How about 32650 LiFe cells here?
Not to be rude, but if you are even considering 9000mAh eBay cells and laptop pulls, you are very far from the knowledge and capability needed to build a safe e-bike battery pack.
Laptop pulls are not what you want for an e-bike. $0.50 9000mAh eBay cells will be even worse.
You need high-discharge cells; those cells are not.
You need fairly well matched cells; those cells are not.
…
Now that I’ve insulted you 
, here’s the helpful part:
You need to be looking at bulk prices for quality name-brand cells.
Samsung 25R would be a good starting point as the standard for a good high-drain, decent capacity cell. 2500mAh, 20A rated, $3.50/cell in qty>100 on imrbatteries.com
For lower cost, maybe Samsung 20Q - 2000mAh, 15A, $2.75/cell in qty>100.
For greater capacity but less current (i.e. you better not plan to use the 1000W BBSHD, and plan to turn down your BBS02) you could use Panasonic NCR18650B’s (3400mAh, 5A, $4.40/cell in qty>100)
“Moderate” discharge rate cells can be adequate for e-biking. Unless you are gearing for kart track GP competitions of a handful of laps, runtime is also a wanted feature in this world, I believe.
In the aforementioned Aliexpress store, one can buy 40 pieces of LiitoKala 26650-50A cells for a tad above $160 ($40.67 a 10-pack). With that bunch of cells, a 10S4P pack could be assembled, reliably delivering 36V × 80A = 2.88KW of thrust power. I'd say that would be a fast enough e-bike, though such a pack wouldn't be slim. Half the cells, half the power and weight.
Samsung ICR18650-26FMs for $2.21 a pop ($11.04/5-pack), they aren't that good power delivery wise but still may suffice if enough of them are assembled together to meet our expected power output requirements. 
Also, despite what other people may argue, hybrid packs can be assembled in order to get a combination of capacity and burst power output to overcome some hills.
Cheers ^:)
Lol… I wasn’t considering 9800 or 9900mAH fake cells guys…lol I hope I made that clear in the first OP….
I know the Panasonic cells are like the holy grail of 18650 cells right now but it stinks there no bulk producer of them for cheap… come on tesla…build that gigafactory…
Honestly, all this battery stuff is completely new to me… like what the heck is a BMS? I guess you have to have it? lol…
My goal is to produce a battery that is a 48v around ~100 cells…however many I need to even the capacity per voltage bank…
“Battery management system”. Balances batteries as capacity changes over time/cycles, keeps 1 cell in a series-chain from running down too low, all sorts of fun useful things that keep your battery pack from going supernova in your crotchal area.
Basically, in this case, you don’t want your ebike to become a crotch-rocket. That would be a Bad Thing.
Might I suggest that it’d be cheaper in the long run to just buy a completed (replacement) battery pack? This way, you get the cells, the BMS, the (weatherproof) enclosure, etc., and all the homework is done for you.
Kind why we buy completed flashlights instead of machining our own aluminum blocks… Sometimes it’s just easier and cheaper to buy off-the-rack.
For all of the reasons already stated above, you don’t want to cheap out on cells.
You will regret it.
You said “What I’m looking for is around $1-$1.90 per cell at around 2000mAh”.
This is like going to a car dealership and asking for something with 4 doors
for $350 per month. It is not a good way to go about it and you will not likely end up
happy with the results.
There are more factors you need to be considering.
How many amps do they need to be able to put out?
How does the voltage sag under load?
Do they have CID/PTC protection?
There is a lot more to it than just mAh and cost.
You should join an ebike forum to get some ideas of what is feasible.
I take it you haven’t, because you would already know the minimum acceptable cell for your configuration and the cheapest place to get them.
Nothing will be worse than for you to go to the time and expense of building this,
only to find out that it sucks and you should have used better cells.
Or even worse, that it overheats and burns up.
Good luck!
Barkuti, I think that math is wrong. A 5000mAh cell like the Liitokala 26650 in 10S4P would be 36V 20Ah,which is 720Wh, which is a medium sized pack.
But 18650s will pack tighter and can supply enough juice. 10S6P HG2 for example would be about the same capacity (648Wh), plenty of current, and for about the same price (I’m seeing $2.87/cell for what appear to be genuine HG2 in bulk) in a more compact pack. About 8% smaller by my quick napkin math and questionable recollection of circle packing.
The Liitokala are pretty good value though, no doubt.
sac02, I wasn't speaking of capacity, I was referring to power handling. I said “reliably delivering 36V × 80A”; since the LiitoKala 26650-50A cells have proved to handle 20A per cell, with a 4P arrangement the pack would deliver 2.88KW of power (3.8+HP) without issue. 10S6P HG2s would handle more, but with somewhat less capacity and thus lesser cruise runtime. Hell if you can't go up to 45+MPH with that power on a e-powered bicycle (albeit you'd have to make a pit stop in less than ¼h)…
$2.87 an HG2 pop? Where?
Cheers 
Yea,
So little back story. The whole ebike thing is new to me. Completely new…heck I don’t even have my bike yet… Basically apartment living has really reduced what I can have…so my parents still have my bike…I think its just like a Giant mountain/city bike…can’t even remember. My idea is to bike to work since I spend more on parking than retirement per month right now and convert it to an ebike also since I don’t want to be hot and sweaty for work…woohoo. I live 4.8mi from work so that’s pretty easy. It can sometimes take me 30-45minutes to go that 4.8mi traffic is so bad so it might help on that end…
I was going to buy a geared motor Chinese conversion kit and run it on a separate chain while still keeping my pedals and gearing for the rear tire….The hub motors look alright but yea…still not sure yet. I guess batteries are more expensive than I thought…
@Philaphlous: did you consider a small motorbike? Honda GROM/MSX 125 for instance?
