Laptop power test with killawatt

Question

I thought I had gotten away from this topic since I replaced the netbooks with 2 in 1 windows tablets. Then I received back a 17 inch HP that I had given Mom a few months before she died.

Now the tablets can charge off of a USB or 120v. The Laptop is 120v with the charger output rated for 19.5v, 2.31a, 45w max. The first thing I tested was the draw with just the power brick plugged in, it was0.0w with a occasional blip of .03w.

I plugged in the laptop sleeping and it drew a average of 12.9w around 75% charged. I'll have to see what it draws off/on and fully charged. I can see the charger turning off when at 100% and off.

I turned on the computer and it drew 20-25w depending on what it was doing. Downloading a video or spinning up the DVD was higher but usually 20-21w. Laptop on but sleeping pulls .4w

I took the battery out and started the computer, after it started it averaged 10w and would draw as much as 16w briefly depending on what you do.

So if I keep the slab of granite, I won't be carrying it around which means I don't need the battery to be charging all the time. 10-16w for a 17 inch, quad core is pretty doable.

I'll put the battery back in and see what it does fully charged.

mrwizard · Answer

Typical example of what I was saying in a recent inverter threadLaptops don't us the max power rating on the brickThey use very little power most of the time

naio · Answer

Good experiments!Was the 20-25w when it was 75% charged (and charging) or 100%?Would be interesting to know if it uses that much just maintaining a top charge.

jimindenver · Answer

The 20-25 watts was when the battery was 75% and charging. Once fully charged and running the draw was very similar to not having the battery in at all. So once the battery is charged the brick only checks its status when the watts blip up to 0.03.

There are a few reasons to remove the battery even though it seems the brick stops charging it. First is when batteries do get old they can require charging all the time because they are never full. Second is I believe it's advised to remove the battery if not needed for long periods.

naio · Answer

My current laptop follows the (evil!) Apple model of having no user-removeable battery :(

strollin · Answer

In order for the laptop to consume anywhere near the max power rating of the brick, the battery would need to be nearly drained and charging, the display on full brightness, speakers playing audio at full volume, the hdd seeking and writing, the DVD being accessed, the USB ports powering peripherals AND need to be running hot so the fan would be at full speed.

Most likely no one would ever use that much power, but it's possible, so it must be allowed for.

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Laptop power test with killawatt

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