Their 5000 and 5500 might really be different batteries. The capacity I see most people measure is 4700. I’m guessing the 5000 battery must normally measure around 4700mah and the 5500 might normally measure around 5200mah.
Does it tell you internal resistance?
Yes, plus / minus 50
If I knew in advance that this battery is not so bad, I wouldn’t have ordered some Liitokala 5000mAh black…
They are pretty bad as far as high drains are concerned (according to Sofirn). About the same performance as a Panny B 3400mah 18650 cell.
Yes, I know… but I don’t care about high drain to get a higher brightness… I prefer capacity over high drain…
Perhaps I’ll change my mind once I tried the 5000mAh Liitokalas… 
I think Sofirns 26650 should work okay in the SP33. The most amperage I’ve seen the light draw is 5.8A.
It is the voltage sag I was worried about when using the Sofirn SP33 v2. High drain batteries always have less voltage sag which helps the “typical” boost driver have more Turbo run time. This particular boost driver seems a bit different.
I’m not sure if this driver looks at voltage sag or just the voltage when turned on. It’s an odd driver. I wish someone else would test it out.
It seems to loose Turbo right at a resting battery voltage of 3.70v.
Yes, this is also my observation. 3.7V (or a little bit less) is also the (rested) Voltage when the red LED kicks in. The (rested) Voltage when the red LED blinks is somewhere between 3.0x and 3.1V.
The red blinkings is also the only alert that kicks in during operation.
Overall I am quite satisfied with this LVP resp. low voltage warning…
No LVP shutoff?
Didn’t test it because even a blind man sees that the battery gets exhausted at around 3V… I try to avoid to torture my batteries… knowing that Sofirn LVP is not very reliable resp. often very late…
The specs says it does:
※ Low Voltage Protection: the light turns off automatically when the voltage was lower than around 2.6 Volts; The Turbo will be disabled autocratically when the voltage is lower than 3.4 volts; It steps down to lower modes automatically when the voltage is lower than 3 Volt
Good to know in case the light accidentally gets left on .
Today my Liitokalas 26650 5000mAh arrived. I am just testing the capacity. But what I can already tell at this point in time is, that the Liitokalas have much more ‘high drain’ character:
Charging the Sofirn to 4V with termination current OFF resulted in a rested Voltage of only 3.90V. Both of the Liitokalas go only down to 3.95V… a behaviour what typically high drain batteries show…
I received the SP33 yesterday. Fantastic light ! But mine has a problem. The @15lumen Eco Mode will not come on when the torch is cold. It just remains very very dim…about 1/100 lumen…The head has to be heated before it brightens up I’m thinking Driver Problem? I contacted Tracy at Sofirn…Hopefully Sofirn will make it right. 
. $hit Happens.
How cold?
room temperature…it’s not cold in South Texas
room temp now is 70F Heat from Turbo makes it work….but it still flickers…there is a problem
when I say cold….I mean at room temperature. When the light sits and cools off…the worse is on start up. Get it good and hot on turbo/high….Eco kicks in but it flickers.
That’s not good. It’s probably a defective temperature sensor thinking it’s too cold, so the boost driver functionality at ambient temperature is affected.
Basically, either request a replacement driver from Sofirn, or a replacement.
EZ choice…Ain’t no way I would attempt to replace anything in a glued together torch with electronic switch…I’m way past Prime for that sort of thing… Therefore, Replacement is only option.
I show how to pop out the driver in my thread. You just need to unsolder the led wires and tap it with a rod to break the glue. I was nervous about it at first, but now it’s not so hard.
Thanks Jason. But I will not tear down a new out of the box torch . Not worth the headach Besides, it’s too challenging for me nowdays. Nerves aren’t as steady as they once wre….sighhhh….never get older just get as old as you can… 
Hopefully, Sofirn will step up on this one.
I somehow missed this post...
When I first received the fire flashlight, I charged the new battery that comes with it, just to see how long it would last on maximum.
I realised this flaslight with the stock battery, will loose brightness using the maximum output. I believed it would step down to a lower intensity level, but actually seems to get weaker and weaker as the battery discharges Anyway, I guess this has to do with the flashlight and not the battery itself.