About this replacement
SCANGRIP MAG3 COB LED — 3.7V Li-ion Replacement Battery (03.5711)
This is a 3.7V 2600mAh (9.62Wh) lithium-ion cell for the SCANGRIP MAG3 COB LED work light. It fits the MAG3 COB LED and related models including 03.5070 and 03.540. Swap it in when the original cell no longer holds a usable charge.
- MAG3 COB LED platform compatibility: These models share a single-cell 3.7V architecture with the same physical 18650-format cell and connector orientation. The driver board expects a flat-top cell within a specific internal resistance range — this replacement meets that requirement without triggering false low-voltage shutdowns.
- Bench tested on actual hardware: We cycled this cell through the MAG3's driver circuit across all output modes. The BMS held stable under sustained COB draw, and the protection circuit tripped correctly at the low-voltage cutoff threshold without nuisance shutoffs at partial discharge.
- Single-cell replacement protocol: The MAG3 runs one cell. If you are replacing it because capacity dropped significantly after the light spent months unused, run a full charge cycle before judging performance — deeply discharged Li-ion cells often recover their rated capacity after one proper charge, not immediately on first use.
Why the MAG3 COB steps down output before the indicator reads empty
The MAG3's driver uses brownout protection to step down brightness when cell voltage drops below the driver's minimum threshold — typically around 3.0–3.2V under load. This happens before the low-battery indicator triggers, because the indicator reads resting voltage, not loaded voltage. Under high COB draw, the loaded voltage can dip below the driver's floor even when resting voltage still reads acceptable. Switching to a lower output mode raises the loaded voltage back above the cutoff and restores stable output.
MAG3 won't power on after long storage
A cell stored discharged below roughly 2.5V may read zero or near-zero on a multimeter — the protection circuit has tripped to prevent over-discharge damage. Many chargers skip cells in this state because they detect no voltage. Connect the battery to the MAG3's original charger and leave it for 15–20 minutes; the charger's trickle stage can bring the cell back above the BMS re-enable threshold. If the cell recovers to above 3.0V and accepts a full charge, it is safe to continue using.