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World Community Grid Forums
Category: Community
Forum: Hardware Chat Room
Thread: Laptop Battery and AC switching to save electricity |
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Thread Status: Active Total posts in this thread: 13
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ericinboston
Senior Cruncher Joined: Jan 12, 2010 Post Count: 265 Status: Offline Project Badges: 
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Hi all. I have 20 identical laptops running WCG 100% 24x7. If they are on battery, they will crunch for about 1.5 hours.
----------------------------------------I was wondering, would it be beneficial (as well as possible via software or some kind of wall timer) to turn the AC off on those laptops for 1.25 hours and let them run on battery and then turn the AC back on for 2 hours to charge the batteries back up...then repeat this forever. Therefore, I would save about 25-30% of my electricity costs. 1)Is there any software that would force Windows (also a few 2017 Macbook Pros) to use battery even though the AC is still plugged in?...and do this on a schedule as I described? If not, anyone know of a fancy wall timer that I could program to turn the AC on/off multiple times each day? This wall timer seems to be able to work for my needs: https://www.amazon.com/Century-Heavy-Digital-...fRID=ZP32YB4W04FGC3RXPRFW I would have 10 laptops plugged into it via 2 power strips...the laptops only draw 75 watts each so about 750w total draw through this timer...I don't think it will kill/burn out the timer...right? It's Rating: 115V, 60 Hz, 15A/1725W 2)Will the battery get hot(ter) by being in use? I have the laptops in a cool basement and they are opened about 30 degrees and layed on it's edges...so the battery and CPU area and fan are never touching the floor. I would imagine that since laptops are designed to use their battery, this should not be an issue. 3)Will this process of almost draining the battery and then charging to 100% kill the battery much sooner? I don't need the batteries to last 5 years but at least another 1 year. I also would not assume this would be a problem because there has to be a fair percentage of laptop users that drain and fully recharge their battery at least 1-2 times a day. Anything else I have not considered? Thanks!  [Edit 1 times, last edit by ericinboston at Jun 20, 2018 2:34:34 PM] |
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andgra
Senior Cruncher Sweden Joined: Mar 15, 2014 Post Count: 195 Status: Offline Project Badges: 
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ericboston,
----------------------------------------The answer would be no. You would in fact spend more power by doing this. You are right that when running on batteries you would "run for free" but when reconnecting AC power again you will both run the machine AND recharge your batteries. As the process of discharging/charging a battery is not a 100% efficiency cycle you will actually consume a bit more energy by doing like this.
/andgra
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ericinboston
Senior Cruncher Joined: Jan 12, 2010 Post Count: 265 Status: Offline Project Badges:
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ericboston, The answer would be no. You would in fact spend more power by doing this. You are right that when running on batteries you would "run for free" but when reconnecting AC power again you will both run the machine AND recharge your batteries. As the process of discharging/charging a battery is not a 100% efficiency cycle you will actually consume a bit more energy by doing like this. Hi and thanks. Although I have not done any tests, I do have a power meter to test your theory. But let's say with my batteries at 100% and using AC, I am drawing 75watts. I then unplug for 1.5 hours so I am not using any electricity. I then plug back in for 1-2 hours (I don't know exactly how much time it takes to charge but I am testing today) and it uses 100watts and it takes 2 hours to charge...that would mean I used 50 extra watts which is still less than 75 it normally draws. Again, I will do some testing but hoping I can save a bit on my electricity. But I'm also not going to spend all kinds of money on timers and such to save $3/month. :) In general I wish the solar panels/technology was more cost effective here in Connecticut. My house gets massive amounts of sun and I could put 40+ panels on my roof...but Tesla/Home Depot 3rd party wanted $40k and it would still only provide 90% of my power. I am told by friends that Tesla is insanely expensive and I could probably find someone for $18k. But even that just sounds like a bit of risk. I am holding out for the day it's $10k. |
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Former Member
Cruncher Joined: May 22, 2018 Post Count: 0 Status: Offline |
Is it possible to run the laptops on AC with the battery removed?
