Using a battery to 0%. Dangerous or not?

Some sources, like the NBR guide, say "Never discharge your battery to 0% – as this can render your battery useless."

Other sources I've read say: a newer notebook has technology on board that prevent discharge beyond dangerous levels. There's no danger in using the notebook to 0%.

Who's right?

 

I would say both. Lithium Ion batteries should not be discharged to zero, but that doesn't necessarily mean doing so will kill your battery instantly. It does mean that if you make a habit of it your lithium ion battery isn't going last as long as it could have if you used it within the recommended parameters.


First post on my new Alu. Macbook. First Apple computer I've used since the late eighties.

 

Well some sources say that you should discharge to zero percent the first two or three times you charge the battery.

While others say you should never discharge to that level.

Saying both are right isn't really an option here

 

I believe they recommend this to allow your power management software to synchronize with the battery. I think Lenovo recommended this when I got my new R61. Also, I believe their battery refresh utility discharges the battery fully then recharges it. The most important difference here is that they don't recommend discharging the battery and letting it sit at zero for any length of time. Most information I've read recommends storing lithium ion batteries at around %65 (I believe anywhere between %40 and %80 would be fine). These recommendations have been around for a long time and battery technology has undoubtedly improved since then. I've accidentally left my R61 in sleep mode and found the battery dead several days later, but after charging I noticed no ill effects to the batteries performance. This doesn't mean I make a habit of it.

Here is a link that mentions the battery calibration you speak of:

http://www.batteryuniversity.com/parttwo-34.htm

One final note, I would say that these are general guidelines for all lithium ion batteries, but if the manufacturer of your specific battery recommends something else I would follow their advice first.

 

From past experience, I'd say discharging to 0%, even just occasionally, can lower the overall battery capacity over say a period of one year. Lots of variables, but I wouldn't. I'm sure someone out there has a chemistry or chemical engineering background can explain the reasons why - I would be interested to learn about why, though most people would just like it to affirm their decision about discharging.

 

Everything I've read about lithium ion batteries - batter technology articles and whatnot - says they do not like to be 100% discharged.

 

discharging to 0% is no good.
When you discharge the batteries that low, you are removing basically everything left in them, so the chemical reaction is basically down to zero. I know that if you continue to do this the plates in the battery get oxidized much faster, and loose potential for storing current.
I stay safe with my battery, my alarm goes off at 20% and the next warning goes off at 12% shutting the system off.

K-TRON

 

I think so too.

But some sources say that modern notebooks have a built in protection preventing the battery to be completely drained to 0%. They say there is no danger in using your notebook untill it runs completely out.

 

What do you gain from letting it get to 0% rather than say 5%, perhaps 20minutes, but generally speaking I just can't see a normal operation where people would plan to let their system battery drain down to 0%. I would guess that unless your system software and battery are perfectly calibrated you risk data loss whenever your battery meter gets below about 10%. I can understand an emergency situation where you HAD to get something done and took the battery down to near zero, but if it was something important wouldn't you finish it, shutdown and recharge? Why would you finish the task and then leave your computer on to drain the extra couple percent? I guess what I'm saying is that I just don't see how taking a battery down to zero (or even below %10 for that matter) fits into any normal usage pattern.

 

Recommendations for deep discharge are a relic from the days of nickel based batteries. Lithium cells don't like deep discharge but the on-board electronics should shut the battery down when the voltage gets too low. Just to add to the confusion, some notebooks allow the user to set a maximum charge level.

My own battery settings are alarm = 5% and shut down = 1%. Since my E6400 and NC10 are both capable of about 6 hours on battery, I don't want alarms appearing when there is over half an hour remaining and shut down with 15 minutes remaining, although most likely I will have shut down or be recharging before I reach those limits.

