Just like their AA, AAA, and C cell cousins, laptop batteries create an electrochemical reaction that forces a stream of electrons from one place to another. And just like household batteries, laptop batteries have a positive and negative terminal where electrons are received and sent, respectively.
Laptop batteries, however, have unique characteristics compared to household batteries
- They are rechargeable
- The laptop battery is composed of multiple internal cells
- They contain a small printed circuit board
- Their overall shape of a laptop battery and the location of their terminals vary from model to model
Rechargeable batteries are significantly more complicated to design than a non-rechargeable battery because the electrochemical reaction that provides power must be reversible. As Lawrence Berkeley Lab's staff scientist Frank McLarnon explained to Scientific American.com:
"When a battery is discharged, an electrochemical oxidation reaction proceeds at the negative electrode, and an electrochemical reduction reaction occurs at the positive electrode. When one attempts to recharge a battery by reversing the direction of electric current flow, the opposite takes place: a reduction reaction proceeds at the negative electrode, and an oxidation reaction takes place at the positive electrode.
"In the case of the rechargeable battery, the electrochemical oxidation-reduction reactions are reversible at both electrodes…In the case of the non-rechargeable battery, when one attempts to recharge the battery by reversing the direction of electron current flow, at least one of the electrochemical oxidation-reduction reactions is not reversible. When the battery is charged, the overall reduction reaction that proceeds at the negative electrode may not be the true reverse of the oxidation reaction that proceeded when the battery was discharged.
If the laptop battery process isn't exact, then unwanted build up can take place on either terminal over time, which can cause a dangerous short-circuit.
Also unlike a household battery, laptop batteries are composed of multiple internal cells. These cells are arranged in series and in parallel in such a way that the laptop battery has a higher voltage level than the individual cells. Laptop batteries also contain a small circuit board that controls the way the cells are recharged. Without this board, the laptop battery would not function properly.
Of course, the most obvious difference about laptop batteries is that their physical shape is different from the traditional cylindrical form of a AA, AAA or C battery. Laptop manufacturers custom design their laptop battery packs to conform with the overall functionality of the laptop model. Some laptops and their laptop batteries are engineered for their light weight and small size, others for their ability to replace the functionality of a desktop system. As a result, one size can't fit all in the world of laptop computers. This causes laptop batteries to vary across different models.