I am running my HP laptop with the battery removed. I know my ASUS netbook would only run with the battery installed. An old Gateway labtop would also run run with the battery removed. |
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supdood
Senior Cruncher USA Joined: Aug 6, 2015 Post Count: 333 Status: Offline Project Badges: 
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Ericnolongerinboston--One major point:
----------------------------------------Battery lifespan is based mostly on cycles. The more you cycle the shorter the life. With some battery chemestries there is a real risk of fire or explosion (or runaway thermal reaction is battery-speak) from using batteries like you describe for long periods. I think the risk of torching your house vastly outweighs any electricity reduction you may get. An additional note on solar: Go with a reputable local installer. You'll get better service and they are more likely to be responsive if you ever need maintenance. Also the short payback times with our high electricity costs in New England make it a low risk decision. |
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TonyEllis
Senior Cruncher Australia Joined: Jul 9, 2008 Post Count: 290 Status: Offline Project Badges: 
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A few points to add to this discussion.
----------------------------------------Many consumer grade power meters provide very inaccurate readings when used to measure the power consumption of switch-mode power supplies, which is what the vast majority of laptop AC adaptors are. They are fooled by the low power factor and high crest factors. It takes a meter costing a few thousand dollars to give you accurate readings. Also note that whilst on battery most laptops will change their power mode to power save - often reducing the CPU frequency - this saves battery at the expense of speed and responsiveness. It is possible to create a custom power profile to do the same while running from AC. Thus your readings comparing usage under 100% AC as compared to use with intermittent AC charging periods will likely be skewed by this. Most laptops cannot be configured to run BOINC at 100% CPU as that results in over-heating and/or very noisy fans running a high speed. Experiments here indicated the most efficient way to run BOINC on a laptop without over-heating was to set BOINC to run the CPU at 100% and create a custom power profile that reduced the CPU frequency such that the CPU was running at an acceptable temperature. This can be achieved under both Windows and Linux operating systems...
Run Time Stats https://grassmere-productions.no-ip.biz/
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flynryan
Senior Cruncher United States Joined: Aug 15, 2006 Post Count: 235 Status: Offline Project Badges:
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There is no free lunch (you can’t get more power out of the battery than you put into it). There’s no way that running on battery for a time reduces power used in the long run, unless performance also suffers). Remember energy cannot be created or destroyed (law of conservation of energy.)
----------------------------------------The battery would last less than one year if it were charged and discharged say every 4 hours. That’s over 2000 cycles Per year on the battery. Only the best lithium ion batteries could do that many cycles without significant degradation or bricking of the battery. Have you drained all the batteries and then run the system at 100% CPU while recharging the batteries? Your post doesn’t make clear if you have done this, and what your power consumption is at that point. [Edit 2 times, last edit by FlynRyan at Jun 21, 2018 4:10:10 AM] |
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Former Member
Cruncher Joined: May 22, 2018 Post Count: 0 Status: Offline |
Is it possible to run the laptops on AC with the battery removed? I am running my HP laptop with the battery removed. I know my ASUS netbook would only run with the battery installed. An old Gateway labtop would also run run with the battery removed. This is much better, for the battery, to remove it when it's fully charged... the continuous pass-through current wears them down. [Edit 1 times, last edit by Former Member at Jun 21, 2018 6:05:08 AM] |
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Former Member
Cruncher Joined: May 22, 2018 Post Count: 0 Status: Offline |
The battery would last less than one year if it were charged and discharged say every 4 hours. That’s over 2000 cycles Per year on the battery. Only the best lithium ion batteries could do that many cycles without significant degradation or bricking of the battery. On a related note, battery warranties are generally separate from whatever warranty is on the rest of the device, and are, generally, only 1 year warranties. Fortunately, laptop batteries are also usually not a huge expense to replace. |
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Former Member
Cruncher Joined: May 22, 2018 Post Count: 0 Status: Offline |
What I'm about to say may not be true in all situations and is, of course, just my opinion, but I would recommend leaving the batteries is the machines and leaving them permanently on mains power. Here's why,
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