Laptop Battery Saving Scheme

[springnr]

My Lenovo power manager settings are set to start charging at 25% and stop charging at 40%. I try to remember and cycle the battery every month or two. This way the lithium cells are standing by in storage mode at a partial charge of 40%. There is a button to select full charge if you are going to be using the laptop on battery power.

[ERD50]

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Originally Posted by M Paquette I recommend taking a look at: Battery Information Table of Contents, Basic to Advanced The site was written by Isidor Buchmann, the founder of Cadex Electronics. This company builds battery analyzers, test systems, and chargers. My former employer used these gadgets in the design, test, and evaluation of batteries for a variety of products, including photoguy's battery... The site has a LOT of information on the very different ways that different types of batteries need to be handled to maximize life, oriented towards non-engineering folks. It's well worth a look.

Thanks, I've been looking through that. A couple pertinent bits:

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How to Prolong Lithium-based Batteries - Battery University Most Li-ions are charged to 4.20V/cell and every reduction of 0.10V/cell is said to double cycle life. For example, a lithium-ion cell charged to 4.20V/cell typically delivers 300–500 cycles. If charged to only 4.10V/cell, the life can be prolonged to 600–1,000 cycles; Charging to 4.10V/cell the battery holds about 10 percent less capacity than going all the way to 4.20V. In terms of optimal longevity, a voltage limit of 3.92V/cell works best but the capacity would only be about half compared to a 4.20V/cell charge (3.92V/cell is said to eliminate all voltage-related stresses).

So double the lifetime of the battery by accepting 10% lower capacity seems like a good tradeoff for me (maybe not the mfg, who wants to advertise max battery hours/charge).

After unplugging for a few minutes, my Power Manager reports 96% and 11.9 V. I assume that there must be three cells in series, so 3.97 V per cell? But there may be some other small voltage drops in that reading?

Anyhow, I'm going to go through a few cycles and record these voltages to get some ideas.

-ERD50

[Lsbcal]

I've had my wife's laptop battery out of her system for months. She uses it basically as a desktop PC so no need for the battery. Pulled it out when it was at 100% charge (I think). I've been feeling guilty about it because I had read (as others posted here) that I should get it down to 70% or so before storing.

Just checked this battery now and it's now at 77%. So maybe after months a battery looses some when stored out of the laptop?

I've put a post-it on the stored battery now with the charge state and date.

I too have a Nexus 7 for mobile web surfing. Just bought the minisuit bluetooth keyboard recommended by Al and it works nicely. Technology moves on.

[Totoro]

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Originally Posted by Lsbcal So maybe after months a battery looses some when stored out of the laptop?

All batteries lose charge slowly, even when you are not using them. Rechargable batteries lose charge faster.

[pb4uski]

Update - the original battery, which had not been keeping a charge and was then replaced and stored for about 18 months seems to be working fine now. Fine enough that I'm not planning to buy another replacement right away.

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Originally Posted by pb4uski I am having something interesting happening. A little over a year and a half ago my laptop battery was not keeping a charge so I bought a replacement for ~$30 and threw the old one in a drawer. Recently the newer on wasn't keeping a charge and I was about to buy another replacements. As part of deciding the replacement I found the old original batter and put it back in the laptop. It took a full charge and seems to be holding it and working fine. Perhaps it just needed a sabbatical.

[TromboneAl]

Looks like the four hours/day of charging keeps it pretty close to 100%, so I've dropped it to four half-hour sessions.

[photoguy]

MPaquette -- thanks for posting the link to batteryU. I've been going through the section on prolonging battery life.

On my MBP it shows a battery voltage of 12.8V which I assume three in series for 4.26V each. This appears to be very bad for longevity and according to the tables would yield way less cycles than the 1000 cycles rating of the computer. I feel like I am still missing something here.

I hadn't realized that the combo of heat AND full capacity was so bad for the battery. Next time I run a cpu heavy task, I'll check to see what temp my battery reaches.

[ERD50]

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Originally Posted by TromboneAl Looks like the four hours/day of charging keeps it pretty close to 100%, so I've dropped it to four half-hour sessions.

How low does it typically get at the end of the 'off time' of your timer cycles (~ 3 hours during the day, now ~ 3.5 hours if I'm following you).

I'm trying to guesstimate from MP's link if the added charge cycles do more harm than a battery sitting near 100% charge all the time.

