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Battery on my laptop is 4%, I don't have original power supply at the moment and I have some work to do.

Is it safe to ask a friend to give me his power supply from another type of laptop?

What parameters to look for to see if this is possible?

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migrated from Nov 13 '10 at 18:26

This question came from our site for system and network administrators.

Do you mean "power cable" or "power supply" (with its associated cable(s))? – Dennis Williamson Nov 13 '10 at 19:42
Sorry, I meant the whole thing - cable from the wall to the laptop. – kliketa Nov 14 '10 at 15:21

One size does not fit all. Buy something like the thing at picture below (would replace to CC version later), pick a matching connector, set a correct voltage.

Lower power (e.g. 60W instead of 90W) is OK, just the battery charge time will raise. Same for higher (used to feed 30W netbook with 110W supply). Voltage should be the same!

alt text

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I have used a 90w power supply on my dell and it seems to charge much faster than my current 65w unit. Since my 65w unit blew it works very well with the 90w unit. Hope this helps!

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Same power ( voltage and Amps )

Well its doesnt have to be perfect but similar..

As an example

(19.5V - 7.7A) 20V - 7.8A is fine..

Obviously the power adapter to connect should fit / be the same

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Better off a little higher on the amperage and voltage than a little lower, although for short use, it shouldn't make much difference. Try to avoid large variances. – MaQleod Nov 13 '10 at 18:58

Obviously, the connector must fit. Other than that, the voltages need to match. There is some tolerance, but it's hard to give a solid number of what will still work and what might even harm your computer. Lower voltages are safer, but 5% deviation will be fine either way.

Another thing to look out for is the polarity as reversing it could be damaging, probably isn't but a power supply with the wrong polarity definitely won't work. Luckily, it is very uncommon to find laptop power supplies that do not adhere to the rule of the inner terminal being positive.

Current is largely irrelevant. How many amps are supplied depends on the load, not on the PSU which simply specifies the maximum current it can handle. If your laptop draws more power than can be supplied, the machine will either shut down or draw power from the batteries. Worst case scenario for a current rating too low: you need to power the machine down and wait for the batteries to recharge. Worst case for 'too high' a current, the recharge crazy fast.

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My Dell D510 is OK with another Dell power supply. Original was 19.5v with 3.3 amp output. The 'extra' power supply is 19.5v with 4.6 amp output. Your mileage may vary. Take pictures of your laptop on fire if it doesn't work out, and let us know. Since, I'm only supplying a single data point. My guess is, that you can probably be within about 0.5v tolerance and 50% of the amp output... but I"m only guessing on that. Oh yeah, you'll find that the physical connector varies among manufacturers, so you'll need a 100% match there.

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Usually higher wattage power supplies for Dell will work replacing a lower wattage power supply. Most power supplies are voltage regulated, so the output current is only what the laptop needs is provided. So a higher wattage power supply of the same voltage shouldn't be a problem. I have seen a Dell Latitude XT2 show an error using a higher wattage power supply, but this is a very rare case. This information shouldn't matter even with other brands as long as the power supply is regulated (as far as I know all laptop manufacturers would be using voltage regulated power supplies. Good news is that for nearly the past 10 years most manufacturers have started to use the same power supply connector and regulated voltage for their whole product line Hope this helps. I use Dell at work, and one of my home laptops is an ASUS that apparently isn't working, found this as I was searching. Hope this comment is helpful to someone.

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