Electronic – Reading and understanding electrical specs on laptop AC adapters


My Dell laptop comes with an AC adapter with the following specs:

65 W
Input AC: 100 - 240 V, ~1.5 A, 50 - 60 Hz
Output DC: 19.5 V,  3.34 A

My HP laptop:

65 W
Input AC: 100 - 240 V, ~1.7 A, 50 - 60 Hz
Output DC: 18.5 V,  3.5 A

I have 3 questions:

  1. On the Input AC, why 1.5 A vs 1.7 A? I just have one type of power outlet for everything, such as lamp, TV, refrigerator, etc. So this number is not too significant?

  2. The output DC voltage and current are different. Would it be safe for me to interchange the adapters, i.e. use the HP laptop with the Dell AC adapter and vice versa. Which way would be safe and which is not?

  3. If there's another adapter with the same output DC but higher wattage, would I be able to use it as well?

Best Answer

First, the over arching thing is that if the voltages match and the charger can supply more current the the original you were given, you are fine. If it supplies less, it may still be enough, especially if the battery is already charged.

  1. Your wall socket will general be able to deliver in excess of 15A(depends on your country). The input current they expect is based on how much power their circuit actually uses.
  2. Actually, their voltage is different, which is normally a larger issue for the adapters but the reason that interchanging is somewhat safe is for a hidden reason. Let me note first, plugging in a mismatched adapter can damage your device, and easily, if it is not able to handle the voltage you are going to supply. Most adapters user a communication protocol to verify the adapter was purchased from the original equipment manufacturer(OEM). If they do not detect this they often limit their power draw to "protect" the charger. This gives the advantage of protecting the charger if it is underrated.
  3. Yes, you should be able to if the computer believes it is acceptable to use(no comm protocol to recognize a mismatched adapter). This voltage output is what primarily determines function. In electronics voltage controlled circuits are much easier to generate and use. This gets a bit too detailed, but I hope this information helps.
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