As always, click for bigger images!!!

Official Specs


I got these directly from Vapcell, and I’m not even seeing them in stores yet.  Based on other similar cells by Vapcell, I’m going to guess these are aroun $12-15 each.

Short Review

A very good cell.  These seem to be a great performer at higher currents, and certainly to the place I tested them, at 20A.  Data would indicate they’re capable at currents higher than 20A.  

Long Review


These cells ship in one of these 2-up padded zipper pouches.  

And the cells themselves are wrapped in a plastic shrink wrap.  

Build Quality

Here are some closer shots of the cell.  

The wrapper is quite nice, both in quality and look.  The cells also have a QR code, and a scratch off proof of authenticity area.  


The size is dictated by the name of the cell:  21700.  21mm in diameter, and 70mm long.  The final “0” indicates this is a cylindrical cell.  I measure the cells at 21mm in diameter, and 69.8mm long.

The below image really just is included to demonstrate how much length a protection circuit adds to a protected 18650.  

These cells won’t fit in the Convoy S2+, but you all know how big those are!  (You have a Convoy S2+, right??)


I’ve tried to keep the scales similar, so over time the charts will be generally comparable.  Also if you ever wonder how long testing these cells take, have a look at the first chart and do some math.  Every cycle has a 1 hour wait between, and most there has to be a charge cycle between each discharge, too.  Testing cells takes…. a while…..  But I’m a data junkie, so this is fun.

Discharge tests




“Bounce back” is what the cell voltage does when the cell rests after a discharge. Interestingly, after heavy discharge rates, the cell bounces back higher.  This corresponds to a discharge amount of less energy, and does mean that there’s energy left in the cell.  So if I selected the cell with the highest bounce back (ie the cell that was discharged at the highest current), then discharged it to 2.8V at 0.2A, I’d still find that there was a lot of energy still in the cell. And I have finally figured out what I think it so interesting about “bounce.”  A poorly performing cell will bounce back higher on high discharges.  That’s because the IR is higher, and because the cell performs much worse under high loads.  So a good performing cell (like this one) will bounce back much less because it’s much more capable of high discharge.  And we can see that here.  This cell is capable well past the tested 20A, and so at 20A much more of the energy is used from the cell.  Hence less bounce.  I don’t really have anyone else telling me that, so I could be grossly wrong.  Or maybe I just proposed a new metric for cell quality.  ¯\_(ツ)_/¯

Charge Test

Temperature at High Currents

Power, Constant

Internal Resistance

Most often (read: always), internal resistance is mentioned as a spot value.  In truth, the IR changes over time.  Due to cell age and cell heat among other things.  A graph of IR is interesting because it can show, for example, when a cell begins to “die” – at which point the remaining energy will be “harder” to extract.  This is when the IR spikes.  In the graph below, that’s around 750-800mAh.  These graphs are also useful for determining if a cell would be good for a hot-rod flashlight, for example.  


This is a good cell.  In fact it’s so good I have to be careful to not use it in lights like the Fireflies E07 or PL47 – too much current capability!!  


  • These cells were provided by Vapcell for review. I was not paid to write this review.
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1 thought on “Vapcell 21700 Cell Review”

  1. Pingback: Astrolux FT03 Luminus SST40 Flashlight Review – ZeroAir Reviews

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