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

[anon(5503495)]

Time to go pull out the timer I use to schedule turning on and off my Christmas lights.

hahahahaha I know right?!

 

[James8561]

for me, the charger LED goes off when the phone's 100% charged, indicating that current has been stopped. someone confirms this with a volt-meter please.
btw i heard that li-poly batteries have internal electronics that prevents overcharging because if these are overcharged they'd catch fire and explode. so no i really don't think there is overcharging with these phones

 

[Deleted member 199301]

I really wish for a good long term review. Or one of these companies releases their research on the subject.

 

[conanheath]

This has been discussed previously in another thread. Phone stops charging when it is full. When it is charging, phone is warm. When you wake in morning phone is cool to the touch. It stops charging and may turn on and off throughout the night and will not burn up your battery. Unless there is a malfunction which I haven't seen posted. Now as for wireless stand being a power vampire. I have no idea nor do I care. I'll pass on a cup of coffee once during month and pay for it. Your phones will be just fine. Since I started using my wireless my battery life has been great compared to what it was first couple of months pre wireless and Portico.

 

[EBynum]

Anybody want to contact Nokia Care US to ask the same question I did (see first post in this thread) to see if they get the same answer from another rep? Just curious...

 

[pogi920]

I don't know if its wired charging is affected of it coz I use to leave my 920 on overnight charging..

 

[astondg]

I've had issues with my 920 freezing on the wireless charger overnight and I was told by Nokia Care that the phone shouldn't be left on the charger for more than 2-4 hours. They didn't specifically say that it would overcharge the battery though.

I think it's ridiculous that we have to take the phone off or unplug the stand, particularly as I also charge while I'm sleeping and I won't be waking up to do either of those things. I have considered putting it on the charger early in the night and taking it off when I go to bed but then I have to leave my phone in the bedroom for a few hours while I'm somewhere else and the evening is when I use the phone most for personal calls, etc. The phone and these accessories have really been promoted as things to integrate with and enhance your life, I don't really want to have to worry about when and how I charge them.

 

[EBynum]

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:

"As Ray has mentioned bump charging can cause issues.

when Lithium based batteries were first released, it became very obvious very quickly that they had the chance (as is with many batteries) of going in to a melt down or exploding. as batteries pack in phone are made of many cells all connected, it can only take one cell to go faulty, that then starts a reaction in the pack that cause excessive heat build up, that then becomes so hot that it can cause severe burns or explode. So many years ago they started installing safer types of lithium cells called lithium ion or nowadays lithium polymer cells, they all have a small electronic circuit that controls the charge and discharge rates.

in many cases (not always) the electronic boards even count how many times the batteries are charged, once they hit a certain number they stop accepting charge, this can be as low as 250 times. However this is mainly for many of the older version of these cells.

So bump charging can shorten the life of the battery pack. As ray said it does stop charging but then if it drops enough, it will start again. So where you thought you had charged your battery once, may in effect have been charged maybe 2 or 3 times during a single night. Remember its not the amount of charge you put in, in this case but the number of charges you do.

These circuits are put in for safety reasons, and not to make you buy more of these battery packs. People have had third degree burns to their ears by the use of mobiles in the past, hence why the safety devices were put in."

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.

Here's the link to the thread if you want to read it yourself:
ridiculous... battery lifetime rule - Nokia Support Discussions

On another Nokia Discussions thread, user cjlim wrote, "Ideally you should disconnect from charger soon after charging stops, but doesn't have to be immediately because the phone stops the charging process when battery is full. Not possible to overcharge. However not good to leave it plugged in too long after because top up charging will start if the battery level falls below a certain value."

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.

 

[EBynum]

I've had issues with my 920 freezing on the wireless charger overnight and I was told by Nokia Care that the phone shouldn't be left on the charger for more than 2-4 hours. They didn't specifically say that it would overcharge the battery though.

Interesting. Did Nokia Care state that leaving the phone on the charger is what caused the freezing? I wonder if the "bump charging" I wrote about in my previous post causes the phone to freeze. I would think that it shouldn't, but I suppose it's possible. Did Nokia Care give you any further explanation?

 

[Coreldan]

Modern batteries have these chips to avoid overcharging. Li-ion batteries already had them, the battery would stop accepting any more power after it was full for safety reasons. The charger might be stupid enough to go on, but the battery shouldn't be accepting overcharge.

 

[Tafsern]

Must be wrong. My wireless charger stops charging when it's full. If it stops charging the phone, there is no possibility that it's still charging in some magical way.

I will continue to charge it overnight, couldn't really care. My work payed for the phone, they should fix it if something breaks

"Overcharging Li-ion batteries is not a problem and does not affect the battery life span. These batteries can be charged 300 to 500 times, and they have an internal circuit to stop the charging process at full charge. The control system prevents overcharging, which can cause the lithium ion battery to overheat and potentially burn. This is why the Li-ion batteries are more expensive. The only way for the Li-ion battery to overcharge is if the charging system malfunctions, and then the battery will heat up while in the charger."

 

[Evan_ISS]

Time to go pull out the timer ....

