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Does it hurt battery to leave plugged in?


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Showing 1-25 of 31 posts in this discussion
Initial post: Oct 12, 2011 2:18:00 AM PDT
Buttercup says:
This question is directed mostly toward the Kindle Fire, but I think applies to most of the rechargeable devices we use. The Fire's battery life is eight hours, approximately, best case scenario.

If I'm sitting on my couch reading, playing a game or whatever, does it hurt to leave it plugged in while I do so? Because if the battery runs down and then I decide to leave the house, it won't be fully charged, where if I leave it plugged in while I sit there, and then leave and take it with me, it goes with a full charge.

I remember years ago hearing that you needed to let your devices run down or nearly run down before recharging batteries. I'm really unclear about the procedure for keeping the newer batteries charged.

If one of our resident techies could clear up the proper ways to protect my rechargeable batteries, while being able to start with a full for use when away from a power supply, I would appreciate it.

Thank you!

In reply to an earlier post on Oct 12, 2011 2:40:56 AM PDT
Can't see why not leaving it continually plugged in will do it any harm. My Netbook is plugged in 24/7 and never had a problem. My Android tablet has at times been left on charge for a couple of days.

I think there would be some sort of auto cut off to protect the battery.

Posted on Oct 12, 2011 6:51:24 AM PDT
Not sure but users manual hopefully will provide guidance. Plugged in while using it should not affect battery. I do know that my laptop manual suggests that you do not leave the device plugged in continuously when the battery is fully charged. It usually depends on the type of battery installed in the device. Different battery types have different characteristics.

Posted on Oct 12, 2011 6:56:13 AM PDT
K. Rowley says:
I use to bring my PSP to work and use it as an MP3 player and to listen to movies on - and kept it plugged in all the time. Never has any issue with doing that in the 2~3 years I was using it like that.

In reply to an earlier post on Oct 12, 2011 7:12:35 AM PDT
Bufo Calvin says:
Buttercup, the only really bad thing you can do with the kind of battery in the current Kindles is let them run down completely, from what I understand.

However, overcharging a Lithium-Ion battery also may be a risk. I'm not sure how smart the Kindle is about cutting off the charge once it hits 100%. A quick search tells me that people think it is a concern to leave it charging, but I'm not sure how accurate that is.

You may find this interesting:

http://batteryuniversity.com/learn/article/charging_lithium_ion_batteries

Posted on Oct 12, 2011 7:14:48 AM PDT
Lithium-ion batteries will not last as long (total lifespan) if they are kept fully charged all the time. The optimal situation is for a battery to be at 40%. For instance if you're not going to use it for a while, don't store devices fully charged.

However, if this would negatively affect your enjoyment of the device, I wouldn't worry about it. Worst case, you'll have to have the battery replaced, say, after 2 years instead of 3 (this is just an analogy - I'm not saying it would be exactly 2 or 3 years)

Posted on Oct 12, 2011 8:57:38 AM PDT
Bufo Calvin says:
Thanks, Eltanin!

Yep, I normally charge mine in the "middle half"...not in the first quarter, not in the last. However, you can't help charging if you plug it in via USB to transfer files...for everything except the Kindle 1.

Posted on May 27, 2013 5:25:17 AM PDT
I leave my Kindle fire plugged all the time using the clock app. Would that help to not overcharge it?

In reply to an earlier post on May 27, 2013 5:32:21 AM PDT
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In reply to an earlier post on May 27, 2013 5:34:47 AM PDT
Dragi Raos says:
I had impression that limiting factor in LiPoly batteries is number of charge/discharge cycles. Then again, I don't know what power management circuitry does when the battery is fully charged and device is plugged in: it could conceivably disconnect the battery, or let the device be powered from it with occasional "topping off". I remember 40% as being quoted as optimal charge level for long term storage of batteries.

Anyway, there is another factor to consider: Micro-USB sockets are quite fragile (those on first generation of Fires were quite notorious for that). Using the device while plugged in increases chances of damaging the socket.

