Hi, Does anybody know if I use a 5V, 0.8A adaptor plugged into my car's cigarette lighter to charge my MP3 player (that is supposed to be charged with a 5V, 1.6A charger), will it do any damage, to either the MP3 player or the charger? My guess is it should be OK, since the current output from the charger is less than what the player can take, but a colleague reckons that the player will try to draw more current from the supply and do some harm to either it or the charger. What do the experts think? Many thanks. Bob
You'll cook off the charger. You're asking a unit tagged for 0.8 amps to supply twice its rated output. Not a good situation no matter how you look at things.
Your guess is totally wrong, in every way that it possibly can be - It's exactly the reverse of reality.
The *DEVICE*, not the supply, determines how many amps will be drawn from the supply. The supply's rating is an "I am capable of pushing up to this many amps if you need it, but no more" number. The device's rating is an "I'm going to try to pull this many amps from the supply" number. If the device's number is higher than the supply's number, the result is going to be a fried supply. How the supply cooks off is going to be a function of how overloaded it is - A slight overdraw may just quietly go "pfft" and let out a wisp of smoke. A major overdraw can literally turn the supply into a bomb.
When choosing a supply for a device, the specified voltages must always match, or the device is likely to be either damaged (if volts too high) or non-functional (volts too low), and the amp rating of the supply must be equal to or greater than the amp rating of the device, or the supply will likely be damaged.
Your colleague is correct. You're almost certain to fry the charger if you make the attempt.
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No your colleague is correct. The current sucked out of the charger depends on the load. The MP3 player spec says it needs 1.6A so your 0.8A charger would be overloaded.
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