General :: How To Prevent Battery From Getting Full Charge

This question seems a little (a lot) odd. because naturally we want our battery to get fully charged to get the most stamina out of it.

but i read a while ago that for Li-Io batteries the most efficient charge range are 10%-90% so basically that means the full charge -discharge cycles aren't good for the battery but harmful as it cause them to die faster..

anyway i considered this reading as a good theory until i bought a sony vaio laptop which had a battery preservation feature (it limits the maximal charge to 80% or 50% depending on the option) and for more that a year and a half my battery still performed well (less than 4% degradation) so i thought this was a real deal after all.

still the use cases for a laptop and smartphone are vastly different (the laptop can sit with 50% charge just fine since it will be on charge most of the time while the smartphone has to get the maximum amount of energy to last without a charger)

so is there (or can it be made) an app that can limit the charge (to 80% or 90%)