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I was using a friends laptop and decided to boot into an install of tinycore on a flash drive. This laptops battery is already pretty much shot because it is left plugged in all the time no matter what the use, and before I booted into it the level was at about 60%, which means about 40 minutes in windows. When I booted into tinycore, there was only about 10 minutes before it shutdown completely. I noticed the fans were on high and the air coming out was rather hot, but why does that happen?

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First, leaving a laptop plugged in all the time is the best case for battery life. Simply put, with the laptop plugged in, the battery manager can do whatever it thinks is best for the battery life, whether that's charging it, floating it, or discharging it. With the laptop unplugged, there is no option but to discharge the battery, whether or not that's best. (Batteries are completely different from what they were a decade ago. The old rules no longer apply.)

My bet is that tinycore either doesn't have adequate power management support or it's not enabled. Another possibility is that power management is set to low (or disabled) in the BIOS but those settings are overridden with the Windows power management settings. Linux will follow the BIOS if not specifically configured with an override as well.

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You aren't entirely correct about battery, either. I've ruined several laptop batteries (whether 2005-era or 2011-era) by leaving them plugged in 24/7. My 2005-era iBook had 4-5 hours of battery in 2009 when I began leaving it on, plugged in 24/7. Its battery was ~45 minutes within a month. My first work laptop (a Lenovo T410) had ~30 minutes after 4 months (down from 3-4 hours) because of being plugged in most of the time. But you are spot-on about the power management. +1 for that. –  CajunLuke Sep 22 '11 at 0:54
    
I'll go with the experts and the studies over anecdotal evidence. You have no way to know it was "because of being plugged in most of the time", and that simply doesn't make any sense. How could giving the charger more options make things worse unless the charger was horribly broken? –  David Schwartz Sep 22 '11 at 3:08
    
I have heard from others that the same has happened to their battery in this laptop. My best guess is even if the battery is fully charged it draws from the battery instead of the wall adapter and leaves the battery in a constant release and charge cycle slowly wearing it down. –  a sandwhich Sep 22 '11 at 13:13
    
@David The charger isn't as smart as you seem to think it is. When they're plugged into a wall, the battery is used a tiny bit, then recharged that tiny bit. Also, plugged-in computers run the CPU and GPU harder, generating more heat. Even with modern Lithium-ion and Lithium-polymer batteries, that's still pretty much the worst-case scenario. And (still anecdotal from your point of view), that's the only way I've ever seen anybody ruin a laptop battery: by leaving it plugged in all the time. –  CajunLuke Sep 22 '11 at 14:21
    
The studies say that a typical laptop lithium battery has an expected life of about three and a half years or about 300 charge cycles, whichever comes first (assuming you don't abuse it). –  David Schwartz Sep 22 '11 at 20:44

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