh Ni-MH

Esotec 901021 / 101100 — 3.6V Ni-MH Replacement Battery (92000401)

This is a 3.6V, 2000mAh Ni-MH rechargeable cell for the Esotec 901021 and 101100 solar light systems. It replaces OEM part 92000401. The battery stores charge from the solar panel during daylight and powers the LED fixture after dark.

• 901021 and 101100 compatibility: Both models run the same 3.6V rail with an identical connector footprint and BMS input threshold. One cell covers both without any modification.
• Bench tested on actual hardware: We cycled this cell through solar-simulated charge input and confirmed the BMS accepted charge current at the correct threshold. Capacity held at rated 2000mAh across multiple discharge cycles.
• Panel angle matters on first charge: After fitting the new cell, place the solar panel in direct, unobstructed sunlight for a full day before the first night run. The Esotec panel outputs sufficient current only under direct sun — ambient or partial shade light sits below the BMS minimum input threshold and the cell will not charge.

Why the Esotec solar panel fails to charge a fresh replacement cell

Small solar panels on garden lights typically output between 100mA and 300mA under full direct sun. The Esotec BMS requires a minimum input current to begin a charge cycle — fall below that threshold and the cell stays flat even on a bright day. Shade from a fence, overhanging branch, or roof overhang cuts panel output sharply. If the light sits in a spot that receives fewer than five hours of direct sun, the cell will never fully charge regardless of ambient light levels.

Light turns on at dusk but goes dark within a few hours

This happens when the cell reached only a partial state of charge during the day — not a fault with the new battery itself. The Esotec system draws a fixed current from the cell; a half-charged 2000mAh cell simply has less stored energy to deliver. Check that the panel is angled perpendicular to the sun's path and free of surface dirt, which can cut transmission by 20–30%. After repositioning, allow two to three consecutive full-sun days to confirm the cell is reaching a complete charge. A fully charged cell at 3.6V nominal should sustain the LED through a typical overnight cycle.