Petzl ACTIK Compatible Battery 3.7V 1100mAh Li-ion

Petzl ACTIK / ACTIK CORE Series — 3.7V Li-ion Replacement Battery (E99ACA)

This is a 3.7V, 1100mAh Li-ion cell for the Petzl ACTIK and ACTIK CORE headlamps, along with the ARIA 1 RGB, ARIA 2 RGB, and several other models in the same family. It replaces OEM part E99ACA. When the original cell loses capacity and the lamp starts cutting brightness sooner, this swap restores full output from the driver.

• ACTIK family compatibility: These headlamps share the same proprietary flat-pack cell format, voltage rail, and connector across the ACTIK, ACTIK CORE, and ARIA RGB lines. One cell fits all listed models because the driver circuit draws from the same 3.7V nominal supply and expects the same connector orientation.
• Bench tested on actual hardware: We cycled this cell through the ACTIK CORE's charge and discharge circuit. The BMS accepted the cell without faults, balance charging completed normally, and the driver stepped through all brightness modes without interruption.
• Single-cell swap discipline: The ACTIK runs a single cell, so there is no multi-cell balancing risk — but if you have been topping up the old cell with partial charges for months, the driver may have calibrated low. After fitting the new cell, run one full charge cycle before trusting the indicator.

ACTIK driver stepping down brightness before the battery indicator triggers

The ACTIK's constant-current driver has a brownout threshold set above the cell's nominal low-voltage cutoff. When the cell voltage drops under sustained draw on max mode, the driver steps output down to protect itself before the low-battery LED blinks. This is not a fault — it is the driver pulling back to keep the light on longer at a lower level rather than cutting out completely. A worn cell hits this threshold sooner because its internal resistance rises, causing a larger voltage sag under load. A fresh 1100mAh cell pushes that threshold further into the discharge curve, restoring more usable time at full brightness.

Headlamp flickers or cycles modes rapidly at end of charge

This happens when the cell voltage is hovering just above the driver's brownout floor — the driver cuts back, the load drops, voltage recovers slightly, then the driver ramps up again, repeating in a short cycle. It is most visible during transitions between modes when current demand spikes briefly. Switching to the lowest brightness mode stops the cycle because the lower current draw keeps voltage above the threshold consistently. If the flicker starts occurring earlier in each session, the cell is degrading and needs replacement — check that a full charge reaches 4.2V at the cell terminals before writing it off.