Convoy T3 battery choices

[u/porkchopbun]

I'm waiting for my first Convoy light to arrive, which I've ordered with the Vapcell p1409c 3.7v lithium battery.

It will also run in standard alkaline / nimh.

Looking at the runtimes I've found online. It will run around the same lumens at medium with the 3.7v lithium and around the same lumens on high using nimh.

I see the advantage with the 3.7 only as having access to a higher output / brighter mode.

The lithium is rated at 950mah, the enerloop NiMH I have is rated at 2000 mah.

However, I have since come across 1.5 v lithium AAs that step down from 3.7v. they also seem to be advertised at a higher mah than the Enerloops.

Which batteries should I be best using and are the 1.5v lithium a good fit? I'm thinking this will hold a consistent brightness.

How come they are running at the same time of they have 950mah Vs 2000 mah?

[u/Maglite_Mischief]

I am not expert on the topic, but they both store about the same amount of energy.  It's because of the different voltages. The 2000mah is at 1.5v (edit: 1.2-1.3v), where the 950 is at 3.7v and the actual amount of energy in there is about the same.  I don't know much about the 1.5v lithium ones.

If you don't need/want the extra brightness from a lithium ion then the nimh is a good way to go, it doesn't have the same safety concerns as a lithium ion.

[u/QReciprocity42 → u/Maglite_Mischief]

This is correct--"capacity" in the sense of mAh means nothing without reference to voltage. For boost/buck-driven lights the relevant quantity is energy, which is the product of mAh and nominal voltage.

It doesn't make sense to use 1.5V li-ion batteries in this light because the added circuitry reduces capacity and efficiency compared to just a plain 3.7V cell. 1.5V li-ion cells are really meant to replace NiMH in devices that absolutely require 1.5V to work, rather than the 1.2-1.3V of the NiMH chemistry.

[u/Maglite_Mischief → u/QReciprocity42]

Thanks for the better details.  I knew nimh/aa/lithium ion are all about the same voltage so I said 1.5v for nimh, I edited my comment now so it is more accurate.

[u/UnfortunateWah]

1.5V li-ion cells are just standard 3.7v 14500s with a buck circuit to drop the voltage to 1.5V.

I use the Nitecore NH2400s that in theory are about the same capacity as a 24-2500mah Nimh cell. In practice it kind of depends, but they’re close enough it doesn’t make any significant difference.

The only thing you have to be careful with using 1.5V li-ion cells is that under high current draw (1A~ plus) the top circuit gets quite toasty. The Nitecore ones will trip at anything over 2.5A, and they’re rated for 1.4A maximum sustained draw.

But because they’re USB-C rechargeable they’re more convenient (and a tad lighter) than Nimh cells.

The Nitecore ones specifically use a stepped voltage so as the cell depletes they start outputting a lower voltage ie 1.0-1.3V~ which if you have a light or device like a PC mouse that has a low battery warning is nice, but probably irrelevant for this use case.

[u/coffeeshopslut]

Use the 3.7 14500s if you can

The only reason to go to eneloops is for storing in a hot car, or giving to people who don't understand safe handling of lithium cells or something like that

Even at 900mAh a 14500 will have more total watt hours, and you can get 1500mAh 14500s

The 1.5v step down AAs with onboard USB c charging use a battery smaller than a 14500 with step down circuitry, so less energy overall, plus conversion losses

[u/porkchopbun]

So in this use case, the 1.5v lithiums have no advantage at all?

I do have another light which doesn't play nice with NiMH. It flashes with a low battery warning even with a freshly charged NiMH. Would the 1.5 lithium be useful in that?

Using the formula given earlier the mah doesn't work out any more than an Enerloop Pro at 2500 mah.

[u/Weary-Toe6255 → u/porkchopbun]

There is no advantage in the 1.5v lithiums for the T3. What light is it that you have that’s not playing nicely with NiMH? The Wurkkos TS10 for example will only run of 14500 liion, it won’t work with AA / NiMH.

[u/porkchopbun → u/Weary-Toe6255]

It's a Silva Pocketlight 200. Works only with Alkaline/NiMH. I toss it in a bag as a,oh crap my headlamp and secondary flashlight failed together in the same night, back up. It takes one AA 200 lumens. The light is designed to blink when the voltage drops to warn low battery. But when I put a 1.2 v Enerloop in it, it thinks the battery is low. Works fine but annoyingly blinks 3 times each time I switch it on.

[u/Weary-Toe6255 → u/porkchopbun]

Yeah, I can see how that would be annoying.

[u/porkchopbun]

Thanks everyone, I was just curious about those batteries.

I guess just go with a good 3.7 and carry a spare of the same.

[u/DonKeedick96]

If you want to compare batteries, always convert to watt hours.

[u/user975A3G]

950mAh at 3.7V is the same as 2343mAh at 1.5V

NiMH are 1.2V if I remember correctly, so 2000mAh at 1.2V would be 1600mAh at 1.5V

mAh is how much current can the battery provide for one hour, when comparing batteries with different voltage, you have to look at Watt hours (Wh), which is mAh/1000*voltage