# Using a 19V (3.42A) power adapter instead of a 20V (2.0A) for my Lenovo laptop. Is this safe?? (Laptop battery is non functional)

Im ready to accept "long term" degradation to my laptop if i can remain lazy and not go having to find a perfect replacement adapter. Third world electronics scares me (Im in the third). As long as i can run my laptop without my files being wiped out.

Thanks

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Voltage is a measure of electrical pressure (think of it as water pressure). Amperage is the amount of current (imagine this as the amount of water available). What you have done is decrease (slightly) the pressure, but increased the amount of available electricity. Overall you have a higher wattage (volts X amps) plug.

The question is, is this dangerous? Not in the amounts you have stated. You are providing more amperage than is needed, but only the amount that is needed will be drawn as long as the voltage didn't increase.

Your voltage is a little lower (by .5%). This is likely within the tolerance of your equipment. I don't see that you are in an unsafe situation, or that you are going to damage anything.

In short, if this works when you plug it in, it works.

Speaking of polarity, here is the (almost) polar opposite of your question

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There is utterly no problem using a supply that has higher current than the load needs. What happens when you plug a little "night light" that uses 7 watts at 120 volts - that's about 0.06 amps - into an outlet that can supply 15 or 20 amps normally, and far more than that into a short circuit before the fuse blows? The light lights up. Same when you power a little tiny bulb from your car battery (capable of tens of amps continuous). Current = Voltage divided by resistance; current is the dependent variable. A higher-current source does not force all the available current through the load. –  Jamie Hanrahan Mar 28 at 3:43

In addition to what @Everett mentions, note that the polarity must match. Some connectors have + on inside and some outside. It is usually marked.

Centre Positive.

Indicates that the centre (tip) of the output plug is Positive (+) and the barrel of the output plug is Negative (-).

Centre Negative.

Indicates that the centre (tip) of the output plug is Negative (-) and the barrel of the output plug is Positive (+).

Also some systems check the adapter and complain if not to spec.

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Dave brings up an important point that I didn't address. Pushing 3.5 Amps at 19 volts backwards through the device (reversed polarity) can do bad things if there isn't a diode in line to prevent this. Even then you'll likely blow the diode and brick the laptop until a new diode is soldered in place. –  Everett Aug 13 '12 at 18:17