Whilst the efficiency of a battery electric system is greater than a HEPS, batteries just do not allow for the range flown by most aircraft. Electric cars and trucks are less sensitive to battery weight and a battery electric system is the ideal solution for them, but this is just not the case for aviation.
An electric car in used normally in the city is unlikely to use its full charge on every trip, which is good for the battery and will allow for a high number of cycles on the battery, perhaps 1500 cycles, or more, and if the battery continues to degrade in a car, then you get a little less range and a little less maximum power – not the end of the world.
With aircraft, it is undesirable to carry around lots of extra battery that you don’t use, that is if you want to carry passengers. So, each flight, the battery uses almost all of its charge. This is tough on the batteries, which means they degrade quicker and might only be good for 400 cycles or so. Unlike a car, if an aircraft has reduced power or range, it becomes a safety issue, so you must replace the batteries once they degrade a certain amount.
All of this increases the operating cost of the battery electric system. Whilst it may still be cheaper to run than a fossil fuel turbine engine, combined with the range limitations, battery electric becomes a less attractive option for most commercial routes.
If batteries were better then Stralis would much prefer to pursue this option, given its superior efficiency, simpler system and zero-emissions, not even water. Unfortunately, it just isn’t the case, even with the most optimistic future projections of battery performance, we cannot see them being able to support any but the shortest of flights, which won’t have much impact on emission reduction.