I do not mean to hijack this thread. but I also need to replace the battery in my laptop. my question is about how many cells. being a mechanic all of my life. I have been used to lead/acid type of batteries. with that type of battery, each cell makes 2.2 volts. so on laptop batteries, does this hold true as well? will a 9 cell battery make more voltage than a 6 cell battery? and if it does, will the extra voltage harm my computer? also, does anyone make a plug in charge cord to use in an automobile? to charge a laptop from the cars charging system? I have a Dell Precision M90.