Finding the Right Model of Adapter
Get the laptop’s model number. This is usually printed on a small sticker affixed to the underside of the laptop.
Get the power requirements for the laptop. This is also printed on a
small sticker affixed to the underside of the laptop. It may also be
printed near the laptop power port.
finding out the voltage & current
To find out the voltage & current, turn your laptop over and look
for a label, sticker or writing which shows the voltage and current, it
should look something like the examples below. The voltage figure will
have a "V" after the number i.e 19V and the current will have a "A" or
"mA". i.e 3.15A. You can also find these shown on your original AC adapter if you have it.Ensure that the voltage for your adapter matches
the voltage (a difference under 1V is okay to accept) of the product
that you are buying on batteryadaptershop.com.The current for the
adapter may vary as this will only cause differences in the time it
takes for you to charge your device. However, it is not recommended that
you buy a laptop ac adapter with a lower current than your original.
Buying a laptop adapter with a higher current will not affect your
laptop in any way.
The following will cause damage to your device:
Reverse polarity
Higher voltage adapter than device rating
The following will cause harm to your power cord or adapter:
Reverse polarity
Lower current adapter than device rating
The following might not cause damage, but the device will not work properly:
Lower voltage adapter than device rating
Higher current adapter than device rating
Soure from : https://www.batteryadaptershop.com/article.html?p=4
