Rechargeable batteries do eventually die -- permanently. Whether it's a cell phone, digital camera or laptop, if you plan on regularly depending on the battery for more than a year, you better be cautious. Rechargeable batteries will eventually hit the point of no return, which means as much as a $200 replacement for laptops. For quick tips on battery bliss, click the "read on" button and scan the bold portions. For those who require detail and like my witty asides, read everything eight times, bold or not.
Li-ion Reliance
First of all, battery care can vary greatly depending upon what type of battery we're talking about. Most rechargeable batteries in modern devices are Lituium-ion. So, rest assured that pretty much any MP3 player, camera or laptop you bought in the past 5 years is Lithium-ion. Double-check on the battery's label, if you're unsure. As long as it's Lithium-ion, you can trust these words.
The Cycle of Cycles
A Li-ion battery can tolerate 300-500 cycles. A cycle is a "complete use" of the battery. Whether you use it 100% of the way through once or 50% of the way through twice (with one charge in between) or 25% of the way through, four times (with four charges) -- it all adds up to 100% of a use, which is one cycle. So, a battery that lasts one hour will effectively get you 300-500 hours of use.
You want to reduce the number of cycles or "complete uses" that you go through.
If you have a Mac, you can see how you're doing so far by opening the System Profiler and looking under "Power" (Apple > About this Mac, then click "More Info").
Reducing Uses
The first thing you can do to reduce cycles is to get more usage out of each cycle -- conserving power when you're using the battery. Additionally, energy conservation leads to a lower current draw, which increases longevity. Rosario wrote a great, simple post on how to conserve life on one cycle with your laptop. Apple has an article for iPods (including some notes about lifetime), as well as one for notebooks -- these rules apply for all Li-ion batteries. But Apple sells batteries -- they profit from your screw-up. So, here's my take, with some additional research.
During down-time keep it plugged in. Most devices are smart enough to stop charging the battery and start powering via AC once the battery hits 100% capacity. The only thing that can cause a cycle to happen now is the battery's natural power-loss (from non-use).
So, the battery might momentarily drop to 99%, then the device will charge it that one percent and chill at AC power until it happens again. This has to happen 100 times to complete a cycle. So, if you're going to use the AC power for more than a day, remove the battery altogether. (Beware that some devices won't work at all without the battery in.)
Heat is a Li-ion battery's worst enemy, especially on a full-charge. This is another reason to remove a battery if AC power is the primary resource (because a running laptop gets hot). It's also unwise to leave an iPod or cell phone in a hot car or microwave. Heed my warning: heat is probably the number one cause of diminished lifespan.
Frequently, battery removal can help resilience. If you're removing the battery for a while, be sure to follow these rules: keep it dry, keep it cool (a refrigerator is the best) and keep it about 40% charged. Never store it de-charged.
Li-ion batteries tend to last longer with partial discharges. Avoid running the battery until it's last drops by recharging it every time you stop using it. Lithium-ion batteries cannot get "memory," like other rechargeable types.
A few regular maintenance things: Do at least one cycle, once a month to keep the electrons moving. If you're using it less than once a month though, you're probably not so concerned with it's lifespan anyway. You will also want to do one complete de-charge (and immediate recharge) about once every 30-50 uses to re-calibrate the battery. If you don't your gadget will start showing you a phony charge percentage and potentially deem the battery dead when in fact it's not. If you're a typical user of the doohickey , this probably happens once a month anyway.
Know your warranty because you might want to completely throw caution to the wind if it's around 2-3 years. Most lithium-ion batteries won't last that long -- even on a shelf. If you have a typical one-year warranty, and you're a frequent portable user, it might behoove you to treat your battery poorly and shoot for 500 cycles in one year. The manufacturer should replace a dead battery under warranty. Make sure that your warranty covers battery replacement. Some don't.
Friday, January 11, 2008 by 
