Sunlite 88158-SU Compatible Battery 7.4V 2600mAh Li-ion

Sunlite 88158-SU — 7.4V Li-ion Replacement Battery (88158-SU)

This 7.4V, 2600mAh Li-ion battery replaces the factory cell in the Sunlite 88158-SU emergency lighting fixture, including the LED FIX BB213 and Strip variants. It supplies the backup power the fitting draws during a mains failure event. Voltage and capacity match the original specification exactly.

• 88158-SU, LED FIX BB213 and Strip compatibility: These fittings share the same 7.4V charge rail and connector pinout, so one cell covers the full range. The onboard charge controller expects a two-cell Li-ion pack and will reject packs outside the 7.4V nominal window — this cell sits within that acceptance band.
• Bench tested on actual hardware: We ran this cell through a full simulated mains-fail cycle. The BMS handed off to load cleanly at cutover, held voltage above the low-voltage cutoff threshold throughout the test duration, and returned to float charge without error on mains restore.
• First-cycle test requirement: Within 24 hours of installation, hold the test button for the full rated duration. This lets the charge controller register the new cell and confirms the BMS accepts load before your next scheduled compliance inspection.

Charge indicator staying red after new battery installation

A fresh Li-ion cell shipped from storage often rests at 3.5–3.6V per cell — below the float acceptance window the 88158-SU charge controller expects. The controller sees this as an out-of-range input and holds the fault state rather than starting the charge cycle. Leave the fitting on mains for 12–24 hours. Once the cell climbs into the acceptance window, the controller enters normal charge mode and the indicator moves to green.

Emergency light dims partway through a duration test

This happens when the new cell has not completed a full conditioning charge before the test is run. The cell holds nominal voltage under light load but sags once the LED array draws sustained current. The fix is to charge the battery for a full 24-hour period on mains before running any test cycle. After one complete charge, the cell delivers its rated 2600mAh at stable voltage across the full test duration.