Their biggest success, I am told, was however single use batteries and the (unverified) rumour that I was told is that they built a matchbox sized singe use battery that in theory could power a car for 400 kms.
Unless it was run off of antimatter this is just flat out made up. Even if you start with the assumption that that matchbox sized battery was 100% solid aluminum that was oxidized to aluminum oxide to release energy and 100% of that energy was usable power that still only gives you 2.2MJ of energy. To put this into perspective a 15 gallon tank of gas contains ~1940MJ worth of energy and while an internal combustion engine is relatively inefficient, it's not like it's going to use almost a thousand times as much energy to go the same distance.
Man I wish HN had reply notifications.