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All the laptop chargers I had until now sparked whever I plugged them in. This is true for my old charger (the bulkier / rounder Dell model) and the new charger (the flat Dell model) with two different Dell laptops, however until recently I didn't give it much thought.

Then, in the last couple of months:

  • I shorted out a conference room and melted the floor a little (the wire caught fire)
  • The second charger (also a Dell original) died, taking the power strip with it

I'm wondering:

  • Is it normal for laptop chargers to spark when plugged in? Specifically new, original Dell chargers
  • Is there a "correct" way to plug / unplug chargers? Do I need to first unplug it from the wall and then from the laptop / do I need to first plug it into the wall and then into the laptop?
  • May the problem be caused by the fact that I leave sometimes the charger plugged into the wall without connecting the laptop for longer periods of time (up to a day)?

PS. I'm talking about Europe, so 220V and this happens in many places (at home, at my parents, at work, in hotels I trave to, etc)

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Are you sure these are 220V European chargers and not 120V American chargers? It is not normal, and is potentially dangerous, for a charger to spark every time you plug it in. –  Jim Sep 21 '11 at 16:31
    
Yes, they are all 220V chargers (actually they are "universal" - it says 100V - 220V on them) –  Cd-MaN Sep 21 '11 at 16:46
    
It really depends on the quality of the wiring that you normally use. Have you checked to see if your chargers are on any recall lists? –  Ramhound Sep 21 '11 at 17:11
    
Where, exactly, so the sparks come from? –  horatio Sep 21 '11 at 19:06
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@Synetech How do you not blow a fuse?!?!??!?!??!?!?!? That's 10 AMPS for popcorn. (I hope you leave that thing unplugged at night :D). | To OP: The spark may also be some static electricity or if the air is dry and it might cause a small ark... but if it is large you may want to get it checked out. –  Annonomus Penguin Dec 28 '13 at 2:01
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8 Answers

up vote 7 down vote accepted

A small spark is normal. The type of power supply on laptops is a switched-mode power supply. With this type of device there is often an "inrush current" that appears as a spark when the prongs of the plug first hit the receptacle contacts (spark usually appears in mid/higher end adapters where a capacitor is used to keep interference down, it is the capacitor that initiates the inrush current and causes the spark).

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My Dell charger always sparks when I plug it in. Slightly disconcerting at first! –  Jonny Wright May 30 at 19:09
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I know this question is old but I dislike the accepted answer.

The spark you see is completely normal. The reason nothing to do with 'in rush' ( wth is that...?) current or capacitors. It has to do with inductance.

Any wire loop (any conductor has small inductance), such as a transformer, has an inductance. The transformer has a magnetic field (or lack or one) and when you plug-in or unplug the cord, current flows/stops and the magnetic field changes. Nature abhors a change in flux (change in the amount of mag field) and a counter current is induced by the inductor. This current causes the spark.

There is no difference in how you connect the wires. The ring on the end which goes into your computer is the ground. It is designed to contact first, thus providing a path for transient currents to discharge before anything else. Plug it in slow...it shouldn't matter at all.

Leaving a charger plugged into the wall without being connected to your computer is not likely to be harmful. You might consider not doing this if you think the power supply is getting old. The electronics inside are pretty robust and what really taxes them is when a large current is being drawn. There's a lot of power conditioning going on in there to clean up the power to be clean enough for a micro controller.

In case you care, a switching power supply is one that avoids the need for large expensive transformers and uses a complicated circuit to lower the wall voltage down to 15VDC from about 60 VDC ( 120VAC / 2 from rectification ). Image flapping a switch on and off, where 'on' is clamped to a value, like 15V. If you do this fast enough, the pulse train looks like a constant DC. Except there's a ton of noise and garbage from the switching...

Computers' CPU don't use that much current, but all the peripherals sure do...DVD, montior, HD's, speakers, etc...

Good question. While not an EE I did study electronics in school, have a BS in Physics and work on electronics hobbies at home.

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"Computers' CPU don't use that much current" - They use more current than anything else... CPUs easily draw 70W+ under load, and some graphics cards peak at over 400W under load - That's more than 30 amps. –  Darth Android May 30 at 19:11
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Is there a "correct" way to plug / unplug chargers? Do I need to first unplug it from the wall and then from the laptop / do I need to first plug it into the wall and then into the laptop?

Connect everything first, then as the last step connect the charger to the wall. Make sure that you insert everything all the way as fast as you can by applying a lot of pressure, loose contacts are a known cause of sparks. It also sounds like there is something wrong with the Dell chargers you have, look for alternative options. Just make sure the output is similar in terms of Voltage and Ampere...

May the problem be caused by the fact that I leave sometimes the charger plugged into the wall without connecting the laptop for longer periods of time (up to a day)?

No, while this does use some power it doesn't damage the charger under normal conditions.

