20S1P - Is That Even Possible

[ebiken00b]

Hi folks.
I have an Alibaba ebike vendor claiming a 72v75AH battery in their bike. When I asked about the details, they said it was made of 21700-type cells with 3.6v per cell, and sent me a few pictures of the battery. While its dimensions and weight seem reasonable for the amp hours, a denomination of 20s1p doesn't make sense to me. Does anyone have any input on the brand and the configuration/rating claims?

 

[neptronix]

Today's largest 21700 cell has about 6ah of capacity.
No mention of the brand of cell they're using?

Any uncertainty in the specification should be a signal to back out for the buyer; very easy to get ripped off on batteries from a China seller ( & you can't send it back )

 

[ebiken00b]

Today's largest 21700 cell has about 6ah of capacity.
No mention of the brand of cell they're using?

Any uncertainty in the specification should be a signal to back out for the buyer; very easy to get ripped off on batteries from a China seller ( & you can't send it back )

I will try to find out the brand but it's the 20s1p that's throwing me off. How can more than 1 cell be parallel to itself?

So let's say that each cell is 5ah. To get 75ah, one would put 15 of them in parallel, which should be notated as 20s15p, if my assumptions and math are correct. If said cell is only 4ah, the spec should be 20sp19 (rounding up from 18.75).

However, given how that battery box is shaped, 20s15p seems more likely, so 300 cells total.
Also, using an approximate weigh of a 21700 cell as 72gr, we get 300 x 72 = 21.6kg, out of a total 24kg, leaves 2.4kg for the internal packaging/box/wires, etc, which also appears within reason.

Presumably (oddly) the battery manufacturer stated how many cells are in each series and not the entire battery packs' abbreviation.

I'm guessing nobody has heard of Ailorenergy or Nanjing Teluoyi Electronic Technology companies (per the label) as a battery manufacturer?

More to come, thank you for helping me find some center in this.

 

[Diggs]

I've seen some tricky marketing done on Aliexpress and Alibaba. They'll add the cells in series for voltage and "total" amperage. (Yes, there is 75ah in 20 cells each at 3750mah.)

 

[BlueSwordM]

The only other possibility is a legitimate 21700 cell: 21mm wide, 700mm tall

 

[chuyskywalker]

21700 cell: 21mm wide, 700mm tall

lol, I legit only every write 1865 and 2170 for this exact reason.

To the OP: it could possibly be that they are using some kind of pouch cells. Or it's just ineptitude.

 

[docw009]

They do make 3.6V75AH lithium-polymer pouch cells. A battery that size with Lipo seems scary. Do it in LiFeP04 pouch with less AH and more safety,

 

[ebiken00b]

Just got a reply from seller after some painstaking inquisition. It is indeed a pouch cell that they called a "Ternary soft sheet battery"
In other consideration, Dewalt does use pouch batteries as their newest way to save space/weight, and I have used their newest in their highest rated impact gun for 5 minutes at a time of hard impacting on some very stuck bolts. Granted I trust Dewalt's battery mfg and QA process... but still a point on the pouch cell scoreboard, no?

So the mystery has been resolved, there are 20 of these pouch cells in that box, each with approx. 3.6v and 75ah, making for a 72v/75ah total.
Now it's a matter of being a testbunny for this ebike/battery combo or not... I will keep you folks posted on which way I end up going and the results.

In the meantime, thank you for all the input and help that got us here, and any further comments or thoughts are of course welcome.

 

[ebiken00b]

As an aside, their rating of 20,000 watt for the ebike, while having a 72v system using a 200amp controller is also suspicious, given how that should be a max of 14,400 watts, but that's a story for another thread.