Does anyone know of an application that will keep a laptop's battery from charging past a certain percentage?
My laptop has a nice little feature that lets me set a limit to the battery's charge (100%, 75%, or 40%) and it will not charge past that, even when the laptop is off. I understand that since it works while the laptop is off, it's definitely somewhat hardware-related, even though it is software-controlled. However, I would like to port this ability to other laptops, since both my own experience and my understanding of how Lithium-Ion batteries work tell me that limiting the charge will extend the overall lifetime of a battery. Is there an application, or Windows tweak (both Vista and XP) that will allow me to prevent laptop batteries from going past, say, 75% charge? I understand it would only work while the laptop was on and booted, but that's better than nothing.
And while we're at it, how about doing it on Ubuntu as well?

Thanks

This post has been edited by Anomaly: Nov 6 2009, 02:50 PM

Most laptops automatically stop charging at 100%, because realistically the whole point of a laptop is to be portable. If you only charge it 40% you're kind of spending more time charging it back to 40% every time rather than going back to 100% and letting it discharge normally and often getting a longer battery time to boot. Providing they don't get totally discharged (as in totally discharged, ie totally dead), a complete discharge (to a reported 0%, which is rarely the true charge rate anyway) and recharge is usually the best procedure for most batteries.

The feature in question is probably a BIOS option which means it will not be transferable to other units. Even if such a software solution was available for Windows, as soon as you shut the unit down the thing will carry on charging past whatever you set, making it, in my view, pointless.

This post has been edited by Neil Jones: Nov 6 2009, 04:29 PM

Well, yeah, I understand they stop at 100%, that was just to say there was an option for a full charge. I also understand the point of laptops is to be portable. However, in my case, 95+% of my laptops' on-time is while plugged in. I also understand that it obviously wouldn't work while the computer is off, but that just means pulling the plug out upon shutdown, which is a very minor inconvenience.

I'm sorry if my language was confusing, but when I said longer battery life, I was referring to, for example, how many years before this battery becomes so bad that it needs replacing. I didn't mean how long it can last between charges.

My understanding of Lithium-Ion (what all my laptops have) batteries in general is that spending a long period of time at a full charge will degrade the battery's shelf-life much quicker than being stored at a partial charge. Since my batteries hardly get used, being on A/C power all the time, I thought i might try to extend their total lifetime (not their charge) by limiting the level to which they charge.

Anyways, I'd rather not debate the effectiveness or practicality of it, because in my specific case there is no real drawback, but just see if anyone knows of such an application.

Please bear in mind forums like these appear in Google, so whatever I say or you say will be read by somebody else in the future. Your situation may apply to somebody else who reads this in three years time. Therefore what I've said in the previous post may not be of any interest to you now, with all due respect, but a Googler in 2012 may find it useful.

With regards to prolonging battery life in a laptop, all batteries of this type decay as soon as they're made. The average life of these sorts of batteries is about 3 to 4 years under normal circumstances. All rechargeable batteries have a finite lifespan and will slowly lose storage capacity as they age due to secondary chemical reactions within the battery whether it is used or not. At a 100% charge level, a typical laptop battery that is full most of the time at 25 °C or 77 °F will irreversibly lose approximately 20% capacity per year.

Before I reply, I'd like to say that I'm not trying to argue (I hate forum arguments, or arguments in any setting), but just trying to make a point that something which I asked would be useful to me, and perhaps to others that use their laptops in a similar way (plugged in just about every second it's on).

I realize the inevitable decay of batteries, and I'm not going to try to argue against it. I've had batteries decay and go bad on me. Yes, no battery will last forever. However, from everything I've read about prolonging the shelf-life of Lithium Ion type batteries, I think I can get maybe 1 or 2 more years out of it by keeping it at a lower charge level. Since in my case, it's just about always plugged in, I'd like these couple extra years. A point to add is that the recommended charge level to store lithium ion batteries at is 40% (not my number, but is from just about every source I can find). My battery is being "stored" (not actually being used, just sitting in my laptop while it's on A/C power) almost all the time.

Basically my whole reason for doing this is to get an extra 1-2 years out of a battery before replacing it, because that matches up better with how often I buy a new laptop. Not having to shell out $150 for a new battery (darn those expensive suckers) for each laptop would be nice.



And a typical Lithium Ion battery (the kind my laptop uses, and I believe are very common in them) that is kept at 40% charge at 25 °C will irreversibly lose approximately 4% capacity per year. Jump the temperature up to 40 °C (closer to laptop temp, in my opinion) and a 100% charge loss is at 35%/yr, and a 40% charge loss is at 15%/yr.
Source: http://www.batteryuniversity.com/parttwo-34.htm

That said, does anyone know of just a utility I asked for in the first post?

This post has been edited by Anomaly: Nov 12 2009, 03:13 PM

point blank...no...there's no such utility that i know of...that HAS to be a custom function of your laptop (make and model?) and i've never seen an app that would control charge levels and that MUST require some form of hardware intervention to accomplish (you can't stop a battery from charging without stopping the electricity from going into it...so there has to be some form of redirection going on with the power supply)...even if the computer is on, there's no application or tweak that would allow for this if the hardware doesn't exist

if you're worried about your batteries getting "used" when they're not really being used (i.e. while plugged in) simply pull the battery out while the computer is plugged in. problem solved it won't be receiving electricity and can't stay at 100% charge. your computer will run fine without the battery in place as long as the power stays on (of course, if you have a power outage then the thing is going down)

I'm positive that there IS a hardware component to it, being that my laptop has a button on it that allows override of the limit, even if powered off (laptop is a Sager NP2090. I don't think that exact model is made anymore, but there may still be the similar NP2092). My question was for a software solution, but from the strength of the "no, there isn't one", I'd now assume that Windows has no control over when it starts/stops charging, but rather just gathers charge data and reports it on-screen. I'll have to stick to the pulling-out-the-battery one. Having it automatically stop was just so much easier tho... Oh well, thanks anyways!