This is the last in my bunch of Vapcells. I’ve held it til now because it’s a mix of most and least interesting…. First off it’s an IFR chemistry, which means it needs special charging. Secondly it has massive current capabilities. Read on for some testing!
As always, click for bigger images!!!
These are $7.99 at Liionwholesale.com.
An interesting cell, capable of massive currents for short times. I’d probably skip it just so I didn’t have to worry about charging it incorrectly.
These ship in Vapcells zipper pouch. The individual cells also have a plastic wrapper.
These IFR (LiFePO4) cells are wrapped in a red Vapcell wrapper. It’s a nice wrapper.
The top is a four prong terminal.
Officially: 26.6mm x 65.1mm
I found these to be slightly thicker than normal 26650 cells.
I’ve tried to keep the scales similar, so over time the charts will be generally comparable. Of course since these are IFR cells, and the charge characteristics are different, this is basically a one-off with different scaling. IFR cells shouldn’t be charged over 3.6V. In my testing I charged to only 3.5V, since I found 3.6V or higher cells just dropped off so quickly anyway, that the extra bolus of energy was more or less meaningless. Also these can be discharged a little more deeply – I discharged to 2.0V, but I think they can handle even lower. Not that it’d matter – below around 3.1V the capacity has basically bottomed out anyway (see the graphs!).
These cells don’t last long at even 20A (rated to 55A), but the temperature stays fantastically low.
Basically after 2.9V, the capacity nosedives. Not much point in even going to 2.0V, much less any lower.
It almost seems like these cells perform better at high current than mid current – bounce is lower at 20A for example, than 10A.
“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!
I use one of maybe 4 chargers mainly at home. The SkyRC MC3000 of course handles LiFePO4 fine. But also does the Nitecore UMS4, but you’ll need to select the LiFePO4 setting manually. I’m sure many other chargers handle this type cell just fine, too.
My “B” cell temp data was very suspect so I’m just going with the A cell only. The temperature at 20A just barely even blips up. And in a 10 minute discharge, there’s plenty of time to get heat out of the cell. So this is a great temperature result.
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.
These are great cells for high current devices. I don’t know if I’d recommend them for flashlights since you’ll need to take special care to charge them correctly, however. But if you just need a cell that can churn out the current, then this is a good choice. Unfortunately the capacity is only 2600mAh, but that’s the price you pay for such high current.
A further problem with using this in a flashlight is that at the fully charged voltage, many lights will already see this as “stepdown voltage” and not output their highest values, despite the cell being able to dispense high current at this voltage. So these will work in lights, but will work best in only specific lights (that is lights attempting to hit a certain wattage instead of only relying on cell voltage as a guide.)
- These cells were provided by Vapcell 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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