Extending the life of a battery

OK, batteries are a boring subject. But laptop batteries are expensive to replace, so time spent in their care and feeding can pay off in postponing the inevitable a bit.  

Recently, in Slate, Farhad Manjoo offered tips on extending the life of batteries in How To Charge Your Laptop. The article offers tips for laptop computers, phones, cameras and other gadgets.

I know many people that keep their laptops plugged in all the time. Turns out this decreases the life span of the battery. Laptops that are used on electricity for days on end, should have their battery removed. When possible, the battery charge level should be between 20 and 80 percent.

Heat decreases the life span of a battery, thus its best to charge a laptop battery when the computer is off - less heat.

Batteries that won't be used for extended periods of time should start out 40% charged.

I've seen more than one laptop manufacturer recommend periodically draining the battery down to zero and back up to 100%. The article points out that this this does not prevent the battery from losing capacity but it does help re-calibrate the charge meter.

HOW DEAD IS THE BATTERY

The article didn't address a pet peeve of mine - learning just how dead the battery is.

All batteries lose the ability to store a charge over time. For example, a battery that can store 10 units of power when new, may only be able to store 7 units of power a year later.

Typically, as a laptop computer user, you have no idea that this has happened. The computer will continue to display, for example, that the battery is 100% charged despite the fact that its now holding 30% less power than it used to.

One nice thing about ThinkPads is they come with software that does report this. For example, an old ThinkPad of mine, dating back to 2005, reports that the Design Capacity of the battery is 61.92 Wh but that the Full Charge Capacity is down to 32.11 Wh. When it reports 100% capacity, the available horsepower is only 52% of what it was when the battery was new and likewise reporting itself to be at 100% capacity.

I tested the trial edition of Passmark's BatteryMon on a couple laptops and it was also able to report the initial design capacity of the battery and its current maximum capacity.