Looking for inexpensive 18650 cells

Batteries and Chargers Rechargeable Batteries
18

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…

19

@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.

20

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.

21

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 ^:)

22

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.

23

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 :wink:

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 :slight_smile:

24

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

25

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.

26

We’re talking about 2.6A drain current. I’d think the 26F should be able to handle it fine.

HKJ link

27

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.

28

OK so back to thinking 48v cell…lol

I’ll be happy when I can just get my bike….

29

look for either cells with welded tabs, or a welder, do not solder cells.

30

I'll add that, even for brand name cells, usually the specced capacity is a "peak" value, usually only achieved at a reeeeeeeally low discharge rate.

The LiitoKala 26650-50As, on the other hand, have proven to deliver their specced capacity even at a moderate discharge rate (2C, 10A). Thus, in practice it would be much wiser to build the pack with these instead of 26Fs. A better pack could be built with brand name high discharge cells, delivering more peak power, lighter weight, and even matching in capacity. The price, though, would be considerably higher.

If I were to build such a pack, I'd go 14S3P LiitoKala 26650-50As. In an electric vehicle, the batteries are like the engine itself, and the electric motor is sort of like the transmission. This is probably not fully understood by many people, but the battery is key. With an oversized battery the stress is considerably reduced, as the load and cycling is by any means proportionally lower, guaranteeing plenty of mileage; if you also usually keep and use the pack charged at up to just 2/3 of full capacity, it'll last for ages. And hell, grab a 3KW motor and burn some rubber on the traffic lights megaLOL!

Cheers ^:)

P.S.: cells can be soldered safely with a low temp solder like Rose's metal. Check the following pictures:

31

In the USA, 750W is the maximum legal motor size on an e-bike. Do you have similar restricitons over there?

Of course people use more than 750W, when was the last time you saw someone get pulled over by the cops for their electric bicyle being too powerful? :person_facepalming:

I’m a roadie and I’ve been trying to get a cop to ticket me for a speed limit violation on my bicycle for years with no luck. I would pay that fine with exuberance and then frame and hang that speeding ticket in my living room as a trophy. :+1:

edit: I’ve soldered cells with no issue in the past for other items, and generally don’t have an issue with it - but not for a bicycle battery pack. The extended and high levels of vibration WILL eventually lead to a tab cracking off and possibly shorting, I 1000% guaranty it, maybe not today, this week, or this year, but if you use it long enough it will I promise. That would not make me comfortable with that much energy between my legs.

edit2: does solder have a fatique endurance limit like steel, or no limit like aluminum? I’ll have to Google that later.

32

Depends on what solder you use, Google ‘Tin wiskers’ to see the extent of the problem, especially with the drive to remove lead from solder over the years

33

IMO, this is a quote worthy of recognition!!!

All of it, BUT especially the part below…… :+1:
.

34

yes, they can, but it takes some skill and proper tools, it also may take few trys to get it right, worst thing, is you wont know you killed the cell right away, overheated cells lose capacity pretty fast, and quietly die,

35

If I were into assembling battery packs, more than probably I'd grab a spot welding device.

As I said before, though, low temp soldering a pack is pretty feasible if done carefully, even if it is aimed for an application with undue vibrational stress. It just takes proper pack design. There are plenty of inexpensive battery brackets/holders to be helped with. Foam wrapping and/or interspersed foam sheets can make a hell of a diference. Slightly longer than needed and bent cable connections are of help also, allaying interconnective stress.

Oh! If in doubt, a full pack's interconnections can be solder refreshed (reheated/reshaped solder joints) relatively quickly. But, as I said before, better make sure to use Rose's metal and a strong acidic flux like Goot Super Soldering Flux.

Sheeesh!

Cheers ^:)

36

so I’ve seen kits like these: http://www.ebay.com/itm/250-W-24-V-electric-brush-motor-f-bicycle-ebike-gear-reduction-410-1-2-chain-/152216561502?hash=item2370d0675e:g:ZB8AAOSwLpdW9Btz

They’re brushed motors correct? ugh… if so I hate dealing with brushes… heck who knows where I’d get replacement brushes and how soon I’d need to replace the brushes… just seems like more of a hassle…

37

Well considering when one cell explodes in a vape unit it usually blows several teeth out. A pack of 50+ would have to be like a pipe bomb going off under you. Might even blow both legs off