openinverter forum

Again, it all comes down to how the cells are built up chemically and then also how they are built up physically. Thickness of each of the layers ect.

If you want a true "symetrical" cell super caps are the way to go. However they have large drawbacks in terms of energy stored.

It all comes down to drive cycles, you keep looking at data but you do not know the full context around a number there is not point comparing it to another another number.

Some context would be fantastic, could you explain a few of the tradeoffs inherent in the battery specs?

I'd would like some more details on typical drive cycle life too and how high current use affects them if you have any links?

I'm also not clear whether you are saying the charge/discharge characteristics are typically fairly symmetric or strongly asymetric?

I've already done the sums on the super cap option and the numbers needed, even for relatively modest energy levels, are unrealistic both in terms cost and size (didn't bother working out the weight!)

High power cells are physically constructed differently. Internally they are constructed as if they were many smaller cells in parallel, by interleaving. Certainly the hobby lipos I fully discharged and opened up were.

doobedoobedo wrote: ↑Fri Mar 24, 2023 1:43 am High power cells are physically constructed differently. Internally they are constructed as if they were many smaller cells in parallel, by interleaving. Certainly the hobby lipos I fully discharged and opened up were.

Thanks for that, that would make sense. The reduced inter-electrode distance and increased electrode area would reduce cell resistance. I suppose essentially it's trading power density for energy density (the space taken up by the extra electrodes doesn't contribute to energy storage).

I've been wondering about endothermic and exothermic reactions and whether that might explain some asymmetry in the electro-chemistry. A google this morning threw this up https://ntrs.nasa.gov/search.jsp?R=20070032054 which indicates that charging can be endothermic while discharging is always exothermic so from a thermal point of view charging should be less stress on the cells that discharging - more research required!