Leaving a fully charged phone on a wireless charger can overcharge the battery

[Davidkoh]

Here's whats going on.

Does the wall wart and wireless charger stop charging the batter when its 100%: Yes.
Will the chip inside the battery allow the battery to over charge?: No.
Will the battery while hooked up to a charger discharge enough over night to initiate a new charge cycle?: Yes.
.

How long are you sleeping to let the phone first charge and then discharge enough to start charging again? At complete idle only the discharge would be at least 8 hours. I've noticed that it takes long for my phone to go from 100 to 99% to begin with. If I remove it from my charger at 7 am it usually does not go below 95% before noon, even if I stream music for 2-3 hours.

 

[lancguy]

Confirm, had my phone on the plate all night. Woke up this am and was cold to touch on the back of the phone.

 

[ryker002]

This scared me at first, cause every night and everyday before I go into work I always put my phone on the wireless charger, but come to think about it seems everyone else its right. The charging symbol goes away after the phone is full charged and I'm sure if the charger comes back on its only to add the extra charge that the phone dissipated when being on.

 

[ragingklu]

A free battery class! Sweet.

Thanks for sharing the info guys.

 

[rdjward]

I've just been searching through the Discussions forum on Nokia's web site and I found a similar thread. One user (rayhipkiss) wrote, "The battery does stop accepting charge at 100% but it will start to discharge and when it reaches something like 95% to 98% will start charging again. This is known as bump charging or over charging and can damage the lifetime of the cells."

Then another user (jraduga) gave this further explanation:

[[/I]So what I get from all this is that once the phone detects that the battery is full, charging will stop; however, once the battery drains to a certain level, it will start charging again until it hits 100% then stops. Then this process repeats again once the battery discharges to that specified level again. I think this process of "bump charging" is what is meant by the term "overcharging" in Nokia's user manual statement, "...overcharging may shorten the battery's lifetime." If a battery has a finite number of charge cycles in it's lifetime, then "bump charging" would shorten the lifetime of the battery because it uses up more charge cycles.

So when you leave a phone on the charger overnight, the phone will not charge continuously. It will stop charging when the battery is full, so no worries about the battery overheating and damaging the battery. But what could be bad about leaving the phone on the charger all night is the "bump charging" that can occur, which over time can shorten the lifetime of the battery. Of course I'm not sure to what extent this "bump charging" can reduce the battery's overall lifetime. It may only be a small amount that we'd never really notice anyway. I think this is all starting to make some sense to me.

So I guess the bottom line is that it's OK to leave the phone on the charger overnight if that's what's convenient for you. It shouldn't damage your battery in the sense that it's going to become overfull and overheat. Just be aware that it could possibly use up your battery's charge cycles faster and reduce the battery's overall lifetime. If, like me, you like to err on the side of caution, and can charge your phone while you're awake, then just follow Nokia's advice and take it off the charger when the battery is full.

This thinking is wrong. These small 1 to 2% top-offs do not have the same effect on the battery as full cycles. In fact, it is better to lightly top off cells more frequently than to do a more full discharge.

 

[rdjward]

I've been a electrical engineer for 30+ years now and I've been around a battery charger or two
The phone companies design around a 2 year life cycle for a phone and battery. And yes your are correct, what I talked about above most people will never see because they get a new phone every two years. My designs however have to last well over two years, with sometimes up to 20 years. What I talked about does wear out a battery faster over a longer time period. While a 98% to 100% charge cycle is minor compared to a 15% to 100% charge cycle, its still a cycle in the batteries eye.

Lith ion batteries are complicated beasts. You can have a room full of experts and they will all have different opinions on whats the best way to charge and discharge a battery.
]

Electrical engineer here as well, admitedly with alot less experience though. The issue here is that yes a smaller discharge cycle is still a "cycle" in one sense. But it must be remembered that when cells are rated for a certain number of cycles they mean full discharge cycles. A ten percent discharge is not just "a little different" than a 100% discharge. It isn't even just ten times easier on the cell, it's more than ten times as easy on the cell. Now not to get too in depth, but high charges have the disadvantage of speeding up the natural detoriation of the chemistry within the cell (thats why they recommend discharging cells before long term storage). But regardless, for the average person, frequent shallow charging is the way to go if you can, especially for a device being used daily. Now for something used infrequently (like a laptop you use for an hour a week off the cable), it may be more beneficial to spend more time in a lower charge state. My cell personally rarely goes below 80% in my Lumia cause I charge it all night and at work. My 2.5 yo Blackberry still holds about 80% or more of it's original battery life after this treatment.

