Replacement Laptop Charging Adapter Demystified

Laptop charger

Much confusion surrounds the replacement of laptop power adapters.  There really are only a few things that you need to know when shopping for a new power supply.

The bottom of most laptops will contain information regarding power requires:

Minimum laptop power requirements

This is the minimum power required to run this laptop.  In the case of my Toshiba, it needs 19 volts by 3.95 amps.  Multiply the two numbers together and you get 75 watts.  Volts x Amps = Watts.

The wattage is only a potential amount.  Laptops are not “force fed” power by the power supply; they draw in power from the power supply as needed.  There are circuits in the laptop that regulate how much power it takes in at any given moment.

  • DC 19 volts is a constant for this laptop.  The replacement power supply must match that number.
  • 3.95 amps is the minimum number of amps required, but that number can go higher.
  • The end tip that plugs into the laptop must match the manufacturer’s original specifications.

A replacement adapter that is DC 19V x 1.58A is only 30 watts and will not work.  But a replacement adapter that is DC 19V x 4.74A is 90 watts and will work.

Think of it in terms of a desktop computer power supply.  They range from 180 watts to 1600 watts, but the voltage is always the same.  Which one a manufacturer puts in a desktop system is dependent upon internal amperage requirements and cost.

Always check with the laptop manufacturer’s website before purchasing a replacement power adapter.  For the example above, Toshiba recommends a 120 watt power supply replacement (19V x 6.3A), even though the original power supply was only 75 watts.

Don’t worry.  Your laptop will not explode if you replace the power supply with a recommended higher wattage power adapter.

Feel better now?



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