Hasn’t been mentioned here yet, one of the best in class Ampace JP40, another tabless cell design like the 40PL, can outperform both the 40PL and P50B depending on needs.
This turned up on my radar after joining @Battery_Mooch patreon (Everyone should join right now! Not telling you what to do but yeah, do it). Saw the 40A and 100A discharge graphs compared to the P50B and 40PL and hoooly shit. Given a choice I would be building a new pack with this for sure, it’s also cheaper than the 40PL.
The title is kind of clickbait, 140a rating is at max 5 second pulses only.
E-score at 40A continuous (in W/hr, best to worst)
Would you say that either of these cells would give you a noticeable performance boost in say a 18s4/5/6p configuration over a P45B?
Are they really worth it for high performance boards or racers?
Well it really depends on how high performance we are talking and how many cells you want to fit.
The highest power compact vesc that’s available (so not counting little focers, tronics, etc) is the makerx D100S, which can do 200 motor amps and 100 battery amps per motor at 21S. To put down all the power you can you want 4wd, I prefer around a 25-75% power distribution at least for the low end.
So that would give about 266A battery current at 21S with 25-75% power distribution that I would ideally like to get from a 4P pack. Before voltage sag that’s about 88V * 266A = 23400W. And at 4P that would be 67A per cell. If we count voltage sag into it and maybe not full SOC to start the race, that’s probably around the 18kW range. Which I think is definitely getting into the territory where these super-cells make sense.
I don’t think there’s many people who are at the skill level at the moment to push 18kW, but for those who are these cells make sense. I am pushing 13kW at the moment from a 21S4P P42A cells and regen braking 13kW as well… Sag is atrocious. And I want to push more power and braking for high speed. I do plan to rebuild my racer’s battery to one of these new super high power cells in the future, probably next spring.
That said, if you can fit a 21S6P battery pack, you could probably get by with P45B for this power level. Or P42A even if you are fine with quite bad sag.
And currently the most common power level for a raceboard is 12-13kW.
This is only a fraction of the story though, different cells will have different discharge characteristics, different cell temperatures and different cutoffs. The 40PL is overtaken by the JP40 at the roughly 7 second mark (at 40A) and maintains a higher voltage for the remainder of the discharge. That’s why it’s best to look at the graphs and decide for yourself based on your own needs.
For the cheaper end of the spectrum I mean, P42A are still used sometimes so now lower capacity and more price won’t be putting off the molicel fan boys.
Also another useful case for these super high power cells is pushing a ton of power out from small battery packs. For example for a mountainboard built for jumping the weight savings would make a ton of sense. I am planning my mostly lightweight mountainboard build at the moment.
It’s going to be 21S, 1:7 gearing, 6375 reacher motors, D100S. I want to put down a ton of torque and power. But to keep the board lightweight, I’m going to be running a 1P battery pack, that’s about 1.5kg weight saving from 2P.
So I’ve got 21 cells to get as much power as possible. Mooch’s really interesting patreon only testing for the 40PL vs JP40 vs P50B shows that it’s possible to use these new cells at insane current levels***. I am probably going to be aiming for 100A. Not sure which cell I am going for yet, at the moment I am considering getting a 40PL and a P50B and do some of my own testing to see which does better pulses.
At 100A I can expect about 280-300W per cell, 21S that’s about 6kW max, yes sag is going to be atrocious. From a 1P pack 6kW is absolutely crazy though!!!
***However, asking 100A from a single P group is really dangerous, and you really have to know what you are doing, monitor temperatures constantly, spec series connections accordingly, to not light shit up on fire. And if my own testing of the cells doesn’t go as expected adjust specs lower. It’s probably going to be my most challenging battery build up to date, and I do not recommend others to copy. But I am very interested to see if finally it’s possible to forget lipo for such requirements.
Arc-welding of any kind (tig, it looks like in this pic) on liion round cells is incredibly dangerous. There are professional machines which can do this safely, but that does not look like he’s using one. The chances of blowing through the cell can is very high with this welding method. It can result in a damaged or dangerous pack, even if it appears fine coming off the builder’s bench.
There are much safer and easier ways to get copper series connections on a pack.
Not to mention that this builder doesn’t seem to bother with fishpaper rings on the positive cell terminals, which is its own kind of danger.
Looks like that builder did not avoid the center of the cells when spot welding, and without a nickle cap, he must be using huge welding amps to get the copper to weld to the battery.
I did 0.1mm copper with a 0.1mm nickel plated steel cap, but 0.1 copper and 0.15 pure nickel cap, and my welder/weld battery were not powerful enough.
It’s possible to get nickel plated copper which can be spot welded by a regular kweld. That’s my plan but that material is hard to find. I’ve got a contact who said he can sell me some a month or so ago, just sent him a message to see if it’s still possible. Then I would stock up enough for my offroader’s 21S1P and racer’s 21S4P build.
