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This past week, I have had multiple people ask me about dealing with laptop batteries that are either dead or no longer last more than a few minutes. Throughout all the years I have helped Mac users, nothing has frustrated users more than batteries dying after six months, 18 months, or anytime that the user still owns his or her laptop. Why is this the case? I could say that users do not have a good understanding of how batteries work. I could say that computer companies do a poor job explaining the lifespan of a battery, or worse, lie about it. But the hard truth is that we, as laptop users, demand the impossible: a battery that never dies and never loses capacity.
In this article, I want to explain a very small amount of battery technology, provide a few tips on maximizing your battery life, and give advice on determining whether a battery has naturally died or is defective.
Battery Technology
Today, all major computer manufacturers use Lithium Ion batteries. Lithium, as a metal, is lighter than the older battery technology: nickel cadmium and nickel metal-hydride. If you use rechargeable batteries in your home appliances in common sizes like AA, AAA, C, D, or 9-volt, those are still nickel metal-hydride batteries.
Because lithium is lighter than nickel, you can literally pack more of it into the same space, and the battery will be lighter. That’s great for the laptop user on the go, but it’s also more expensive: a new battery from Apple costs $129 (except for the 17″ MacBook Pro). Lest you think that’s expensive for a computer battery, a quick check at Dell’s website reveals batteries from $125-$300. At HP, equivalent batteries are $125-$150. You can get less expensive 3rd party batteries, which I’ll talk about in a minute, but for now, I want to emphasize that the prevailing technology is Lithium Ion, and that computer manufacturers tend to charge the same amount for batteries.
The Life of a Battery
Batteries have a different life from other computer components. My father purchased a Mac 512k in 1986, and it still runs flawlessly today. That means the logic board, screen, speakers, cables, and everything else inside the computer is still functioning. Sometimes, components fail much earlier. Fail is the keyword. They work one day, and they don’t work the next. While batteries can fail like any other component, all batteries can be completely consumed, meaning their capacity can be used up. The hard truth sentence for this reads: Every time you use your battery, you’re bringing it closer to its death.
How can this be? The metal inside your battery needs to be charged, and when I say “charged,” I mean that the metal literally needs to be given a positive or negative ion charge (if you can think back to your high school chemistry class). Over time, less and less of the metal can continue to be charged, and eventually, your battery cannot be charged enough to power your machine.
You might then ask: ok, so how many times can I charge my battery before it dies? Well, and I’m sorry I have to say this, but it depends. Most lithium ion batteries have a maximum life span of 500 “cycles.” That means your battery probably won’t last more than 500 cycles, and it could definitely last less.
For batteries, a “cycle” is basically a full battery charge. With the older nickel batteries, computer manufacturers recommended that consumers not charge the battery until it became completed empty. That way, you’d get the most out of your cycle: charge the battery to 100%, use 100% of the battery, and start over. With the newer lithium ion batteries, this is no longer true. You can charge the battery whenever you want, and you will not prematurely kill your battery. This is good news. If you start using your battery at 100%, let it drop to 50%, then plug it back in, you’ll only use up half a cycle when it fully charges.
But let’s think about this more closely: if you use your laptop every time, and you use a fully battery cycle every day (meaning, during part of the day, you’re running on your battery and use its full capacity), your battery is probably not going to last more than a year and a half. You’ve got no more than 500 cycles and 365 days in the year.
What’s worse is that each time you use a battery cycle, the battery’s capacity slightly diminishes. Over time, that means your battery won’t last as many hours on a full cycle, even though it charges to 100%.
Maximizing Your Battery’s Life
Just like everything we love, we want to be with our batteries forever (mostly because we don’t want to shell out money for a new one). There are a few things you can do to prolong your battery’s life, but if you’re a true road warrior, they probably won’t be much help:
- Don’t use your battery! This has to be #1. If you’ve read the article this far, you know that to use your battery is to kill your battery.
- How do you avoid using your battery? If you use your laptop at home or at work, it should be plugged in 100% of the time it can be. I know that if you’re sitting at your desk or on your couch, it’s nice not to have a cord hanging off the end of the laptop, but you’re using up your battery’s life for your slight convenience.
- Hopefully, you’ve learned that computer software that taxes the processor (like games and video/audio/photo editing) as well as software that requires parts to move (like watching a DVD) chews up battery power faster than word processing or other, basic tasks. Ideally, if you need to use your battery, try to do the work that requires the least use of the processor while on battery and then plug the laptop in when you have to do the processor-intensive tasks. In this way, you’ll use less of your battery’s current cycle, prolonging its life.
- Do anything else you can to prolong your battery’s cycle. This will not only prolong the overall life of the battery but also the amount of time you can run on the current cycle. For example, you could turn your brightness all the way down. You could spin down hard drives when not in use (see the Energy Saver System Preference). You could avoid plugging anything into the laptop while using the battery.
