# Any good sources for 18650s?



## Tomdb (Jan 28, 2013)

where you from, this will help alot with finding a supplier.


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## SirNick (Jun 14, 2015)

Good point, thanks. I'm in Anchorage, AK.


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## Hollie Maea (Dec 9, 2009)

What per unit cost are you expecting?


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## SirNick (Jun 14, 2015)

I saw some on Aliexpress at around $3.50/cell, which would be fantastic.

From there, I have my pick from any number of sources that could be a black hole into which I can drop money with no tangible return; or 100% authentic knock-offs; or suppliers that can't (or won't) ship to the US...

So, ideally less than the $8 apiece I might be able to find from the vaping dealers online.


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## prensel (Feb 21, 2010)

I did buy 1080pcs of 29E three weeks ago here in Europe for just $3 each. building a 36SP30 pack


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## SirNick (Jun 14, 2015)

Local vaping shops were a bust - they're more interested in high-discharge cells like the 25R.

I did manage to find a seller on Amazon willing to ship qty 4 for testing. There's a seller on eBay with lots of 200 for a reasonable price. If they're legit and shipping ends up reasonable then I may be set.

These things are hard to find in the wild. I take it manufacturers are only interested in selling to pack OEMs, which I guess makes some kind of sense.


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## Hollie Maea (Dec 9, 2009)

SirNick said:


> Local vaping shops were a bust - they're more interested in high-discharge cells like the 25R.
> 
> I did manage to find a seller on Amazon willing to ship qty 4 for testing. There's a seller on eBay with lots of 200 for a reasonable price. If they're legit and shipping ends up reasonable then I may be set.
> 
> These things are hard to find in the wild. I take it manufacturers are only interested in selling to pack OEMs, which I guess makes some kind of sense.




I've heard a rumor that Samsung is short on cells at the moment. Haven't verified yet but it might be hard to get any in volume for a while.


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## SirNick (Jun 14, 2015)

Hm, maybe that's a good thing if demand is going up. Could mean higher volume production and hopefully some economy of scale. (Here's hoping anyway.)

My target car is being stripped to the pans for body and paint, so it'll be at least spring before I'm ready to start assembling anyway. I can wait a bit.


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## SirNick (Jun 14, 2015)

No, afraid not. It's a nice design, and a noble attempt, but... IMO, 18650-based packs have two main advantages:

An extensive selection of cells to cater to particular design goals; and...

The ability to combine them in any s/p configuration to fit physical size, voltage, current, and capacity requirements.

Pre-built packs have a way of negating both of those advantages, and therefore aren't likely to be an attractive solution. If I were to guess, this is probably the main reason you don't see the big DIY EV players participating in this market.

For e.g., my primary drivers are available volume under the hood, 100 mi range, and voltage/current compatibility with the HPEVS / Curtis combo. In my case, that means 23.5-25kWh at 200Ah with INR 29E cells. Significant deviance from those parameters would mean a complete redesign, so 80Ah modules aren't going to cut it for me.

Naturally, someone else will have their own unique constraints, and so the likelihood of keeping both of us happy is fairly slim.


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## SirNick (Jun 14, 2015)

Yep, I understand.

My application requires 70-80p, so two of your modules (60p) would not be enough. On the other hand, three modules would be too many -- in a 30s string, 90p would be too much extra cost, extra weight, and it wouldn't fit. Even 80p is a tight squeeze. I can only fit them if the modules are arranged to take complete advantage of all three dimensions.

To be honest, pack building is not really hard, it's just tedious. But if someone were to solve some of the minor engineering problems, they could help the community tremendously, without the inventory issues associated with manufactured packs.

E.g., right now, I have to buy cell retainers (the eBay interlocking blocks) from one guy, nickel straps somewhere else, a welder from the guy on ES, have anode and cathode plates machined, and work out whether I want to try and weld nichrome wire, laser cut fusible links into the nickel strap, take my chances soldering to the cells, or forego cell protection altogether. Then I have to come up with a way to strap together the plates.

