Question #1:
Do you know any source on the internet where I can find beamshot comparisons? Because the XHP 70.2 version of the M21B just entered the market, I think there are no comparisons available, yet. Weerapat Kiatdumrong modded a M21B using a XHP 70.2, but his videos (I like them!) are not perfect to compare the XHP 50.2 to the 70.2.
Maybe there are some good beamshots comparing both LEDs in other flashlights while using the same kind of reflector.
Question #2
Am I right to assume the following?
Given the higher efficacy of the XHP 70.2 over the XHP 50.2, the 70.2 will put out higher lumens compared to the 50.2 when the ampere rate is the same.
When both LEDs produce 1000 lumens, the XHP 70.2 will consume less ampere than the XHP 50.2 resulting in longer battery life.
Question #3
Is there a difference in the heat being produced by both LEDs? Regarding point 2 of question #2, the XHP 70.2 should stay cooler while putting out the same amount of lumens compared to the XHP 50.2.
When both LEDs are powered with 5A or 6A, will the XHP 70.2 stay cooler or will it be as warm/hot as the XHP 50.2 but just put out more lumens?
Question #4
I read that the XHP 70.2 might be floodier compared to the XHP 50.2.
But given the higher efficacy of it, can it’s beam reach the same distance as a XHP 50.2 flashlight, because the lumens output is higher? Or will the higher output be absorbed by a more floody beam pattern so that the maximum beam distance is not farther compared to the XHP 50.2?
Mine with XHP70.2 is very floody. Lots of light to about 100 metres. There is really no hotspot, just flood. I have enlarged the reflector hole myself, so I can’t be sure if the production version has the same reflector. XHP50.2 version is quite similar but throws better.
On your question #2 yes to both. On question #3, the XHP70.2 will be cooler when driven to the same lumens as the XHP50.2. When both are driven to the same current both will produce the same amount of heat. The larger LED will bleed out the heat better with the larger base area. It might be slightly cooler, but your entire light will have about equal heat. On question #4 XHP70.2 will flood better and the XHP50.2 will throw better. When both are run at the drivers 5-6 amp max capacity the XHP50.2 will still throw better given those size reflectors.
The M21B XHP 50.2 I ordered runs with a 5A max driver. At least the product description says so. Does that mean, that 5A is the “output” and 3A is the “input” that will really run the LED? So my battery will provide 5A, but the LED can only convert 3A of it into light?
Wow. Can you clarify this, please? Does it mean that both versions will consume the same amout of power from the battery, but the XHP 70.2 can convert more of it into lumens? Or will the flashlight work longer while using a XHP 50.2?
Not exactly.
This is volage and curren over the LED. Over the battery Watss are same divade by driver efficiecy. Ususally 0.95.
Other topic to think. On 100% mode current over led is valid in some batery voltage range: 4.2V - here the nuber is unknown. Usually 3.8V.
No. LED voltage is not the same thing as battery voltage and because of that LED current is not the same thing as battery current.
See Ohm’s law.
Let’s assume the LED runs at 6V while lithium ion battery voltage is usually between 2.8-4.2V (nominal ~3.6-3.7V).
So if XHP50.2 runs at 6V and if the LED drive current is 3A than that is 18W of power.
P = V*I = 6V*3A = 18W
Now let’s say your battery voltage under 18W load is 4V then what is the battery current?
I = P/V = 18W/4V = 4.5A
There’s also efficiency to think about so the current the battery sees is higher than that but let’s not go there.
Now think what happens to the battery current when you discharge the battery by using the flashlight and it’s voltage drops but the power stays the same.
That means the XHP50.2 and XHP70.2 examples he mentioned run at different power levels.
If XHP50.2 6V 3A then that is 18W
If XHP70.2 6V 5A then that is 30W
Lumen output depends on the specific LED’s efficiency, how many lumens per watt.
At max output the XHP50.2 is roughly 130lm/W while the XHP70.2 is roughly 140lm/W.
Though do keep in mind that if you reduce the current then the efficiency goes up. How much depends on the specific LED.
While flashlight runtime mainly depends on the capacity of your battery and the power of the flashlight but there are more factors.
But with the above example of 18W XHP50.2 and 30W XHP70.2 with identical batteries the XHP70.2 flashlight will have shorter runtime at max output.
But if you run both flashlights at same output (lumens) level then the XHP70.2 will have slightly longer runtime because of the higher efficiency I mentioned.
This is a great thread. I just ordered an M21B with the XHP70.2 in the staight 4 mode at 5000k, from Simon last week. I have a few Sony VT6’s on order for it and see how it compares to my aging Eagtac G25C2. I was seeking a floodier all ’rounder and I believe it will fit the bill.
If I had the gear to do it, I would be happy to measure. If anyone is local to me (N. Jersey, USA) and has gear, and wants to measure it, feel free to IM and I would be happy to arrange such. Of course, that's once it arrives. Given the upcoming holidays, and shipping from China right now, that may not be until 2022. :(
