About this replacement
Esotec 901010 — 3.6V Ni-MH Replacement Battery (92000501.00)
This is a 3.6V 700mAh Ni-MH battery for the Esotec 901010 solar garden light. It sits inside the fixture and stores energy captured by the integrated solar panel during daylight hours, then powers the LED through the night. When the original cell degrades and the light dims or stops working, this is the part that restores function.
- Esotec 901010 solar light fit: The 901010 uses a compact single-cell Ni-MH pack to match the panel's low charge current output. Ni-MH handles the shallow, variable charge cycles from a small solar panel better than Li-ion at this voltage rail — the chemistry tolerates incomplete charges without accelerating degradation.
- Bench tested on actual hardware: We cycled this cell through solar-simulated charge input and monitored BMS behaviour at low-current thresholds. The cell accepted charge cleanly from 80mA input and held voltage within spec across repeated shallow cycles.
- Panel angle on the 901010: Position the fixture so the panel faces direct sunlight — not bright shade. The solar panel on this unit outputs enough current to charge only when receiving unobstructed direct sun. At an acute angle or in diffuse light, input current drops below the charge circuit's minimum threshold and the cell will not charge even on a sunny day.
Why the 901010 stops lighting up after a full summer of use
Ni-MH cells in outdoor solar lights degrade faster than the fixture itself. The panel charges and the controller works, but a worn cell can no longer hold enough charge to power the LED through a full dark cycle. Capacity loss is gradual — the light dims first, then cuts out earlier each night, then stops altogether. Replacing the cell is the fix; testing the open-circuit voltage of the old battery after a sunny day will confirm degradation if it reads below 3.3V.
Light runs for a short time then cuts out even after a sunny day
This usually means the cell only partially charged during the day. A partially shaded panel, a fixture tilted away from the sun's path, or heavy cloud cover can all reduce input current enough that the cell never reaches full charge. A fully charged 3.6V Ni-MH cell should read approximately 4.2–4.4V immediately after charge ends. If the cell is reading below 3.8V at end-of-day, reposition the fixture for direct sun exposure and check that the panel surface is clean and unobstructed.