Does anyone know how the 1000V limit is defined? If it is the highest voltage anywhere in the system at any time you would definitely have to limit the number of series cells - to 1000/4.35V (the maximum charging voltage of a LiHV cell) = 230 series cells.Vanja #66 wrote: ↑Fri Jun 14, 2024 9:08 pmI've mentioned battery size and Amps as a general relation, 2026 PU will be limited to 1000V, so the peak current won't be lower than 350A. C rate depends on battery capacity (Ah), which is the parameter teams can play with. 4MJ is only 1111Wh of capacity, which can be achieved with 4-5kg of LiPo batteries. ES has to be at least 35kg (with casing and everything) so batteries can be oversized for bigger capacity and lower C rate.

I guess we can assume batteries will have around 6kWh (25-30kg of LiPo cells in this case) capacity to keep it round and simple, so at 1000V max capacity (for a LiHV cell) that's 4.3V per cell, ie 232 theoretical cells and that's working voltage of 858V - meaning 7Ah of batteries. At 408A (350kW at 858V), you have a C rate of 58C which is quite ok, there are cells that can go over 100C. So if you reduce capacity to 3kWh you are at 115C and if you drop to 2kWh you are already at 175C which is usually too high.

If you limit your LiPo cells to their nominal voltage of 3.7V and settle for 270 theoretical cells to reach maximal=nominal 1000V, you are "down" to 6Ah capacity, but your current is now also "down" to 350A and this keeps C rate at 58C of course. Lower current means less heat and higher number of cells means closer Voltage between min and max SOC for each cell and in this case cells will practically stay around 3.7V the whole time since you are only using 1.1Ah of 6Ah of capacity. This will also extend their working life a lot, compared to having them go from 4.2V to 3.2V and back 2-3 times a lap.

OTOH 1000V might be the maximum operating voltage of the MGUK, in which case higher voltages might be possible in the ES and therefore a higher cell count.