^this.

I have the wireless charging plate on a timer, used to have it for 4 hours (3am-7am) but now have it for 3 (4am-7am) as even from almost flat it is enough.

The phone is always on 100% when I Ieave home at 7am, battery life is amazing.

 

[Al_2]

I put my phone on the wireless charger around 11pm and don't take it off till my alarm goes off at 7am.

My phone gets noticeably warm when it's on the wireless charger but when I take it off at 7am it's stone cold and indicates 100%, which would seem to say it's not been charging for a while...

 

[Reflexx]

I wonder how many charges the battery in the 920 can accept.

There's over 600 days between contracts. I sometimes charge several times a day.

If it is only 300, I'd hit that in fewer than 75 days. (if you count when I pick up the phone off the charger, then out it back on).

I expect that we don't know the technical details yet. I hope the phone runs well for 2 yrs. Then I'll just pay for someone to install a new battery and hive it to my dad.

 

[typhon62_1]

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.

So the problem is the battery will go through several charge cycles while being hooked up to a charger all night. This doesn't harm the battery per say, but does eat into the battery's life. These batteries can only handle a finite number of charge cycles before going bad. Buy a timer, set it for 3.5 to 4 hours and you'll not have any problems.

It drives me nuts when people design stuff that wants to be "on" while charging. This is whats causing the problem. My Moto Android phone could be charged in a powered off state and I never had to worry about this. They're saving a few pennies per phone not having a dedicated charging circuit in the phone. A lot of phones these days seem to use the phones main processor to manage the charging these days...

 

[ImmortalWarrior]

A charge cycle is a full discharge. The minor cycles you speak of are insignificant. I've mentioned it before, when I interned at RIM I got to see several presentations from the battery team on the issue. Lith ion batteries will last longer if you charge them more often and do not let the battery discharge more than just a minor amount.

A full discharge is worse than 100 partial discharges. I've seen the charts and the studies on the issue. You are all being paranoid. Charge your phone every night regardless of how much power is left and 9 times out of 10 you will have very few problems.

I can attest to this because I've never had to replace a phone battery for that very reason.

 

[thecaringkind]

I must agree with the last post. All of this sounds like pure conjecture. The battery was designed to last at least 2 years no matter how many charging cycles it goes through. Some perform better or worse than others all based on daily use/habits. Many of us end up getting a new phone every two years or less anyway so I don't see where any discernable decrease in battery performance would end up being an issue anyway.

 

[jimski]

Been leaving my phones on charge overnight all my life and never had a battery die. Sure, they may start to lose a (small) percentage of their capacity after a year or so, but they all still worked fine after 18-24 months, and longer.

And yes, both my 900 and Surround bump charge, cycling between 96 and 100%. Often, the Surround will only be at 98-99% after a full overnight charge. I also top off my battery regularly with USB portable chargers. So my phone will typically connect to a charger and reach 100% at least once, probably 800-900 times a year. And they work fine.

If this were true, OEMs would build a circuit into their chargers that would turn off automatically after the "maximum" required period to charge a dead phone. 4 hours for example. You would need to disconnect/reconnect to reset. Not sure how that would work with the USB port on your PC though.
Sent from my Lumia 900 using Board Express Pro

 

[typhon62_1]

A charge cycle is a full discharge. The minor cycles you speak of are insignificant. I've mentioned it before, when I interned at RIM I got to see several presentations from the battery team on the issue. Lith ion batteries will last longer if you charge them more often and do not let the battery discharge more than just a minor amount.

A full discharge is worse than 100 partial discharges. I've seen the charts and the studies on the issue. You are all being paranoid. Charge your phone every night regardless of how much power is left and 9 times out of 10 you will have very few problems.

I can attest to this because I've never had to replace a phone battery for that very reason.

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.

I should have said at the end of my post is that leaving a phone charge over night is not going to do any harm to the battery/phone over the normal lifetime of a phone/battery. I thought my three items at the top of my post said this, but after actually reading my post I can see it didn't I also should have said: "If your worried about this, buy a timer, set it for 3.5 to 4 hours and you'll not have any problems".

Better things in this world to worry about, like how my 920 turns into a toaster oven every now and then...

 

[Brutos UK]

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.

So the problem is the battery will go through several charge cycles while being hooked up to a charger all night. This doesn't harm the battery per say, but does eat into the battery's life. These batteries can only handle a finite number of charge cycles before going bad. Buy a timer, set it for 3.5 to 4 hours and you'll not have any problems.

It drives me nuts when people design stuff that wants to be "on" while charging. This is whats causing the problem. My Moto Android phone could be charged in a powered off state and I never had to worry about this. They're saving a few pennies per phone not having a dedicated charging circuit in the phone. A lot of phones these days seem to use the phones main processor to manage the charging these days...

Having the phone switched on or off is irrelevant, the charge/discharge still counts as part of a cycle. But as you and others have said the batteries are protected and the wireless charger turns it's self off. So it's not a problem.

Mobile batteries will easily last a few years without any noticeable drop in performance, people should stop worrying.