9 Replies Latest reply: Sep 15, 2010 9:56 PM by Steve Sussman
mr88cet Level 1 Level 1 (0 points)
In another thread, I saw somebody claiming that it takes 6 hours to recharge an iPad from flat to full. I haven't actually timed it yet, but I'm pretty sure it hasn't been taking mine that long. Probably more like 3-4 hours, best I can recall.

What sorts of times have you been seeing?

Mac Pro 2.8GHz 8 Xeon, MacBook Pro 17", iPhone 4, iPad 3G, Mac OS X (10.6.4)
  • lllaass Level 10 Level 10 (155,870 points)
    Three to four hours should be the norm. Theoretically, it should take 2 1/2 hours to fully charge with the supplied 10 watt wall charger. However, the charging circuit is not 100% efficient so it takes longer than 2 1/2 hours.
  • mr88cet Level 1 Level 1 (0 points)
    Thanks for the reply.

    I ask because I'm setting up a light timer to charge it for more less a minimal amount of time per day, so that I can keep the battery cycling, rather than burning in (so to speak) on the charger.

    I think I'll set it for two hours initially, between 4AM and 6AM, since I don't often use the whole size of the battery (unlike on my iPhone!).
  • mr88cet Level 1 Level 1 (0 points)
    Ah, I just realized that I'd better slightly modify that plan.

    I originally wanted it to charge it up for the couple hours before I wake up, so that it'll be fully charged when I wake up. That as opposed to charging it the first couple ours after I go to bed, in which case it would be asleep most of the night burning a little bit of power, and thus not quite fully charged when I get up.

    However, starting charging at 4AM would mean that it would give me its "thank you for attaching me to a power source" chirp at 4AM, thereby waking me up every night!
  • synriga Level 1 Level 1 (0 points)
    Connect your iPad to the wall charger before you go to bed and forget about it till morning.
  • David M Brewer Level 6 Level 6 (9,270 points)
    The charger shuts off when the iPad is fully charged. There is no need to put a timer on it... Besides you can use it at that point to power the iPad from the wall. I've had my charger/power supply on my iPad 24/7 since the day of release. Only to take it off the charger when I take it with me. And use at home to power the iPad from the wall so it is at 100% when I take it with me. Your trying to reinvent the wheel.
  • mr88cet Level 1 Level 1 (0 points)
    Well, I wasn't so much concerned about whether or not the charger would shut off after fully charging the battery, but about using the battery in its ideal way.

    However, according to this:

    http://www.batteryuniversity.com/parttwo-34.htm

    I see now that I am in fact remembering incorrectly that lithium-based batteries' ideal usage is similar with Nickel-based batteries. Nickel-based batteries work best when you cycle them: Fully charge, then fully discharge, fully charge, etc. Apparently that is not true of lithium-based batteries. Lithium batteries work best when you discharge only as much as needed, and recharge them periodically.
  • mr88cet Level 1 Level 1 (0 points)
    More precisely, what I remembered is that Lithium batteries allow a limited number of charging cycles. That web page I cited said that to be 300-500. That then is, I have heard, why Toyota uses a NiMH battery on the Prius hybrid drive system - that battery tends to be charged and discharged frequently during normal use. Nevertheless, according to this website, regardless of that question, you're still better off discharging it only partly.
  • araym Level 1 Level 1 (5 points)
    More precisely, what I remembered is that Lithium batteries allow a limited number of charging cycles.


    That is correct, lithium batteries do indeed have a certain number of charge cycles before performance is degraded. One full discharge is the same as two half discharges, for example. So to maximize lithium battery longevity, you want to minimize the number of charge cycles. (One full discharge per month however is good for a variety of reasons but in general keep it fully charged if you can.)

    FYI Apple has some iPad battery information and recommendations online at: http://www.apple.com/batteries/ipad.html
  • Steve Sussman Level 1 Level 1 (55 points)
    The iPad charger does have vampire drain so leaving it plugged in all the time will cost some energy, and therefore will impact the electric bill and the environment. Plugging it into a timer certainly mitigates that so while plugging the charger into a timer may not affect your iPad battery life, its still not a bad idea.