I'm looking to replace the battery for my asus laptop model U43F. As I have searched, I have found that you can get batteries with different voltages. This website below says that you can usually purchase batteries with a different voltage than the original battery and be just fine. It used an example that AC Adapters used in many laptops are rated at 19 volts and supply more voltage to the computer so that it can charge the battery as a reason why the voltage of the battery is not so important. Is that correct reasoning? Everywhere else people seems to think that you should only get a battery with the same voltage as the original battery. http://www.laptopbatteryexpress.com/Laptop-Battery-Batt...
I am with the above poster. The battery should match voltage and have at least the same or higher current rating(mAh or Ah).
I think the other site was try to reffer to the difference between battery voltage and charger voltage.
The laptop has as voltage regulator that changes the incoming voltage to whatever the battery needs. Now in some cases it may have a wider range(Wider range would allow you to use higher or lower voltage), but its not worth finding out the hard way.