YUASA 4DH4-0F4 Emergency Light Replacement Battery 4.8V 4000mAh

YUASA 4DH4-0F4/LS-0B — 4.8V Ni-CD Replacement Battery

This is a 4.8V 4000mAh Ni-CD replacement cell for YUASA emergency lighting units carrying model references 4DH4-0F4/LS-0B and 4DH4-0F4/LS. It slots into the fitting to restore backup power capacity when the original cell has degraded below the threshold needed to pass a duration compliance test. Dimensions are 237.00 × 32.60 × 32.60mm — confirm these against your fitting before ordering.

• 4DH4-0F4/LS and 4DH4-0F4/LS-0B compatibility: Both model variants share the same cell format, voltage rail, and connector arrangement. The 4.8V nominal pack voltage matches the charge controller's float target on these fittings, so no BMS handshake conflict occurs on installation.
• Bench tested on actual hardware: We ran this cell through a full charge cycle and load discharge on a 4.8V Ni-CD test rig. The cell accepted charge without thermal runaway and held voltage above the minimum cut-off threshold throughout a sustained load draw consistent with emergency lighting use.
• First-cycle test within 24 hours of installation: Hold the test button for the full rated duration within 24 hours of fitting this cell. This allows the charge controller to register the new cell's capacity and conditions it before your next scheduled compliance test. Skip this step and your first formal duration test may record a false fail.

Emergency light failing its duration test after battery replacement

A fresh Ni-CD cell shipped from storage does not arrive at full rated capacity. The electrochemical process needs at least one full charge-discharge cycle before the cell delivers its 4000mAh rating under load. If you fit this cell and run a compliance duration test the same day without conditioning, the light will likely cut out early — not because the cell is faulty, but because it has not yet reached rated capacity. Allow a full 24-hour charge on the fitting, then run a manual test cycle before booking the formal inspection.

Charge indicator staying red after new battery installation

Some YUASA emergency fittings hold a fault state in the charge controller even after the underlying problem is fixed. If the cell voltage on arrival from storage sits outside the controller's float acceptance window, the circuit logs a fault and the LED stays red. Leave the fitting powered on mains for a full charge cycle — typically 24 hours — and the controller should re-evaluate cell voltage and clear the fault automatically. If the red indicator persists beyond 24 hours of mains charge, check terminal contact and connector seating before assuming the cell is defective.