Macbook Pro shuts down with 40% battery left... does not just go to sleep

Question

Hi,
Our MacBook Pro has started to shut down with about 40% battery left. After it has shut down, I press the button underneath the computer and 2 our of 5 lights light up on the battery. I wouldn't mind if it just went to sleep but I totally have to restart it and lose everything I have been working on when it died. The computer used to go to sleep when the battery got to 0%, then I could plug it in and keep working.
I don't know if it's a software issue or a battery issue or a firmware issue.
Any tips would be MUCH appreciated.
Thanks a lot.

Answer 1

I have read so many articles across the internet with people experiencing this problem. This is the conclusion I came to.
I could not calibrate my battery as my system would hard power down before it got anywhere close to draining the battery entirely. The last 10 cycles on my battery were attempts at calibrating. The most common cause would be because the battery in our macbook pro does contain something close to the charge being reported by the computer, but cannot deliver it. Your fuel gauge is probably not incorrect, especially when the leds on the battery itself show a charge that should be capable of running the machine. Even if it is not calibrated correctly. The internal resistance of the battery itself has compromised the batteries ability to deliver the amperage necessary to run our machines. After finally realizing this, I turned my screen brightness all the way down, and sat all my power settings to max battery life without allowing the machine to go asleep. Then, I went to sleep myself =). In the morning it appeared as though I had a successful calibration and the machine did not power down hard. Depending on how bad of shape your battery is in, this may or may not work. Either way, it didn't matter much. Even with my fuel gauge being correct, if my screen brightness was cranked up and I was doing anything somewhat processor intensive, my battery failed to provide the needed amperage and powered down my system hard again.
The battery really does have the amount of power it says, it just cannot deliver it as fast as needed. At a slower rate, it will work. A replacement battery is needed. I cannot explain the strange jumps/dips in storage capacity but would guess these numbers are a guide, and more than one environmental factor can change this number. Also, once the internal resistance builds up inside the battery and the inability to calibrate happens, it compunds the problem.
My machine is a first gen intel macbook pro. A few months after I bought it, I had battery problems and apple replaced my battery. My machine is 31 months old, it's battery is somewhere around 27. I tried to get apple to replace my battery and they told me no. I was 40% healthy @ 207 cycles. Many people complain about this but it seems reasonable to me, I didn't argue. I do believe my battery failed prematurely, however, it was due to a few factors and I do not think it was the batteries fault. My machine was one of those nice overheating first generation macbook pros. To make the matter worse, one of my internal fans stopped working. I knew this as my istat pro program showed me 1 fan @ zero rpm. I figured I had applecare and had work to do, so continued to use the computer for several months. I did quite a bit of video encoding and processor intensive work. When I would get to work in the morning, my granite desktop was really cold, however, after a half hour or so with the macbook pro running the heat would dissipate through it and warm it up nice and comfortable! lol, some may not think this is funny, but it worked well for me. I frequently had over 180 degree cpu temps and the bar above the keyboard being too hot to lay your hand on and keep it there. I am sure some of this excess heat contributed to the premature failure of my battery. The type of batteries in our machines are killed by heat, charge amount, cycles and age. Probably in that order for most users. So, can I blame apple because my unit ran hotter than it should have because their fan failed! eh, maybe, but I am happy with this laptop overall. I have never had a single laptop for more than 15 months and have had this one for over 30 now.
I ran across this site somewhere, it may have been another user on these forums, I cannot remember. http://www.batteryuniversity.com/partone-19.htm On this page, it talks about our batteries, the effects of heat and level of charge in combination with age. At 77 degrees F., charged to 100% (which is very typical of our machines, or close to it) after one year the battery is 80% as good as it was when it was new. At 32 degrees it is as 94% as good as new after one year. Jump up to 104 F. and the battery is only 65% as good as new after 1 year. Sometimes my computer is running for days and sometimes the environment is warm. Add that to the heat produced by the machine itself and I bet the battery sustained 100 degree temperatures for long periods of time. Just for fun, at 140 degrees and 100% charge in our lithium ion batteries, after only 3 months the capacity is only 60% of its new capacity.
Anyways, that is my battery story. Sum up. The inability to calibrate is due to the batteries increased internal resistance and inability to deliver the charge at a rate needed by your computer even though it appears healthy, or somewhat healthy. You may be able to calibrate by making your laptop drain less power, turn screen brightness all the way down, turn airport & bluetooth off, let hard disk sleep, and let it go. But that will not stop the hard shut down problem, although the fuel gauge will be more accurate. Think of it like this. a 100 gallon fuel tank on a car full of gas. The fuel gauge is correct, it is full. However, the fuel line connecting the fuel tank to the engine is made of a space age material that shrinks as it ages and is exposed to heat. Eventually the fuel line shrinks to the size of a coffee stirrer or small straw. When the motor is turned off the fuel seeps into the small straw. Start the motor, it begins to sip the fuel from the straw. Rev it up (encode video), the motor demands more gas but cannot get it. The motor stalls out (your computer shuts off). Same idea somewhat. Sorry so long