from Hacker News

Contrasting a BYD Blade prismatic cell and Tesla 4680 cylindrical cell

by blackeyeblitzar on 3/11/25, 3:51 AM with 2 comments

• by ggm on 3/11/25, 3:58 AM

  Thats fascinating. I was believing the tesla cell mechanism was incremental improvements on well understood battery design tech which can be done at scale by machines, using existing fab methods. It has improvements but as I understood it, Panasonic basically said "we can tool this up to make amazingly good rechargeables for you" and Tesla partnered up to great success. the BMS is also good, and the behaviour of the system as a whole.

  The traditional battery tube/cell process is cooking a jam roly poly in a factory on long tables, to be sliced up as you roll it. So you make a LOT of roly poly at a time for one application of a layer. Rolling things up is well understood for mechanisation. BYD stack layers on layers and then can them which is possibly harder in some ways, depending how you cut the cake.

  The BYD Blade is a different canning principle, but like all cells its a layer cake (a jelly roll is a layer cake in the round) -but appears to have 3 extra processing stages. I could believe that incurs a cost, but also that it makes other elements of construction easier. It isn't as simple as "an extra step is an extra cost"

  They both seem to have very close thermal and energy outcomes. It looks like the BYD has less "canning" cost per unit charge held from the pie charts. Maybe that helps the margins?

  Arranging round things into bigger stacks incurs space losses. They can be beneficial for cooling I guess, but if you integrate cooling in the cell design, this becomes lost space. So "overall density" could be higher for a blade design just because flat square/rectangular things pack denser than round ones.

• by blackeyeblitzar on 3/11/25, 3:51 AM

  This interesting study analyzes the similarities and differences between battery cells from BYD and Tesla. At a high level it describes the cells this way:

  > BYD uses a large prismatic cell format, while the Tesla 4680 cell is a large cylindrical cell with a significantly lower volume

  It looks like the Tesla cells have higher energy density:

  > Comparing the cells on the cell level, the energy density of the Tesla 4680 cell outperforms that of the BYD Blade cell by margins of 1.5× gravimetrically and 1.8× volumetrically

  But the BYD cell has better cooling and is more suited to fast charging:

  > Thus, when designing a system with the same power requirements, the cooling needed for the Tesla 4680 cells must dissipate approximately 2× more heat per volume than that needed for the BYD cell at the same load. Therefore, the LFP electrode design is more favorable for designing a cooling strategy for fast charging.