# Using a 16V power adapter on a laptop rated at 19V. Safe? **URL:** \ **Category:** Factual Questions\ **Created:** [January 2, 2006, 7:46pm UTC](https://boards.straightdope.com/t/using-a-16v-power-adapter-on-a-laptop-rated-at-19v-safe/338108 "2006-01-02T19:46:29Z")\ **Posts on this page:** 8\ **Page:** 1
**Author:** ![xash](https://avatars.discourse-cdn.com/v4/letter/x/c6cbf5/32.png) [@xash](https://boards.straightdope.com/u/xash)\ **Post date:** [January 2, 2006, 7:46pm UTC](https://boards.straightdope.com/t/using-a-16v-power-adapter-on-a-laptop-rated-at-19v-safe/338108/1 "2006-01-02T19:46:29Z")
The power adapter of my ASUS laptop just conked off yesterday, probably due to a power surge. The ASUS power adapter is rated at: Input: 100-240V~ 1.5A 50-60hz Output: 19V DC 3.42A The ASUS laptop is rated at: Input: +19V DC 3.42A, 65W Today I tried using my IBM ThinkPad power adapter to power up my ASUS laptop. It worked. However, I’m wondering if it’s safe to use the IBM power adapter to power the ASUS laptop for extended use. The IBM ThinkPad power adapter is rated at: Input: 100-240V~ 1.9A 50-60Hz Output: 16V DC 4.5A Is it safe to use the IBM AC power adapter to power the ASUS laptop? Why or why not? Thanks. ---
**Author:** ![UncleRojelio](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/unclerojelio/32/3160_2.png) [@UncleRojelio](https://boards.straightdope.com/u/UncleRojelio)\ **Post date:** [January 2, 2006, 7:57pm UTC](https://boards.straightdope.com/t/using-a-16v-power-adapter-on-a-laptop-rated-at-19v-safe/338108/2 "2006-01-02T19:57:17Z")
I couldn’t tell you with 100% certainty yes or no, but the lower voltage of the Thinkpad adapter may cause the laptop’s power supply to run hotter than normal. This will shorten the life of the power supply. ---
**Author:** ![Q.E.D](https://avatars.discourse-cdn.com/v4/letter/q/51bf81/32.png) [@Q.E.D](https://boards.straightdope.com/u/Q.E.D)\ **Post date:** [January 2, 2006, 8:03pm UTC](https://boards.straightdope.com/t/using-a-16v-power-adapter-on-a-laptop-rated-at-19v-safe/338108/3 "2006-01-02T20:03:03Z")
The answer is: it depends. If the laptop further conditions the power internally with some sort of regulating device–which is likely, since computer supplies are normally 12 V and 5 V DC–then the lower voltage adaptor may not cause problems. As above, there is no certaintly here. Personally, I wouldn’t run it like this too long before getting the correct power supply. OTOH, I used to have a Casio electronic keyboard which was rated for 9 V, but I ran it for years on a 12 V supply. The only difference I could note was a slight increase in the brightness of the LED indicators. Some things tolerate out-of-spec voltages better than others. ---
**Author:** ![astro](https://avatars.discourse-cdn.com/v4/letter/a/9dc877/32.png) [@astro](https://boards.straightdope.com/u/astro)\ **Post date:** [January 2, 2006, 11:37pm UTC](https://boards.straightdope.com/t/using-a-16v-power-adapter-on-a-laptop-rated-at-19v-safe/338108/4 "2006-01-02T23:37:32Z")
You’re more likely to damage the IBM PS or the ACER battery than the ACER notebook circuitry, but the specs are close enough you can probably get away with it for a while. Long term it’s likely one component or the other will be over stressed. I’m guessing your Acer battery is the most likely component to be negatively affected, and notebook batteries arenlt cheap. ---
**Author:** ![Q.E.D](https://avatars.discourse-cdn.com/v4/letter/q/51bf81/32.png) [@Q.E.D](https://boards.straightdope.com/u/Q.E.D)\ **Post date:** [January 3, 2006, 12:10am UTC](https://boards.straightdope.com/t/using-a-16v-power-adapter-on-a-laptop-rated-at-19v-safe/338108/5 "2006-01-03T00:10:34Z")
Good point about the battery, **astro**. Batteries, particularly NiMH types, can be sensitive about charging conditions. NiMH batteries are very touchy about charging voltage, so much so, that using a NiCd charger to charge them can drastically shorten their useful life. I don’t think one or two charge cycles will hurt them too much, but don’t make a habit of it. ---
**Author:** ![SenorBeef](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/senorbeef/32/2220_2.png) [@SenorBeef](https://boards.straightdope.com/u/SenorBeef)\ **Post date:** [January 3, 2006, 2:49am UTC](https://boards.straightdope.com/t/using-a-16v-power-adapter-on-a-laptop-rated-at-19v-safe/338108/6 "2006-01-03T02:49:45Z")
In a related but more general question: I have a walkman that’s supposed to require 6v, but a 4.5v adapter seems to work fine. A lot less complex than a computer’s power need - so as a general rule, does undervolting stuff cause damage? ---
**Author:** ![Q.E.D](https://avatars.discourse-cdn.com/v4/letter/q/51bf81/32.png) [@Q.E.D](https://boards.straightdope.com/u/Q.E.D)\ **Post date:** [January 3, 2006, 2:57am UTC](https://boards.straightdope.com/t/using-a-16v-power-adapter-on-a-laptop-rated-at-19v-safe/338108/7 "2006-01-03T02:57:09Z")
> [@SenorBeef](#): > > …as a general rule, does undervolting stuff cause damage? Depends on what it is. Purely solid-state stuff? No. It might not work at all, but overheating ought not to be an issue. But, things with motors may run hot–low voltage makes motors run slow or even stall, and this can cause the motors to exceed their design current. This probably won’t be much of an issue for very small motors, like those in a Walkman, though. ---
**Author:** ![xash](https://avatars.discourse-cdn.com/v4/letter/x/c6cbf5/32.png) [@xash](https://boards.straightdope.com/u/xash)\ **Post date:** [January 3, 2006, 6:03am UTC](https://boards.straightdope.com/t/using-a-16v-power-adapter-on-a-laptop-rated-at-19v-safe/338108/8 "2006-01-03T06:03:51Z")
Thanks for the helpful answers. I used the IBM power supply today (one charge cycle), and bought a power supply from Frys this evening. They had one with adjustable voltage settings.