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I bought a Compaq Presario CQ41 laptop 5 weeks ago, and even though it is a laptop, but most of the time I attached power supply to it and didn't bother to remove the battery prior to that when I was working and seeing movies.

The laptop is usually on for at least 16 hours a day, 7 days a week.

One thing I notice is that the battery's capability seems to be depreciating fast; a fully charged battery would gone flat in 1.5 hours time, down from 2 hours 5 weeks ago when I first bought the laptop.

Is this laptop ( or the battery) defective?

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3 Answers

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That sounds about normal for the extreme usage you're getting out of the machine. Lithium Ion batteries degrade at a rapid pace when left at a 100% charge plugged in.

To quote Battery University, an exceptional resource for information on batteries:

The speed by which lithium-ion ages is governed by temperature and state-of-charge. Figure 1 illustrates the capacity loss as a function of these two parameters.

alt text

On the far left, you'll notice that a battery operating at 60 degrees will have a typical user charge level of 60% after 3 months. You aren't using your laptop like the average user though, keeping it on over 16 hours a day, all day, everyday. I'll bet the battery is at least 60 degrees. This kind of usage has sped up the degrading process rapidly.

I'd recommend reading further into their article on How to prolong lithium-based batteries.

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The original question mentions usage of 5 weeks, the worst case on the chart suggests 60% remaining capacity after 3 months at a rather high temperature of 60 C. – James Snyder Jul 13 '10 at 13:48
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@James Snyder: He has 75% left and is likely running it at higher than 60c - regular degradation does seem to be the likely culprit here. – Phoshi Jul 13 '10 at 13:50
It's possible, but I think it's unlikely. CPU temperature is not the same as the temperature of the battery. Admittedly this is with a different manufacturer and CPU, but I've just tried pegging both cores in a C2D MacBook Pro (13"), and while the CPU does get up to 85 C, the case temperature near the battery remains below 30 C even after some time. The original questioner should check what the battery's capacity is (current v rated). This could just be workload or error in early estimates. A 25% drop in 5 weeks of heavy usage is extreme. This degredation answer makes a lot of assumptions. – James Snyder Jul 13 '10 at 19:19
@James, the chart is 60% after 3 months of regular usage @ 60c, not 16+ hours a day usage. But thanks for the unqualified downvote ;) – John T Jul 13 '10 at 19:46
OK, this is getting ridiculous, but I'll respond again 1) By definition, it would be qualified since I posted a comment. ;) 2) The chart doesn't say anything about normal/abnormal usage at 60 C, it refers to keeping a battery at 100% and 60 C. Using a computer for 16 hours a day indicates zilch about temperature. If he's watching video and surfing the web for that time, 60 C is insane. All in all, my interpretation based on the quantity of information provided in the original post (not extensive) is that it's presumptuous to conclude that temperature is the problem. That's all :-) – James Snyder Jul 14 '10 at 1:22
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This sounds extreme. I've had a number of laptops that have fared far better with heavy usage over the course of a year or more. There are a number of factors that influence capacity including CPU load during usage, number of cycles the battery has been through, and temperature at which the battery is stored and used. Another post suggests that temperature might be to blame, but you would have to double the rate of decay in the worst case scenario on the chart for it to make sense in your case. Not to mention that cooling allowing the battery to heat to 60 C during normal usage, seems problematic to the point of suggesting defective cooling.

Try this to check your battery.

You also might want to calibrate your battery. Here's also some information from the manufacturer on maximizing battery life.

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