-ERD50

[ERD50]

I think you may be on a wild goose chase. It's hard to say, but some of my reading at this link:


How to Prolong Lithium-based Batteries - Battery University

makes me think that my suspicions may be warranted - you will spend less time at 100% charge, but the drawback is that you are actually running your battery through several charge/discharge cycles each day. And unless you can get your timing down to the point that you don't fully recharge to the 100% level during the ON time, it's not clear but it could be the charging to 100% that is part of the problem, not just the sitting at 100%.

And if you get your timing to only charge back to say 80%, you might be dead by the end of the day if you misjudge the timing and/or your usage changes - in 4 cycles you might go 40-80-30, then down to 30-70-20, and then 20-60-10 ... near shutdown levels next.

This needs feedback, which is why the software/firmware utilities could be very effective. Those limit the charge level, but don't add any extra drain on the battery - they power the laptop direct when they hit XX%, you are powering it from the battery and recharging, which is a wear-out factor.


Maybe the simple answer is close to an earlier idea you had. Buy a second battery, but don't just put it on the shelf - once a week, let it drop to 70%, then swap it. This will result in each battery spending half its time at a better level, but only adds one ~ 30% charge cycle once a week, rather than 4 charge cycles a day.

Easy to do once a week, no risk of going dead, you always have full capacity if you do wish to go mobile, you have a backup battery, and you get hours of your life back fiddling with timers and monitoring charge states

-ERD50

[TromboneAl]

Is there a particular paragraph in the reference that you find compelling?

That first table is misleading. You get more cycles with a 10% DoD, but you will need many more for the same amount of run time.

Note that I never have a risk of going dead. I'll just get a warning at 20% and just tap the timer to "Auto On." Worst case is that it will go from 20% to zero while it's sleeping, but I don't think that will happen.

Plus I never have to go mobile.

The one thing that so many sites say is that staying at 100% all the time is the devil.

With your system there's the stress of shutting off the computer, turning it over, and popping in/out batteries. I don't like that, and I don't think my laptop does either. Let me check ... No, it doesn't like that idea.

[ERD50]

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Originally Posted by TromboneAl Is there a particular paragraph in the reference that you find compelling? That first table is misleading. You get more cycles with a 10% DoD, but you will need many more for the same amount of run time.

I didn't see that as misleading, I think the point they make is that ten cycles of 10% is roughly the same in degradation as one cycle at 100%. I was just trying to relate that to doing something like four cycles a day at 30%, compared to almost never going through a charge cycle.

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The one thing that so many sites say is that staying at 100% all time is the devil.

Agreed. I'm just trying to figure out if the multiple daily charge-discharge cycles of your approach is better, worse or a wash. We probably can't figure it out with any confidence, but it makes me wonder if it is worth pursuing if there is no clear benefit, and possibly could make it worse?

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Note that I never have a risk of going dead. I'll just get a warning at 20% and just tap the timer to "Auto On." Worst case is that it will go from 20% to zero while it's sleeping, but I don't think that will happen.

OK, so you have it set to sleep after XX minutes - I guess that does pretty much eliminate the odds of it going dead during the OFF cycle. I was thinking in terms of how I use mine, I'm lazy, so I don't have it sleep, so I don't need to wake it up when I come back after a short time away. Ahhh, but this would only be while under battery power (I do set it to sleep after a while on battery) , hmmm, but that would be most of the time with this approach. Not a big deal, just a very minor annoyance for me.

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Plus I never have to go mobile.

Right, not a big deal, just another possible negative against the unknown positives. I rarely ever go mobile, but I never know when I might. Then there is always the possible power outage at the wrong time. Long odds, but not a positive.

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With your system there's the stress of shutting off the computer, turning it over, and popping in/out batteries. I don't like that, and I don't think my laptop does either. Let me check ... No, it doesn't like that idea.

Do you need to shut down to replace the battery? Seems that some people say they routinely run w/o battery. Agreed, there is a slight risk in swapping once per week, but that's pretty minor.

Actually, I think my 'system' is going to be to continue to do nothing at all. I'm just checking my 4 YO laptop, charged all the time, and the battery seems close to its original capacity. The only thing close to a battery 'problem' with any of the many laptops in our family was DD's MacBook had one that just met the criteria for replacement under the Apple extended warranty, but it still was in pretty good shape after almost 3 years.

I'm still thinking the built in FW/SW approach is the only real solution - simply stop charging at XX%, switch to line power, but don't discharge the battery while on line power.

