Emergency Driver and Battery Pack Compatibility: A 7-Point OEM Checklist

Short answer: an emergency driver and its battery are one tested system, not two interchangeable commodities. The driver's LED load window, charging voltage, charge current and cut-off logic must match the cell chemistry and capacity, and the whole combination — not the parts separately — is what the rated duration and the test reports refer to.

1. LED load window and power

Confirm the driver's supported forward voltage and current range, its output power in normal and emergency mode, and whether it is constant-current or constant-voltage. An emergency module designed for a 3 W LED string will not hold a 20 W fixture at the required light level for three hours, and a mismatched load can trigger protection behaviour that appears only during a power cut.

2. Cell chemistry and nominal voltage

LiFePO4, NiCd and NiMH packs have different nominal voltages, charge profiles and temperature behaviour. LiFePO4 is common in modern self-contained fittings for thermal stability and long cycle life. Never substitute a pack of a different chemistry or nominal voltage to "make it fit" — the charger thresholds and the battery monitoring logic are calibrated to the original cell.

3. Capacity, rated duration and derating

Rated duration is 1, 2 or 3 hours as required by the building code, and it is measured at the end of battery life as well as when new. Check capacity in Ah and Wh (Wh = V × Ah), the declared duration at the lowest ambient temperature, the cycle life and the recommended replacement interval. A 3-hour rating at 25 °C is not a 3-hour rating in an unheated warehouse.

4. Charging parameters

Ask for the charge current, maximum charge time from a fully discharged pack, constant-voltage set point, cut-off threshold and any temperature-compensated charging. As a worked example from our own published AS-B109 exit sign specification: a 3.2 V 1800 mAh LiFePO4 pack is managed by an MCU at 200 mA charge current, up to 10 hours charge time, with a 3.60 V ± 0.05 V constant-voltage threshold and cut-off at 3.65 V. Those numbers belong to that model only; another SKU has different values, so always request the datasheet for the exact combination.

5. Changeover, self-test and indication

Confirm the response time after mains failure (EN 1838 requires 50% of required illuminance within 5 seconds and 100% within 60 seconds for escape-route lighting), the behaviour of the indicator LEDs, and which tests the unit performs: short function tests and full duration tests, either on an internal clock or addressable over DALI Part 202. A driver that cannot report a failed battery leaves the fault invisible until the next outage.

6. Protection and mechanical integration

• Overcharge, over-discharge, short-circuit and reverse-polarity protection; verify what the unit does in emergency mode, where some protective dimming must be disabled.
• Thermal layout: the battery should not sit against the LED heat sink or the driver's hot components, as heat is the main driver of capacity loss.
• Wiring, connectors, polarity and the physical fit inside the housing — including the cable gland and gasket so the assembled product keeps its IP rating.

7. Documentation for the whole assembly

For OEM/ODM projects, require a document set that names the driver + battery + LED combination: product-safety test report (EN 60598-2-22 / IEC 61347-2-7 as applicable), declaration of conformity, UN 38.3 test summary and SDS for the exact cell, photometric data for the assembled fitting, and the self-test or DALI behaviour description. If any component changes during production — a different cell supplier, a different capacity, a new LED bin — treat it as a change-controlled revision and re-verify duration and charging. A "similar" cell is not the same product for either safety or shipping purposes.

Common mismatch failures

• Battery replaced with a higher-capacity pack of the same size, but the charger never reaches full charge within the specified time, so the annual duration test fails.
• Narrow-beam LED head selected for its lumen figure, leaving the escape route below 1 lux between fittings.
• Different cell supplier introduced mid-production with no new UN 38.3 test summary, causing the shipment to be held at the freight hub.
• Driver protection dimming the LED in emergency mode, so the fitting passes a bench check but fails the illuminance calculation.

Quick answers

Can I pair any 3.2 V LiFePO4 pack with a 3.2 V emergency driver?

No. Capacity, charge current, cut-off thresholds and monitoring logic are calibrated as a set. Use the cell specified for that SKU, or have the combination retested.

Does a bigger battery automatically give a longer duration?

Only if the charger can recharge it within the required time and the thermal and mechanical design remain valid. Duration is a property of the assembled, tested system.

What should I ask for before tooling an OEM project?

Sample units of the exact driver-battery-LED combination, the duration test result at the minimum ambient temperature, photometric data, and the SKU-specific safety and battery documents.

About Anshine — JiangMen Anshine Technology Co., Ltd. is a Jiangmen, Guangdong-based manufacturer of LED emergency luminaires, exit signs and emergency power supplies for B2B buyers. The company was registered in 2025; our founding team has about 20 years of experience in the emergency lighting industry. To request documentation for a specific model, use the enquiry form on this website.

Standards and transport rules change. This article is general buying guidance, not a declaration of conformity or legal advice. Verify the current edition of each standard, the applicable national annex and the requirements of the authority having jurisdiction, and always request SKU-specific documents before placing an order.