How Do I Choose A Replacement Laptop Adapter？

First you should find out what type of Adapter your laptop takes by looking out the sticker on the bottom of your laptop. Those specifications can also be found by looking at your Adapter.

As the picture shows:

The Model number of the Adapter is CPA-A090,

Part number (labeled as "P/N") is LENOVO36200414

Output votage Rating of 20V

Output Current Rating of 4.5A

Voltage Rating

AC/DC: Power adapters can output either ACor DC. You must make sure it matches the Adapter need. Most adapters and devices are DC. You can finger it by looking at the symbols: a "~" symbol means AC, a "￣" with a dashed line means DC.

It’s important to use the current voltage.If a laptop says it needs a particular voltage,then you have to use that voltage. Both lower and higher could be bad. A too high voltage may damage your laptop ,a too low voltage may not work properly.

Current Rating The adapter you choose can not be less than the current rating of the laptop but there is no harm in it being higher.

Wattage Most laptops will list voltage and current but not the Watts, there is a way to convert. A 20V 4.5A Adapter would have the watts of 20*4.5=90W

Polarity of Connector Make sure you have the right polarity of the Adapter.Your laptop on the symbol marked the polarity is center the positive and outside the negative, if adapter picture really can not see what is the polarity of the label, you take a closer look if the symbols and notes on the laptop is not the same, it is absolutely not.

The end summary

Laptop model numbers can often look similar, so make sure the model numbers match exactly. First check the voltage and wattage. It does not matter if the amperage on the charger is higher than the amperage on the laptop.

Make sure you have the right polarity of connector and the voltage and wattage is good then you can charge your laptop.