Apart from that, if you know nothing about ebikes and bateries then you have a lot to read and learn before you may consider building your own pack and bike.
Li-Ion batteries are somewhat delicate and need some care to work properly and safely. They should not be overcharged, overdischarged or overloaded and in a battery pack you need some electronics to make sure this does not happen to any cell - BMS. That’s why cordless tools usually come with a pack and a dedicated charger - and not bare 18650 for instance.
Yea. I don’t have $4k to drop on a grom. I’d love to though. But ebike right now is the way to go. Especially since i wouldn’t have to pay for parking that’s a huge plus for me.
I’m in the early stages so I’ve got alot of learning to do. Heck I bet my bike needs new tires and alot of tlc before I even consider the ebike route.
14S li-ion BMSes at SZXJR Aliexpress' store
The 30A BMS there has balance function and a fair price.
Some crazy new BMSes up for grabs there. Look:
Now that's some serious sh1te power handling! Could venture on the highway! 
Cheers ^:)
This was the link I was referencing: $2.87 HG2 qty>100. But looking at it more closely today I have doubts about authenticity - that particular listing has mostly good feedback (only 1 or two people claiming fake), but there are obviously fake batteries all over DHgate, so I’m not so sure about the site in general for battery purchases.
I’m seeing prices on AE around $3.75/cell for what appear to be authentic Panny B’s in bulk if OP wants max capacity, or the Samsung 26F you posted for best cost, or maybe LG HE2 (2600mAh, 25A) for $3.25 for decent capacity, and high drain.
If your knowledge on ebikes and especially li ion batteries and bms systems are limited, then I’d buy a normal bike roll of duct tape and some large firework rockets, much safer, as at least Yourll know what direction the flames will come out from 
But seriously, I was looking at building an ebike and battery packs etc - have loads of 18650 cells- in the end I bought a ready made ebike from the small ads, was many in there, often from people who buy them on a wim, use them a few times and stick then away in the garage, I bought a bike with less than a 100 miles on it for 25 % of what it would have cost new, and about the same as building one from Chinese bits.
It’s certainly worth checking out that route first 
I'm looking at these now: https://www.fasttech.com/products/1420/10002357/6499800-authentic-samsung-icr18650-26f-3-7v-2600mah Looks like $2.84/cell which is pretty good and they're "2600mah" which in reality if its even 2200mah that'd be pretty good IIR... Maybe I'll scale back the battery some... I only need it to go maybe 8-10 miles round trip...Drop the voltage to 36v and maybe half the capacity... Every now and then Fasttech will run a 15% off sale...hopefully in the next few months my job situation will settle down and I'll be in a good state to pick these up at 15% off too... I'm thinking I'll do 36v pack, 40 cells for a 10Ah battery cell... Probably a 10-20A BMS should be enough. I'm not sure how much wattage I'm to be looking for with an ebike motor...I see anywhere from 250w to 1800w..lol
That 26F you linked is the same cell that Barkuti mentioned above at $2.21/cell. Cells from name brands will have the rated capacity - Panasonic, Sanyo, Samsung, LG. Only the “xFIRE” type cells lie about their capacity, and you will never see a spec/data sheet for one of those crappy cells.
Here is the best resource you could possibly imagine for good info and independent testing of batteries: http://www.lygte-info.dk/
I think 36V is low in the world of full-size ebikes. Maybe some “toys” are 12 or 24V, but most real ebikes are 36, 48 (overvolted to 52), 60 or even 72V. Higher voltage means less amp draw for the same power output, and hence less strain on batteries.
Will you plan to have a second charger at work? If so you could get away with a small battery pack and re-charge during the day. But I would rather just have the one charger at home and divert that $ towards a bigger battery pack.
You said your 4.8 mile commute can take 30-45 minutes - really? Is that actual moving time, or all-inclusive time including waiting at lights and such? Grab an app like Strava and clock your actual moving time, I bet it’s closer to 20 minutes. Also, do you want the e-bike to do nearly all the work, or do you plan to do much of the work and just use the motor to help get up / keep up with traffic at certain points, or tackle that one really nasty hill?
Using the 26F in 14S2P, (28 cells, $62batt cost, 52V, 5.2Ah, 270Wh) you could run a small 250W motor about an hour. But that will be fairly stressful on the 26F as it is not a high-drain cell by any means, and 250W is small by e-bike standards. But you would get about an hour runtime out of that battery/motor combo.
26F in 14S4P (56 cells, $124batt cost, 52V, 10.4Ah, 540Wh) would be more than sufficient, and more appropriate, I think. And still only $124 in batteries. And you could get about an hour out of a 500W motor, which is much more helpful.
Liitokala 26650s in 14S2P (28cells, $114 cost, 52V, 10Ah, 520Wh) would handle the drain better than the 26F14S2P and be slightly cheaper than the 26F 14S4P.
We’re talking about 2.6A drain current. I’d think the 26F should be able to handle it fine.
I meant “fairly” stressfull in the meaning of long-term durability/life of the cell, not risk of short-term damage. Discharging a cell rated for 5.2A safe continuous discharge at 2.6A will work, but it will be more stressful - and shorten its subsequent overall life - than discharging a 20A rated cell at 2.6A.
OK so back to thinking 48v cell…lol
I’ll be happy when I can just get my bike….
look for either cells with welded tabs, or a welder, do not solder cells.