Bugger me kingpins. Think about it. This is like using the power of an alternator to run your car while it's recharging your battery. Y'see - I think this is why HEVs have been so slow to move to lithium - recharging a discharging lithium battery is bad according to the sciency folk. They're currently doing it but it degrades the battery according to the maths. I think this is why they have persisted with the nimh battery - it recharges during discharge with no probs.
And they used a rotary design. Now that's stupidly simple. You need to be a petrol head and a little bit of a conspiracy theorist to understand why the rotary design is so funny. I like it - but it's a funny how the design was 'allowed' when it comes to ICE designs from decades ago.
