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?

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?

 

[Anton]

Hi there and welcome to the forum!

You're correct that 20S1P is misleading. The battery specs point to something different. Also the size, weight and the pictures show a much larger battery.

I spotted a URL in one of your photos which lead me to the manufacturers website "ailorenergy". I then found the page which shows the battery pack you are looking at: https://teluoy.com/product/电摩电源-72v-75ah/

After translating the page from Chinese into English, it hinted that the 20S1P pack is "Soft package". Soft package cells are also known as pouch cells. You may have seen them in laptops and power banks. They are very lightweight and fit into small spaces.

Based on that bit of extra information from the website, I somehow don't think you'll be getting 21700 cells in this battery. 21700 cells are known as hard package cells.

I would say that the downside to using a battery with soft package cells on an ebike is that they are not as durable as a battery with hard package 21700 cells.

 

[ebiken00b]

Wow, Anton, your googlefu is very advanced, much appreciate the deep dive.
So you're saying the guts will likely look like this:

Not to be a pest, but is there anyway you may have a guesstimative approximation on the durability delta between hard and soft packaged cells? Like is it 1 yr vs 10 yrs, or like 5yrs vs 7 yrs? Ballpark... I tried searching that stuff just now and no luck.

 

[Atavar]

More like 5 years vs first hard bump.

 

[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.

 

[Anton]

From reading online, I see that pouch cells / soft package cells are popular with e-motorcycles to save on weight and space.

So why aren't pouch cell batteries common on ebikes?

My theory is that batteries using pouch cells might cost a bit more to manufacture to the correct size and shape.They also need proper compression so that they hold their shape, and some form of outer protection.

With cylindrical / hard package cells, you can easily customize the shape of the battery by adding or removing a cell here or there.

With pouch cells, you would need to go back to the start and redesign the actual cell to end up with different shaped battery.