How to find the laptop battery specifications
There are different types and sizes of laptop batteries. To determine what laptop battery you have, remove the battery from the laptop and look at the top or bottom of the battery.
The Dell battery, pictured here, is a Li-ion battery. Its type is Li-ion II, its rating is 10.8V, 4050mAH, and its charging current of 2.5A. Its unique part number (P/N) is also listed.
Many laptop manufacturers provide details on their website for which batteries their laptops use, including model numbers and part numbers. Check your laptop manufacturer's website to get battery details for your laptop model. The website may also allow you to purchase a new battery or provide a link to where you can purchase a new battery.
If your battery is not labeled or you're unable to read the information on the battery, consider using a third-party utility that's capable of giving you detailed battery information. For example, BatteryCare is a free software utility capable of doing this.