If it is a good "universal" charger, it will have voltage selection slide switch somewhere to choose the value closest to your needs and not just plug adapters.
Although never connected directly to your internal batteries, DC-DC convertors onboard charge the battery cells for optimal efficiency based on a required input range, and then others for providing the on-board DC requirements.
Also buck regulators often have a wide range of input voltages but exceeding these unknown limits in your case might exceed the breakdown voltage of input capacitors and regulators, which may cause premature failure. Using double the voltage is pushing it. Don't guess find out from the Mfg or get a proper range.
Look for a voltage selector switch or a universal with range options to suit your environment.