-ERD50

[TromboneAl]

I agree that, surprisingly, we don't know the relative effects of always on versus constant charge/discharging. The FW/SW solution is something that I'd never even thought of -- do you think that's what the Lenovos do?

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Do you need to shut down to replace the battery?

You certainly don't need to, and a lot of people don't. Others advise against it. I see it as slightly risky, but perhaps that's just a general concern about making physical changes while something's powered on. Physical stress, including stress to the pins, is probably more important.

With my last computer, I disabled automatic sleep, but with this new one it's part of my security system. It sleeps after only 10 minutes of activity, and just needs a swipe of the wonderful fingerprint scanner when it wakes up. Thus, if someone breaks into my house, my data (web site passwords for example) will likely be safe.

And here's my interesting discovery:

Last night, the battery was at 34% when I put the computer to sleep, and the charger timer was set to stay off.

This morning, when I woke it up, it was still at 34%.

So, with my new scheme, the battery will spend most of it's life neither charging nor discharging (or discharging slowly), and at a charge level significantly lower than 100%.

[ERD50]

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Originally Posted by TromboneAl I agree that, surprisingly, we don't know the relative effects of always on versus constant charge/discharging. The FW/SW solution is something that I'd never even thought of -- do you think that's what the Lenovos do?

Yes, I've done some web searching, plus my general knowledge of how these work says that is exactly what they do. It only makes sense. And that is why I can't find generic programs to do this, they need to write new settings to the propitiatory firmware in the charger circuitry. Traditionally, they charge to 100%, then stop charging and power the laptop from the line. They are not powering from the battery after hitting 100% - that would result in just as much battery cycling as if you typically ran it mobile. Charging to 100% allows them to advertise maximum 'run time' on a charged battery. That's less important now, with so many of us using our laptops as desktops >90% of the time.

See post #21 for a good description.

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And here's my interesting discovery: Last night, the battery was at 34% when I put the computer to sleep, and the charger timer was set to stay off. This morning, when I woke it up, it was still at 34%. So, with my new scheme, the battery will spend most of it's life neither charging nor discharging (or discharging slowly), and at a charge level significantly lower than 100%.

I'm not surprised at all that it used near zero battery during sleep. Sleep is very efficient these days.

And I think your conclusion is wrong. True, it will be at < 100% overnight, neither charging or discharging. But your daytime usage requires these charge/discharge cycles. Roughly 4 of them @ roughly 30% each, is roughly 120% cycled each day. The earlier links indicates ~ 300-500 cycles before degrading to 70%. So on the generous end, that means 500 cycles divided by 1.2 cycles/day, is 417 days, about 1 year and 2 months.

I really don't think the "staying near 100%" issue is degrading batteries to that degree - but the numbers I've found so far are a bit fuzzy. But I've seen those 300-500 cycle numbers consistently.

Here's a compromise - in the evening, shut off line power XX minutes before you expect to be done for the night, to let it discharge to 85-95% before sleeping for the night (the sleep setting could be set to a time that gives this approximate value, and it would be automatic). Then just charge it up on first use in the AM, and leave the line power on all day.

That gives you > 1/3rd of the day at a lower charge level (helps to some degree - though I can't say how much), and an average 10% charge cycle per day. Switching to the pessimistic end of the range, 300 cycles divided by 0.1 cycles/day, is 3000 days, about 8 years and 2 months. Beyond the life you probably expect anyhow.

From that batteryuniversity link, charging to 4.1V versus typical 4.2V doubles the charge-cycle life of the battery, and 4.1V only reduces run-time capacity to 90%. And the effect is eliminated below 50% charge level (3.92V), so further reductions are not helpful.

How to Prolong Lithium-based Batteries - Battery University

-ERD50

[springnr]

The laptop manufacture is the most likely source for battery control, as the software needs to be written for specific hardware. Another place to look for a control setting might be in bios or a bios update?

My Lenovo stays at 40 percent even when turned off and the charger plugged in. The software allows custom start and stop charging settings, the 40% was entered by me as a stop charging parameter. At 40% level if i lose wall power there is still over an hours worth of run-time on the battery, plenty of time to finish up and shut down.

[M Paquette]

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Originally Posted by springnr The laptop manufacture is the most likely source for battery control, as the software needs to be written for specific hardware. Another place to look for a control setting might be in bios or a bios update?

