There may be parasitic drain after the light goes out. Since yours was still on there certainly was drain. Once the battery is significantly drained it doesn’t take much to pull the voltage down lower. Mine stays fairly bright and simply goes out….gone. It will not start again. I have not left it that way so don’t know what happens if that is done.
On over discharge there is the potential for permanent damage. Depends on the battery quality, age, and degree of discharge so there is no clear answer. Seems 3.0v is pretty safe, 2.8v is OK, 2.5v IMO is pushing it but not a catastrophe. Once you get down below 2.0v it’s not so good. Then you get into the whole debate of what’s the battery worth to you vs. the potential for damage and harm?
The problem does generally show up with charging, but there are reports of problems during use. But the specifics of those are often difficult to clearly determine. I’ve got some lipos (for RC flying), that were new and I accidentally discharged to 0v. I ‘boosted’ them with a NiXX charger, and then charged them normally. They puffed a bit but continued to operate like normal 2 years later. They ARE marked, kept in a fridge at storage charge, and ONLY charged just before flying. Obviously I didn’t toss them, but I SURE AM watching them.
Thanks for the infos. Will definitely be marking it, and using it for low-risk applications.
I usually recharge my batteries when they reach about 3.6V - I hate the thought of walking my dog, and not being able to use turbo mode, since most of the lights that I own draw a high current and cause a considerable voltage sag. That’s why I have plenty of VTC6 and 30Q lying around and I used one for the DV-9, otherwise a high drain battery would probably be overkill for this light. The one that I used had been recharged less than ten times.
With nightstand lights, I’ve been testing how long they last in the lowest mode. But after this experience I’ll probably put an end to that, and check the voltage more regularly. Or I’ll just use my Olight S Mini with CR123A - those cells almost seem to last forever!
I’ve got some low capacity ‘junk’ cells. I use those for testing unknown situations. Not of much use for high draw applications but work OK for other stuff.
With battery in place and back off, turn the switch on. Then screw it slowly in. It will light when it makes contact. Or reverse the process. You can tell when it loses contact. Plus, that tiny amount is not enough to compromise waterproof integrity if that is an actual issue.
Some dive lights use screwing the back in/out as the way to turn them on. It’s simple, effective, and removes one other source of potential water entry via a switch.
But that puts the tailcap and rest of the light at 2 different potentials, VASTLY increasing the potential for corrosion with the slightest scuff to the anodisation. The water acts as a bridge across the non-contacting pieces.
I’d much rather have the magnetic slider that the DV-S9 has. Zero chance of ingress from there.
Mmmm, the light I currently have that works that way is plastic so corrosion is not an issue. It’s by Underwater Kinetics and is designed and specifically made for diving by a diving light company. There are similar dive lights via similar companies.
One of their high power LED actually has a heat sink that comes out thorough the front lens since it does not have a good path to heat sink the LED pill via the plastic body. My 3xC-cell light has a full length metal tube down inside the body to draw heat out of the pill and distribute it.
The UK light is fine. It’s a backup light so rarely gets used. I’m looking for something smaller, lighter, and working toward migrating more exclusively to Li-on. Single cell lights are now almost as good as my 4 year old canister light. Not quite, but pretty close.
Just took some beamshots and the UltraFire doesn’t look more green than a different light with CW emitter, so it’s probably just my eyes that have become accustomed to neutral white tints.
This particular switch is pretty clever. There are no springs and the only part for potential corrosion is the magnet in that little slider. A couple other “dive lights” with Hall sensors I got have springs and things on the outside. Sure, no hole through the light for a switch, BUT the mechanism is cheap carbon steel and rusts out fast in saltwater immersion use. This is the first light I’ve gotten that does not do that. Seems reasonably solid.
FWIW, the seal on the back of a twisty is just as vulnerable when static as dynamic as long as the O-rings are in good shape, well lubed, and not contaminated with cat hair or other debris. Most floods of a properly designed light are user errors. MANY floods on Chinese lights are due to shoddy materials and poor workmanship. I don’t trust ANY of them until checked out thoroughly and defects corrected……if possible.
It’s one thing to have a light fail on a dark walk. It’s entirely another if you are depending on it during a dive. That’s why we carry 2 (or more) lights.
Took the UKing (pretty close to the DV) on a dive yesterday. Used it for 1 hour with a Lii-26650. Worked fine, nice spot. Came back with half capacity.
Salt. This wasn’t a deep one, 60 feet/68 minutes. What I like about this light is the apparent lack of external springs that rust out in many of the other models of cheap dive lights not ACTUALLY designed for serious diving. This one might work out. Oh, and NO modes…just the slider from dimmer > full on. Gotta like that.
