1. ccbeachmama45's Avatar
    Since I got the lollipop update on my Nexus 7, I've noticed that it's taking A LOT longer to charge. I mean HRS!! If it gets to 20% or lower. Even when I switch it to Airplane mode or turn it off completely, it will still take a good 2-3 hrs to get back to 100%. I just got the Nexus 6 a few weeks ago & I'm considering trying the charger that came with it on my tablet to see if it makes a difference. My husband, however, says that it would destroy my tablet if I used my phone charger on it. Has anyone else been having issues with their Nexus 7 charging since the update? Do you think that the Nexus 6 charger would really destroy my tablet? Thank you in advance for any input 😊.
    02-17-2015 03:52 PM
  2. Rukbat's Avatar
    1) Never let the battery get below 40%. That's not Google, that's lithium batteries. You're cutting the battery life in half by discharging to 20%. With a tablet, a dead battery means a trip to the shop, labor costs and a more expensive battery than a phone you can just pop the battery out of. (They charge more because it has a few cents of parts added - and because they can.)

    2) The recommended charging time for a lithium battery is 0.75C, or 3/4 the capacity of the battery. Adding in inefficiencies (no energy conversion process is 100% efficient), the fastest you can put a full charge into a lithium battery without endangering it is 1 hour. Taking 2 hours extends the life a bit. (With proper care, a lithium battery can last 10 years. With improper care, you can completely kill it in 6 months.)

    3) One of 2 things will happen if you use the phone charger on the tablet:
    a) If the phone charger can't supply as much current as the tablet wants to draw, it'll take even longer to charge.
    b) If the charger can supply at least as much current as the tablet wants to draw (it can supply 10,000 Amps, it won't make any difference - I charge my phones from a 30 Amp supply), the tablet will charge in the same amount of time it does now - assuming that the charger you're using supplies at least as much current as the tablet wants to draw.
    (Where did your husband get his electrical engineering degree? Dental school? They didn't teach what he's claiming when I got mine. Maybe they invented a new kind of electricity since then.)

    4) If the tablet is running when you're charging it, some of the "charging" current is actually going to run the tablet, so there's less for the battery, so it takes longer to charge. The more the tablet uses, the longer it takes to charge.

    The tablet is designed to draw a fixed amount of current to charge the battery, you can't change that. And if you're charging the tablet when it's turned off, it doesn't matter what version of Android is in it - it's not running, so it won't affect the charging time. (If you haven't cleared the system cache - that's in Settings, in Storage - press Cache and it'll ask if you want to clear it - do it now. An update clears cache bit by bit and that chews up a lot of power. Doing it all at once is more efficient,)
    02-17-2015 04:08 PM
  3. brosko's Avatar
    1) Never let the battery get below 40%. That's not Google, that's lithium batteries. You're cutting the battery life in half by discharging to 20%. With a tablet, a dead battery means a trip to the shop, labor costs and a more expensive battery than a phone you can just pop the battery out of. (They charge more because it has a few cents of parts added - and because they can.)

    2) The recommended charging time for a lithium battery is 0.75C, or 3/4 the capacity of the battery. Adding in inefficiencies (no energy conversion process is 100% efficient), the fastest you can put a full charge into a lithium battery without endangering it is 1 hour. Taking 2 hours extends the life a bit. (With proper care, a lithium battery can last 10 years. With improper care, you can completely kill it in 6 months.)

    3) One of 2 things will happen if you use the phone charger on the tablet:
    a) If the phone charger can't supply as much current as the tablet wants to draw, it'll take even longer to charge.
    b) If the charger can supply at least as much current as the tablet wants to draw (it can supply 10,000 Amps, it won't make any difference - I charge my phones from a 30 Amp supply), the tablet will charge in the same amount of time it does now - assuming that the charger you're using supplies at least as much current as the tablet wants to draw.
    (Where did your husband get his electrical engineering degree? Dental school? They didn't teach what he's claiming when I got mine. Maybe they invented a new kind of electricity since then.)

    4) If the tablet is running when you're charging it, some of the "charging" current is actually going to run the tablet, so there's less for the battery, so it takes longer to charge. The more the tablet uses, the longer it takes to charge.

    The tablet is designed to draw a fixed amount of current to charge the battery, you can't change that. And if you're charging the tablet when it's turned off, it doesn't matter what version of Android is in it - it's not running, so it won't affect the charging time. (If you haven't cleared the system cache - that's in Settings, in Storage - press Cache and it'll ask if you want to clear it - do it now. An update clears cache bit by bit and that chews up a lot of power. Doing it all at once is more efficient,)
    Man you sure are our resident lithium ion battery expert! Keep up the good work and thanks for the info.
    02-17-2015 05:42 PM
  4. physioprof's Avatar
    Unfortunately, the information in #1 is false. A little Googling will reveal that modern lithium batteries can't be damaged by discharging them. The internal control systems turn off the power before the charge gets low enough to damage the battery. It is completely false that discharging below 20% will cut the battery life in half.
    UncleMike likes this.
    02-18-2015 04:50 PM
  5. brosko's Avatar
    Unfortunately, the information in #1 is false. A little Googling will reveal that modern lithium batteries can't be damaged by discharging them. The internal control systems turn off the power before the charge gets low enough to damage the battery. It is completely false that discharging below 20% will cut the battery life in half.
    Who are you go question are resident battery expert?
    02-18-2015 05:42 PM
  6. parchping's Avatar
    Get a higher power charger, such as these:
    Wall Chargers,Plug-in Chargers,Power|ANKER

    My Nexus 7 charges noticeably faster with the Anker 18W charger than on the one that came with the Nexus. No numbers, sorry.

    Steve
    03-20-2015 07:51 PM
  7. ohmslaw's Avatar
    Get a higher power charger, such as these:
    Wall Chargers,Plug-in Chargers,Power|ANKER

    My Nexus 7 charges noticeably faster with the Anker 18W charger than on the one that came with the Nexus. No numbers, sorry.



    Steve
    So I guess my question is can the supplied charger provide enough current to get the quickest charge. I never saw a number on the max Nexus 7 charge current. Also is the supplied cable large enough to pass the max current to the Nexus. If the cable is undersized charging may get longer.
    You know this question comes up a lot.
    03-21-2015 06:43 PM
  8. jerrykur's Avatar
    I have noticed anything, but I don't use a USB charger unless I absolutely have to. Rather I use wireless charging and just leave the Nexus 7 on the charging pad 24/7. That helps to ensure that when I pick up the device it is at 100%. FWIW, I use Nokia DT-910 most of the time. It charges the Nexus 7 right through the Poetic case.
    03-22-2015 10:38 AM

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