what happen when you keep phone connected after it's charged on a portable charger?

LlF

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I understand this may vary from 1 phone manufacturer to another, but if someone could help explain to me in general what would happen if i keep a fully charged phone connected to a portable charger, assuming there are still some juice left inside.
something similar to "trickle charging" of NiMh charger?

another question, say i'm air traveling, so it's more or less okay to keep them connected: the phone is at 20%, I charge it to full. Should I disconnect until the phone battery drops low again, or should I keep them connected as long as possible?

I guess I should use them in a way to maximize the run time... but if another way is more beneficial to the longevity of the devices, I would like to know too.
 

StarHalo

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I've never owned any one cell phone long enough to answer this, most phones are defunct long before the battery even begins to show signs of wear. I've had to replace a car phone charger, but not a battery.

In theory since the phone is a computer, it should be very smart about how it doles out charge, and you should be able to leave the phone plugged in indefinitely. But even if things go wrong, most cell batteries are ~$5.
 

idleprocess

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Unless you charge the phone's battery externally, the phone will typically manage charging. I also suspect that most removable cell phone batteries have protection circuits to prevent overcharging in external chargers.
 

LlF

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So it doesn't really matter one way or the other...? the only difference I can see is that if I keep them connected the phone battery will get few less charging cycles?
 

richardcpf

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There is absolutely no risk in leaving the phone charging... Most phone has 2 protection, one in the phone itself and another in the battery. Phone manufacturers always try to make it as safe as possible. However doing this repeatedly will reduce your battery health.

I often monitor my phone charge with a USB amp/volt meter, and it slowly drops from 1A to 0 from 75% up. Also most of the portable chargers have an auto off function if very little power is being drawn.
 

Ratton

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I have been told by the people at my phone store that most cell phone batteries are generally replaced because people leave their phones on the charger all the time! :caution: I personally don't like leaving any charger and battery plugged in all the time. :shakehead Each to their own!!!
 

mattheww50

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I have been told by the people at my phone store that most cell phone batteries are generally replaced because people leave their phones on the charger all the time! :caution: I personally don't like leaving any charger and battery plugged in all the time. :shakehead Each to their own!!!

Years ago when the phone batteries were NiCd or NiMh, that was probably true. Generally these batteries could be safely charged at about C/10 indefinitely, however over time the overcharging results in the loss of electrolyte, and the battery capacity will fall. The secondary issue is the rate at which chemical energy can be converted into electrical energy is controlled by the surface area of the electrodes. Unless the battery is periodically fully discharged, the effective area of the electrode will slowly be decreased by the aggregation of the crystals storing the chemical energy. This reduces the surface area and results in increased internal resistance of the battery. At the point the battery can no long provide sufficient power for the transmit function, the battery and phone are effectively dead.

Todays Li-ion cells will not tolerate the charging methods used for NiMh or NiCd batteries. Very bad things happens when Lithium cells are either overcharged, or overdischarged. As a result usually both the phone and the battery contain circuits to prevent either from happening. So the mechanisms that slowly killed most NiMh and NiCd batteries don't exist in today's Li-Ion powered phones and chargers.
 
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ShineOnYouCrazyDiamond

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No you are wrong about the just being NiMH or NiCd batteries. The problem has to do with the battery being constantly maintained at 100% if you keep it plugged in all the time. The phone's circuitry may make sure that the battery isn't overcharged, but it is not going to properly cycle the battery as it would if you charge it say every night.

Keeping a battery lithium constantly charging/charged at 100% is the worst possible thing you could do for it. This will kill its cycle life in very short order. It's the same thing as keeping a laptop plugged in all the time.

To prove a point in this regard I have an older IBM ThinkPad which has software where you can control how high the battery charges. I have it set to 75% max charge and leave the laptop plugged in all the time. I have a 4-5 year old battery in it which still has good cycle life to it. Before I put the setting to 75% I would totally destroy a battery pack in a year by leaving it plugged in all the time.
 

reppans

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Agree with Shine On..

Have a read through Battery Universities "How to Prolong Li-ion Batteries". After high heat, attaining and maintaining high states of charge seem to be the biggest wear factors for Li-ion cells, and then depth of discharge after that. There was an army study (cycling large sample sizes of 18650s under different charging habits) that support BU.

