The cars are fundamentally different, different aero, different grip, different dimensions. It's not simply the battery.The reason for the overtakes is because they are not pushing, all trying to save battery. If they run out of battery they won’t finish to be disqualified so leads to overtaking. A little different to very other formula where the limiting factor is grip.
It's a hugely more enjoyable sport to watch. Reminds me how much I used to enjoy F1 and how utterly sterile it is these days. Given the surge in popularity since the Netflix docu you'd think they would be pulling out all the stops to improve the quality of the racing.