Understanding Voltage and Current Ratings in AC DC Adapters

Voltage (e.g. 19V)

When purchasing a replacement power supply or adapter, it's essential that you choose one with same voltage as the input voltage printed on the device or within the user manual.

For instance, if your device (such as a laptop) specifies 19V input, you should aim to replace with a like for like adapter that provides 19V of power. Not doing so could cause permenant damage to your device.

While this is all straight forward, there are a few caveats. Most devices allow a small tolerance of 1V either side of the original input rating. So if you have an 18V, 18.5V, 19.5 or 20V adapter for your 19V device, it will be safe to use. 

In the unlikely scenario you've identified your device through our smart search and find a replacement product has a different voltage rating, please get in touch to speak to a member of the team who will be happy to help.

Amperage (e.g. 3.5A)

Amperage is usually displayed on a charger by A or Ah symbols. In a nutshell, the Amps rating on a power supply, charger or adapter explains the maximum amount of current that it can safely provide in an hour.

Any amperage of charger rated above what's required for your device is safe to use with your device, providing the PSU voltage is the same as the input voltage or within a tolerance of 1 volt.

For instance, if your device (e.g. a laptop) is rated as 3.5A, it's acceptable to use a higher rated power adapter as the amperage of the adapter displays the maximum current it is able to provide, and your device will only ever draw the amount that it needs.

Conversely, if you use an adapter with a lower amperage than the device specifies, it may take longer than expected to charge or have the potential to cause your device to malfunction or overheat.

As we've mentioned, our power supplies are designed to be a precise replacement for your original bundled charger or adapter, but if you have any specific questions please do get in touch and we'll be happy to advise.

Wattage (e.g. 60W)

The Watts or W rating on a power supply is used to explain the maximum of power that the power supply is able to deliver.

We don't list the wattage of our power supplies on the website, but calculating the wattage of a power supply can be achieved with a very simple calculation:

Simply multiply the Amperage with the Voltage, e.g. 30A (Amps) x 5V (Volts) = 150W (Watts).