Battery for MG-X throwerXM-L 850+ lumen?

Hi,
I recently purchased MGX thrower 850+ lumen flashlight.
What battery would be better for this flashlight.
1x18650 OR 1x17670, OR 2xCR123A

Also What run time would i be looking at if i get 4000mah 18650 vs 2400mah running the flashlight in 1000mA medium mode.

thanks

There are no 4Ah 18650 batteries, so whoever is selling that is lying to you. The highest capacity 18650 battery that I've seen is a 3.4Ah battery, and there might be some 3.6 Ah batteries, but those are special bulk order. These batteries are usually $15-20 each depending on who sells it and if they have protection or not. Personally, I've been getting rid of my cheap 18650 batteries and bought some better ones now (Keeppower). AW, Eagletac, Pila, and some more are also good brands to look out for, check the electronics and batteries section for more.

The 17670 is a smaller Li-ion battery then the 18650, so it will give less runtime and probably similar output.

As for output, I'm not sure if 1x Li-ion battery is enough, or if 2x CR123s gives you more output.

As for runtime, it is easy to calculate. Assuming we have a 2.4 Ah 18650 battery, the battery's capacity is:
3.7V X 2.4 Ah = 8.88 Wh.

The LED is consuming:
3V X 1 A = 3 W (3V @ 1A from Cree's data sheet)

Assuming the driver is 85% efficient
3W / 0.85 = 3.53 W total power to both the LED and driver

Now we get to runtime:
8.88 Wh battery / 3.53 W draw = 2.5 hours runtime.

2x CR123 = 2 * (3V * 1.5 Ah) = 9 Wh

Actual runtime will differ depending on driver efficiency and voltage characteristics, as well as the battery's characteristics.

wow.....so much knowledge in such a simple to understand manner....

I am humbled

Good and simple explanation Gunner12. And this kind of comparison sometimes is valid only in theory, the Li-ion battery often outperforms CR123 in runtime despite similar total energy because of the lower internal resistance, that's one of the things you are telling in the last section?

Yeah, the battery's internal resistance isn't factored in since that changes depending on the charge of the battery and means more equations.

If you really want to be accurate, you could also factor in the AC characteristics of the battery (since the driver might not be continuously drawing power from the battery). The driver's efficiency probably also differs depending on the input voltage, they are usually more efficient if the input voltage is close to the output voltage. At that point, it might be easier just to plug in the battery, and do a runtime test

Lighthound has AW's batteries, you could also get them from AW in the CPFMarketplace. The other ones, I've seem then on sale on eBay, but only buy from trusted store, and there are also other stores online like hkequipment that seem ok.

Some year ago I entered into the Li-ion area. First I got a few 14500s, these I got especially for my Xeno E03 lights. For these I got a 4Sevens single bay smart charger. Some month ago I ordered my first 18650s and 17670s as well, and included a Pila IBC charger in the order.
Some lights who can't use 18650 can use 17670 and that's good. Actually the information about this fact could be better among the dealers.
All my 14500s and 17670s are AW brand. The 18650s are EagleTac and AmpMax. I order my Li-ion cells from UK.