I bought the Panda 2M CRI mid-2019 based mostly on bmengineer's most excellent review. I link to it here for the tech details:
Let me say from the start, I like this headlight. A lot. It ticks all the boxes for me:
- Three-strap retention that offers plenty of adjustment to fit over a heavy wool winter toboggan, as well as my bare noggin. I don't like single-strap headbands. At all. They're a deal-killer for me.
- Extremely flexible UI. Many hidden adjustments that could add value & flexibility. I've used the Panda 2M CRI for many hours exclusively with the native UI as it comes out of the box.
- The warm tint, useful flood & great CRI is very pleasing & hugely useful to me. YLP hit a home run with this headlight at a fair price.
The Panda 2M CRI was extremely useful during a recent interior painting project. White ceiling, light grey walls, white trim. Not a lot of contrast between the light grey wall color and the white of the trim and ceiling. The Panda 2M CRI allowed me to clearly see the corners where the wall met the ceiling and trim, making neat, straight cut-in much, much easier using paint that didn't have much contrast when up-close, especially when wet. No amount of additional workspace lighting of any kind was nearly as effective. The workspace floor or stand lights were either always in the wrong place, shining into my eyes from the sides causing glare, making me work in my own shadow unless I constantly re-positioned them or, just didn't have the spectrum to clearly see the subtle color differences easily.
The Panda 2M CRI solved all of those problems. No shadows. No glare. Subtle differences in color plainly visible at any angle.
I'm not a pro painter by any stretch, just a DIY homeowner. The resulting cut-in between wall & ceiling, and wall and trim is straight & sharp. I couldn't have done it without the Panda 2M CRI.
Now, on to the problem, and a warning.
Tailcap = positive (+) end cap w/magnet.
Headcap = negative (-) end cap without magnet. Also supplies mechanical lockout.
Unscrewing the tailcap with a cell in the tube while both caps are in place can break the positive conductor off of the tailcap board. Here we see the tailcap board inverted, spring up. The (+) lead in the tube is next to it's broken solder joint on the tailcap board.
An 18650 cell is apparently to be placed in the tube by unscrewing only the headcap, inserting the positive end first, toward the tailcap.
Both caps have fairly stout springs.
If the tailcap is unscrewed while a cell is in place, the tailcap board that has both the (+) spring and the (+) lead from the tailcap board to the driver board soldered to it can spin along with the tailcap. The tailcap board is not keyed to the tube in any way, just sort of a snug-ish fit into a very shallow shelf cutout at the end of the tube. On mine, unscrewing the tailcap while the cell was in place broke the tiny wire that is the (+) conductor from the tailcap board to the driver board because the tailcap board spun at the same time. The break happened at the solder joint where the (+) wire that runs from the tailcap board to the driver board is attached. The (+) lead runs from the tailcap board to the driver along a groove machined into the inside of the tube.
The directions in the manual clearly state the Panda 2M CRI can be mechanically locked out by unscrewing either tubecap. I believe that's an error, as the tailcap itself does not appear to be part of the cell circuit; the tailcap board serves that function. See highlighted text top left.
It was an easy enough fix:
Remove the lens cover (four T-6 Torx screws).
Unsolder the (+) lead from the driver board. The (+) lead is easily accessed once the lens cover is removed. The hardest part was finding insulated wire small enough to fit the groove in the side of the tube. I sourced a length of wire from a low voltage pin connector harness out of a dead UPS.
The tiny centering rings on each LED are not glued down or captive in any way; I looked for five minutes before I found one that got away.
There was a tiny dab of what might be glue on the tailcap threads. It wasn't enough to keep the tailcap from rotating when I grasped both caps to unscrew one in order to change the cell. I applied a dab of blue Locktite to the tailcap threads when I reassembled.
I also placed a small disk of very thin, stiff plastic (cell insulator used for shipping) between the inside surface of the tailcap and the tailcap board, to help break the stiction between them if the tailcap is ever rotated again.
Hope this helps keep another user from experiencing the same problem with the (+) tailcap conductor.
If YLP sees this, I'd like to suggest:
1) Key the tailcap board much more securely to the tube to keep it from rotating with the tailcap.
2) Correct the lockout instructions.
3) Glue the tailcap in place more securely.