- Finally, and this one should not be overlooked: avoid exposing your laptop to excessively high or low temperatures. Apple recommends you keep the laptop between 35º-95º F (~2º-35º C). Exposing the laptop to higher temperatures can permanently damage the laptop, including the battery. Exposing the laptop to lower temperatures can temporarily damage the laptop, but it will recover when it warms up. What does this mean? Don’t keep your laptop in your freezing or boiling car!
- If your laptop was kept in your 20º F car, you’ll probably find that your battery won’t last as long the next time you use it. That’s a wasted cycle. But if you had let your laptop warm up to at least 35º F before you turned it on, the battery cycle would have lasted its normal time. It’s like warming up your car on a cold winter’s day.
Replacing a Bad Battery
I hope, at this point, you can understand that if you’ve been using your laptop nearly every day for two years and the battery now only holds a charge for 20 minutes or can’t charge at all, it’s depleted — not defective. Your battery wasn’t supposed to last longer, and you need to replace it if you want a battery that lasts longer.
If you bought a battery three months ago and it only lasts 45 minutes on a charge, that’s a different story. Unless you’ve been going through a full charge 15 times/day (which is impossible), your battery is not depleted due to use. You should consider having an Apple Store or service center test it. In your case, there is probably a defective charging component inside the battery, preventing it from holding a longer charge (rather than simply being “used up” by repeated charging).
What happens when your battery is somewhere in between? Is it consumed or defective? This is the last hard truth: there’s no easy answer. Dealing with underperforming batteries will be a difficult experience for the foreseeable future.
Do you disagree with my explanation of battery life cycles? Have you found better ways to conserve your battery? Have any tips on getting your battery replaced under warranty? Let everyone know in the comments.
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Matt,
That was one of the better articles about batteries that I’ve read in a very long time. It was concise, to the point and very easy to read.
I just wanted to let you know that though Apple batteries are not removable from the laptop, Apple does participant in the Call2Recycle program to recycle dead batteries. Because they help to fund the recycling program, it’s completely free for consumers. In addition to Li-ion batteries, the program accepts all small, dry-cell rechargeable batteries (Ni-Cd, Ni-MH, Ni-Zn, Pb) also found powering cell phones, cordless phones, digital cameras, camcorders, power tools, mp3 players, PDAs, cordless vacuums, electric razors & toothbrushes, tw0-way radios, etc… Anything that requires plugging into a wall socket to charge.
At the end of a rechargeable battery’s life, Call2Recycle melts them down, extracts reusable metals (such as nickel, iron, cobalt, lead, cadmium). Nothing goes into the landfill.
So while rechargeable batteries eventually wear out and can no longer hold a proper charge, the good news is that they can be recycled. And through Call2Recycle.org, they can be recycled easily and for free.
Thanks for the informative post Matt. What do you think about “calibrating” batteries (i.e. using all of your battery’s charge to the point where your computer shuts off, letting it sit awhile, then charging it back up all the way). The Macbook manual says to do this once a month. Is this really necessary/useful?
Sid,
It’s not *necessary,* but it can be useful. Basically, flushing your entire battery can have the same kind of positive effect as does restarting your computer: if there are any bugs floating around, they should be wiped away. Sometimes, the controller on the battery will not accurately determine which cells to charge nor their capacity. This could result in charges that don’t last as long as they could. By completely depleting your battery, you give the battery controller an opportunity to properly scan every cell in the battery, which can result in longer lasting batteries.
Great, informative post. Thanks for taking the time to explain.
Please explain why my battery capacity is higher than normal and is 8 months old with 249 cycles?
I was just wondering how exactly to bypass using the battery in order to prolong its life and charge capacity: is it enough to merely leave your computer plugged in to the power cord anytime that you use it? Or do you have to physically remove the battery from the computer and then plug in the power cord to run? Obviously removing the battery from the new unibody’s is impractical since they are built in, especially in the 17inch, but does leaving the power cord in while the battery is in really not use the battery at all?
Nope, you don’t have to worry about this. The System Management Controller inside the computer manages the power current, and it will automatically bypass the battery if there’s a full charge. Otherwise, you’re right, it would really reduce your battery’s life.
In a Mac, does the System Management Controller need MacOS to work, or is it something at a lower level, independent on the OS? E.g. does it still work if I install Linux?
The SMC is actually two parts. There is firmware, which will run no matter what OS you are using. Then there is controlling software, which varies from OS to OS. The battery charging stuff seems to be just in the firmware. The OS really can only read information from it. On Ubuntu Jaunty these days it’s in /proc/acpi/battery/BAT0 if you look at the file named “state” it will actually have the last full capacity in mili watt hours. You can watch this number drop with each cycle of your battery…. so sad really.
Fan control seems to be a mix of both.. On ubuntu I can set the minimum fan speed just like “SMC Fan Control” lets me in Mac OS X.
I wanted to correct one bit about this otherwise great blog on modern battery care. ( That I thank you writing. ) A lithium-ion battery should actually be fully cycled about once each month at a minimum. Although lithium-ion batteries don’t have “charge memory” like NiCd batteries, they will lose “charge mobility” if left fully charged for long periods of time. The ions sort of become “stuck” and don’t want to go around the circuit. ( The technical term is “internal resistance” ) By cycling the battery every once and a while it stirs things up and keeps the charges mobile.
