This is a troubleshooting knowledge rather than a direct response to the buyer.
All four lights use NL2150 21700 batteries. The only removable part of the light is the tail cap.
1) If the light is DOA, ask the buyer to remove the battery, and check the light tube and the back of the tail cap to see if the white insulating disc is removed.
2) If the light stops working after a few weeks/months/years, ask the buyer to follow the steps below to test the light.
(Nitecore batteries usually are good quality ones. However, consider asking the buyer to check/replace the battery if the light was purchased years ago.)
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To help us identify the issue, please follow the steps below to test the light.
1. Remove the battery from the light. Use a clean cloth to wipe the threads on both the light tube and the tail cap.
2. A common issue is a loose plate inside the tail cap. Please check the attached image to tighten the plate. We recommend using a pair of needle-nose pliers to grab the dents and rotate the plate clockwise.
3. Install the battery and fully tighten the tail cap.
4. Connect the USB-C charging cable. If the blue charging indicator starts to blink slowly, let the light charge for 4+ hours and test it again.
Does the light work properly now?
