Heads up on a beginner mistake by an old pro. I had half a dozen lights next to my chair as I ran through my routine biannual maintenance on my lights. Clean threads, remove, clean, relube & reinstall "O" rings, drop in new cells, measure the old looking for parasitic drain, polish glass, wipe inside & out with Sentry cloth, etc, etc.
After working on 4 Olight Batons(positive terminal down on battery), I grabbed my D4VN. You guessed it-I put the battery in backwards! And without protection it could have been really bad-just 60 or 90 seconds passed when I tried to pick up the light(I say tried because it was so hot my thumb blistered where I touched it). I had been charging batteries so I had three Lipo-Guard fireproof charging bags out-I grabbed a kitchen mitt and tossed the light into the bag and took everything outside(to disperse the toxic fumes that can be released when a battery "vents"). I was able to unscrew the bottom cap and remove the cell. The wrapper was split, bare metal exposed but no flame out or venting. I went back outside 5 minutes later, and despite it being 62 degrees Fahrenheit, the light was still too hot to touch. An hour later, I assessed the light and all seemed ok, a new cell and it worked perfect. Just to be safe I ordered another D4VN(Love this light)! The cell read 2.92v. I put a new wrapper on, and recharged it. It terminated at 4.18v, an hour later it was 4.16v and for two days has held that voltage. I will still trash it as insurance and I still have 20-30 other Q30's. Please learn from my stupid mistake-this D4VN & all Emisar D* lights are awesome lights, but without reverse polarity protection the results can be painful, dangerous and costly. It taught me that I really need to be as attentive and cautious with lights/batteries in the same manner I approach my guns. Some may think that is overkill, but I'm ok with that...
Added clarification:
after replacing batteries in a flashlight (Olight S1R Baton) that required the positive terminal towards the tail cap, I also inserted a Samsung Q30 into my D4VN with the + terminal towards the tailcap(This is BACKWARDS from what is required), without reverse polarity protection, this could have had a catastrophic ending.....