There are extreme cases where someone will leave a laptop plugged in for 2 years. The battery will have no cycles, and when they unplug the laptop it instantly loses power. That’s because the internal resistance of the battery is so high it can move the charge fast enough to power the machine. The trick is finding a happy medium.
In addition, even if you treat your battery perfectly, it still won’t last more then 3 years. Lithum-ion batteries lose capacity even if not cycled often. The storage temperature, and charge level storage dictate how fast they degrade. In most laptops, hot! and stored at 100%, they degrade at about 35% per year. So after 3 years you’ll have around 20% capacity left… if you’re really really lucky!!
Once again, great post. I have been considering a Macbook Pro but the idea of a built-in battery seemed completely wrong for me. I don’t have much to contribute in terms of technical or chemistry, but I wanted to add something after reading Anthony’s post. My first laptop battery was a disaster, because I kept the laptop plugged into the AC supply with the battery 24-7. It retained pretty much 30 minutes of power when 100% charged after about 2 years.
When I got my second laptop, I made sure the battery was removed if I planned on leaving it on AC for at least the next couple days. In a way, I used the battery only once every 2 months, and I have to say, its been 5 years since I bought that laptop and when I last tried the battery on a full charge, it lasted me 4 hours. So I do think there is a way you can treat your battery well.
To Apple’s credit. Their recent “built in” batteries are “replaceable”. Just not “user replaceable”. If you kill the battery apple will replace it for about as much as other modern laptop batteries cost. Likely what they found is most people never remove battery for the life of the laptop ( even if it is good for it ) So they can use this typical behaviour to save space on casing, and add more battery giving more run time. You can’t please everybody all the time, but they do have the longest running 15 and 17 inch modern laptops.
>>”That way, you’d get the most out of your cycle: charge the battery to 100%, use 100% of the battery, and start over. With the newer lithium ion batteries, this is no longer true.”
I have to say that I disagree with this, although it seems logical and believable, my own exprience has denoted otherwise. Anthony started to explain, but then went on to say that they decrease in capacity 35% per year, even when used properly. With this I disagree as well.
I have a white macbook that I purchased in december of 2007. I work on my laptop, and spend probably 10-12 hours on it a day. I rarely shut it off, but just put it in sleep mode. I try to keep it plugged in when I can, but I always fully charge it if I am going to charge it ( no partial charges) then if I unplug it, I will run it to 0-6% before plugging it in. I know this is “old-school” nickel battery behavior, but in practicing this, My macbook’s battery currently:
- stil lasts a good 4-5 hours (6 if no audio or video is playing and the screen is at its dimmest)
- is at 96% capacity
- has 632 cycles on it
So although lithium claims to not have any charge memory, or whatever the “technology” and science behind it say, my experience has prooved otherwise to me.
p.s. my wife has the same computer as me, that she purchased 6 months before me, it has a capacity of 74% and 550 or so cycles. She does not share the same charging habits as I do, but they have still both lasted longer than claimed in this article and claimed by apple.
Those are great numbers for cycles and capacity loss. There are likely a few things at work giving you such amazing capacity longevity, and great cycle life. My guess is it all comes down to our pesky friend ”’temperature”’. The 35% degradation I stated is what “some” research puts lithium ion at when stored at 100% charge, at 104 degrees Fahrenheit. I personally think it’s a bit high… so does your experience. The number is probably less for more recently manufactured batteries.. ( they are getting better. ) However, temperature is still king here. Most people that “work” on their laptops don’t really _WORK_ their laptops. Sure sometimes firefox gobbles up 100% of the CPU for a minute or two while watching a youtube video… but how many people run their laptop CPU and memory full out for hours on end each day? ( *my hand goes up in the back* ) In addition, I have a macbook pro.. which does a great job of conducting all that heat evenly over the battery, warming it nicely. Now… to avoid the problems I run my fans at 6000 RPM solid… but everything still heats up. This is my guess as to why my macbook pro batteries last about a year before beginning to lose capacity faster then my decreasing attention span with each passing season of “Lost”.
The plastic macbooks seem pretty good at keeping the heat away from the battery. That should help extend the life tremendously. I don’t know what tricks have been employed to protect the latest generation of batteries sitting inside those uni-body aluminium cases…….
Hi,
Your xplanation was very clear and u to the marks thanks a lot for your tips. My questions is ” If the laptop stays plugged in always, will it affect the battery in any ways like overheating and so forth”..?. Can you just xplain this issue.
vj:
Just from my experience, I wouldn’t do that. If you’re keeping it plugged in, leave the battery out of this. The battery will last a lot longer that way. I left my battery at full charge but removed from the computer. Will usually leave it that way for 2 months, before I’ll remember I need to ‘use’ it occasionally. The charge usually drops to around 80-90% if left unused for a couple months, but if you charge it back to 100%, you can still get 4 hrs worth of juice. Why charge and discharge the battery, if you don’t have to?