via the draconium flux capacitors (and i presume any other capacitors), you can place any number of draconium blocks on your hot bar and only use 100m rf per slot to turn them into charged draconium blocks

meaning you could charge an entire stack for 100m rf rather than 6.4b RF

this happened on FTB Infinity in case that's important but i doubt it

Thanks for pointing that out. Consider it fixed!

Does this mean it won't charge in the inventory anymore? Or only that it drains full energy?

it will drain the correct amound of energy for the number of blocks in the stack.