General

To amplify- look on the original charger. It will give the details about the output capacity of the charger, which you will need to match with the replacement charger.

Look for a label or molded on lettering that talks about the Output.
You'll need to find:
-Voltage (something like 15v. or 12v. or whatever)
-Current (something like 750ma or 1A or similar)
-AC or DC (the voltage may be shown as 12vAC or 15vDC or similar)
-Polarity (there may be a diagram with two horizontal lines, one going to the center, one going to a circle around the center. The one at the center will be marked as either "+" or "-". Not all chargers give this detail, and if it says "AC" on the voltage there won't be a polarity diagram.)

The charger you buy should have the SAME voltage as the original.
It should have AT LEAST the same current, but higher is OK.
It should be the same AC or DC as the original.
A universal charger may allow you to switch the polarity so if it doesn't work with the polarity switch set one way, try it the other way.

Like djp said, knowing the computer brand and model number would allow looking this info up online.
Note- the battery specifications don't affect the charger. You need to check the charger specifications.

Another thing to try would be to use the Amazon search box and type in your computer name and model and "charger" to see what comes up.
They may have a charger already checked out as appropriate for your computer.

It would be better to post the specs of the original charger if possible. A laptop's power delivery system, which includes both the charger and the battery, is designed based on the power requirements of the core computer components. Posting the laptop model is the next best way to determine the power requirements of the system.

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