HP and Compaq are the same company. HP is one of the easiest brands to find battery part numbers. There should be a white sticker with a barcode on every battery, and on this sticker, there is what HP calls a “Spare” number. Usually the sticker shows, “Replace with HP spare” and following that are 6 digits with a dash and 3 more digits. There are various other numbers stamped on HP batteries that you can use to cross reference if the white sticker is damaged or missing. These numbers start with “HSTNN” and then a dash and several numbers and/or letters. On certain batteries, there is also a number/letter code near the HP logo. This code is two letters followed by a few numbers.

Examples of HP part numbers: MU06, KI04, 593553-001, HSTNN-104C