Wait- I thought that was for NiCd batteries and Li-ion batteries where suppose to always be topped off? Furthermore going below 15-20% charge hurts their max charge level?
*By cycle he means running it down and charging it up?
Assuming we're talking about lithium ion chemistry, The most significant thing that will impact the longevity of the battery is heat, and keeping the battery at a high level of charge generates it. In particular, if you're always plugged in and the charging system is keeping it at 100%, this will impact the longevity in a meaningful way.
Not sure about Macbooks, but my laptop has settings to control this. I typically have it setup to only start charging when the charge drops below 40% and to stop at 85%.
Some other points:
- It's preferable not to discharge fully. Very deep discharge can damage the battery, although all modern batteries have circuits to protect against this.
- For long term storage, ~40% charge is best. That's why new phones typically come charged at around this level.
Yeah, can someone who knows how this shit works chime in? There's a lot of conjecture on the internet but few answers. Apple's advice seems to be "don't worry, be happy, don't let it be in a discharged state for a very long period of time, occasionally cycle through it".
I'm on my third battery for this 2009 Macbook unibody (granted, the first one was water damaged but still…), and 300 cycles in it's starting to give me Service Battery warnings and I must be doing something wrong.
There seems to be no exact science with Li-ion battery life. Even defining "life" is difficult, since some people say the batteries "life" ends at 80-50%.
Of all the things I've heard about Li-ion batteries, the only ones that haven't been refuted are:
- Li-ion batteries like living at around 70%. More or less will decrease their life
- Li-ion batteries will always lose 30-50% capacity in 3 years even if they're just lying on a shelf due to their chemistry
- Li-ion batteries dislike heat. More heat reduced battery life. Coldness will temporarily reduce capacity, but has no long-term effect on lifespan.
"Apple does not recommend leaving your portable plugged in all the time. An ideal use would be a commuter who uses her notebook on the train, then plugs it in at the office to charge. This keeps the battery juices flowing. If on the other hand, you use a desktop computer at work, and save a notebook for infrequent travel, Apple recommends charging and discharging its battery at least once per month.
[...]
If you don't plan on using your notebook for more than six months, Apple recommends that you store the battery with a 50% charge." [1]
I wonder if using your laptop plugged in at your desk 90% of the time, but carrying it around to use in meetings the other 10%, is as good as their "ideal use."
Well as long as there continue to be long, drawn-out, rambling meetings, we're good to go! Although in that case, a short battery life is a feature: "Oops, I'm at 5%! Be right back while I fetch my charger!"
It's straightforward to do experiments, control factors affecting experiment, collect data, process is well understood electrochemistry... only thing that might make it "not science" is that it's too well understood so you may claim it's just engineering instead :)
When I'm sitting at home with my laptop plugged in for a long time, I usually just unplug the battery from the computer and set it next to the desk. Is this an ok idea?
The battery is still used even if you leave your laptop plugged in -- it uses the extra juice when the system is under high load. I have used my 45-month-old MBP plugged in 99% of the time, and coconutBattery shows 97% capacity at 38 cycles.
Deep cycling only helps calibrate the battery charge indicator, but doing so will lower the battery's capacity simply because you're cycling it.
Li-ion batteries do have a memory effect also, but it is apparently quite negligible.
Li-ion batteries should NOT be topped up for extended periods; this will shorten their lifespan considerably.
When storing a li-ion battery for an extended period, it is best if the battery has around 30% charge.
However I am not a real expert on this kind of stuff, please don't take this as gospel, if there is a qualified battery expert who can chime in here, please do :)
Wait- I thought that was for NiCd batteries and Li-ion batteries where suppose to always be topped off? Furthermore going below 15-20% charge hurts their max charge level?
*By cycle he means running it down and charging it up?