Most notebooks also include a battery calibration facility which normally undertakes a full charge / discharge cycle undertaken by the BIOS, in order that the remaining capacity can be properly calibrated. However, this may not be infallible. I have recovered disappearing capacity on batteries by disabling the critical battery action (easy with XP, not so easy with Vista) and running the battery until genuinely empty (my Zepto 6024W would run for 9 minutes with the gauge on 0!). Repeating this several times with full charge in between has reduced the reported wear.

john

 

Interesting stuff John. But what I don't get: first you say deep discharges are a relic from the past. Then later you say you have reduced the wear on the Zepto battery by deep discharges/charges.

I've seen several reports that two/three deep discharges and charges at first can increase the fully charged capacity. I'm inclined to believe it. I'm going to test it on my new NC10 battery.

The point is possibly increasing the capacity of the battery like John described with his Zepto.

 

The question I have is are you really regaining lost capacity or are you simply allowing your system to recalibrate with the battery and display the true battery capacity? I believe with a lithium ion battery all you are really doing is recalibrating the system.

 

Good point. Either way, I'd be happy with it.

On my brand new battery RMclock says designed capacity 57720, fully charged capacity is 55500. That's about 3% wear.

On a different system with different battery, RMClock said exactly the same.

 

The problem you’re seeing is really a misunderstanding about what 0% is. Batteries for laptop are made from cells. A battery might have three sets of three cells (9 cell) or 2 sets of 3 cells (6 cell). Batteries are only used from one voltage to another.

For lithium it might have a minimum voltage of 2.7V and a max of 3.7V. Your laptop knows this and thus will tell you 10% when you’re at 2.8V. We can see though that 2.7V is not really zero voltage; but, it is 10% of the “usable” voltage. If you go to 0%, or 2.7V here and don't charge your laptop ASAP it will self discharge below 0% because it will go from 2.7V -> 0V given enough time (infinite technically because discharge is a percentage of current charge, but it will get very low during finite time of say a week or month). If it goes too far below 2.7V than your laptop will not charge it as a safety precaution since dropping to low destroys the chemistry and makes the battery highly resistive. As you attempt to charge all the electricity is turned into heat and then the battery can explode, oxidize rabidly (burn) or some other dangerous, bad thing.

This is why you shouldn't go to '0', because you still lose charge after that point and too far will block you from charging it again. You can open a battery and use specially tools to trickle (slowly) charge each cell back up your minimum voltage, but it lowers overall capacity, is expensive, and most people don't have these special chargers.

With a laptop, you will wear your battery out faster, but unless you leave it for a month after it reaches '0%' you won't have a problem because safety factors are always included when designing a laptop.

If you don't need to go to 0%, avoid it. If you do? Then feel free and charge it at least a little if your going to be storing it for weeks afterword.

 

Most operating systems won't allow you to discharge to 0%. It reserves at least 1-2% before entering hibernation or shutdown process. Now of course you can override it some way or form, but from my understanding Windows still reserves "some" battery.

 

Uh oh, guess I better stop doing that.

 

I always discharge my battery to 0% before recharging it up. Result? Stellar battery capacity after 11 months (still 99% of the design capacity)
I used to discharge it to about 10% then recharged it. Result? 80% of the design capacity only after 6 months.

 

Modern Li-ion battery systems in laptops never get charged or discharged completely because it reduces their cycle life. If you have a new laptop and it shows 0% battery it actually has about 20% of its energy left, likewise if you see 100% it is actually only at 90% of its theoretical capacity. The engineers have essentially traded energy density (Watt Hours per unit mass or volume) for increased cycle life. Chevy has taken this to a farther extreme with their much hyped "Volt" It will charge to 80% and discharge to 30% again in an effort to extend the batteries cycle life, also as the battery ages and loses performance (in the Volt) the 30-80% envelope will expand always keeping the total available capacity the same until the battery has decayed to less than 50% original charge. (normally secondary (re-chargeable) batteries are said to have reached the end of their cycle life at 80% original capacity). no laptop battery system that I am aware of has an expanding cycle frontier like the volt.

conclusion? it is not dangerous at all but it will reduce cycle life somewhat.

