Control your Fans
We trainers and programmers might have many geek groupies, but this time I am not talking about those. The second thing to take control of is the fans that keep your CPU cool. Those rotating fans have motors that are putting a small but constant load on your battery.
Using the “About this Mac” page I was able to determine the difference between full fan speed and lowest fan speed to be up to 100 mA. Compared to the regular energy use of around 1300 mA this gives you up to 15 minutes more working time.
My favorite tool to help you take control has the obvious name “Fan Control” and is available for free from Lobotomo. With this you don’t set the speed directly but with three sliders you adjust the red line which determines the RPM to use for a given CPU temperature.
Real Geeks Undervolt
While playing with settings like fan speed might have an impact on available idle time there is little you can (usually) do to extend battery time when doing something useful. Typing code lets your CPU idle most of the time anyway.
The last bastion to tackle if you posess the strong determination of geeks is undervolting your CPU. We all know that Watt = Volt times Ampere. So if we can manage to decrease the Volts necessary for the CPU then also the energy usage under load will decrease.
The tool for this purpose is CoolBook Controller which gives you such control for the price of $10. At the maximum load the CPU is using 1.1375 Volts default. CoolBook Controller has a built in testing facility that allows you to decrease the Volts for a given frequency. This way I found that my MBP can also work with 2500 MHz with as low as 1.01V, but then it would get unstable.
In real life you would only decrease the voltage by two or three steps to not risk the system becoming unstable under stress. The makers have achieved up to 14 degrees of difference in temperature under stress. Less temperature also equals less cooling required.
But like all things concerning over-clocking or under-volting this is not for the faint of heart.
Warranty Replacement Battery Tool
According to Apple the 15″ MacBook Pro Battery is designed to retain 80% of its factory capacity after 300 loading cycles. If you are using your MBP daily and constantly like me then this number equates to approximately 6 months.
The original capacity of my (early 2008 model) MacBook Pro Battery was 5400 mAh but as of this writing it is decreased to 3112 mAh. This is way less than the 80% (4320 mAh) that are normal.
Ordinarily it would be difficult to prove to Apple that you get much less than the 3 hours of working time advertised. If it weren’t for the fabulous and free tool Coconut Battery which makes it crystal clear.
Having only slightly more than half the original capacity starts to cause me problems because this means that my two hour train rides are no longer fully covered. Obviously I am going to go to my Apple authorized dealer later and send it in for warranty exchange.
Finally a Piece of Advice
Once you have gotten a new battery then you should try to discharge it fully before fully loading it. This helps to retain the maximum possible capacity. These days many people use a MacBook as Desktop replacement keeping it constantly connected to the power adapter.
The jury is still out whether such practise is good or harmful for the battery. Modern battery management should be able to minimize impact and the latest models of MacBooks don’t even allow for removal of the battery out of paranoia.
But what you should do in any case is this: at least once a week is to fully discharge your battery before fully loading at again. This “battery training” exercise allows the battery management system to calibrate and “keeps the battery juices flowing” (Apple lingo, not mine)
And all of this will increase your mobile coding stamina to its maximum, pumping those heavy Cocoa objects. Maybe just enough to have a syntax orgasm the next time you are coding on a train or plane. Good Luck!