I use a light timer to manage charging for my tablet/smartphone with non-removable batts... cost me a few extra seconds at night.
 

Conte

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What will happen is the phone will charge the battery the it will continue to power itself off the portable until it s dead.

Unless you plan to do often an door long periods of time, I would not worry about damaging the battery.
 

Esperologist

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"Chargers for cellular phones, laptops, tablets and digital cameras bring the Li-ion battery to 4.20V/cell." From Battery University's 'BU-808: How to Prolong Lithium-based Batteries' article.
This implies that cell phones have a built in circuit to prevent overcharging of the Li-ion battery. That means it will stop charging the battery until it is depleted enough for it to decide to start charging it again.
If it is a question of heat... cell phones heat up (from my experience) when in use or being charged, so the cell phone just needs some time to cool when it heats up.
Leaving the device plugged in at all times should be fine, unless it is in use at all times. My laptop is a little too powerful for the battery it has, so I only get about 1-2 hours unplugged. If I play Civ5 (and this only happens with Civ5) then I can play with my laptop plugged in and I have about 4 hours before my battery is drained - yeah, while plugged in it drains the battery!
 

ShineOnYouCrazyDiamond

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Even taking into account that the circuitry will not overcharge the battery, it is still bad. Assume the phone charging circuitry is smart enough to stop charging and just use the power adapter to power the device you are still basically keeping the battery in storage at 100% which, in the long run, will reduce the overall life of the battery versus going through charge cycles. If this is an Android then not to big a deal as you can just buy a new battery, but if it's an iPhone then you'll be worse off cost wise if you need a new battery.

It's probably not as bad now as it was 5 years ago. I manage mobile devices where I work (about 500 of them) and people used to be asking for new laptop and Blackberry batteries all the time because they would just leave them plugged in and when they went to travel they'd find they had no battery life. We still get a lot of battery life issues for mobile devices, but not as bad as before.
 

SemiMan

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I have been told by the people at my phone store that most cell phone batteries are generally replaced because people leave their phones on the charger all the time! :caution: I personally don't like leaving any charger and battery plugged in all the time. :shakehead Each to their own!!!

Yes but people at phone stores have no clue :).

With current cell phones and people running 300 or more almost full cycles a year, it is not surprising that batteries can be useless after a year.

Lion cells used in phones do decay when fully charged and even more when warm, but with modern smart phones usage is so high that charge cycles are generally a bigger wear factor.

Semiman
 

SemiMan

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No you are wrong about the just being NiMH or NiCd batteries. The problem has to do with the battery being constantly maintained at 100% if you keep it plugged in all the time. The phone's circuitry may make sure that the battery isn't overcharged, but it is not going to properly cycle the battery as it would if you charge it say every night.

Keeping a battery lithium constantly charging/charged at 100% is the worst possible thing you could do for it. This will kill its cycle life in very short order. It's the same thing as keeping a laptop plugged in all the time.

To prove a point in this regard I have an older IBM ThinkPad which has software where you can control how high the battery charges. I have it set to 75% max charge and leave the laptop plugged in all the time. I have a 4-5 year old battery in it which still has good cycle life to it. Before I put the setting to 75% I would totally destroy a battery pack in a year by leaving it plugged in all the time.

Laptops and cell phones have different usage models.

Cell phones are rarely left on a charger 24/7/365 like many laptops except between work and home.

Laptops are also much hotter than cell phones internally.

Semiman
 

idleprocess

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With current cell phones and people running 300 or more almost full cycles a year, it is not surprising that batteries can be useless after a year.

Lion cells used in phones do decay when fully charged and even more when warm, but with modern smart phones usage is so high that charge cycles are generally a bigger wear factor.
With the average person seemingly set on getting 0%-100%-0% out of their smartphone on a daily basis (gotta get 3 stars in all levels of Angry Birds Redux 3 Turbo: The Beginning), I suspect the spread is a bigger factor in li-ion cell operating lifespan than the daily recharge to 100%.
 

