All laptop computer batteries have electrical specifications that include its volt and milliAmp hour rating. These terms are abbreviated as we see in the following example: 10.8V, 4000mAh
What do these terms mean, and why should you care about the specifications of laptop computer batteries?
Volts - or V - are an electrical measure of energy potential. You can think of it as the pressure being exerted by all the electrons at a laptop computer batteries negative terminal as they try to move to the positive terminal.
Amps - or A - is an abbreviation of Ampere, a 19th century French scientist who was a pioneer in electricity research. Amps measure the volume of electrons passing through a wire in a one second. One Amp equals 6.25 x 1018 electrons per second.
Amp hours - or Ah - measures capacity. That is what we want to know about laptop computer batteries - how long can it deliver a certain amount of charge before it runs out. As with all metric measurements, Amps can be divided into smaller (or larger) units by adding a prefix. In the case of laptop computer batteries, a milliAmp hour (mAh) is most commonly used. Note that 1000 mAh is the same a 1 Ah. (Just as 1000mm equals 1 meter.)
Note that Amp hours do not dictate the flow of electrons at any given moment. Laptop batteries with a 1 Amp hour rating could deliver ½ Amp of current for 2 hours, or they could provide 2 Amps of current for ½ hour. To understand how much current your computer pulls from its battery, see our article on "Laptop Power Consumption and Battery Life".
Typically, laptop computer batteries will use 1 to 3 Amps per hour, depending on the model's processor speed, screen size, screen brightness adjustment, usage of the CD, DVD, or Floppy drives, and other factors.
Keep in mind that slight variations in voltage generally do not impact the performance of your laptop. We see this all the time with universal and external batteries. The original laptop battery might be specified at 10.8 Volts, but customers using a universal part can operate their laptop safely at either the 10 or 11 Volt setting.