Those would work in 0.2efficiency... i like it.
Dont complain, if you want the full power of the uranium get yerself a nuclear reactor.
...Wait are we talking about 1 uranium > 1 battery or more batteries per uranium? If the second case i can only agree if its 2 batteries per uranium.
I was thinking about 4 uranium cells per battery, to have EU/t output high enough even with 0.5 eff. and longer running time.