In reply to an earlier post on May 27, 2013 6:41:54 PM PDT
Thanks, for your reply. I downloaded a clock app to my Kindle Fire. It is so digital and so nice. I have just left my KF plugges in so I could use the clock. I imagine I should just buy a clock like sane people would do - LOL - but it is so pretty! I do have a habit of leaving my device plugged in all the time and have noticed that my battery doesn't last very long when I do unplug it and read. Surfing the net and reading email, I realize takes a lot of battery power, but I do believe my battery doesn't stay charged as long as it should - I may be totally off base here.

In reply to an earlier post on May 27, 2013 6:51:14 PM PDT
Last edited by the author on May 27, 2013 6:52:44 PM PDT
Any device can overcharge. There is circuitry to help prevent overcharging, but it has been known to malfunction. Making the statement that kindles cannot overcharge is patently false. That said, it is very unlikely to overcharge under normal conditions. A poor quality or malfunctioning charger (think generic chinese charger) is much more likely to cause problems.

Lithium batteries have a reduced lifespan if they are kept fully charged or if they are fully discharged. The optimum range is 15% to 90% to maximize battery life span. See http://batteryuniversity.com/learn/article/how_to_prolong_lithium_based_batteries for more information.

You will probably not notice the difference in normal use, though.

In reply to an earlier post on May 27, 2013 7:27:49 PM PDT
>>Any device can overcharge. There is circuitry to help prevent overcharging, but it has been known to malfunction. Making the statement that kindles cannot overcharge is patently false. That said, it is very unlikely to overcharge under normal conditions. A poor quality or malfunctioning charger (think generic chinese charger) is much more likely to cause problems.<<

My mobile phone charger (which fits the kindle) has a discharge/recharge cycling feature once the phone is fully charged, so that it's not being over-charged. The generic charger I have does not. It makes sense that the charger which does not have that safety feature will be more likely to overload the battery.

In reply to an earlier post on May 27, 2013 8:15:55 PM PDT
Last edited by the author on May 27, 2013 8:18:31 PM PDT
Many smart chargers will charge the battery, then allow it to discharge to 90% and maintain it at that level. That provides the maximum balance between battery life span (charge/discharge cycles) and usability length. In addition, the device itself will have some regulation circuitry built in to prevent overcharging. For the most part, these work, but they can fail like any other device. One big contributing factor is cheap chargers (especially for devices like laptops) that do not have proper voltage/current/noise regulatory circuits.

This link related specifically to an iphone charger (5v, 500 mAmp) which is the same input and output that a kindle wall charger would have (and the same as any generic USB charger).

http://www.righto.com/2012/03/inside-cheap-phone-charger-and-why-you.html
http://www.righto.com/2012/10/a-dozen-usb-chargers-in-lab-apple-is.html

I highly recommend the article and comments, as they do a good job explaining why it is a bad idea to go cheapo generic on power supplies. I will also say never buy any generic chinese power supply from ebay or from the amazon marketplace. It is not worth damaging your device to save a few bucks.

