Well then do you plan to tweak this setting, like changing the cutoff voltage to 5-6V?
As far as I can see many people plan to buy this light as in-car / in-garage back-up light, which requires using lithium primaries. If it doesn’t work with two lithium primaries then many people will not consider buying this, or request for return when they find out lithium primaries don’t work.
Or, at least pin an attention info on product page saying lithium primaries won’t work.
IMO, the fact that the T4 works with 2xAAs and has a 519A option makes it very attractive for someone like me who wants an AA light using my NiMH cells which are basically never used 
maybe your light is defective?
has anyone else confirmed that two Lithium Primaries, do not work?
I believe I saw someone on reddit claiming their T4 doesn’t work w/ lithium primaries either.
My T4 is due soon. Maybe I’ll run a test and see.
Yep, it’s a cool little torch. No regrets whatsoever despite the lithium cell issue.
Possible, but seeing as it works with 3 of 4 chemistries, I gotta go with it’s a function of the LVP parameters as others suspect. Will wait for UNBLF to report his findings, and see if I can find reference to the r/flashlight mention. It’s puzzling that the LVP kicks in between 4V –6V, but two lithium primaries only produce 3.6-3.7 volts in series. Is there some percentage of tolerance on either end that may account for the trigger? Again, I’m no electronics genius, so there’s obviously more to the picture.
same math conclusion here
that is why I suggested your sample is defective, since it is NOT between 4-6V w lithium primaries
the best way to solve your issue is to communicate privately w the seller, and I hope you end up w a light that works on Lithium too
the failure to work on Lithium is a bug, not a feature
"Low voltage warning: Yes(14500) / No (AA)"
So no LVP for AA,
So I can't really use Ni-MH AA because there's no LVP for them, so I'm risking over discharging.
But can't really use alkaline AA (because if they leak, they will ruin the flashlight)
lithium AA apparently don't work (we have to wait for others to test)
So it's actually a 2 x 14500 flashlight, that can take normal alkaline AA battery im emergency, but they shouldn't be stored inside of it.
Ps. On web page, it only says AA, no type is specified.
A bit over the top. Lock out the light when not in use. Charge or change your batteries and using Alkaline or NiMH AAs is not an issue. Most AA lights have no low voltage protection so the T4 is no different.
Not quite. The discharge curve for Ni-MH is very different from Li-ion: the voltage pretty much stabilizes at 1.2-1.3 during the entire run, and then rapidly drops off, as opposed to decreasing near linearly. A consequence is that when its rest voltage is at around 1.1V, even a small amount of current drawn from it would immediately sag its voltage to below usable, which means the light would rapidly dim by an order of magnitude; it doesn't take LVP to notice that. Once you take out the battery again, the rest voltage would rise up again, resulting in no damage.
In a sense, the Ni-MH chemistry comes with intrinsic LVP. Also, the Ni-MH chemistry is more robust than Li-ion, and it takes much more abuse to do the same amount of damage. I've recently found a stash of 10-year old Ni-MH's that test at 0.00V. My charger revived more than half of them with no apparent loss in capacity (compared to the labeled capacity anyways, not excluding the possibility that the capacity is underrated). Doing the same to Li-ion would be far too dangerous.
thanks for the link
looks like the T4 has a driver bug, making it incompatible w Lithium Primary
question… would Eneloop work as well as Lithium Primary?
I think this is a valid and undersold aspect of NiMH, and partly why a few of my most-used lights remain NiMH.
That makes 2 of us. One of several reasons I bought it.
For longer term storage it seems the only option. They just aren’t as temperature tolerant as straight up lithium, or so I’ve read. I don’t have much experience with NIMH. I just bought a 4 pack of AAA standard eneloops to use in some recently acquired WK1/WK2 pen lights. The only rechargeable AA’s I have are the green Energizers (which I used to test viability in the T4), and have been using them in my AA Tool backup work light. However, that’s brought in from my van nightly and rarely sees temps below 15°F.
Mine came today. It works great with Eneloops. I haven’t tried it with Energizer Lithium primaries. I’m going to be pretty unhappy if it doesn’t work, because that’s the scenario I bought it for.
Lithium Primaries and Eneloop, operate in climates where I do not operate. LOL
google sez:
“Lithium primary batteries can continue to function properly at temperatures from –67°F to 302°F”
“Nickel–metal hydride (Eneloop) cells can operate in the temperature range of –4°F to 113°F”
“Alkaline batteries are best suited for operating temperatures between 14°F and +113°F”
“The use of a lithium-ion battery is possible in a temperature range of 50°F to +131°F”
I did not realize until now, that LiIon does not work below 50F… that does not ring true to me… I just put a LiIon light and an Eneloop light in the freezer, to test for myself…
There are Li-ions rated –40 degrees. Normally at a cost of capacity and max amp.
Molicel claim their P26A, an extremely high drain 18650, can do –40C. Haven’t tested yet.
Ive had these two lights in my Freezer for 4 hours… they still work. One is LiIon, the other is Eneloop:
.
I also have three lights in my car with AAA Eneloop, and they still work too. We have had a cold winter, as low as 10F… It seems the batteries are doing fine… they also live in the car in summer… which gets up to 90F outdoors… in the car much higher… I do not store LiIon lights in my car.
I do have a LiIon Jumper pack that lives in my car. It seemed unaffected by freezing weather, as it worked to start my car on one of the colder days this winter…
for my needs, Lithium Primary seems unnecessary, since Eneloop is working fine.