In computer systems, battery charge control is usually split between a state store within a removable battery, which holds basic battery information like charge/discharge state typically in units that map to milliamp-hours and battery age in charge/discharge cycles, and a microcontroller and charge regulator chip within the computer. There is often a temperature sensor in the battery package as well. The microcontroller has it's own firmware that reads the status of the currently installed battery and adjusts to do 'the right thing' based on the battery charge/discharge state and age of the battery in cycles.

These tend to be specific to battery chemistry and manufacturing details

[NW-Bound]

This talk made me curious, so I looked in the BIOS of my HP laptop, but saw nothing about limiting the charging state of the battery. When plugged in, it will always charge up to 100%.

It is true that they have a microcontroller dedicated to maintaining the battery, independently of the laptop CPU. Else, the CPU has to be running all the time just to take care of the battery. And then, if "Windoz" locks it up, the battery may end up in flame.

PS. What I saw in the BIOS is that the CPU "knows" the S/N of the battery pack. Interesting that they bother to track it.

[target2019]

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Originally Posted by NW-Bound This talk made me curious, so I looked in the BIOS of my HP laptop, but saw nothing about limiting the charging state of the battery. When plugged in, it will always charge up to 100%. It is true that they have a microcontroller dedicated to maintaining the battery, independently of the laptop CPU. Else, the CPU has to be running all the time just to take care of the battery. And then, if "Windoz" locks it up, the battery may end up in flame. PS. What I saw in the BIOS is that the CPU "knows" the S/N of the battery pack. Interesting that they bother to track it.

The HPs I have are the same as yours. There is no Bios setting for extraordinary battery control. It sounds like Lenovo is out front on this.

[TromboneAl]

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Originally Posted by ERD50 Here's a compromise - in the evening, shut off line power XX minutes before you expect to be done for the night, to let it discharge to 85-95% before sleeping for the night (the sleep setting could be set to a time that gives this approximate value, and it would be automatic). Then just charge it up on first use in the AM, and leave the line power on all day.

Yes, perhaps I'll do that. I don't use the computer as much in the afternoon, and rarely after dinner, so I'll just figure out the best time to stop charging.

Those depth of discharge figures probably refer to depth from 100% (e.g. 100 to 90% for a 10% discharge). Perhaps they would be different if it were always in the 40-70% range (e.g. 70 to 60% for a 10% discharge).

As NW-Bound says, I'm really wasting my time here. A new HP battery is only $49. But the engineer in me hates to see the battery at 100% all the time. I have a good hammer (the digital timer), so this problem looks a lot like a nail.

[ERD50]

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Originally Posted by TromboneAl ... Those depth of discharge figures probably refer to depth from 100% (e.g. 100 to 90% for a 10% discharge). Perhaps they would be different if it were always in the 40-70% range (e.g. 70 to 60% for a 10% discharge). ...

Right - while that link provides a lot of valuable info, it is reported under specific conditions. I don't think it's easy to tell what happens if those conditions change slightly. AFAICT, their numbers about battery 'health' (Lenovo uses this term to differentiate between the time you get on a single charge - which is always confusing when doing a web-search) and charge % are reported in degradation of total charge/discharge cycles. But if you run it almost exclusively from power, I'm guessing it takes months before you achieve even one full cycle ( like ~ 33 cycles of charging between 97% and 100%, which would be replenishing self-discharge only, which is pretty slow). So what effect does sitting at 100% have with almost zero cycles - hard to say?

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As NW-Bound says, I'm really wasting my time here. A new HP battery is only $49. But the engineer in me hates to see the battery at 100% all the time. I have a good hammer (the digital timer), so this problem looks a lot like a nail.

Yes, if there was a clear benefit, even a small one, then any little thing you do is 'worth it' IMO. The reward/effort ratio is high, even if both numbers are small. But the benefit of this idea, w/o the actual FW/SW control to avoid adding charge cycles, is very questionable.

One data point, FWIW - I just looked at DW's MacBook Pro using the 'coconut battery' app. Unit is 62 months old, 444 cycles, and at 77% of original capacity ('health', not charge level). So that's about a 24% charge cycle per day average. She moves from room to room with it, so it is often plugged in, but I guess it runs down if she moved and didn't bother to take the plug with her.

Anyhow, if she charged a full cycle a day, that would be >1800 cycles, and I doubt it would still be useful. But again, if it only charged to 70%, who knows?

-ERD50

[SumDay]

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As do Dell laptops with windows 8 as well.

Wow, I finally found one thing to like about Windows 8.