Cordless tools using 20700 / 21700 cells

[spinningmagnets]

Metabo so far...

http://www.coptool.com/cordless-power-tool-lihd-battery-cells-18650-vs-20700/

The pack is listed as a "6.2-Ah LiHD", and is used on their metal-working and concrete tools, which have been the most powerful in any contractor-grade cordless tools (impact drill, angle-grinder used for cutting steel, etc). 36V is ten cells in series, so...the pack looks so small, I suspect it is 1P. Of course, that would mean that these cells are 6200-mAh each?

But...if it is 20 cells at 10S / 2P, then...the pack would be larger, right? Its rated at 21A, and that sounds right for a large 20700 cell in 1P which is maximised for range...

https://www.ohiopowertool.com/p-164...0-36v-9-angle-grinder-kit-62ah-613101640.aspx

edit: the 18V shown is 5S / 2P...sooo...the 36V of the same size would be 10S / 1P?

 

[Warren]

Fewer cells means fewer straps, fewer spot welds, lower resistance. We should see these in e-bikes this year...long before most will see them in a Tesla.

 

[Hillhater]

Metabo so far...
. 36V is ten cells in series, so...the pack looks so small, I suspect it is 1P. Of course, that would mean that these cells are 6200-mAh each? ......

More capacity than has ever been suggested previously for 20700 cells ?...practically double the best 18650's...doesnt seem to be realistic . :?
So someone needs to get some for testing to confirm.
21A seems low for a high spec power tool also ?

 

[spinningmagnets]

This is why it is news...the more capacity you have, the less amps it can put out. Like this:

20A__2500-mAh___25R

15A__3000-mAh___30Q

10A__3500-mAh___35E

35E has 40% more capacity, but half the amps of the 25R, so...this is not crazy to suggest. When that paradigm is scaled up to the larger 20700, who knows? but I agree, want to have a real test by a trusted person.

 

[redilast]

It is probably using 2P of the NCR20700A.

 

[Hillhater]

35E has 40% more capacity, but half the amps of the 25R, so...this is not crazy to suggest. When that paradigm is scaled up to the larger 20700, who knows? .

...But the point is ,..the largest capacity commercial 18650 is 3.6Ah,..presumeably limited by current chemical technology.
The 20700 has 33% more volume than the 18650, so we could expect 33% more capacity...4.8Ah !
But 6.2 Ah is 72% more capacity ??
So, i agree ..they have to be 2p configured.

 

[TheBeastie]

18650s were ideal for the laptops since the 90s as you don't want a cell fatter than 18mm wide, but now fat chunky-laptops are very much near dead since its all pouch based if not even tablet form only now its all over.
So there is no true mass market home for 18650s and it's logical they will move to wider cells for power tools since 18mm isn't crucial anymore.

 

[Hillhater]

^^^^^ So. Why not just move to the established 26650 format as the manufacturing systems already exist ??

 

[TheBeastie]

^^^^^ So. Why not just move to the established 26650 format as the manufacturing systems already exist ??

I eyed buying 26650 cells for a long time for my neodymium battery pack project since the larger surface area for contact would be ideal, but 26650s have always been a combination of being way too expensive for the Ah and just dodgey only brands.
This has led me to believe that the bigger players at least in history believe 26650 is to big of a cell size. And obviously, Tesla making there own 21700 size which is only 3mm bigger in width feel the same way.

The best argument I have seen against 26650 in general is to think of it like grouping a bunch of large barrels next to each other, the gap between them is so big you could put your arm through the middle of them but if you had a set of smaller pipes you can't, its the effect of having larger circles grouped together actually wastes space.

 

[spinningmagnets]

Just found this. Not verified yet, but interesting...

Bosch 6.3 Ah EneRacer battery pack uses NCR20700A
Metabo 625343000 18V 3.1 Ah LiHD Battery Pack has 5 NCR20700A’s in them
Metabo 625341000 18V 6.2 Ah LiHD Battery Pack has 10 NCR20700A’s in them
Metabo 625344000 36V 6.2 Ah LiHD Battery Pack has 20 NCR20700A’s in them

http://budgetlightforum.com/comment/1084200#comment-1084200

 

[travellin]

Russell did a teardown and analysis on the DeWalt 20V Max 6.0Ah pack (DCB206) and found NCR20700A cells:

https://syonyk.blogspot.com/2017/04/dewalt-20v-max-60ah-pack-teardown.html

 

[Hillhater]

^^^^^ So. Why not just move to the established 26650 format as the manufacturing systems already exist ??

The best argument I have seen against 26650 in general is to think of it like grouping a bunch of large barrels next to each other, the gap between them is so big you could put your arm through the middle of them but if you had a set of smaller pipes you can't, its the effect of having larger circles grouped together actually wastes space.

Not a very convincing argument !
If you do the maths, you will find there is no difference in the "unused space" if you use big barrels or small pipes !

 

[Overclocker]

 

[spinningmagnets]

I don't know why Tesla didn't just go with the existing 26650 format, but...if any ebiker wants to build a pack out of 26650's, they are available anytime they want.

 

[Punx0r]

I think they are disadvantaged with thermal dissipation (inside of cell to outside) due to relatively high volume compared with surface area.

There also isn't anywhere near the choice of quality cells on the market as 18650.

 

[Hillhater]

I think they are disadvantaged with thermal dissipation (inside of cell to outside) due to relatively high volume compared with surface area.

There also isn't anywhere near the choice of quality cells on the market as 18650.

I thought SM was suggesting that Tesla could have made 26650s instead of going to a new 21700 format.

 

[spinningmagnets]

Yes, that's what I was referring to, but...I am certain Tesla has done a lot of computer modeling, and also physical tests to verify their computer results. If the 26650 was acceptable I think they would have used it, and there must be some reason they like the 21700 better. My best guess is that it would shed heat better, as PunxOr suggested.