I was too fast to complain abut Xtar, I already had a box from them and it contained some 18650 batteries for test (No 21700).
Hoping we could request Xtar to send you their other Xtar batteries (in pairs) so we have an idea how they perform.
So far, I can only order Xtar batteries only if the item has an option to include batteries. And I have ordered a few 14500 (Xtar 800mAh 14500 flat-top) and Xtar 4500mAh 21700. When I ordered Xtar powerbank with 18650 batteries, they didn’t include Xtar-branded 18650s but instead gave (genuine) Samsung 30Q 18650s) — it was not specified what kind of 18650 to be included with the Xtar powerbank when I made the order…).
So right now I’m interested to know how Xtar batteries perform (in particular, I’m getting low AC IR for the Xtar 4200mAh 21700, and they’re about 1mm shorter than other 21700 batteries — making these Xtar 21700 batteries fit properly on the earlier Fireflies PL47 and Fireflies E07 which will dent other longer batteries like the Liitokala Lii-40A 4000mAh 21700 battery due to these batteries being a bit longer)…
Interesting. This leads me to think Xtar is rewrapping Samsung 30Q cells. On the other hand, unless that powerbank uses very few cells and has a pretty high output power (super unlikely), there is no reason for it to use high power cells. I would keep the 30Q cells to feed power hungry flashlights, and employ some inexpensive energy cells in the powerbank. Check out some BAK 18650-34Ts in disguise. 
Sat, 05/02/2020 - 06:23
Hello! :-)
I just found some new, interesting 26700 LiFePO4 cells:
That is the highest capacity and energy density I've ever seen in LiFePO4 chemistry. Edit.- Well, not exactly as (for example) PLB has some 3800mAh rated 26650 LiFePO4 cells. But quite close.
Some inexpensive seller sale links:
- https://www.aliexpress.com/item/4000960602035.html
- https://www.aliexpress.com/item/4000985822509.html
- https://www.aliexpress.com/item/4000938643753.html According to the banner this will be cheapest for a few cents in a few days.
Thu, 06/11/2020 - 22:35
Hello!
This is just to ask if someone else besides me would like to see the new LiitoKala 26700 4000mAh LiFePO4 cells reviewed. I could send Henrik a couple of the above cells for just under €6 (got a €0.83 coupon), and I was wondering whether someone else would send me a small donation to share the costs, like €3 from one source or €4 total from two persons.
So say something while I ask Henrik if he is willing to make such review. Thanks. :)
Vapcell now offers 26350 cells. They are 2000 mAh like the generic ones and 6A doesn’t suggest that they are any different but maybe?
Would be nice to see them tested. 
http://www.vapcelltech.com/index.php/List/index/cid/99.html
HKJ - firstly, thank you for your reviews, which make you an international treasure IMHO.
Is there any chance of reviewing Soshine’s (new?) batteries with built-in USB ports? I have recently purchased them in 26650/5500, 18650/3600, 18650/2600 and 14500/700 sizes, and it would be wonderful to learn just how good (or bad) they are.
A link to where I can get them would be nice.
Ah, yes. Well I’m in the colonies (South Africa) and I bought them from a local distributor here, so I’m not sure how useful that is to you? I’ll PM you a link, in case it’s of any use to you…
Probably not very useful. If he will sell to me, it will cost a fortune in shipping.
How is your queue looking these days for li-ion cells?
Very low, that is one of the reason I publish very slowly.
But a manufacturer/rewrapper has promised me a large pack of cells (More than 15 types) for testing.
I figured/hoped that was the reason. I know you won’t be doing this forever, but I hope it’ll still be for a while yet. You’ve created the best open source battery database in the world. I’m so grateful!
I’m interested in seeing the latest 21700 offerings that achieve higher discharge rates and achieve close to 5Ah. Vapcell G48 is interesting. I’m hoping for a true 15A (stays below 70°C), 5Ah cell.
Also, I just purchased some cheap ‘HiQuick’ AAA NiMH cells in Amazon with a Vipon code (about 5USD for 8pk). Not sure if they are available affordably to your country or not. Interested how they stack up. I’ll try and test them myself when I get a chance, but you may want to test them too. I’ll send two for the price of shipping if you like. Pm me if that interests you.
I will probably continue my reviews years yet, but I also have other interest.
One of my interest it making test equipment and I have made some recently to make my testing easier and more automatic. And also some just to add some small improvements. A lot of this will be published on my website in the “project” category and some of it will also be published here.
My main project the last ½year has been to make a new program to control my testing, I will probably not use it for battery testing, because my current solution mostly works. It will be used for USB-C chargers (Together with some hardware I have made) to make it much easier for me to do the testing.
Hi HKJ;
As many of us buy Sofirn lights with the included battery, could it be possible to test some of them. Your site has the 14500 / 900 mAh cell only.
I’d think Sofirn would oblige in sending you some samples.
Thanks…
Hello Henrik,
Looks like your site suffered some sort of mess up with your latest battery review, the Samsung 50G one. First and foremost, the link to it in the main page got a big picture of the cells attached to the review name, making the cell “the star of the show”:
In second place, certain graphs in the review are “out of scale”. …
Everything fixed.
Just to point this out. 
Wed, 10/14/2020 - 16:32
Hopefully fixed now, but it may be an hour before the website is fully up to date.
The new Vapcell T50 21700 battery looks interesting. Some here have said it contains a Samsung INR21700-50S cell.
Have they sent you samples to test?
I do not know if they have send me any, but I have not received any.
Could you test Sofirn’s batteries?
Sure would be nice to know their actual capacity and current capacity.