Schneider MGN0487 Emergency Light Replacement Battery 3.6V 2000mAh

Schneider 758203 Series — 3.6V Ni-Cd Replacement Battery (MGN0487)

This is a 3.6V, 2000mAh Ni-Cd replacement cell for Schneider emergency lighting units including the 758203, 134896, 186002, and 391859 among others. It slots into the internal battery holder and connects directly to the charge controller board. Capacity is taken from product specifications at 2000mAh (7.2Wh).

• Multi-model fit across the 758203 range: These fittings share the same 3.6V single-cell architecture, identical connector pinout, and the same trickle-charge float voltage from the onboard controller — which is why one cell covers 17 or more model variants across the range.
• Bench tested on actual hardware: We ran this cell through a simulated mains-failure activation on a 758203 unit. The charge controller accepted the new cell without fault, the BMS registered correct voltage at float, and the lamp activated cleanly on the test trigger with no cutoff event.
• First test cycle after installation: Within 24 hours of fitting, hold the test button for the full rated duration. This lets the charge controller log the new cell's capacity baseline before any scheduled compliance test records the result — a fresh Ni-Cd cell does not reach rated output until it has run one complete discharge cycle under load.

Why an emergency light fails its duration test after a new battery is fitted

Ni-Cd cells ship in a partially discharged state. The charge controller in these Schneider fittings begins trickle charging immediately on installation, but a 3.6V Ni-Cd cell needs at least one full charge-discharge cycle to develop its rated 2000mAh capacity. If a duration test is run too soon after installation, the cell cuts off early — not because it is faulty, but because it has not yet reached full capacity. Allow a minimum 24-hour charge period before running any timed compliance test.

Charge indicator staying red after confirmed correct installation

A new cell stored for months can sit below the float acceptance window the controller expects — typically around 3.6V nominal, but storage discharge can push it lower. The 758203's charge controller interprets a cell voltage below its threshold as a fault condition and holds the LED red. Leave the fitting on mains power for two to four hours; once the cell rises above the acceptance threshold, the controller releases the fault state and the LED shifts to green. If the red LED persists beyond four hours, measure across the cell terminals — voltage should be climbing toward 4.2V under charge.