I'd like it if the Better Future batteries had a slight amount of passive energy generation. The observed effect of this would be like multiplying the battery life by a small amount, rather than just adding to it. In fact, they could probably have two blocks: A battery that simply stores a fair amount of energy, and a slightly larger fuel cell, which stores a small amount of energy, but also generates some. Due to how fuel cells work, it would require a slight drain on fuel, but if it only generates energy when energy is below 80%, then it shouldn't be a big burden on fuel availability. This would also help with their power hungry anti gravity blocks.