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Can we charge a 5V 1A phone with a 2.1A or 2.4A charger?

Phone cable charger
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Can we charge an iPhone or an Android phone (Samsung, Sony, etc…) that accepts 1A with a 2.1A iPad charger? Or even with a generic 2.4A charger available at FNAC?

And conversely, can you charge a 2.1A iPad with a 1A iPhone charger?

Charging your phone

Charging a phone or any other electrical or electronic device is very simple. There are just two things to know:

You have to look at the power needed to charge your device, that is to say the voltage and the intensity. It is usually written on the device or on the battery of the device (it is the voltage and current IN):

  • Mobile phones typically require 5 volts and 1 Amp.
  • Tablets generally require a voltage of 5 volts and a current of 2.1 Amps.

The voltage

You should also know that the Voltage must be STRICTLY the same. You can only charge a device that requires 5 volts with a 5 volts. But generally, chargers all deliver 5V; the question is more about amperage.

The amperage

On the other hand for the intensity expressed in Ampere or mA there is just one rule to respect for a good charge: it is necessary that the amperage of the charger is higher or equal to that of the device. If your device requires 1 Amp charging current, you will need a charger that delivers at least 1 Amp to charge it well; so yes with a charger that gives 2A or 3A or 4A or etc etc, it’s also good, because in fact, the charger’s current is the Max current it is capable of delivering! So if your laptop only requires 1 Amp and you have a charger that goes up to 2A, that’s fine! The device to be charged will only take what it needs in terms of charge. On the other hand, if your laptop needs a charge current of 1A and your charger can only provide a maximum current of 0.85A (or 850 mA), the device to be charged will not charge well, and may even be unusable because there is not enough power in the battery! So even if you leave a day or a year to charge your device that requires 1 A of charging intensity, with a charger that can only give 0.850 A, the device will not charge well even in 1000 years!!!


  • To charge a device well, you must have exactly the same voltage between the charger ( voltage out ) and the device to be charged ( voltage IN ), ie 5Volts = 5Volts.
  • On the other hand it is necessary that the intensity that the charger can deliver, is always higher, than the intensity necessary to charge the battery of your device. So with a charger of 2A or 3A or etc etc, you can easily recharge a battery that requires only 1A in charging intensity.
  • On the other hand, if your device requires 1A of charging intensity, you can’t charge it well with a charger that delivers at most only 0.8A for example.

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