we are all on the same track, what about a bluetooth headpiece, anyone here prefer one over another for iphone 4?
IT's ok to charge it whenever you feel like it but you should also get in a habit on doing a full cycle once a month (charge to 100% then run down to 1%).
Not arguing, but does that remain true? I suspect that the speed these things become obsolete makes any attempt at battery conditioning moot? I do remember Apple recommending a once-per-month complete discharge and then to let it "rest" for a few hours before recharging, but I'm not sure that's still the case with these Li-Ion batteries? OTOH, I guess it can't do any harm. Cheers, Ian
I try to always let it go down as much as possible when re-charging, and with that I do the 100%-1% (or off) probably once a week, but generally I charge as needed. I had a 3G for a good 3+ years and didn't see any difference in battery life. Currently using 3Gs.
It's interesting that you can find next to nothing about possible damage to LiIon cells from "wrong" charging cycles. One of my students tried to find out about it (for car-use batteries), but found nothing. Three possibilities: Big secret (unlikely), student was lazy (not unlikely), no damage (likely). IIRC the cycle life of a LiIon cell is not determined by the number of cycles (ie charge->discharge->charge, no matter how much you (dis)charge every time), but by the total amount of energy you put through it (ie, discharging and charging 50% for 100 times has the same effect as (dis)charging 100% 50 times.) What damages LiIon cells quite badly however is over-voltage. If the "natural" voltage of the cell is, let's say, 4.0V and you apply 4.2V, it will suffer. Other (older) battery technologies could withstand higher voltages as there were chemical side reactions which took the energy and released it afterwards. This is however not the problem of the user, the charging device will take care of issues like that.
A quick google search brought up the following: http://batteryuniversity.com/learn/article/how_to_prolong_lithium_based_batteries However, they also give the following measured data - the number of cycles at a certain depth of discharge until the battery capacity reached its end of life limit (arbitrarily set at 70% here, I've seen 80% as the limit, too). I added the third column with the total amount of energy put through (which is the value you want to maximize). 100% DoD - 500 cycles-> Total energy = 500 times max. battery capacity C_max 50% DoD - 1500 cycles -> 750 * C_max 25% DoD - 2500 cycles -> 625 * C_max 10% DoD - 4700 cylces -> 470 * C_max So in their measurements, a maximum total energy turnover is achieved with a 50% discharge before charging again, which contradicts their own advice to use small depths of discharge. Another factor that comes into play is the initial state of charge. Charging to and discharging from 100% might lead to another cycle life than starting from 75%. Oh, and if anyone likes to dive into more details: http://www.google.de/url?sa=t&source=web&cd=3&ved=0CC4QFjAC&url=http%3A%2F%2Fwww.che.sc.edu%2Ffaculty%2Fpopov%2Fdrbnp%2FWebSite%2FPublications_PDFs%2FWeb26.pdf&rct=j&q=liio%20cycle%20life&ei=oxYzTtPnM5O38gOo8ZmhDg&usg=AFQjCNErf3hFR_xbb97PWANFESgt9sPU6w&cad=rja
Still on the Apple website http://www.apple.com/batteries/ipad.html http://www.apple.com/batteries/iphone.html
Indeed. Florians research above suggests that may not be optimal however...... A conundrum indeed Cheers, Ian
Apple does not say it's optimal for the battery life: Their state of charge calculation needs to be "calibrated" every now and then by letting it know the lower and upper boundaries.
My bad! I didn't bother checking the links....... Thanks! So, to answer Agup's request for translation, it seems that optimum life is achieved if re-charged when at ~50%. [And knowing 50% reliably needs the complete discharge/rest/recharge cycle of course.....] Cheers, Ian
50% with that specific cell! Then, they did not do a 60% cycle or a 75% cycle, and we don't know the initial charge (although we can suppose it was 100%). I suppose the best solution is to just look that you don't fully discharge it too often, but don't plug it in whenever possible either. Which most likely is what you do anyway.
Well, Apple said that with the newer version of lithium ion batteries, they would post no memory effect problems. Though from an engineer's point of view, maximizing the cycle ice of a battery would require you to charge it on the proper levels. I try to bring mine down to 10 to 15 percent before I hook it up to the computer or the wall outlet. It is good to know that the battery's performance would not deteriorate but better be sure.
It is actually in theory better for the phone to be charged through a computer as opposed to be charged on the wall all the time. It is designed from the ground up to be charged as a usb device.
