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(Kobo Forma) Battery 99%
#1  Odyssee 07-05-2019, 05:54 AM
Charging my Forma, it reaches 99% and then it takes a very long time to reach 100%. I read somewhere that this is a sort of safety valve against overcharging. Should I leave it at 99% or go on until 100%. I mean from a perspective of battery health.
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#2  Lusephur 07-05-2019, 08:54 AM
Leave it at 99% what difference to your usage will 1% make?
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#3  Odyssee 07-05-2019, 10:01 AM
you may be right but that doesn't answer the question.
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#4  davidfor 07-05-2019, 10:11 AM
Quote Odyssee
Charging my Forma, it reaches 99% and then it takes a very long time to reach 100%. I read somewhere that this is a sort of safety valve against overcharging. Should I leave it at 99% or go on until 100%. I mean from a perspective of battery health.
I'd be curious to see where you read that. I can always do with a good laugh.

Don't worry about it. Li-Ion batteries are not going to be damaged in either way. They will also not be damaged by only charging to 80% and not completely discharging them.
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#5  lachlan091 07-05-2019, 10:34 AM
Charging it to 100% is recommended, there's no such technical issue if it takes few more minutes to charge rest the 1% let it be, needs to fill juice up.
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#6  davidfor 07-05-2019, 10:43 AM
Quote lachlan091
Charging it to 100% is recommended, there's no such technical issue if it takes few more minutes to charge rest the 1% let it be, needs to fill juice up.
And there is no technical reason for always charging a Li-Ion battery to 100%. It won't harm anything not to.
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#7  Odyssee 07-12-2019, 02:21 AM
Thank you guys. You have put my mind to rest. :-)
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#8  JohhnyMix 07-13-2019, 12:25 PM
Well, the best way to charge it so up to 80 or 90% so that the trickle charge wont kick in and also never let it go down to 0%
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#9  FrustratedReader 07-13-2019, 02:54 PM
There is no "trickle" charge on Lithium. Even on NiMH it's better to cycle. Only Lead Acid and NiCd would typically have a trickle charge.
The charging system will stop / start cycle according to cell condition. As it ages, it's lying if it really means 100%, what it means is "charged as much as is safe".
Long term storage if the cell is disconnected or there is a real "off" is best cool, never freezing and between 50% and 90%, often 2/3rds (67%) is chosen.
The Kobo does seem to have a nearly real off. The Kindles don't, so they can't be put in a drawer and forgotten, they maybe ought to be plugged in every 2 to 4 weeks, I'm not sure.
All models will behave strangely if the battery is too flat to operate but not actually dead. Unlike NiCd and Lead Acid, force charging (directly, any decent internal charger won't) totally dead Lithium cells is a fire risk.

So it's safe to leave fully charged gear that's properly designed, plugged in. Except a lot of the chargers are fire risks and generate RFI, even official ones.

There is no memory effect either, that's not even a thing on Lead Acid or NiMH, only on the NiCd.

Don't leave fast charging devices unattended or on a soft surface if they are the kind that ever warms while charging, i.e. some phones, tablets and power tools.
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#10  TechniSol 07-19-2019, 01:49 PM
Some older laptops with Lithium Ion batteries adopted the charge to "100%" and don't charge again unless below a certain trip point, usually 90 or 95%... My 2008 or so vintage Lenovo X200T displays this behavior because of Lenovo's additional software despite having been updated to Windows 10. Never saw any harm in it as Lenovo may have simply been hedging their bets or noted a possibility that they'd set too high a limit in the hardware cutoff of their design, or just found that rapid cycling due to the laptop being plugged in was causing heating and lessening battery cycle life, etc...

It's quite likely that most competent engineers will leave a little headroom if they're defining the cutoff points in software or hardware rather relying on a third party hardware solution, and even most of them seem to stop just a bit short of the battery manufacturer's specs which are likely a tad conservative as well. Safe, rational engineering at multiple levels often saves even the reckless engineer's ass when they "get a little nuts"!

Any well designed piece of equipment will allow charging to near the battery's high end, but not exceed it for danger of explosion, meltdown, etc. Most modern lithium packs have built-in low & high end cutoff circuits, I've even added them to individual Lithium Ion 18650 cells used in my LED flashlights for discharge protection, but there may be a few products still floating around without them.

PS. It can be a little disconcerting with these protection circuits/cutoffs built into flashlight batteries, as they can suddenly shut off to prevent too high a current or too low a voltage. But I mostly keep them well charged, and employ a spare or spares as may be needed. The nice part is they also prevent short circuit and you can reasonably safely toss a protected battery in your pocket without worrying about change, etc. shorting it and causing a thermal meltdown. They also allow me to easily carry a spare protected 14500 battery which fits my pocket everyday carry LED flashlight with adjustable power levels, dazzler function and beam width/focus. Yeah, I know, but it throws a focused beam my phone can't, fits in my mouth when I need both hands, and I often don't carry my Kobo Glo around outside at night! ;-)
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