Been a while since a cell review, so what better time than today! This is the Sony/Murata VTC5D, a 2800mAh unprotected flat top 18650, capable of high drain. Read on for testing!
As always, click for bigger images!!!
These are $7.49 at LiionWholesale.com, with price breaks starting at 3 cells!
A very capable cell! I’m happy to have them in my rotation. Price is not so bad, too.
Individual cells ship in their own tiny box. Purchases of two or more cells from LiionWholesale.com also receive a plastic box for storage. The cells ship in the individual boxes.
These are high quality feel cells. I like the thin wrapper, but that’s entirely personal preference. In all ways, they’re exactly like a 18650 should be.
The positive terminal has the three prong build.
I measure the cells at 18.33mm in diameter, and 65.05mm in length (with the 0.05mm likely being the tape I use to prevent shorting my calipers.)
I’ve tried to keep the scales similar, so over time the charts will be generally comparable.
At 0.2A and even 0.5A, the cells meet their claimed 2800mAh rating.
These cells are rated up to 35A, and I test only up to 20A. What we’d expect to see is that the bounce at 20A is “fairly low” since the cell should be very capable at higher currents. And that’s what we see – even at 20A, the bounce back is fairly low.
“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.
I rate this as a very good cell. Excellent high drain capabilities, and reasonably high capacity, with mid range cost. A very good cell.
- These cells were provided by LiionWholesale.com for review. I was not paid to write this review.
- This content originally appeared at zeroair.org. Please visit there for the best experience!
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