Posted on May 28, 2013 5:25:49 AM PDT
Soulrider says:
The problem as I see it is we don't know specifically what the charging characteristics are for the Kindle or different models of Kindle. Some devices like my laptop have a feature where it doesn't start charging the Lithium-Ion battery until it gets down to 95%. The reason for this is because, being a laptop, most people keep it plugged in when they can. This might be most of the time for some people but it varies. The idea is that if it were to charge whenever it was plugged in it might constantly be charging because it's using a little bit (even while plugged in) charging a bit, using a bit, etc. This constant charging and discharging a % or two at a time is not good for the battery. Therefore they designed the circuitry in my laptop to wait until it gets down to 95% which should mean that it's been off the charger and is below 95% and needs charging. It just keeps it from charging every few % while plugged in. Some devices have circuitry in them where if the device is plugged in it just won't use the battery at all. It will only default to using the battery IF not plugged in. If that were the case with the Kindle then it wouldn't matter if you left it plugged in all the time. We just don't know (at least I don't) what type of circuitry they have used in the Kindle. As far as leaving it on the charger and over charging it I don't think that's much of a concern because there should be protection circuitry as others have mentioned that shut off the charging after so many volts are reached (usually 4.2 volts for Lithium-Ion although I've never seen mine reach 4.2 volts as indicated by the Battery HD app). MY suggestion and what I go by is to NOT leave it plugged in all the time as I don't want to take the risk that it's using from the battery a few % and then charging a few % and so on as long as it's plugged in. Lithium-Ion batteries do have a life of just so many "cycles" of charging/discharging before they wear out. Any device that uses this type of battery will notice after a period of time (maybe years) that it just doesn't hold a charge as long and eventually may not hold a charge at all. I personally use my Kindle down to 15-20% and then charge. That is unless I know I'm going to be going out or on a trip and I want it fully charged then I'll charge it sooner. That isn't a hard and fast rule for me either. Sometimes if it's only down to 40-50% in the evening I'll plug it in to charge over night so it's fully charged in the morning. I just won't let it run down all the way as has been stated because that isn't good for Lithium-Ion batteries. Beyond that they don't have a problem being charged at ANY point (even a top off) as long as you keep in mind there is a certain number of times (ultimately) that you can charge and recharge. As someone pointed out 40% is the best state of charge for Lithium-Ion batteries. This applies if you are going to not be using a battery or device or an extended period of time then it is advisable to charge it to 40% (or thereabouts). Regardless of what % of charge you leave it in, a Lithium-ion battery like most batteries will simply lose a certain % of their charge over time until they are dead. Granted with Lithium-Ion that loss is fairly slow and they have a long shelf life if not used (many years).

In reply to an earlier post on May 28, 2013 6:25:51 AM PDT
J. Gatie says:
Cripes dude, throw in a paragraph or two.

Posted on May 28, 2013 6:52:49 AM PDT
Last edited by the author on May 28, 2013 6:53:37 AM PDT
All Kindles use Li Ion Polymer batteries. They don't have a memory effect and there's little or no danger of overcharging them. It's best to top them off regularly and there's no problem charging them overnight. This article explains how to charge and maintain them properly: http://lifehacker.com/5875162/how-often-should-i-charge-my-gadgets-battery-to-prolong-its-lifespan

The most important advice is at the end of the article: "Keep these things in mind and your battery will last longer. That said, remember that you don't need to be super strict about these things. Don't sacrifice practicality just to keep your battery alive-if you're in a situation where you don't have a charger, it's okay to discharge it to 0%, or charge it up to 100% if you want to do so for a long plane ride. Remember that your battery is going to die in a few years, no matter what you do-even if you just let it sit on a shelf. So don't go overboard: use your battery as you need it. "

In reply to an earlier post on May 28, 2013 7:45:37 AM PDT
James R. Scarborough says: "The most important advice is at the end of the article:"

Part of that is bad advice. Never let a Lithium battery reach 0%. That is allowing the battery to drop dangerously close to the cut off level where the battery will permanently shut down to protect itself. It gets worse if something goes wrong with that protection circuitry and it's allowed to drop even further. If that happens it could potentially cause a short circuit.

http://batteryuniversity.com/learn/article/charging_lithium_ion_batteries

Basically, 100% is OK as that only lowers the total life of the battery. 0% is very bad as that can potentially kill the battery, or even cause a short.

In reply to an earlier post on May 28, 2013 8:20:44 AM PDT
Last edited by the author on May 28, 2013 8:25:00 AM PDT
Dec says:
So the question for me becomes,

"Does the 0% rule apply to all Lithium ion batteries, or just the older generation ones? Is Lithium ion polymer battery a fuller name for Lithium ion battery, or are they a newer, better class not subject to the 0% cutoff rule?"

And, "Are there battery types or technologies that are not subject to the 0% rule and if so, what are they, or why are they not made available or popularized?"

And, "Would it be better to invest in such technologies and incorporate the cost into making available a better product upfront instead of solely relying on replacing normal-worn, unusable batteries every ~3 years?"

