Li-Ion Prismatic Battery?

[trappermike]

Can someone please explain to me the difference between the usual Li-ion cylindrical cell battery and a "Prismatic" Li-ion battery? Is there some significant difference in performance,cost,etc? Any advantages or disadvantages?
In the photos they don't appear to be a "Pack" of cells shrink-wrapped together with a BMS....
I'm curious as I found a manufacturer offering e-bike size packs,so I'm wondering why I've heard little mention of these :?
I am waiting for them to reply to me with some specs and info,price etc.

 

[dogman dan]

Near as I can tell, the actual battery inside each type is basicly the same. All involve sheets of electrolyte material and seperator sheets. The simplest type is pouch cells. All the sheets are layered inside a pouch, and a big capacity is acheived by more layers inside or larger sheets. Often the pouch pack is taped or shrink wrapped to help it expand less. Next is prismatic, which is basicly a pouch cell inside a square container. Why the container? Because keeping the cells pressed in tight improves performance. Then round cells, which have an advantage of being able to keep the cells even more tightly packed and contained when they want to expand. In a round cell, the stack of layers is rolled up inside.

Round cells can also have a performance advantage because of size. A really large sheet, like found in huge prismatics does not perform as good as a small sheet. So the electrons in the tiny can of an 18650 cell have less distance to travel.

Lastly, the particular chemistry, the kind of electrolyte sheet, and the kind of cathode material, or other manufacturing details way beyond my understanding can greatly affect the performance of one battery type or another. So it's not so simple to say, round is better, or prismatic is not.

As a general rule, it can be easier to fit round cells into an odd shaped pack, like a triangle, or triangle with a t on it, like the shape of the state of texas. This is the shape of the frame triangle on some bikes, a triangle with some space left out for a shock.

Pouch cells can be the lightest, and least volume. So they can be good for a pack intended for a rear rack, where keeping the weight low is important.

 

[trappermike]

I have not received any info on the 36v-10ah prismatic battery yet,but I noticed they also sell individual 3.7v-10ah cells.
The dinensions were very small,a 36v-10ah pack of cells would be 7"L-2.5"W-5.1"H , 7.4 lbs! Pretty small and light! I have no idea if a pack of these need a BMS...
I only found a few specs so far,but life cycles appears to be only 500,maybe this is why they are not popular.
I think most likely the cells are very cheap to buy. The cells are metal encased,with studs and nuts for terminals.

 

[texaspyro]

Prismatic/pouch cells tend to be much more space efficient than round cells when you build up large packs. But round cells can be cooled better in very high power applcations. Both effects are due to the space between the cells when you start stcaking them.

 

[dogman dan]

Sounds like lipo. We know where to get good lipo cheap. Hobby King. Unknown lipo might be the kind that does unexpected stuff.