Thankfully a car battery isn't the answer!
Stanford University has discovered a method using silicon nanowires that can give a conventional laptop battery 40 hours of battery instead of the traditional 4 hours.
Citing a research paper they wrote, published in Nature Nanotechnology, Cui said the increased battery capacity was made possible though a new type of anode that utilizes silicon nanowires. Traditional lithium ion batteries use graphite as the anode. This limits the amount of lithium--which holds the charge--that can be held in the anode, and it therefore limits battery life.
Silicon anodes have the "the highest theoretical charge capacity" according to Cui's paper, but they expand when charging and shrink during use: a cycle that causes the silicon to be pulverized, degrading the performance of the battery. For 30 years, this dead end stumped researchers, who poured their battery life-extending energy into improving graphite-based anodes.
Cui and his colleagues looked at this old problem and overcame it by constructing a new type of silicon nanowire anode.
There are a few issues to commercialising this however it's exciting to see such a breakthrough.
You can get more details HERE