Which Battery Cells are Best?

[Jason McNeil]

Been giving the voltage drop on the KS some scrutiny & the conclusion I've reached is that the choice of cells, the MG1, is really not the best candidate for eWheels.

For example at a load of 4.35A, the voltage drops below the low threshold at only 15% capacity! While it's true that with the parallelization of packs (4), the typical avg load will be considerably less than this, it does explain the low battery characteristics on sustained hill climbs. Switching to one of the latest generation cells will realize about a 50% improvement on the low end of the demand spectrum (2A) & up to a massive 154% increase at 5A loads.  

Edit: it turns out the Official LG graph was wrong (the C rating values should be 0.2, 1, 2, 3, 5) which was the basis for the table, also the IR of the MJ1 is actually 38.

[esaj]

I was going for the MJ1's for the custom-packs at first, but the price would have been a bit too much for me... Not that the MH1's were that cheap either. Maybe it's a cost-issue for KS? Don't know the "world"-prices though, probably when buying in bulk the cells aren't that expensive...

[Jason McNeil]

In the 10,000 volumes, the price for even the latest/sexiest cell is only a couple $, I believe it's comparable to what they're paying now for the MG1. In this instance, I think the choice may had to do more with the historical supplier choice & superficial awareness about the nominal capacity than how it performed under different load conditions. The MH1 is still a cracking good cell, 123% improvement over the MG1 is not something that can be ignored. 

[esaj]

The MH1 is still a cracking good cell, 123% improvement over the MG1 is not something that can be ignored. 

I sure hope so, looks like it's going to be a good while before I get to test them... have to order a new mainboard first, and wait for it to arrive, and if the past performance of shipments in my case is anything to go by (Ninebot something like 45-50 days before canceling, two of my displays actually got here pretty fast, but the third one took over 30 days, then the BMSs...), it'll be a good while. If the winter sets in before I get the part & finish the build, the next time I can ride outside will be probably around... late April - early May next year? 

[Jason McNeil]

You're pretty philosophical about delays, in this country there's so much competition among couriers that if stuff doesn't arrive within 24hrs of ordering, there's a sense that we're somehow let down. It's theoretically possible to place an eWheel order at 1:55pm & receive it before 9am the next day anywhere in the country!  

[esaj]

You're pretty philosophical about delays, in this country there's so much competition among couriers that if stuff doesn't arrive within 24hrs of ordering, there's a sense that we're somehow let down. It's theoretically possible to place an eWheel order at 1:55pm & receive it before 9am the next day anywhere in the country!  

Well, I'm really not holding my breath with this one either, but one can always hope...   With the payment & shipping & customs & domestic transport, there's a lot of things to go wrong, plus I still also haven't got the 4th pack of the new batteries due to that one faulty BMS, which is enroute somewhere. Didn't have much luck with the weather either over the summer, this was one of the coldest and rainiest summers in record, especially June & July. But at least I got over 1400km done on the Firewheel still, would have probably doubled that with better weather.

On the bright side, at least I'll have time to work on the app now (but I guess next my hard drive will break down or something, as I haven't pushed it to any version control yet... ), my next goal is to concentrate on the vibration alerts & bug hunting, so I can get the vee-special edition done and ship his wheel back, before going forward with other things.

Btw, in my humble opinion, and based only on about 20+km of riding, I wouldn't get a 14" Gotway for myself, far too unstable after the speed gets somewhere around 25km/h (Gotway app speed, so probably something like 22-23km/h real speed). It started sort of "rocking" back and forth (ie. tilting forwards and backwards) on a straight, even road, and that was scary... first I thought it's going to either fall or shoot off under me. Guess I'm too accustomed to the Firewheel staying rock steady even at 30km/h in similar conditions. Also the bulky box forces me to stand so that my feet are halfway off the pedals sideways, and the pedals aren't really that comfortable for long steadier rides either (maybe when you're bouncing up and down in paths, your feet don't get numb ). But I must say it was a lot stabler in the hiking paths, probably because the 4 packs can give so much more power than the 2 packs of the Firewheel.

