There is tons of reports to propose limiting the battery charging level around middle in order to maximize the lifespan of battery. Notebooks of many brands had already capable to set the charging level while surprisingly I have not seen this in Acer which is also impossible to introduce one due to hardware design.
What I see replies most are still suggesting stone-aged information like "keeping 100% battery level does not hurt the battery" or "Lithium ion battery has no memory effect" without judging the fact that "keeping middle in battery level can extend the battery life significantly".
This is one of those report you may refer:
http://batteryuniversity.com/learn/article/how_to_prolong_lithium_based_batteries