[appar111]

Just picked up a Mini last week at the Apple store, and had a couple questions.

First off, with Li-Ion batteries of this type, I know that it can get 300-500 recharge cycles out of it. So what counts as a cycle? Is it charging from completely empty, or does "topping off" the battery count as a cycle? Just curious as I'm sure there will be plenty of times where I'll need to charge it from 50-60% back up to full (as opposed to starting from bone dry) and would like to know how this will impact the overall life of the battery.

Also, I read a post about a "deep sleep" hack for the regular iPod (holding menu and play/pause button at same time, plus a few other steps) but will this also work for the Mini? I read that there's also a deep sleep command line that you can enter as the title of a playlist, but wasn't sure if that would work for the Mini also.

thanks in advance,

 

[leon]

"Topping off" doesn't count as a cycle - that's one of the selling points for Li-ion. IIRC that's in fact one of the better ways of using Li-ion.

I've read in several places that Li-ion starts to age as soon as it's manufactured, but if you keep depleting it completly, the aging process accelerates.

 

[akerman]

I'm curious as to what constitutes a battery cycle too... the battery in my IBM thinkpad is only a month old - yet it's already at 43 cycles.. not because I have depleted it 100% 43 times - but because I have discharged it say 10%, and then recharged it again.... its capacity is at 41.96 Wh, design capacity is 47.52 Wh.

I read on batteryuniversity.com, that it's better to discharge 10% and recharge again 10 times, than to discharge 100% and then recharge again. I don't know how that fits with my findings though..

 

[appar111]

I'm curious as to how this would affect my laptop's battery life as well (powerbook G4). I try not to let it get waaaay down unless I'm out somewhere and forgot to bring the ac adaptor with me. I know alot of people who rely on battery only with their laptop when they take short trips out (i.e. coffeehouse, etc.). How much more space can an ac adaptor possibly take up in a bag?

 

[leon]

The problem isn't the AC adaptor's bulk, but that there are usually no outlets available when I need one.

My reference is this Japanese article for which the author went to IBM Japan, Sony's battery-manufacturing arm and NEC for comments. You might find more details elsewhere...

Li-ion batteries are very vulnerable to overcharging/discharging. Although they often use a microchip to prevent mishaps, it's possible that their reference points will slip. When they slip there's the probability that overcharging or overdischarging will take place and that ages the battery quickly. This is also why sometimes, 1 or 2 completely recharge/discharge cycles will restore battery life(and why Apple suggests you do this with a new battery) - you're calibrating the microchip.

Sony says the batteries do last 300-500 cycles, but when exposed to heat their life will shorten considerably. During the battery's lifetime the cathode material will gradually lose its ability to hold lithium ions, heat will greatly speed up that process. Aging may also cause the battery's voltage (as detected at the contacts) to drop, and the equipment shuts down prematurely because it doesn't want to over-discharge. So although Li-ion has no memory effect, it may seem to be plagued by such effect.

My PowerBook tends to run quite hot, even my battery's warm, so that's one thing to watch out. Apple has probably made a problematic choice with the new PBs, because with no battery you lose one of 4 "feet" on the bottom.

At the time of writing (2001), IBM Japan was considering a limit for Li-ion batteries - so that the battery is never more than 80% charged. That's supposed to greatly improve the battery's longetivity.

 

[AndyH]

A must read:
http://www.ipodbatteryfaq.com/