Hi everyone, I have spent a long time trying to work the following calculation out however feel as though my lack of understanding in electronics is letting me down somewhere.

I am trying to power a motor with 65kW of power at 300V, the source of power is from 18650 cells. A single cell provides a nominal voltage of 3.6V and has a capacity of 3.45 Ah. The motor must be powered by these cells for at least 30 minutes.

I first began by calculating the amount of batteries I require in series which was given by dividing the required supply voltage by the nominal battery voltage, this gave me a rough requirement of 84 cells to achieve 302.4V which is sufficient.

Knowing that when cells are connected in series the capacity remains the same, I can say that I will have 84 cells giving 302.4V with a capacity of 3.45Ah.

Now I must address my need to power the motor for 30 minutes, to do this I need to work out how many parallel banks are required. First I begin by determining how much current the motor requires to produce 65kW at 300V. This is done by dividing the power requirement by the voltage input - 65000/300=217A. I convert this to Ah by multiplying by 0.5 (for half an hour run time) and get a value of 108.33Ah.

So now I know my capacity requirement is 108.33 Ah I can calculate the amount of parallel cells I will need as follows:

108.33/3.45=31.4 which I can round up to 32 banks. This means I need 34 sets of 84 cells connected in series to power the motor for half an hour. The configuration can be written as 84S34P.

Overall this gives me a requirement of 32*84=2688 cells, with a rough mass of 45g per cell I get a total weight of 120kg.

I have tried my best to work this out to the best of my knowledge but still feel like I may have made an incorrect assumption somewhere along the calculations. If someone could please let me know if I have gone wrong somewhere then I would be very grateful. Thank you for your help.