[rini17]

Thinking about it, indeed lithium charge/discharge efficiency over 90% is kind of magic :) and not even needing high pressure or cryogenic vessels.

[Hypx_]

All close cycled cells have the same properties. Ultracaps are even better.

[rini17]

Nope. Both NiMH and lead acid batteries are less efficient in this regard. And supercaps have lower energy density, although they are improving quickly too.

[Hypx_]

NiMH is around 90% efficient too. Lead-acid around 85%. Also, li-ion don't do well under high discharge rates and can drop to <70%. It's not a perfect cell technology by any means.