I have recently found 2 products that have helped me to significantly extend the time I am able to work with my laptop away from any AC power outlet.

The first is an external battery from BatteryGeek.net. When choosing an external battery you need to find one that is compatible with your laptop, with suitable voltage and adapters. Luckily the nice people at BatteryGeek will evaluate your power needs and give you a free ‘battery audit’ listing which of their models will work for your particular situation. If you want to power other portable devices with the battery that’s not a problem either.

The next thing to consider is the number of Watt Hours. Basically more is better. Their top of the line models boast 140 WH, while the one I purchase is rated at 130 WH. Considering that the internal battery in MacBook is only rated at 50 WH this should extend my work time considerably! I got the BG 19-24-130 since it was on sale for $170. They tell me it has been discontinued and when the stock runs out you’ll have to choose among the more expensive models.

The other product is an application for the MacBook called CoolBook which allows you to under-clock the Intel Core Duo processor which not only extends your battery life, it also lets the machine run a bit cooler. Basically this let’s me run my 2.0 GHz processor at only 1.0 GHz with a correspondingly lower voltage. Before installing CoolBook my typical internal battery life was 3 hours, but now I can usually get around 4! And at only $10 this is great little piece of shareware. Of course you need to be aware that under-clocking your CPU will cause heavier applications to run slowly, so I wouldn’t use this if you’re going to be editing audio or video.

There must be some way for PC laptop users to under-clock as well. I think it might depend on the BIOS. If you have any ideas feel free to post them in the comments.

Of course this stuff about under-clocking may sound extremely technical and the settings aren’t necessarily that intuitive, but I can assure you it’s worth the effort to extend your battery, keep your laptop cooler and let your fan(s) run more quietly, though if technical stuff scares you it’s probably best to just leave it alone then. The external battery will extend your work time a lot longer, though for a lot more money. For me the best solution is to use both. I haven’t looked for an AC outlet at a cafe for a few months now!