Pierlite BP4S Emergency Light Replacement Battery 4.8V 4000mAh

Pierlite LPM70 / LPS70 Series — 4.8V Ni-CD Replacement Battery (BP4S)

This is a 4.8V, 4000mAh Ni-CD battery for Pierlite emergency lighting units. It fits the LPM70, LPM80, LPS70, and LPC118 fittings, along with more than 20 additional models in the same family. The cell slots into the existing battery bay and connects to the onboard charge controller without modification.

• LPM70 / LPS70 / LPC118 platform fit: These fittings share the same 4.8V charge rail and BP4S connector footprint. The charge controller float voltage and BMS handshake are consistent across the range, so one cell covers the full group without rewiring or adaptor plates.
• Bench tested on actual hardware: We ran this cell through a full charge cycle and simulated mains failure on the LPM70. The charge controller accepted the cell without fault, the lamp activated on mains drop, and the BMS held voltage above the low-cell cutoff threshold through the rated load test.
• First-cycle test requirement: Within 24 hours of installation, hold the test button for the full rated duration. This confirms the new cell accepts load and lets the charge controller register actual capacity before the next scheduled compliance test. Skipping this step can cause a false duration failure at inspection.

Emergency light failing its duration test after battery replacement

A freshly installed Ni-CD cell does not arrive at full rated capacity. Storage time between manufacture and installation leaves the cell partially discharged, so the charge controller has not yet run a full conditioning cycle. The cell needs at least one complete charge-discharge cycle before it reaches the 4000mAh rating. Run a manual test within 24 hours of installation to cycle the cell and allow the controller to establish a proper charge baseline before any compliance inspection.

Charge indicator staying red after new battery installation

The Pierlite charge controller checks cell voltage at startup and will not enter float charge if the incoming voltage sits outside its acceptance window. A cell that has been in storage can read low enough to keep the controller in fault state rather than switching to charge mode. Disconnect the battery, wait 30 seconds, then reconnect — this forces the controller to re-sample cell voltage from rest. If the cell voltage at the connector reads above 4.0V with a multimeter, the controller should accept it and the indicator should move to amber then green within a few hours.