In regards to what Zephir said: that does not make sense, ni-cd and ni-mh chemistries need to be fully cycled but not li-ion (well... some publications indicate that li-ion chemistries like to be periodically deep-discharged every ~20 cycles)

_Nate

 

No offense, but two batteries is hardly a scientific result. Were the batteries identical? Were environmental conditions similar? Were they both manufactured at the same time or were they both manufactured precisely identical lengths of time before use? Just to many variables to actually consider this.

 

Have a read at this http://www.batteryuniversity.com/partone-16.htm

 

I've read that one. They say "Lithium and lead-based batteries do not require a periodic full discharge. In fact, it is better not to discharge them too deeply but charge them more often".

While I've seen several reports of people stating they reached a higher charged capacity after applying some real deep discharges and charges in the beginning, like John on the previous page.

Some guides seem to believe the latter, while some guides say it isn't so.

Oh well, I guess they only way to find out is try by myself.

 

Yes, identical batteries, 2 9-cell in a Thinkpad T60. All variables are kept constant, including laptop using habits, so I think it is very accurate experiment. Time of manufacture has no effect on both, as they read the same design capacity and the same actual capacity at the time of purchase. If you don't believe me I have nothing to lose, just want to share the info with those interested

 

Wow I had no idea it was bad to go to Zero. I hardly use battery power at all and have deliberately discharged it maybe once every 4-8 weeks to let it cycle through. And I know I have seen it shut down around 10%, but I booted it back up and let it go to zero. I think I will leave it at 10%-20% next time and charge it from there, ooops.

Worth noting that I have not noticed anything bad afterwards but I realize I may have just shortened the life of the battery.

 

i don't think there's any one industry that more severely punishes and tests the limits of battery performance than the power tool industry.

here, bigger is better, and li ion is usually better than nimh or nicad. these batteries are typically swapped out when fully discharged to zero and snapped into a quick charger for the next cycle. what's interesting from a user's standpoint is that li ion just stops dead when the battery is low. there's no deliberation about whether you want to prolong cycle duty by recharging at some arbitrary level. you use as long as the battery allows.

but here's the point. under severe use, performance always declines fairly quickly. toss it out and replace it. batteries are considered consumables.

 

There's always a protection circuit built into either the Li-ion battery or the device it powers. These protect the battery from over discharging or charging; the former which could destroy the battery while the latter can destroy a lot more than just the battery.

I wouldn't worry about running a laptop battery down to "0%"; I wouldn't make a habit of it but neither would it be particularly damaging.

 

You may have got a bad cell(pack) or unintentionally heated one up, if you overheat a battery just once that can significantly impact its life. Your results are not typical for Li-ion batteries and if these tests weren't conducted in a controlled environment then they are not (strictly speaking) very scientific. No offense but your conclusion flies in the face of all other data I've seen on this chemistry.

 

Okay, whatever suits your belief. I also have a X61T that i'm draining down to 0 before charging up. Bought the laptop new in January, the battery now is at 98% of the design capacity. Unless there's something contradicting that happens in the future, I don't think I will change my battery using habit anytimes soon

 

I ran my lenovo battery down to 0% last week for the first time. and it broke. I wish i had known this.

 

eh.. what do you mean it broke? there is absolutely no charge? you can't recharge?

 

it went from saying the battery was "good" to "poor" and it was producing no current. i had to get a new battery..

 

Good to know. Thanks for posting.

 

The only real certainty to me is to always charge the battery FULLY before the first use and never run any rechargeable to the point it's knocked out.

All the battery anecdotes don't mean much unless you specify chemistry type, amp/hrs and production date.

Generally, lithiums are lighter, have quicker charge times and a greater number of recharge cycles but don't produce any longer run times than the cd or hd. Some people have had horrible experiences with lithium. Others, not so bad. BTW, lithiums should be removed and recharged as soon as the voltages drop since not all of them have the protection circuitry built in.

Battery age and quality is key. Once the batteries start to dry out, there's nothing you can do. You can have two batteries from the same mfg. that behave very differently because of age and quality. There would'nt be such differing experiences otherwise.

