28kWh isn’t enough for a Formula E race. They swapped cars in the middle of the race back when they used those smaller batteries. They now use 54 kWh batteries[1], though power output is limited to less than a Tesla Model 3.

Next year they’re supposed to increase power output to 350kW, which is comparable to a Model 3 Performance. Of course Formula E cars are much lighter, so acceleration and handling are far better than the Tesla sedan.

1. https://en.wikipedia.org/wiki/Spark_SRT05e