Battery problems for planes are huge. Atleast for a big plane like a 787 MAX the battery to achieve same performance would easily weigh more than the aircraft by an order of magnitude.

I imagine even for bush planes the battery weight will be immense due to the much much lower energy density (it's about 2-3 orders of magnitude and you loose fuel while you fly, batteries don't change weight when discharged).

edit: electric motors do have penalties for high altitude, notably the reduced pressure will make cooling less efficient and reduce the maximum power output (though generally your efficiency overall should remain stable and normal)