Yezl Y3 - a picture breakdown

Mine are roughly 80mm from end to end. Came from the CNQ group buy.

My Y3 and 2 exts, all from GearBest, can run on 2 TF 26650 flames, but can't run on 3 TF 26650 flames. With each tube/cell added, the cell sticks out a little more at the end. It's about 2.5mm sticking out with 2 cells, and about 4mm with 3 cells.

I think yes. 66mm length is ok. Two of those is 132. Two of my battery is 142. That’s about how much the light wouldn’t close completely.

I only checked one of mine, but it seems to be the same size as yours. I will get some 26700’s soon and see what happens.

Thick orings work to fit protected batteries in. Act as spacers. Found a bunch at the dollar store

Yep mine is too, but measuring thread to thread it’s 67.5mm which is the dimensions that count. Given that, any batteries longer cause issues

Just got mine today and it is only 2.05 amps at the tail with one cell and 1.3 on 2s and .9 on 3s.

Based on my experience, that’s about right. Should be roughly 2.5A to the emitter on high with the stock driver with two or three cells. Voltage drop on one cell as measured with a DMM should be slightly lower.

Post #77 here: https://budgetlightforum.com/t/-/24076, I tested with various cells, all in the 2.45 to 2.52A range - bought from WallBuys. Are you sure you got a good DMM setup?

I just re-tested my latest Y3 from the GearBest group buy and measured 2.50A on one TF 26650 flame, and 1.25A on two TF 26650 flames. Are you using heavy DMM leads? The amp tail readings have been very consistent like this across all 5 Yezl Y3's I've gotten: 3 from WallBuys, 1 from CNQ, 1 from GearBest.

Again, the only reliable DMM setup is one with heavy wire custom made leads.

I bought mine from GearBest. I have 12 ga. custom leads. My modded s8 measures 3.74 amps with the same meter. I have measured up to 5 amps with this meter. No wait thats not right, i have measured up to 7 amps with this meter.

I shorted the the r150 resistor and it only measured 2.63 amps on one cell, then i put 2 cells in and it blew the led.

Didnt you measure way over 3 amps with one cell after adding a r100 resistor in parallel?

Post #132 earlier is my R100 results, yes. However, looks like my R100 modified driver died one overnight - no idea what's wrong.

- not sure what's goin on with the one cell configuration there with yours. If it's true 2.05A stock, it's quite different from my 5 pieces and most others

- Yes - shorted resistors using a true buck driver is highly risky - not surprised you blew the LED.

Ok thanks Tom!

Im not sure whats wrong either, but thats about my luck to get something different. I knew it would be risky on 2s, but i had to see since the measured amps on 1s was so low.

Unfortunately i dont have any R resistors at the moment in my stockpile of parts.

Hhmm - my R100 resistor modded driver is now working - problem was it would come up in lo mode and mode changing didn't work. Looks like something flaky in the switch. I was able to get 3.36A measured, but that was on the bench with longer wires, etc. Not sure yet if it's worthwhile re-using it - I don't have a replacement switch solution because it's mounted on the PCB. Think guys have linked replacement PCB mounted switch's - dunno where.

I had took the r150 resistor off and i lost it, but i found two r130 resistors and and soldered both on and now getting 3 amps on 1s and 2.53 amps on 2s. I had a dedomed xm-l2 that i put on.

To help you better understand what happened, think of shorting the sense resistor as putting the driver into DD. Because that’s what happened. Never short sense resistors.

EDIT: Based on your initial results and your modded results, your driver is (and was) operating just fine on 2s. Working on 1s is a pretty tricky situation for a buck driver like this, your driver was (and is) clearly failing to do that 100% properly. The QX9920 is uncommon in it’s ability to work on 1s - most buck controllers just can’t do it. It sounds like you got some bad luck with your driver (assuming your cells are fine). Normally I might suspect that the LED might have an unusually high Vf, but you’ve already had to replace the LED and are still seeing the same problem. I don’t know exactly where the issue might be, but checking the driver for any components that do not look exactly like Tom E’s pics would be a start.

With them shorted it wasnt DD with 1s. Maybe with 2s. With it shorted it was only 2.63 amps on 1s. That was with the other led though.

I guess im happy with the 3 amps on 1s and 2.53 on 2s, it is 1.53 on 3s. I am not happy with the dedomed led, even though the kcd is alot higher, the beam is to narrow for me, so i will get a new led soon or maybe a mt-g2.

How does the mt-g2 compare to the xm-l2 in this light Tom?

DD in the sense that it applies the full battery voltage to the LED. There may have been some pulses of off mixed in there, but I think it’s very fair to say that the LED saw long pulses of the battery voltage. There’s also the inductor providing a little resistance. The controller will attempt to get it’s sense voltage to go up and be unable to since you shorted the resistor which generates the sense voltage. It’s not actually the same thing as a DD driver, but it is a direct connection between the LED and the battery [via the inductor]. TLDR: don’t do it.

Well the MT-G2 turns the beam into more like a good 3 LED light, but the tint and general profile of the beam, to me, is the classic MT-G2 everyone raves about - nice tint, nice single emitter pattern, etc. I measured throw at 43.5 kcd in my 2,329 OTF lumens, 4.6A setup. I would think is the ballpark for being in a thrower host, but could be better because I know the lumens is low and the reflector is rattling - not tweaked to fit well and focused.

FWIW aw73 you may run into the same problems w/ an MT-G2 on 2s that you ran into with an XM-L2 on 1s. You might not too, I sure don’t know. Sounds like you’ve got enough extensions to deal with that anyway.