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Laptop power supplies, does current matter?
Can I use a power adapter with more current but lower voltage on another laptop?

I have an ASUS K50IN laptop which requires an input of 19 V at 3.42 A. Its charger has stopped working (wires cut by rats!). My brother have a charger that is 19 V, 7.1 A. Their polarity is the same and the tip fits correctly.. Can I use this charger on my laptop?

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    Good question, and yosh m's answer is perfect. Just for your own information, an electrical system will draw X amount of current if it is supplied at Y voltage. If you increase the voltage, the current it draws goes up (as well as the power consumption). The device will only "draw" as much current as is able to pass through it (limited by its resistance). As mentioned, however, trying to draw more current then the charger is capable of may cause heating problems. – Breakthrough Aug 3 '11 at 14:13

The current rating on the charger indicates the maximum current it can supply. So it is OK to use a charger that can supply more current, but not the other way around. That is, if you went to a lower-current charger and the laptop tried to draw more current than the low-current charger can supply, you would likely damage the charger (e.g., burn it out) and possibly the laptop. But using a more powerful charger (one that can supply more current) should work fine. The laptop will draw the current it needs and the charger will be able to supply it.

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    These days power supplies/chargers have protection circuits so if you try to overload them, they will just shut down. – psusi Aug 3 '11 at 17:53

This is from the Apple Support Site, but the principles should apply to any charger. As an additional consideration, using an higher rated adapter may use more electricity because it will not be operating as efficiently at lower power levels.

Power adapters for Intel-based Apple portables are available in 45W, 60W, and 85W varieties. Although you should always use the proper wattage adapter for your Apple portable, you can use an adapter of a higher wattage without issue.

For instance If you have a MacBook (13-inch Late 2009) that normally uses a 60W adapter, you can also use an 85W adapter with that computer. You would not use a 45W adapter with that computer; it would not provide enough power for that MacBook. Using an adapter of higher wattage than the adapter that came with the computer will not cause the computer to charge more quickly or otherwise operate any differently than using the adapter that came with the computer.

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The laptop should have systems capable of handling the increased power. There is the power the charger is rated to handle, and then there is the amount drawn by the peripheral, the laptop, in this case.

The laptop shouldn't charge any faster that it does normally, but it is most likely not to be harmed by it either.

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    -1 for guessing. – TFM Aug 3 '11 at 13:56
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    If only I could minus 1 your comment for adding nothing useful to the discussion. Mine was an educated guess based on years of experience dealing with this sort of thing. It's been too many years since I last studied for my Ham radio license and so I no longer recall the specifics of electronic theory regarding this. But, as evidenced by the other answer you added nothing to, my guess was as good as his facts. – music2myear Aug 3 '11 at 14:10
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    Read yosh m's answer if you're interested in the difference. BTW, you can flag my comment as "not constructive / off-topic" if you wish. I just explained the downvote, I could have done it without writing a word (like the other downvoters)... – TFM Aug 3 '11 at 17:39

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