None of that is terribly difficult, but you end up reinventing the wheel, and no one has really come up with a good solution for fusing cells that I've seen.

If someone had access to a CNC, you could make the A/K plates of any size, and work out a fairly simple way to add terminals. An outer non-conductive shell (thin plastic) to keep the sandwich together and that's it.

One way to handle the cell fuses is to put small nickel pads on the end of a fuse wire. That would allow easy welding to a cell, and soldering to the plates. Now THAT would be nice to have available.

And you wouldn't have to bother with Li-Ion shipping regulations.


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## Hollie Maea (Dec 9, 2009)

Dang, our design would probably work for you...6S40P but I can't find enough people interested to do a production run and get volume high enough to get prices down.


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## electro wrks (Mar 5, 2012)

Are these protected cells (or ones like them) the wave of the future in 18650 cell construction?:http://www.lygte-info.dk/info/battery protection UK.html . Or, are they in the too-good-to-be-true category or too expensive?

Over and under voltage, over current, temperature protection -what else? I'm guessing the protection is resettable.


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## Karter2 (Nov 17, 2011)

> ...Are these protected cells (or ones like them) the wave of the future in 18650 cell construction?


 Few of the newer "high capacity, high output", cells use those protection circuits these days. certainly not the cells used by Tesla etc or the Samsung 29E SirNick is considering


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## electro wrks (Mar 5, 2012)

Still, this feature seems like it would be a real plus for the DIYer assembling a safe running battery pack. Is it not practical in the higher output cells, would the expense be too great, or does it add an unacceptable layer of complexity?


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## Hollie Maea (Dec 9, 2009)

electro wrks said:


> Still, this feature seems like it would be a real plus for the DIYer assembling a safe running battery pack.


It really wouldn't. Seems like these things would be be a nightmare once you parallel a bunch of cells together.

No, you want to control your own protection in a way that is appropriate for your application. That means fuses on each cell and BMS monitoring each parallel group.


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## electro wrks (Mar 5, 2012)

Walk us through the nightmare scenario you're envisioning.


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## Tomdb (Jan 28, 2013)

Bad connections, high resistance ones. Leads to heat build up. Which can lead to you know what. 

Getting consistent welds or how ever you connect the cells is the main issue you will face.


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## Karter2 (Nov 17, 2011)

SirNick said:


> . In my case, that means 23.5-25kWh at 200Ah with INR 29E cells. Significant deviance from those parameters would mean a complete redesign, so 80Ah modules aren't going to cut it for me.
> .


SirNick, why are you stuck on the 29E cell ?
I assume you are aware there is a 35E version of that cell available also.
Same performance, but 20% more capacity.
That would mean your 200Ahr would need only 58p or so cells.
Smaller pack , less weight. Less build time.


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## Karter2 (Nov 17, 2011)

electro wrks said:


> Still, this feature seems like it would be a real plus for the DIYer assembling a safe running battery pack. Is it not practical in the higher output cells, would the expense be too great, or does it add an unacceptable layer of complexity?


The protection circuits for over/under voltage protection, and current limiting, in the cell seriously limit the current draw capability as well as adding complexity, size (physically longer cell usually) and of course cost.
Most cells still have a internal temperature/pressure release (CID) that can also electrically isolate the cell in the case of a dead short, but that is a simple mechanical safety that only functions in an extreme situation.


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## SirNick (Jun 14, 2015)

I wouldn't say I'm stuck on that particular cell, it's just a good fit. At a target of around $3.50/cell, and given the number of cells I need to meet voltage, current, and capacity goals, it looks like the pack will fit, weight is acceptable, and the total cost is reasonable.

I figure -- well, I hope -- the pack will last about 5 years and then I'll be looking at a rebuild. I'll have new options available then that aren't now, or aren't economical now at least, and so I'm not terribly concerned with being at the top of the capacity curve for this form factor. It'll be obsolete anyway.

That said, if I find 3.5Ah cells at around $4.20/cell (that is, about 20% higher cost and capacity) then I'm more than willing to change course.

I need at least 24kWh. The rest is just about finding the sweet spot between cost and capacity.


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