The A refers to the current (amperage) that the battery is rated to produce. In my example SD05, it doesn't pull more than 7.1 amps.
Perfect! Thank you very much.
Great review, Nachtfeuerzeug! 
Thank you xevious!
- which is exactly why putting a 40T or other super high current battery in the light is fine and all; but your not getting any more output from the light over the average high capacity 21700 (which run around 10 amps continuous… covering the light’s max draw by almost 3 amps).
So why not add capacity? I ALSO can confirm using my Molicel P42a in my IF25a from Sofirn that it gets hot VERY fast compared to the 50G (which does get as hot, but not as quickly). 
I’m sure there is a “smidgen” more output on the Molicel, but I really can’t see the difference when I light up the back pasture with both the IF25a and SD-05 using the 50G (actually a wrapped 50G called an “Epoch 5k” from 18650batterystore- great company I’ve been buying from this year- ALL authentic and everything disclosed re. their own wraps).
Sorry if I missed it, but are these using 3V or 6V variants of the 50.2? Has anyone pulled the driver?
EDIT: Found this post here
Seems to be 6V… at least that sample was.
The newer version use the 3 volt 50.2.
Thanks pennzy!
Wanting to go high CRI… 144 was my only good option at 6V. 3V opens a lot of doors.
Anybody have information about the new SD05 SST70, and how it compares to the XHP50.2?
(Other than what’s on Sofirn website.)
I would imagine any reviews or beamshots on the website are from the XPH50.2
Seems like they ran out of XHP50.2 and changed to SST70.
They say better throw, it would be nice to see a comparison.
Hey Deeuubee, That's interesting about the SST70. According to Djozz test, https://i.imgur.com/3YlpAhC.jpg
and if the driver doesn't push that Luminus more than 8 amps, it should be quite similar. Perhaps a throwier beam!
Nachtfeuerzeug - Thank you for all the information. It’s overwhelming sometimes trying to figure changes out.
I think I’m just gonna have to guinea pig it. 
I bet it is quite a bit of tighter beam. Wouldn’t be surprised if its nearly double the cd/lm.
What kind of driver did the old and new sd05 uses? Which one are more efficient? I want to buy them but cancelled buying since I don’t know what other difference they made to the light.
The old was regulated and the new is not . Old emitter was 6 v and new is 3 v. There are differing opinions as to which is better. I have the new and the one good thing is it does not have a timed stepdown, only thermal stepdown. This could be a huge difference in actual use, especially in water.
The new one using fet driver?
And I guess the new one have pwm?
Yes, FET driver. I can’t see pwm but I am not sensitive to it.
Pretty sure yes to both (fet/pwm). With that said, this is one of my favorite winter outdoor 21700 lights (in the rev2 with the XHP-50.2; no step down). It THROWS for it’s size and doesn’t heat up as fast as my IF25a. Beam isn’t too bad color-wise either.
I WAS going to do an actual diving review for the (XHP 50.2) SD-05 last August for Sofirn, but Covid “effed” those plans up. We tried again for this X-mas in Cozumel and had to cancel again when Covid got “hot” again this fall.
I have an old SD-02 that worked well for a night dive taken back a few years ago. What was cool is our dive-master was using a small dive light to “strobe” so our group didn’t get mixed up with several other groups on the same reef that night. This was the FIRST time I though of a strobe being VERY useful.
Time will tell on the SST70 and I do hope it’s not too narrow in output. I typically “hang” a few feet off the coral and like turning under for cave or shelf views from between 3 ft. away to 15 ft. I want a nice wide beam but some “punch” on high if I need to see further. From what I can tell on land so far- the SD-05 XHP-50.2 will do good when I get it down (one day) 
What I understand, the old 6V 50.2 is regulated.
The newer 50.2 3V is not regulated.
And the newest sst70 is not regulated.
Am I correct?
The SST70 is 6V which means they must be using the old driver
So the sst70 should probably be regulated?
Waiting for review of the new sd05 with sst70