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I too suspected the charger, but it seems unlikely to have three problematic chargers bought in two different places. –  Cd-MaN Sep 21 '11 at 16:54
    
There is a possibility of an unbalanced power line coming into the building which causes higher than normal line voltage. But generally this would result in burning out light bulbs, etc -- other symptoms that would be noticed. –  Daniel R Hicks Sep 21 '11 at 20:23
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Yes, it's relatively "normal" for a charger to spark when plugging in. Not all will do it, but many high-current chargers will. You may also see a similar spark plugging in a desktop computer.

I've never totally figured out the reason for this phenomenon, but I suspect it's related to the high capacitance inside the charger or power supply. This is the opposite of, eg, an electric motor, which is inductive and where you will see the spark on unplugging.

You should be able to plug/unplug the charger in either order, or leave it plugged in while not connected to the laptop.

And adapters that catch fire (or simply melt down, with the possibility of fire or exposed wiring) should be reported to your national safety agency.

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The cause of this spark is capacitor used to separate circuits in transformer part of charger. It is initially discharged and has "will" to charge as fast as possible - thus the initial "inrush current". IT IS SAFE AND NOT AVOIDABLE although if there is voltage spike at the same time you plug in the charger (low probability-may be caused by shutting down or unplugging device with high consumption at the same time somewhere else in same branch of electric distribution) it may break the condenser and potentially damage the charger.

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Whether a laptop power-adapter will spark or not when plugged in depends on a variety of factors.

Anatomy of a Power Adapter

The adapter “brick” acts as a both a surge protector and a minor UPS (uninterruptible power supply). In addition to filtering and condition the incoming power to even out minor surges and dips in the power, it also has a large capacitor which holds a relatively large current and can momentarily power the system to prevent it from shutting down in the split second of time when the system switches from battery to AC power or vice versa. If you unplug the adapter from the laptop first and then from the outlet, the little LED on it will continue to glow for a minute or so as it slowly drains the capacitor, which is actually one of the reasons for including the LED: to prevent the capacitor from holding a charge for no reason.

If you plug in a full charged laptop, the adapter does not need to charge it, so there will usually be no spark. If you plug in a laptop that needs charging (especially if it has a low battery), then there will usually be a spark as the capacitor in the adapter very quickly fills up and starts charging the laptop. If you then unplug the charging laptop and plug it back in soon, there will usually not be another spark because the capacitor already has some charge in it.

Multi-Episode Arcing

The spark you sometimes see is an electric arc and is caused by a large (often momentary) voltage jumping through the air between two conductors (often close together). Because the adapter is quickly filling up the capacitor and starting to transfer electricity to the laptop/battery, there is a moment where the voltage jumps pretty high. Because the contacts of the plug and outlet are so close together, this voltage is enough to jump through the air and cause the spark, but then everything (usually) evens out very quickly afterwards and levels return to normal.

Size Does Matter

In addition to the capacitor and the battery level of the laptop, another factor that determines whether or not you see a spark is the actual plug itself.

Most electric plugs these days are grounded, and in addition, the ground prong is a little longer than the other two (figure 1). This causes the ground conductor to connect first when you plug it in and disconnect last when you unplug (figure 2). This allows any excess current to dissipate to ground/earth.

On the one hand, this should prevent any arcing because the ground conductor should already be connected by the time that the other prongs connect, so it can easily dissipate any excess charge, but on the other hand, because the charge now has a place to go, and because the charge in such cases is large enough and the distance between the prongs is so small, having the ground connected and ready actually makes it possible for the charge to jump through the air and arc. If it were not connected, it would be at a dead-end and sit there waiting until the adapter is grounded, but that could potentially cause it to overheat or burn out, so it is better to leak the excess charge even if it makes a scary spark.

Inadvisable Tests (…or How I Learned to Stop Worrying and Love the Laptop)

You can test your own adapter by observing whether plugging it in at different angles and under different circumstances to see whether a spark occurs or not in order to determine how to plug it in to avoid it, but as stated, that could be bad for the health of the adapter (and possibly laptop), so it is better to just plug the adapter in straight and use it as designed.

Suggested Design Improvement

One way that could potentially allow for a safe connection while shielding users from the naturally concern-inducing spark would be to redesign the plug and/or outlet so that any spark occurs inside a little plastic enclave in the plug/outlet so that users don’t even notice it when it happens.


Figure 1: Photo of a grounded plug showing the slightly longer ground prong

Photo of a grounded plug showing the slightly longer ground prong

Figure 2: Side-view of grounded photo showing the order of conductor connection

Side-view of grounded photo showing the order of conductor connection

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My original Dell laptop charger did not have a grounding prong and it did not spark. I recently replaced the original with a compatible replacement charger which has the third grounding prong and with this charger I do get a spark each time the plug is about to be plugged into the socket. But I've never had any performance problems using either type of charger.

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It is not normal and it's very strange to happen on 2 different chargers, 2 laptops and many places! This can show there is a problem with both charger handling/storage (or maybe on both laptops batteries or connectors). The 1st thing I would investigate is moisture (or dirt) at the place you store the chargers or laptops while not using.

Another thing that may be useful to check would be excessive magnetic fields or static where you store the chargers.

Does the chargers spark when connecting to the wall without being connected to the laptop?

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