Posted on May 28, 2013 8:24:13 AM PDT
scoutyjones says:
Whenever I see a topic on batteries and what is best for a certain type, there is never ever consensus...no matter if you are an engineer, nuclear physicist or a techno nerd...there is never consensus.
So, I follow that I charge it when I need to and proactively charge it fully when travelling, based on the need. If the battery craps out, I hope it is under warranty or I take that into consideration on my next purchase...

In reply to an earlier post on May 28, 2013 8:38:33 AM PDT
Dragi Raos says:
Sigh...

http://en.wikipedia.org/wiki/Lithium_polymer_battery and links from there.

Wikipedia and Google are your friends.

As for your last question, do you think it is enough to utter the magic word "invest" and physics and chemistry promptly obliges? With possible lucrative uses in areas such as electric vehicles and storage for intermittent power sources like wind and solar, investment in battery research is enormous.

Posted on May 28, 2013 8:44:59 AM PDT
Most manufacturers recommend that you fully discharge li ion batteries (below 5% remaining charge) once a month or so in order to maintain their calibration, although I've never bothered to do so. Li Poly batteries are charged and maintained in the same fashion as other Li Ion batteries.

In reply to an earlier post on May 28, 2013 8:54:09 AM PDT
Last edited by the author on May 28, 2013 8:56:22 AM PDT
James R. Scarborough says: "Most manufacturers recommend that you fully discharge li ion batteries (below 5% remaining charge) once a month or so in order to maintain their calibration,"

To be clear, it's not a battery calibration but the calibration of the % left reporting. It calibrates what the total capacity is so that it can accurately report the % left. How often you do it depends on how often you charge. You can go a few months if you don't do partial charges too often. Also, if a person doesn't care how accurate the % is then they don't need to bother with the discharge/charge calibration. There is no affect on the life or runtime of the battery.

http://batteryuniversity.com/learn/article/battery_calibration

In reply to an earlier post on May 28, 2013 9:15:49 AM PDT
Last edited by the author on May 28, 2013 9:27:33 AM PDT
Dec says:
@Dragi Raos, the reason why I said,

And, "Would it be better to invest in such technologies and incorporate the cost into making available a better product upfront instead of solely relying on replacing normal-worn, unusable batteries every ~3 years?"

was not to imply that potential benefits of such research are not enormous (of course they are), nor to suggest that physics and chemistry are applied best in areas without funding (of course facilitation is important). The reason for my question was simply to put out there for the readership of this thread, that the normal way of doing things often holds people back from the way of progress. Sure, we can just continue replacing batteries the way we've been doing for a decade or so, but there's more likely a better way.

And often, those better ways are prevented from being explored because there are established industries and groups involved who have invested too heavily in the current way of doing things and have a lot to lose from more efficient and better technologies. Perhaps those who are familiar with alternate energy production and zero-point energy, etc. (and I don't mean merely windmills or carbon-stamp inefficient ethanol or disproven trends) could vouch that there are more than a few suppressed discoveries and technologies unfortunately because of human greed and wishes to remain in power and influence.

[Thanks for the link though, I'll check it out. And thanks James R. Scarborough and Thomas Palmer for your informative responses.]

In reply to an earlier post on May 28, 2013 9:49:31 AM PDT
The problem is that battery technology is a specialized chemistry based product and most device companies don't have that capability in house. They have to rely on other companies that do have that capability in house. Batteries have improved vastly over the last decade. Usually the advancements come from very specific product needs. Thin products that need long life batteries (cell phones) and products that need large long life batteries but don't have the typical space needed by round batteries (satellites) have resulted in the Lithium Polymer batteries. Hybrid and Electric cars that need high capacity and very long life between replacements have resulted in batteries that can last 10-20 years. But these advancements are specialized... Lithium Polymer batteries don't have the current ratings needed by things like drills and cars so you don't see it being used on those products (thus why those batteries are still large and cumbersome) and the advancements made to get hybrid/electric car batteries to last 1-2 decades are not yet capable to be made into batteries that can fit into small electronics.

Rest assured... batteries and portable power is one area that is constantly trying to be improved on due to rapidly changing customer (consumer, government, military, medical devices, etc) needs.
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Initial post:  Oct 12, 2011
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