In most cases when a battery fails to take or hold a charge it usually means the battery has "lost" cells and the battery is no longer viable. Running a lithium ion battery down to very low and then charging it back up is very bad on these laptop batteries. These batteries do not get a "memory" like in the old days, these you can leave on the charger all day and it won't hurt them....but running them down and then charging them up will shorten thier life expectancy.