There is some great inovation that i am sure alot of you have already heard about.
Pioneered by the Teslamotors company in the 4680 cell, this new Lithium ion technology has trickled down to our beloved 21700 cell.
I thought it would be cool to have a thread to discuss these cells
I will start!
We made and 18s3p with EVE40PL cells
And used it in a 4wd Magnetic Mod
These EVE cells are so far the only cells available for this type of cell in the US from a reputable source, 18650batterystore.com
I am sure more kinds of cells from more sources will be available soon.
It seems the 18s3p is enough for about 12-13 miles of range on the 4wd and at Poastpace…which is a hard pace to keep up with…just as @MarioChacon…i digress.
I really see these sort of cells changing the future of our hobby and sport, and speaking for myself and my business we fully intend on using these not only in our boards in the near future, but hopefully for many custom batteries and builds for the community.
I saw a youtube video by an E-moto centric guy who claimed the machinery that produces tabless cells, can actually do so faster, than the machinery that produces tabbed cells, as it eliminates a step in the process.
If true, it would seem that most cylindrical cells would head in this direction, even if they are energy cells, and not power cells.
Perhaps those energy cells can then have slightly higher CDR’s.
The Ampace JP40’s are incredible (tabless) performers too but none of the widely trusted vendors carry it yet. This is (possibly) for multiple reasons…which won’t be discussed here.
What battery current did you run this pack at? I saw on your Instagram that you claimed 17kw but I find that difficult to believe as more than just a marketing thing, without some kind of temperature management. @Battery_Mooch rated those at 45a CDR I believe?
Keep in mind…these current draws IF they reach that high only go this high for a few seconds at a time, maybe less, this is not a continues use. ESK8 is a very pulsed application for batteries, especially the crazy high performing esk8s. @Battery_Mooch has done some very interesting high load testing of these cells, if you are subscribed to his patreon you can see the compeling results.
That’s kind of my point. Do you have logs for testing this in a board?
By your assumption, the limit on discharge duration is dependant on how someone rides and possibly the rest of their settings wherever a bottleneck may be. If there isn’t one, then the battery can sag into a cutout, putting aside battery safety. I don’t mean to be a negative Nancy but if you have no way to dictate the pulses or manage cell temp… It may not be wise to apply that practice to everyone.
i was way to focused on racing to record any logs, but once it gets back in, 2 weeks? i’ll try again with logging . i might be healed by then
but, anecdotally speaking, i’m happy with their performance. pullin to 40mph in 50ft or less , twice a lap, all weekend on a 3p, ending at 3.95+V per cell after each race is pretty good. i felt no drop in acceleration, and I’m not gentle with the throttle either
i also accidentally overcharged them to 4.34V per cell (don’t reattempt) and they were totally fine. i abused the beans out of em, i averaged 3A per cell charging no bms too.
it’ll be fun to see the group balance
I respect you and your riding/stats are impressive, but I’m just trying to point out a flaw to artem. You may not stress that pack anecdotally, whether due to your riding style, your weight (I think this is an important factor) or other reasons in the build. But I’ve noticed a trend in all these racing setups on this forum where people are happy to completely compromise safety and we should all be looking out for each other. Esk8 has enough failures as it is, and you and I both want more people to join in on the racing hey.
Trying to understand the fear here. Is the issue by having high settings that we don’t know how long we’re sustaining at certain current levels? Therefore without logging and some sort of management it might get out of hand?
But even if we had some sort of monitoring that would be more for after the fact no? You wouldn’t want it to stop supplying power if it was getting crazy. Same idea behind having brakes and abusing the battery, rather than the other way around.
Yeah the issue is you aren’t controlling the duration of battery current in pulses, you are just hoping that you won’t use the power that often or for that long. That kind of practice will definitely not apply to different loads, different riding styles and different board setups where the battery sag can cause cutouts sending you flying. I know this from personal testing when p42a became the standard and I remember saying the same things artem is saying now. I had to learn the hard way.
You would ideally want something that manages pulse time in seconds and allows time between pulses. RC cars do this. You’d probably also want to be able to manage cell temperature, and if you could have the cells cooled with dielectric fluid. That’s what race vehicles do with their batteries. if the pack gets too hot it will experience thermal runaway. Edit: this is an extreme scenario and it’s been pointed out that esk8 systems would likely not reach thermal runaway temperatures.
I have a hard time understanding your concerns here.
The racing pack so far is one of its kind for us and Poast is fully away of what can happen if batteries are misused. If our fidings determine it needs thermal managment will will figure something out.
Regarding sending someone flying, this seems like bad cutoff settings. As you aproach the lower limits of your SOC your vesc should throttle your perfomance back noticebly assuming your settings are correct, this is an indicator its time to charge and not press on.
I agree with you on the weight stuff, our resident meaty man @Swol_Moon will be getting this in his Mod board aswell, will be a good test.
The Pulse stuff is a good point, although We are comfortable testing the limits of this sort of battery we certainly do not recommend this for the average joe.
Accelerating to 40mph at full beans takes a couple of seconds, the pulse duration limit is physics. A production run pack should be designed so that the pulse is spread between enough cells to be safe. Can you elaborate on the case you mentioned where this strategy failed?
The only way to get the pulse to last more than 3 mississipis is to climb a 30% hill, or gear high enough to burn all your power against air resistance.
@Flyboy and @Skyart I’ll reply to both of you. The vesc low voltage cut off might not be quick enough to save a voltage drop cutout, in my personal experience you can have extreme sag under hard repeated pulls and you either become superman or if you anticipate it you might stay on and wobble around. For this to not happen, your either not using the power you have set or the pack is rated to more power than you are using. The only ‘fix’ was putting my soft cut off much higher than usual, which basically defeated the purpose since you would be slower as soon as you throttle it. That’s the immediate problem I see in using pulse ratings on cylindrical cells. Maybe I saw this more obviously because I purposely used hard conditions to see what would happen. Lipo does the same thing too, but their CDR are usually just so high that you don’t need to use their pulse ratings anyway.
I’m just pointing out that hoping for the best is probably not a good practice that other people on here might also follow. Edit: it’s been pointed out that thermal runaway ceilings are too high for an esk8 system to reach in practice so battery heat pov can be disregarded.
Liquid cooling is really tough to do reliably and typically only needed for very high power density packs…which esk8 doesn’t have. Race vehicles and even standard EV’s use large, expensive cooling systems that have things like $100 connectors to keep them from leaking. That kind of weight and $$$ budget just isn’t available for esk8.
Thermal runaway for the NMC/NCA chemistry cells we use typically starts at over 200°C internal temp for a cell. That would still be over the boiling point of water externally and far above what an esk8 pack could be brought up to in even the most extreme conditions.
Thermal runaway is typically caused by ESC failure, physical damage, or the incredibly rare cell internal defect…not overheating during use.
Running a hot pack certainly shortens cycle life though and that can be balanced against the performance/weight/size requirements for the pack.
Yeah I totally agree, cooling systems would be so silly on an esk8 where it would add weight and cost. That’s a good point on thermal runaway points and how esk8 most likely not reach that, I hadn’t considered how much heat would be required to cause it. I will edit my post incase people don’t see yours.
My concern still stands with the rest of the system cutting out though.
…i digress.