[Blunzn]

vapers use and test lots of 18650 cells for modded ecigs.

not sure, as a batterynoob, if they prefer the same types for sub-ohm vaping/cloud chasing ( https://www.youtube.com/watch?v=wWyI0N8uDNg )

http://dampfakkus.de/akku_liste-nach-groesse.php?size=18650

 

[KaleOsaurusRex]

@Blunzn I know we can learn something from the design mistakes and lessons learned in the e-cig world. In fact, one manufacturer who contacted me to offer manufacturing of a mostly generic lithium-polymer unit has a website with only e-cigs and no unicycles advertised publicly.

The interesting thing is, they must have access to the type of high-drain 18650s vapers prefer, so why would they be using lithium polymer batteries which might be more prone to thermal runaway?

[Blunzn]

hmm tbh no clue ... but if i would guess

Vapers seem to prefer different cell types now not just only just because they are high drain (up to 40A) but also for security reasons. on many sites is stated that IMR, INR, ICR or Li NMC should be safer. I recall some nasty explosion in the modding community some years ago, which got very bad press for the rest of the e-cig users. Closed metal pipes with 2x18650 and NO venting holes make a pretty good pipebomb when using cheap/wrong cells with no protection  

Also many of these cells seem to have a much lower capacity 1500-2500 mah compared to ... how much are the normal cells now ? claimed 4200+ mah ... not really a problem for vaping as you learn quite fast that you always need a spare battery or two, escpecially in the beginning when you'r prone to going back to smoking. In an ewheel ... hmm not sure if i would choose the perfect 200WH battery over an okayish 350WH ...

maybe i try a sub-ohm mod at my next shopping tour.  compared with the normal 4-10 Watt, the 150 Watt mods (2x18650) sound pretty unvapeable, but they would make a hell of a fog machine. remotely triggered, mounted with rgb-led's under the pedals maybe some choclate/strawberry flavor  haha   only problem would be where to pack the huge e-liquid tank or if someone calls the firefighters  

 

 

[Jason McNeil]

10A sustained, burstable to 20A cells should be enough for eWheels, especially with multiple parallel packs. What's exciting about the developments in the past six months, is that LG & Samsung are making cells that have both high capacity & high sustained current without taking massive penalties in either capacity, or voltages that drop through the floor under a moderate load.

[Gimlet]

The problem is that 99% of euc customers don't have any understanding of the high power requirements of eucs. (That's probably why the same old theme of why can't we have 40+kph wheels with safe reliable tilt back keeps being asked).

So given the undoubted extra cost of using cutting edge latest batteries is it surprising that the manufacturers choose cheaper older technology and bigger profits?

Think about it well over half of new members here arrive asking about where they can get the cheapest wheel rather than the best wheel.

[esaj]

The problem is that 99% of euc customers don't have any understanding of the high power requirements of eucs. (That's probably why the same old theme of why can't we have 40+kph wheels with safe reliable tilt back keeps being asked).

So given the undoubted extra cost of using cutting edge latest batteries is it surprising that the manufacturers choose cheaper older technology and bigger profits?

That might be at least part of the story, while buying cells or ready-made packs in bulk is much cheaper than having them made in small batches, they're still probably a very expensive part in the whole wheel (and at least for larger amount of packs per wheel, probably the most expensive). The "big" name EUC-manufacturers seem to use high quality cells, which are usually imported into China... LG and Samsung are South Korean, Sony and Panasonic are Japanese, although I don't know if the cells are made somewhere else, I think at least Sony doesn't even make the cells themselves anymore, but have them manufactured by someone else? Any way, it could be that changing the packs to use different cells would require a whole new batch of tests, and possibly some firmware tweaks or similar. Also, when buying in big bulks, the supply contracts could be somewhat lengthy, so if they've made a deal for say, half a year or years' worth of production, they won't be changing the packs until at least that deal has ended. As it looks like there are new types of cells coming at least a couple of times per year, it might take a while for them to "catch up" with the newest cells, and if it's again a long contract, they'll be "old type" again before the contract ends.

Think about it well over half of new members here arrive asking about where they can get the cheapest wheel rather than the best wheel.

Using cheap wheel for learning seems somewhat usual, one point might be to see if you can actually even learn to ride it. I bought vee's 14" generic just for the purpose of learning, as I was sure I'd scratch it a lot (or even destroy it ) during the training phase. And I did scratch it somewhat, but at least it still works.