Are there REALLY any benefits to battery power cycling?

November 11, 2005 12:52 PM

Battery power cycling - it's offered as advice for poor battery life on pretty much anything, from cell phones to laptops. Heck, T-Mobile told me to do it today after I switched phones and the same battery dropped from 50 hours of standby time to 9 hours. However, I've only ever cycled one thing - a laptop battery - and that dropped its capacity from 4 hours to 30 minutes. Because of that I'm a bit wary, so my question is, what's the logic behind power cycling a battery, and has anyone actually seen any benefits from it?
posted by philulrich to technology (9 comments total)

Apple's web page on batteries is fairly comprehensible and comprehensive — and platform agnostic, to boot. I'd definitely start there for charging tips.
posted by Rothko at 1:07 PM on November 11, 2005

My personal experience is that I regularly run batteries down to the low battery warning on all of my battery-powered things, from laptops to iPod, and I never have the battery troubles other people complain about.

I even did an inadvertent experiment - a friend and I bought identical iPods from the Apple store on the same day. He kept his charging any time he wasn't using it...I waited until the battery indicator was empty. His lasted 2 months before the battery wouldn't hold a charge anymore. He had his replaced and it had the same problem again, about 4 months later.

Mine is still working just as well over a year later.
posted by bikergirl at 1:21 PM on November 11, 2005

Rothko: Excellent link. I didn't know Apple just had a random batteries page. :) The funny thing is, I use my iPod just as they recommend (and just as bikergirl does), and my iPod's battery life is fantastic. I used my iBook like they recommend and, well, it wasn't.

The thing is, I used to use a Motorola V300. I did what bikergirl did with her iPod battery: waited till it was empty, or nearly so, then charged it all the way. Worked fantastically. The problem was, mine V300 got plagued with the same problem I see a lot of them getting on the web - pressing any button, any time, has a tendency to kick you out to the home screen.

T-Mo replaced it with a V300, which I thought would be identical, but no matter what I do, I can't get the same battery performance out of what is presumably an identical phone.
posted by philulrich at 1:32 PM on November 11, 2005

That Apple page has some misinformation, for reasons I went into here, when I asked metafilter about extending the usable life of my new laptop battery. (My assertions and experience also match bikergirl's, in contrast to the ridiculous-until-proven-otherwise advice on the Apple page about what constitutes a charge cycle.)

The answer to your question is that sometimes the battery meter gets out of sync with the actual charge cycle, and discharging and recharging resets that correlation.
posted by Caviar at 2:13 PM on November 11, 2005

Note also that the logic is different depending on chemistry. Eg NiCd, NiMH, Li-ion, etc batteries. While power cycling is done for all of these, it's called for in different circumstances due to being done for different reasons.
posted by -harlequin- at 4:58 PM on November 11, 2005

Bikergirls experiment has nothing to do with Apples advice. They're talking about what a cycle consists of, her experiment was deep discharging vs. overcharging. A more interesting experiment would be repeated 25% discharges vs. deep discharge. Leaving a li-ion battery charging ALL the time is a great way to diminish the capacity, assuming it doesn't have good charger. Talking about the battery alone is a little unpredictable though. All chargers/charging circuits are not created equal.
posted by Jack Karaoke at 5:08 PM on November 11, 2005

>Leaving a li-ion battery charging ALL the time is a great way to diminish the capacity, assuming it doesn't have good charger.

Jack, please explain. I have always understood that a lithium-ion battery is not susceptible to the memory effect that plagues nickel-cadmium batteries. It is that memory effect, I understand, which leads to the recommendation that devices powered by Ni-Cad batteries be allowed to discharge before being recharged.

What do you mean by something not being a "good charger"?
posted by megatherium at 8:05 PM on November 11, 2005

Some chargers can vary the current supplied to the battery. Supposedly a doubling of the current = 5% loss on the # of useful cycles over the battery life. Monitoring the temperature of the battery is also a feature that costs money to impliment, and can affect battery life. I imagine most chargers are really just a compromise when it comes to these factors. If your battery charges in a blink, and is toasty hot when done, maybe it's not being treated right.

Why leaving li-ion batteries plugged in kills them? I don't know. I didn't say that it is related to memory effect, but I have experienced it in cell phones. The only charger I would leave batteries in overnight is an IDX or similar charger. IDX has an FAQ for battery care (previous link), but they don't mention leaving them in the charger, yeah or neah.
posted by Jack Karaoke at 9:09 PM on November 11, 2005

Do and don't battery table in the Battery University
posted by Sharcho at 4:57 AM on November 12, 2005