 

[denzilla]

The whole debate over this would be mute if they would've designed the device with a removable battery. Damn you Apple and the crap trends you start!

 

[goixiz]

maybe an app should be made to not allow charging to a threshold set by the user is acheived (in this case drops below). And if it detects a charging source is present the app can overwrite and allow charging if user approves.

 

[anon(5503495)]

How long are you sleeping to let the phone first charge and then discharge enough to start charging again? At complete idle only the discharge would be at least 8 hours. I've noticed that it takes long for my phone to go from 100 to 99% to begin with. If I remove it from my charger at 7 am it usually does not go below 95% before noon, even if I stream music for 2-3 hours.

I checked last night, and in less than an hour it dropped 5 percent. After it charges full I always have to soft reset my phone to keep it from draining. I can see the percentage drop while on the wireless charger after it shuts off and then the charger will turn back on to juice it up some more. Idk why it drains so fast unless I reset it, its annoying

 

[Squatting Hen]

This. Is. Ridiculous.

We have two 920?s and both are being charged overnight on the wireless charger. To me this is the point of the wireless charger, and I shouldn?t have to setup a timer or an alarm so I can stop the charge. My phone will continue to be charged daily overnight. I have always charged every phone I have ever had overnight, and they have all lasted over two years. I had my last phone for 5 years and it still works. If these batteries do not last at least two years, then there is a problem with them. If the wireless charger causes an issue with the batteries, then it should have never been released in it's current form.

My touchpad has been on it's wireless charger for over a year now, and the battery is still as strong as it ever was. There are times where it sits on the Touchstone (wireless charger) for days before it is used for a few minutes.

 

[Alex Rodriguez Jr.]

I use my charging stand at work. Today I put it on there to charge, and after a couple of hours, I thought I noticed the light turning off and on. I stared at what was now a solid light, and saw it go off for a couple of seconds, and then turn back on for roughly 30-45 seconds, and repeat this cycle. It may be possible that the wireless charging stands don't have the ability to maintain that slight charge that wall chargers maintain to keep it at 100% without overcharging.

 

[Andyshine77]

How to Prolong Lithium-based Batteries - Battery University

 

[badari]

Well, the battery is 22 Euros on eBay. And changing the battery is a 10 min job. ( I changed my black case to a grey one, that is a bit more time consuming). I have two chargers, and I always put the phone on the qi charger. It is nice to have a phone that is always charged. And the USB-connector will keep its snug fit So, when it comes to the battery, I just say: What, me worry?

 

[VoodooKing#WP]

Nope, the thread title is not true. /ignore.

 

[William Gardner]

So, leaving the phone on the charger overnight can cause overcharging and damage to the battery. It's best to remove the phone from the wireless charging plate/stand as soon as it's done charging. If you use your Lumia 920 as an alarm clock and use the wireless charging stand, then it seems to me that it would be best to top off your battery charge before going to bed, and then unplug the charging stand from the power supply when you go to sleep so you don't risk overcharging your phone. Then in the morning, you can top off the battery again if needed.
.

Too bad a lot of people cant even keep their phones off charger overnight without the phone dying.

 

[irvin792]

Well, the battery is 22 Euros on eBay. And changing the battery is a 10 min job. ( I changed my black case to a grey one, that is a bit more time consuming). I have two chargers, and I always put the phone on the qi charger. It is nice to have a phone that is always charged. And the USB-connector will keep its snug fit So, when it comes to the battery, I just say: What, me worry?

/small hijack......grey case? Pics!!!

 

[Letros]

Once the battery hits a threshold voltage the charger stops charging, you can see the light go off on the charging plate/stand.

 

[Alex Rodriguez Jr.]

Once the battery hits a threshold voltage the charger stops charging, you can see the light go off on the charging plate/stand.

It'll turn back on though

 

[bawboh86]

It'll turn back on though

Because the battery stops charging and is pulling only a little bit of power, but not a enough to charge it. Then, when it's gone down 10%, it charges normally again. When it fully charges, it repeats this cycle.

 

[usstuscon12]

This thread is full of fail.