like hoot mentioned - a low draw LED can put almost no drain on battery packs. i mean look how long one of those little keychain LED's that you use for keying into your house lasts on just a watch battery.
with a 12V lithium pack in place, you could probably run that led for DAYS at a time without running the pack low.
i mean look at the performance company's like bosch are getting out of their small drill/drivers/impactors that run on similar battery technology.
thank god for cell phones pushing the advances in battery technology! ok so i'll give some credit to the electric car thing... too... but i think most of it is related to consumer mobile electronics being so popular. that industry smokes the electric car industry in success and sales volume by exponential numbers.