Convoy T4

It’s here…and I like it. LH351D 5000K. (Sorry, I’m not much of a photographer.)


Just an FYI. This light will not work with Energizer Ultimate Lithium primaries. I have run it with Duraleaks and E-gizer NIMH with no issue, and keep it loaded with Vapcell Golds (3A). I’m sure somebody more knowledgeable about this type of driver would have an explanation as to why. I’m guessing has something to do with voltages (?) as the alky’s meter 1.52V, and the lithiums measure 1.81V.
Kinda disappointing, as I like to keep lithium primaries in my stash lights.

That’s a pretty big issue. A light like this is PERFECT for leaving stashed in a car or something with lithium primary cells. I thought about buying one for that purpose but not now.

It’s probably the LVP. The higher starting voltage of the lithium primary cells probably makes the light think it’s running on two dead 14500s and it triggers the LVP.

The cutoff voltage for the LVP needs to be tweaked I guess.

Good point, I didn’t think about the LVP. I wonder what the cut-off is on the low side. Maybe a couple of “gently used” cells might sneak in below the radar (although that kinda defeats the purpose).

When the input voltage is 4-6V, T4 will stop working.

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.


Is there only 4-6V trigger for LVP? What about the Ni-MH? Won't it just drain them to 0V
And 4-6V LVP should not trigger for lithium, as one battery is below 2V, is it really 4V floor for LVP?
Can somebody test LVP with external lab power supply on the T4?
Ps. Oh no. Now I see myself buying external lab power supply, just to test LVP in my flashlights.
Pps. I also wanted to have T4 with lithium AA in it, now I will wait.

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 :stuck_out_tongue:

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



Ok, just read on the web page

"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.

r/flashlight T4 thread comment re: lithium primaries

Just the quote if you prefer not to link:

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.

1 Thank

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.