One more Vapcell! (Actually I still have a few in the wings.) Today it’s the G20, another 18650. Sort of lowish capacity, mid to high discharge…. Let’s see how it looks in testing!
As always, click for bigger images!!!
I’m seeing these for $10.99 at aliexpress.
This is a spec-meeting cell. No complaints. Capacity is low enough you’ll probably want to purchase the G20 for its discharge capability.
It’s an unprotected flat top 18650, so the dimensions are within a margin of error of 18mm x 65mm.
I’ve tried to keep the scales similar, so over time the charts will be generally comparable.
“Bounce back” is what the cell voltage does when the cell rests after a discharge. After heavy discharge rates, the cell voltage bounces back higher when discharge is stopped. 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 voltage (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.
Here is why I think it so interesting about “Bounce.” A poorly performing cell will bounce back higher after high discharges. That’s because the IR is higher, and because the cell performs much worse under high loads. So a good performing cell will bounce back much less because it’s much more capable of high discharge. At high discharge on a capable cell, more of the energy makes its way out of the cell! Hence less bounce.
I more or less figured this out on my own, so I welcome discourse about this topic. Until I hear it’s wrong, I propose this as a new metric for cell quality!
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.
Good cell with moderate capacity and good discharge. Kind of expensive for the specs, though.
- These cells were provided by Vapcell for review. I was not paid to write this review.
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