1. electricpete's Avatar
    By examining logs of the battery monitor widget, I see that the 'stock' battery charger seems prone to continued shallow discharge/charge cycles after reaching 100% if you leave phone on the charger for long periods such as charging overnight.

    In am pretty sure this is bad for the battery.

    One strategy would be to monitor the charging and remove phone from charger once it's at 100%. But that's not always practical.

    Maybe turning the phone off when I put it on charger for the night would help?...I'm not sure.

    Is there a better charger that won't abuse my battery if I leave it on charger overnight?
    01-15-2012 10:48 PM
  2. electricpete's Avatar
    Ok. It doesn't do it every night, but it did it last night.on screen the top graph is voltage and bottom graph is current. Positive current is charging current. The distance from left to right is a little more than 8 hours. 1st hour-phone is not in use, everything constant. Next 1.5 hours phone in use, voltage decreasing, current negative. then put phone on charger in airplane mode with screen off. Next 1.5 hours it charges, voltage increases while showing positive constant current.next 1 hour the charging ramps down., charging current decreases. Then charging stops itself. Next hour no activity, current stays 0 and voltage roughly constant.then it starts charging again by itself with a small decreasing positive current for about an hour!!!!. Then turns off the charging and zero current for an hour. Then current jumps up positive for very brief period with shallow charge starting again just before I wake up, take it off the charger and turn on display...current turns negative right at the end.

    You can't see that 2nd shallow charge very well because it's so short, but you can clearly see the first shallow charge in the middle......after it had stopped charging,for an hour it woke up and charged lightly for an hour.I want it to stay off once it stops charging.

    01-17-2012 06:15 AM
  3. electricpete's Avatar
    Here is a better example.

    Voltage on top, current on bottom.

    It charges, then stops charging. So far, so good

    Then it does three more shallow charge cycles. Not good.
    01-19-2012 05:55 AM
  4. electricpete's Avatar
    Here is a link with some more info ("Battery University"):

    Charging Lithium-Ion Batteries

    The behavior I described in this thread is shown on the right side of figure 1 of the link above, described as "topping charge". It assures the batery is at highest-possible state of charge when you remove it from the charger, at the expense (imo) of long-term battery life. It is a tradeoff, consumer electronics favor max short-term battery life over long-term battery life. As battery ages (long-term degradation), the amount of charge the battery can hold decreases and we'll need to recharge more frequently.

    One thing that may help somewhat is to turn the phone completely off if your are going to charge it overnight. That's probably a reasonable approach. However I'm not convinced that will eliminate topping charge (voltage can drop as the battery comes to equilibrium after charging, even when no current is drawn from the battery).

    If one really wanted to maximize long-term battery life, we shouldn't even charge to 100% and certainly shouldn't leave it on the charger at 100%. But spending extra energy to manually manage your battery during daily charging is probably not worth the time.... considering battery has a pretty good chance to last 2 years at which time it'll be time for a new phone anyway.

    Also, I have noticed that using your phone while charging causes the battery temperauter to go way up, which also ages the battery. If we elect to charge during our personal awake hours to avoid charing overnight... it could defeat the purpose if we use the phone heavily while charging... might as well stick with the easy approach and charge overnight.

    In an ideal world, the phone or charger would allow us to program the charging ourselves so we could leave it on overnight and program to terminate charing at some voltage <100% (like 95%) and/or disable topping. That way we could impose our own preferences for the tradeoff of short-term daily life vs long-term aging. Such capability does not exist to my knowledge (if anyone knows of it, let me know).
    01-22-2012 04:25 PM
  5. dickle's Avatar
    Here is my 2 cents. My PRIMARY use for the SII is for phone communication. I can usually receive 2-3 days of standby with a minimal (~60 min) of talk time. When the battery nears 25-20 %, it is time for an overnight charge. Even though the charge time is <3 hours, I turn OFF the phone at bed/charge time to let the electrons rest and to make available full charger power for the battery charge cycle. The battery full notification jingle usually gets me up to let out that last beer and to then turn on the phone and let a new boot-up begin the day. I go back to zzzzzzzzzz's and let the phone have another couple of hours to top off the charge. I figure it is better to boot while on the charger and let the battery do it's thing while running around un-plugged....

    Just installed the Traffic Monitor and will keep a lookout for any rogue battery burner apps.

    Got carried away with the topic. Should really be posted in the SII thread. Still had good results with my infuse using the same procedure...
    btswein and electricpete like this.
    01-23-2012 07:07 PM