Eaton CRYSTALWAY 3.7V Replacement Battery 5200mAh Li-ion

Eaton CRYSTALWAY / GUIDELED Series — 3.7V Li-ion Replacement Battery (40071353667)

This 3.7V, 5200mAh lithium-ion cell replaces the backup battery in Eaton CRYSTALWAY and GUIDELED emergency lighting units. It also fits models 19821 and 40071354590, among others. When the original cell degrades, the fitting can no longer sustain illumination during a mains failure — this cell restores that function.

• CRYSTALWAY and GUIDELED compatibility: These fittings share the same 3.7V single-cell architecture, connector pinout, and charge controller float voltage. One cell covers the full range without modification.
• Bench tested on actual hardware: We ran this cell through charge acceptance and load discharge on a CRYSTALWAY fitting. The BMS accepted charge within the float window and held voltage under sustained illumination load without tripping the protection circuit.
• First test cycle after installation: Within 24 hours of fitting, press and hold the test button for the full rated duration. This confirms the new cell accepts load and lets the charge controller register capacity before your next scheduled compliance test.

Why a new cell can still fail the duration test on first inspection

A cell shipped from storage arrives at a partial state of charge — typically 40–60% — not fully conditioned to the fitting's charge controller. During a compliance duration test run too soon after installation, the cell may exhaust that partial charge before the rated period ends, logging a failure. The fix is straightforward: allow at least 24 hours of continuous mains-connected charging before running any timed test. After one full charge cycle the cell reaches rated capacity and will hold the load for the full duration.

Charge indicator staying red after new battery installation

Some Eaton fittings will not transition from fault or charge-red to green if the incoming cell voltage sits outside the controller's float acceptance window — common with cells stored several months at low voltage. The controller reads the cell as faulty rather than discharged. Leave the fitting on mains power for a full charge cycle, typically 24 hours. If the indicator remains red after that period, measure the cell terminals — a healthy cell should read between 3.6V and 4.2V. A reading below 3.0V means the cell entered deep discharge during storage and the protection circuit has latched off; most Eaton controllers cannot recover from this state, and the cell should be replaced.