Yeah in that case a discharge BMS can make sense. One more thing to mention though, if a discharge BMS trips during regen braking, the chances of blowing up the ESC are not insignificant.
But yeah an ebike does have mechanical brakes so if you’d be using mostly than feel free to go for a discharge BMS, especially with the black box controllers
Maybe that’s why ebikes don’t generally have regenerative brakes? I didn’t know that this was another reason for bms bypassing for eskate.
Claims can do .15 copper
I was wondering what is the best cell for Esk8 now? Mainly race oriented and high voltage-ish I was thinking 18s….. I was wondering if i built a 12s8p with the molicell p42, can i add 6 more 8p groups to it using more of the same cell?(I bought the original cells about a year ago and built the battery about 6 months ago).. I have not been able to use it bc of space requirement with the pcb it’s on. So it has only been charged and held around 4 volts climate controlled. If I can do this does anyone have a suggestion for it without taking them off pcb? I don’t even know how I would do that either way!?.. thanks
Tabless cells looks to be lots better than P42a, although P42a is still significantly cheaper. Me and @Pecos ran through a couple of packs made of P45b and found that they don’t really offer as much capacity as we thought even under relatively low power draw.
Yeah I am in Minnesota and I’ve been riding at 25 Fahrenheit the last couple days and the voltage drop is crazy.
From what I have seen the Reliance RS50 is kind of the new king along with the EVE 50. Also people have been getting better performance from BAK 45d than molicel p45bs. So I’d say those 3 are tied for first.
@Pecos is running a small pack of BAK45d and it’s looking pretty good. He’s also building me a 20s5p pack from the RS50 cells, I’m curious to see how much range I can get from it. On a 21s6p P45b pack I killed it in 26 miles, granted I was running 4wd but still.
Damn that’s nuts for a 2k kwa pack. I get 40 miles easy on my nomad n3 with a 1440wh. How much do you weigh and what’s your wheel setup?
But also remembered you’re in Seattle so probably a lot of hills lol. I just moved from there to Minnesota, man I miss it so much.
125lbs without gear. 8in Novas set up. I live outside of Seattle so not as much hills actually.
I’ve been really happy with my Bak45D’s.
If I were planning a new pack today, and needed to purchase cells I’d go for RS50’s.
I’m hoping TenPower 50XG become available soon, as they are right there with the EVE 50PL and RS50 at least in terms of voltage drop and temperature rise.
Cycle life untested but the spec sheet claims are impressive.
Ok well now I’m even more curious what motors?
ok, here is what i thing is going on with the p45b and why i think that it just doesn’t math anymore with the other tabless offerings. my theory is that the cell takes a huge performance hit for for capacity even if high draw isn’t continuous but is burst like is typical in estate.
mooch tests on endless-sphere 2022
21s6p of the p45b in a low draw test of 5a down to 2.8v hits 4.2ish ah. this is pretty tight grouping between the 5 10 20a tests so we are already short of the 4.5ah rating at a pretty mild discharge rate up to 20a, then the discharge increase of 10a is making a pretty regular drop of about .1ah per additional 10 amps for 30a and 40a tests. bump the starting voltage down to 4.15v a cell which is more typical conservative setting as well as bump the ending voltage to 3v a cell and the amp hour of performance is 3.8ah at a 20a draw. this is about where i think this pack ended up.
(6px3.8ah) x (3.6x21s) = 1723ish wh pack
Michael is completely bonkers so 60wh a mile is 28ish miles. then de-rate that a little, i usually do an additional 5-10% off of that number and we get 25.2 miles.
even though the pack sounds like it should have more capacity because of the name and being a generational improvement over the p42a the performance really is only a very marginal improvement over the p42a as far as actual capacity. there are just better cells out there that are more energy dense as well as have better performance curves when discharged at 20a or more. that strong hockey stick drop off is what really helps preserve the cell capacity in these use cases and the performance of the p45b is a very steady slope, especially in high power draw situations like @MichaelWA subjects these to.
(Also support mooche’s patron, without the testing he does we would have to rely on the very optimistic manufactures numbers and i never would have figured out why this pack and the other p45b packs that i made for myself just didn’t cut the mustard)
Reacher 6485 151kv rear and 6465 150kv front.
Ok I will look into those. As far as adding in some p groups to my 12s8 p molicel p42 a would that be a problem if the battery’s are from different batch? I would think its ok bc I want to up this to 18 or at least 16 s to put in the redember deck.
It’s generally frowned upon, partly because of the batch mismatch thing and partly because of the amount of work it is to modify well made p groups. If you are adding new groups those new groups need to be a mix of the old cells AND new cells - or batch 1 and batch 2
large groups and adding to each group is less detrimental than trying to do it in lower p count builds or just straight adding or replacing p groups.
Just because you haven’t put any use on these cells doesn’t mean sitting at 4v for months hasn’t aged them a little - if you do just add groups to being the count up just know the battery MIGHT struggle to keep the groups balanced so definitely get a smart bms and make sure it gets all the time it needs to balance properly between charges. Keep an eye on it. It MAY shorten the lifespan of the pack but it could be just fine. Honestly i think it’s better to get some life out of the cells you otherwise aren’t using then not using them.
what you do with your battery is your business, as long as you’re not making someone else a battery and selling it as new with mixed cells and telling them it’s all mached and fresh new - send it - carefully 
Also if you can - discharge the pack you have down to 3.6 3.7ish volts. Think of the voltage like pressure - chemical pressure. It’s less stress and wear on the cells to sit at a lower voltage for months of storage. Not a big problem but definitely better for the lifecycle of them. It’s a small difference that adds up over the long run to the cells lasting longer
I use p45b almost exclusively for the charge speed. On larger packs I still often recommend the p42a
The rs50 has a higher maximum charge current of 15a and the bak45d is no slouch at 13.5a. In my personal opinion they are in the same class as the molicel and with caveats can be changed similarly quickly.
The p42a and p45b are still solid cells but the cost benefit needs to be adjusted. Wild because of how long they sat as the gold standard, my standards are just evolving
Regarding fast charging of Reliance cells.
They allow for a ‘stepped’ charging profile in the data sheet.
15 Minute Step Charging the RS50 (from the datasheet)
10A for 2 minutes.
16A for 3.5 minutes.
20A for 7 minutes.
10A for 2.5 minutes.
This should bring the cell to about 4Ah from 2.5V (“empty”).
Thanks to Mooch for this ^ summary. There is a lot more to it.
Ive been looking at ‘max’ charge rates of all cells a bit differently ever since.