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I doubt about this, but still want to hear what others think. UPS condition power but does laptop's battery condition power?

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up vote 4 down vote accepted

An Uninterruptible Power Supply (UPS) conditions power by including electronics which removes ripple and noise superimposed on the mains AC supply.

It's main task is to provide power from an internal battery if the mains supply fails.

A laptop's battery is purely a DC supply with no ripple and noise, so while a battery doesn't condition the power, there is no noise and ripple to remove, so the effect is the same.

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You can run a laptop from the mains AC supply with the battery disconnected, the battery is not interposed between the motherboard and the power supply, therefore the battery does not have any conditioning effect (e.g. reducing overvoltage). Most laptops have an external switched-mode "power supply" which converts mains AC voltage to a lower DC voltage which is regulated. This probably offers no greater protection than the power-supply unit built into the average desktop computers? – RedGrittyBrick Jul 20 '11 at 9:20
So fluctuating power frquency is a ripple and noise? AC power has ripple and noise but DC power does not? So all i need is DC power and surge protector to be on "UPS like"? – Boris_yo Jul 20 '11 at 13:29
Power frequency generally doesn't fluctuate, but the conversion from 50/60Hz to DC always produces a little ripple. A good UPS will have good filtering, and regulation of output voltage but its main task is to provide DC from a battery if the AC power fails. Batteries can't produce ripple. AC power is converted to DC with very little ripple. The conversion in the UPS should be comparable to a PSU in a desktop as RedGrittyBrick said. – pavium Jul 20 '11 at 13:49

While there is some natural power conditioning when you go from AC to DC, a laptop's power supply does not really replace a UPS or power strip. That is not its function, nor is that built into it.

While you are going to get roughly the same DC whether plugged directly into the wall or a UPS/power strip, there is nothing in front to guarantee that the adapter will not be damaged, and allow damage to your computer if you are not plugged into the UPS/power strip.

There is a reason they sell laptop surge protectors.

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UPS protects against surges. – Boris_yo Jul 20 '11 at 13:13
@Boris_yo I know that, of course, but with a battery, you have less need to protect against brown-outs, therefore, a surge protector is often considered good enough for a laptop. By all means, a UPS is also great. I also mentioned both in the answer for completeness. – KCotreau Jul 20 '11 at 13:16
But you said that whether plugged directly into the wall or a UPS/power strip, there is nothing in front to guarantee that the adapter will not be damaged, and allow damage to your computer. This means that even UPS will fail to protect. – Boris_yo Jul 20 '11 at 13:34
@Boris_yo You are right...what was in my head did not make it fully to the written word. I edited to add to that line. Sorry. In other words, while the power may be the same, the adapter does not have any special power conditioning protections, and it could be damaged, and in turn, allow damage to the computer. – KCotreau Jul 20 '11 at 13:42

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