What aren't there threaded li-ion cells

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Grantmac

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I was thinking about the larger formal cylindrical cells like the QB26800 and it occurred to me how great a pack of those would be if they had threaded terminals like Headway cells.
I understand that it would add weight on a per cell basis so wouldn't be ideal for smaller formats, but we are talking big cells at this point.

Being able to remove individual cells or reconfigure packs easily would be a huge plus.

Thoughts?
 
18650 cells are not designed to be easy of use, but to maximize volumetric power density (packing as much power as possible in the least possible volume). Adding a threaded header would require some sizable extra space.
Also, flat heads + spot welding (by any industrial technique) is a fast, secure and cost effective ways to join together a lot of cells.
 
vl.jpg
 
I've wondered if perhaps theres a market for threaded 18650/26650/21700's, because I can spot-weld threaded studs onto these cells. I decided there is not enough profit in it to make it worth my while...
 
Isn't the issue with spot welding anything to a cell that it causes internal damage unless done very specifically using ultrasonic techniques? Something directly integrated into the cell wouldn't have that issue.

That SAFT VL 8P looks awesome, but given they are listed for use in space I'm guessing well beyond the budget I have in mind.
 
once upon a time a buncha guys over at CPF approached saft for pricing on a possible lion group buy.
saft's response wuz they don't take a piss for anything under a $1 million.

since then i've often wondered, if i won the lottery & called their bluff they would probably up it by 10x.
basically unobtainium/first tier users only because for as long as ES has existed, i've never seen or heard of anyone actually get their mitts on any of their lion offerings in the wild.
 
That's why I'm thinking someone like QB might be more amenable to producing such a cell.

Or I'll stick to recycled EV prismatics.
 
qwerkus said:
18650 cells are not designed to be easy of use, but to maximize volumetric power density (packing as much power as possible in the least possible volume)...
Click to expand...

How can you say that when cylindrical shapes waste over 21% of the volume they take up as dead unusable volume?

To the OP:
The prismatic 26ah Panasonic cells from Ford hybrids and some other electric cars that I use have threaded terminal posts for easy bolt together battery building. Plus they are higher power and better quality that just about any cylindrical cells. While some cylindrical cells have greater gravimetric energy density, their shorter useful life makes them far more expensive in the long run. To me the only advantage of any cylindrical cell is that no compression is required due to their shape. There was a member selling those Panasonic cells with low mileage and age for only $17/ea in the for sale section, an awesome deal for a cell that I don't feel getting warm at the 250A+ that I run, and originally came with an 8 or 10 year warranty,
 
EV cells are definitely where I've been looking. The form factors aren't the greatest for ebike use but it can be manageable. Especially in lower voltage setups with the emphasis on range (my next build) over speed.
 
Threaded connections may be useful to some pack builders, but it simply adds cost and weight when all the connection hardware for a 50 -100 cell pack is considered.
Many DIY users dont even want to pay the extra for professionally added tabs, that can also simplify pack builds.
Saft cells..
My first Ebike was a commercialy built Aprillia that used a very elegantly designed integrated/removable pack of SAFT cells ( 32900’s NiMh). Those cells were still useable 15 years from their (2001) build date !
Larger format cells also restrict pack design and configuration for Ebike use.
 
Hillhater said:
Threaded connections may be useful to some pack builders, but it simply adds cost and weight when all the connection hardware for a 50 -100 cell pack is considered....
Click to expand...

The interconnecting tabs for the series connections (nickel plated copper I think), generally come with the cells. I don't like the star nuts that come with the Ford cells, so I switch them out for standard 5mm locknuts, which cost just a few cents even down here where everything except fresh produce costs more. That cost is way offset by the ton of high quality stainless bolts and other hardware I harvest during EV pack disassembly. It takes quite a while to get through the layers of protective steel to get down to the racks of cells in every ecar pack I've taken apart.

The Panasonic cells Ford uses are the only ones I've found with useful dimensions for ebike use at about 6"x5"x1". By compressing them in 4 stacks of 5s, I was able to easily fit 20s on my EEB with plenty of space left over and a nice tight fit against the side covers to make pieces of doubled up duct tape all that was needed to ensure the pack stays in place on the bike.
 
Hillhater said:
Saft cells..
My first Ebike was a commercialy built Aprillia that used a very elegantly designed integrated/removable pack of SAFT cells ( 32900’s NiMh). Those cells were still useable 15 years from their (2001) build date !
Larger format cells also restrict pack design and configuration for Ebike use.
Click to expand...
saft NiMH D cell were also oem tidalforce but i was specifically specifying their Li-Ion being fairy dust & hoping someone would chime in to prove me wrong.
even their NiMH is difficult to source with the precious few rep's that claim to offer it on their websites, generally they don't stock & will only place an order by the caselot.

and sure, just as big pixels make for a chunky picture, bigger the cell, the fewer nooks you can stuff.
but that's a trade-off i'd make in a heartbeat for cells that run cool like JinCR has.
one of the earliest ebikes i ever saw in a bike shop back in the early 90's (might have been a panasonic) came with 42900 M-cell NiCd.

the op is correct tho, after considerable searching other than saft, your only choice in cylindrical is LiFePO4 or else Lipo prismatic, no nmc or nca bolt on cylinder.

https://www.lithiumion-batteries.com/cylindrical-vs-prismatic-cells.php
lithium-ionen-accumulatorheader.jpg
 
I wanted 38120 A123 8ah cell they ask me if I wantef rgread ends. I found the A123 cell to limited run. As only what they had at 21.00 usd and no more. I tapped out plus big and heavy for ebike. 120amp lifepo4 cell. No crappy headways as always out of balance.
Oh more you need to trust OSN for your cells. Good luck.
 
John in CR said:
qwerkus said:
18650 cells are not designed to be easy of use, but to maximize volumetric power density (packing as much power as possible in the least possible volume)...
Click to expand...

How can you say that when cylindrical shapes waste over 21% of the volume they take up as dead unusable volume?
Click to expand...

How so ? Maybe if you arrange you cells in a ladder pattern. But using honeycomb holder, i think a cylindrical shape is the best thing to do next to hexagonal, especially if you need to leave some space for a coolant. IIRC tesla cells are immersed in a cooling liquid.
The main advantage of a cylinder is it's sturdiness: you can compress the inside much better than in a prismatic cell, hence much less risk of cell inflating due to gases.
 
the shape is simply the cheapest way to make cells and maximize usable volume.
same goes for not having threads, its simply too cheap to spot weld.
 
qwerkus said:
John in CR said:
qwerkus said:
18650 cells are not designed to be easy of use, but to maximize volumetric power density (packing as much power as possible in the least possible volume)...
Click to expand...

How can you say that when cylindrical shapes waste over 21% of the volume they take up as dead unusable volume?
Click to expand...

How so ? Maybe if you arrange you cells in a ladder pattern. But using honeycomb holder, i think a cylindrical shape is the best thing to do next to hexagonal, especially if you need to leave some space for a coolant. IIRC tesla cells are immersed in a cooling liquid.
The main advantage of a cylinder is it's sturdiness: you can compress the inside much better than in a prismatic cell, hence much less risk of cell inflating due to gases.
Click to expand...

Should have stopped while you were behind instead of making the hole deeper.
 
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