Photo credit: Jacob - @Movation
I have switched my "go-to" 18650 for esk8 batteries to the Molicel P26A. I'm going to stop blindly recommending the 30Q, and I wont be keeping them in stock anymore. Here's why I think you should too:
1. Real-world energy delivery VS “rated capacity”
Because simply looking at the Amp-hour rating of a cell gives an incomplete picture of how much range we will get out of our batteries.
(Figure 1 & Figure 2)
Delivered energy explanation and data
The capacity ratings that manufacturers give to their cells are measured at very, very low discharge currents (often well below 1A), and therefore are basically useless for our application where we often draw 10, 20, sometimes even 30 Amps per cell in our high-performance battery packs. Capacity measured in Amp-hours also doesn’t take into account voltage sag at high load, or how hot the cell gets, or how much it ages/reduces it’s cycle life when it is discharged in that way.
A much better way to compare the energy delivery of two different cells at a certain load is to look at how many watt-hours it can deliver down to a specific voltage. (For a more clear breakdown of what Watt-hours are, check out episode 5 of Mooch’s youtube series “Minding your mAhs” where he goes into this topic.)
See the ratings graphics that Mooch made for his tests of the 30Q and the P26A (Figures 1 & 2 above). Take note of the section circled in red. In this portion of the graphic we can see that the P26A actually delivers more Watt-hours than the 30Q at 10A of discharge down to 3.2V (which is pretty close to the default VESC tool discharge cutoff of 3.1V/cell) and delivers nearly the same Watt-hours at 20A discharge than the 30Q delivers at 15A!
What I conclude from the data in this section is that the P26A runs more efficiently and delivers more energy at the Amp levels that we see normally in an esk8.
2. Voltage sag and real-world performance
That’s true. Unlike a lot of other applications for lithium-ion cells, we dont draw constant current. Our current level varies depending on acceleration/hills/duty cycle/etc. So I asked @Battery_Mooch if he could simulate the load that a single cell in a high-performance DIY esk8 battery would see on an average ride.
Turns out, this is kind of a difficult question. What is an “average ride?” Average for who? What kind of riding? What terrain? Weight of rider? Etc.
I'll let Mooch take it away with the explanation of our test, and the data:
What we settled on was a discharge profile that I think approximates a rider who is pushing their board to the limits of their battery, which I feel is valuable because we oftentimes are looking to get the largest performance out of the smallest battery. And as we can see, the P26A runs longer, with more energy delivered, and stayed cooler. It also had less initial voltage sag.
3. Price/availability
As I am writing this in March of 2021, you may or may not have heard that there is a global shortage of many of the big-name lithium-ion cells.
This is due to three factors (that I have heard about, anyway).
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COVID-19. The pandemic (hello to anyone from the distant future who hopefully isn’t living this hell anymore) has caused global manufacturing disruptions in all kinds of markets, including in the battery market.
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Increasing demand for electric vehicles globally. The massive cell orders that EV makers are placing for cylinder cells is eating up the production capabilities of these cell manufacturers, leaving fewer cells to trickle down the market to hobbyists and small businesses like us.
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All of the round cells we buy from the big manufacturers are excess inventory sold on a “gray market” by customers of the big manufacturers, unauthorized sales, or diverted shipments. None of the round cells we use were ever meant to be used outside of a fully protected battery pack (looking at you, mech-mod vapers).
The big manufacturers (Samsung, LG, etc.) are working harder now to get their cells off the gray market because of all the lawsuits by people who set themselves on fire.
What this means is that the Samsung 30Q (as well as many other Samsung cells) are either not available, or only available for massively inflated prices. At the time of writing this, the only reputable cell supplier that I could find who has 30Q’s in stock wants $6.25/cell for 50 cells. That’s nearly double what the P26A is going for.
For my business, I need consistency in both price and availability. Samsung cells simply do not have that right now, and the situation seems to be getting worse, not better. There are several authorized/approved resellers of Molicel batteries in the USA (18650BatteryStore.com, LiionWholesale.com, etc.), meaning they have been able to keep their Molicel cells largely in stock and at a fair price, even through the height of this pandemic.
4. Conclusion:
The P26A performs slightly better than the 30Q in a simulated esk8 use-case, delivering more energy with less voltage sag and less heat generated in the cell. It is also rated for a higher discharge level than the 30Q, so a pack of the same size could theoretically provide more current safely than one make of 30Q’s. (For these tests, we looked at the two cells at the same discharge levels to keep the results consistent and comparable.)
The P26A’s are also cheaper and more easily available to US battery builders, meaning our packs can be cheaper and more accessible to builders of any budget!
That’s enough to convince me. I have just ordered a large stock of P26A’s and I will be making lots of batteries with them. I know several other battery builders such as @glyphiks have jumped on the P26A train as well. As more results come in, I will update this post so we can all see exactly how well these cells are doing across a range of different builds 
Disclaimer
This article is my opinions and interpretations of the data presented. My opinions do not necessarily reflect those of @Battery_Mooch or anyone else mentioned or quoted in this article.