StarHalo

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With the average person seemingly set on getting 0%-100%-0% out of their smartphone on a daily basis

Very true, I enjoy getting the most out of my devices; it's not uncommon for my cell to be streaming with audio out via Bluetooth while I'm reading a Kindle book, and I'll ignore the battery warnings. And don't forget being left in the center console on 100-degree days while I'm at work, and draining to zero when I leave the phone at home for a few days..

I have a feeling this thread will go the way of the "What Happens If You Drop a Laptop In The Tub" thread, just waiting for the Mythbusters to tackle it..

Edit: Should also mention, this iPad2 has 6% battery and 1 Gb available as I'm typing this.
 
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Rosoku Chikara

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This seems like an easy enough answer for one of "our experts" on this forum to check and confirm. (Not only am I not an expert, I do not have any of the necessary equipment.)

I recently purchased a tablet (for the first time), and I tend to keep it connected to a charger when at home, but of course the battery does see plenty of deep-cycling, when I take it on the road. However, currently, it can spend days constantly connected to its charger. So, if this is indeed "bad," I would certainly like to know. (It has an internal battery that is not easily replaced.)

When I look at the battery level while it is on the charger, it reads "100% Charged - Full" even though the tiny battery icon shows that it is charging (or at least, connected to a charger). So, I have assumed (up to now) that in this condition the charger is not doing anything... it is simply connected.

Would someone please take a similar device and see whether or not any current is flowing into their device when in this "100% Charged - Full" state? (I would like to think that there is no current flowing at all. But, I guess it would take an accurate meter to verify that fact.)

I would be happy to contribute the adapters that would likely be required to connect an appropriate meter between the charger and the device...

====================

PS: I just found this post on another forum:

From my own experience as an Android developer, my phone is ALWAYS plugged in when I am at my computer and it is almost always fully charged while I am using it. I have been an Android developer for about 2 years now. I program just about everyday, which means everyday my phone is plugged into my charger while I am programming. I have an old Droid 3 that I use for testing compatibility for Gingerbread (2.3.3). When I got the phone it needed to recharge every other day. Now, unless I use it constantly, it will survive for just over a day. For a 2 year old battery, that is pretty standard degeneration.

If you think about it, everyone pretty much plugs their phone in at night and it will take about an hour to two hours to charge (if the battery is completely dead). That means that the device is sitting on the charger for about 6 hours fully charged every night (if you sleep 8 hours a night). I don't think that a few hours of it on the charger while you are at work will affect your battery's lifespan enough for you to notice.

If anyone has any logical reason or statistically significant data to support the fact that this is a bad idea, then I will eat my words but from my experience I would say that your battery will not experience any significant lifespan decay from you plugging it in at work.

If you want to know more LifeHacker thinks it's a bad idea, but they give no statistical support for their tables

Over at Android Forum it seems the general consensus is that it doesn't matter.

Here at android.stackexchange it seems like the general consensus is that constant charging doesn't really hurt your battery, but you should do maintenance discharges to keep it healthy.
 
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mcnair55

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How it works for me if it helps,my works Nokia gets put on the charger each evening as i arrive home say at about 6 pm ish,it gets switched off at about 6 am the following morning so in theory it takes roughly about an hour to get back to 100% plus 11 hours left on the charger in the on position and i have been doing that for at least the last 4 years with that phone and no issues.

I do the same thing with my works palm top computer again with no issues.
 

BringerOfLight

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I recently purchased a tablet (for the first time), and I tend to keep it connected to a charger when at home, but of course the battery does see plenty of deep-cycling, when I take it on the road. However, currently, it can spend days constantly connected to its charger. So, if this is indeed "bad," I would certainly like to know. (It has an internal battery that is not easily replaced.)

When I look at the battery level while it is on the charger, it reads "100% Charged - Full" even though the tiny battery icon shows that it is charging (or at least, connected to a charger). So, I have assumed (up to now) that in this condition the charger is not doing anything... it is simply connected.
The charge controller will turn charging off when the battery is fully charged. However, as mentioned leaving it sitting around at 100% isn't great for the battery.

There may be some custom firmware/kernel for your tablet that can terminate charging earlier (e.g. at 80 or 90%). Do a search for 'battery life extender'.
 
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