Again, the Manker U21 specs were basically copy/pasted, so I'd expect what I posted in post #48, assuming they copy/pasted the light .
The 1,345 lumens I measured was at 30 secs in my NIST calibrated PVC light box (ok - PVC light boxes can't be NIST calibrated, but would be nice). I'm pretty confident my PVC light box is in the ballpark from testing 100's of lights in it. The lower modes though are quite a bit off in what I measured.
It sounds like 3 of 3 received so far are doing much lower in amps, much lower in output, so....
It's an electronic switch light with no power tail switch - if you did try the 2 cells, you will give the driver board 8V unless you physically block one end of the cells - tape or something. Hhmm - if you had a 26700 cell to try, but think two 26350's are a little longer.
I have a U21 and do have 26700 cells, and 26350 cells.
I really don’t get y’all, hung up on watts. Watts is an after the fact measurement of amperage and voltage. Watts is misleading, as you can get more lumens with less watts, look at Cree’s Product Configuration tool.
You don’t feed watts to the emitter, you feed amperage (current) at the voltage it will accept. Wattage shows it’s efficiency. Like statistics on a football game, a team can blow away the other team in statistics but lose by a big points spread. It’s the same way with the emitters making lumens. Voltage and current produce lumens, watts is a statistic of how efficiently it’s doing so.
Yes but we know how many lumens are produced by a certain wattage according to the data sheets. Efficiency is correlates to the flux bins given. So they all matter equally the same.
When the emitter is placed into a light and fed by a driver the numbers on the data sheet only show best case scenario. So if a light is using a certain number of watts measured at the tail we can assume only that the light is producing less light than data sheet. It cannot produce more.
So… this light is underperforming. Not a big deal, but there is no other way to spin the data. All that said, we need someone to measure the actual light output:)
Not true.
I can be if someone doesn’t understand wat it means and how to use it (not saying you don’t know it btw ).
10 Watts = 10 Watts.
10 volt x 1 amp = 10 watt, 1 volt x 10 amp = 10 watt.
If a emitter is doing 100L/W then you’ll get 1000 lumens. (10x100)
It doesn’t matter if the emitter is a xpl or xhp35. Lets assume they are both doing 100L/W.
Xpl: 3 volt x 3.33 amp = 10 watt x 100 lumens = 1000 lumens.
Xhp35: 12 volt x 0.83 amp = 10 watt x 100 lumens = 1000 lumens.
Point is, without knowing and using those other numbers watt doesn’t say a lot. (for example the lumens/watt efficiency)
But with all those numbers it says everything.
In one thing you are completely right, current is what matters to us. It says a lot about how a led performs, but that’s because we know our leds. (meaning we know what to expect and what it can handle)
I see people that read spec sheets and don’t build lights.
For example, what do your sheets say about an XHP-35 at 4.5Amps?
What do the spec sheets say about an MT-G2 at 16Amps?
Or an XP-L W2 2B at 6.67Amps?
your wattage per lumen figure is going to vary according to the current you’re pushing, so you don’t have a fixed number to work with. Just like the amperage is going to change as the cell dies, and the forward voltage will fall. All you really have is a voltage reading and current reading, everything else is playing the numbers. And the numbers are not nice. What’s the board temperature? The cell temperature? Where’s the constant? There’s not one.
Yes, all these things you mention are not constants. They are variables. Variables make up equations that can be calculated. That is all we are trying to do. With the data reported thus far and as I calculated earlier, this light will not reach 1000 lumens. But we will wait to see. Hoping I’m wrong.
Giorgio, could you please downsize the pictures in your review?
Those huge sizes are quite pointless, they’re not even sharp enough for that many pixels.
Thanks.
O uhm… Nice light! Looks good. :+1:
But 1300 LM can be obtained with an XP-L too and then you don’t need a boost driver…