Hi @alejandra17903
Create a [https://www.windowscentral.com/generate-battery-report-windows-10|battery report] to check the condition of the battery.
Once you have the report, compare the ''Design Capacity'' value versus the ''Full Charge Capacity'' value, as shown in the report. For a good battery they're nearly the same value.
You can work out as a percentage the condition of the battery by using the formula: ''Full Charge Capacity value x 100 ÷ Design Capacity value.''
If the percentage is <35%-40% you may want to replace the battery.
Search online for ''Acer Extensa 2509 battery'' to find suppliers that suit you best. Perhaps check the battery model number (printed on battery) to ensure that you're getting the same model replacement.