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I'm running on UPS power and would like to prevent the laptop's battery from charging, to increase the amount of power available to other devices. Is there a way to do this?

update: The machine is a Dell Latitude D400. If people want more details, just ask.

Also, I'm gathering that I need to explain my desired setup a little better. I've gotten a bunch of suggestions about taking the battery out. I'm not sure if people are suggesting to take the battery out while the machine is running — this, as I understand, is not a good idea with most laptops — or to just remove the battery altogether.

The latter option is not optimal, because ideally I'd like to use the 30-60 minutes of power in the laptop battery and then switch over to UPS power. The details of the switch-over may constitute a separate question, but if I can't find a way to keep the laptop battery from charging, then removing the battery from the machine altogether may be the best way to do this. I'm not sure yet if this machine will run without a battery, but I'll check that out.

Other than the laptop, the UPS is just supporting a cable modem and router and a USB hub.

Again in the idealized version of this setup, all the power management changes would be automated, i.e. not require replugging anything or pressing Fn-keys. I'd like the machine to start using laptop battery power when apcupsd indicates that the UPS A/C is out, and then start using UPS power, but not charging the battery, when the battery is almost depleted.

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cross-posted on AskUbuntu –  intuited Jan 12 '11 at 23:08
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Just take your battery out. –  Keith Jan 13 '11 at 14:08
    
@Keith: Ideally I'd like to be able to use the battery until it runs (almost) down, and then switch over to UPS power. There's at least half an hour of juice in the laptop battery, but I can't really use it effectively because it ends up sucking about that much extra out of the UPS battery in order to charge after I switch over. Of course this is only part of the solution — I still have to find an automatable way to avoid using UPS power until the battery runs down. For now I'm just reconnecting the laptop power supply to different outlets. –  intuited Jan 13 '11 at 16:17
    
Covers how to do it here as well: askubuntu.com/questions/218148/… –  slm Feb 9 at 18:29
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2 Answers 2

There may be. Some 'proprietary' extensions which allow to operate on battery. For example tp-smapi patchset allows to set the maximum charging threshold for thinkpads. Setting it to 0 would prevent it from charging.

Some laptops may not have that possibility in BIOS so you need to post details about hardware to receive any details.

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There's no danger in removing the battery as long as you've got line power. I (used to*) do it all the time.

* I now have a MacBook Pro without a removable battery.

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