Panasonic power tools still use NiMH and they have the longest A-H times in the industry. They also supply batteries to a number of different companies. And here's something interesting. No one else is using NiMH in their power tools except for one... Panasonic. They probably keep the better stuff for themselves.

Toyota Prius uses NiMH. They're heavy but proven. The Chevy Volt is going to use Lithium. Only time will tell how it performs.

 

Well, my sager manual said that the first time using my laptop I should discharge to 0% and then full recharge, although I only let it go down to 2% because I was scared of damaging it (do you think the manual is wrong?).

What happens if you go down to low levels like 1%-5%?

 

I bought a new battery two weeks ago, in the manual it said that i should charge it up and then totally discharge it several times, (telling me that i will loose files when the battery discharges and shuts down by itself while in windows, discharging the battery totally).
The first time it should charge for more than 14hours.

So... i did this, 3 times actually, nothing bad happened to the battery/batterylife, it works just excellent, giving me the batterytime it should!

This is a 6cell Li-Ion 4400mAh 11.1v battery.

Why i had the courage to do this is because i'd just go back to the store and trade it out for a new one if it wouldn't work as it should've


Here's what my manual says (wrote it down by hand exactly how the manual says):

It only says that short-cycle will affect the battery's capacity, meaning that you shouldn't charge it uncompletely and then discharge it totally as it will be affected seriously. Maybe that's what some people has done when they discharged their batterys and their battery died?

It also states that you can leave the battery in the notebook always, as it will not be charged if it's over 95% when it has been charged fully before. Meaning that the notebook will run straight on the AC, as the battery will be as good as it where unplugged. I read in the battery-thread that you should take the battery out if you run alot on AC as it will wear out the battery, but in my manual it says the opposit. How come!?
I sure trust the manual so far as it is working exactly as it's told to be when doing so.

I hope this will be something good to know for anyone wanting to know what the manual really says about all Li-Ion batterys.

 

Yeah, that is what my manual says too.

 

Hehe, i sure wonder what the dude in the battery guide thread got his info from, threating the batterys.
Not much info seem to be correct there according to a real manual.

I just updated my post also

 

This is what my manual says:

New Battery: Always completely discharge, then fully charge a new battery.

Battery life may be shortened through improper maintenance. To optimize the life and improve its performance, fully discharge and recharge the battery at least once every 30 days.

How do I completely discharge the battery?

Use the computer with battery power until it shuts down due to a low battery. Don’t turn off the computer even if a message indicates the battery is critically low, just let the computer use up all of the battery power and shut down on its own.

It also states that "completely discharge" means use all energy until computer shuts down on 0%.

 

Ah, like my manual then. But just in other words

 

Of course I'm not going to advocate anyone go against their manual. The manual is what... the bible.

On the other hand, manuals never go through revisions and addendums, right? How about changes in accepted wisdom?

For example, car manuals typically called for a conventional motor oil change every 6k to 10k miles, too infrequent?

And sometimes, manuals don't even catch up to changes in their own products.

As far as laptop batteries go...
Look, computer mfg's generally don't make bats. They're subbed out.
And on top of that, laptop users don't punish their batteries every day for their livelihoods. Men in the building trades, do. So, I think anyone will be fine with whatever method they decide to choose. This is one area that is improving quickly because of the demands of mobility dictate R&D.
.

 

A car manufacturer that has an oil-service at 6k to 10k miles!? Umm, i've never seen any that has that high between oil changes The usual mileage between every oil change is about the same for any petrol engine, manufacturer doesn't matter in this majority. However, this isn't what we discussed.

My manual comes from the battery manufacturer and not the notebook manufacturer, so yeah i'd say that it's trustworthy to read. And hey, nothing bad has happened. And about to catch up, if that is the case, then why is it up to date (as older Li-Ion batterys according to you in the other thread can be discharged and take damage, the newer ones can't, like this manual says)?

But i can agree with you that anyone will be fine with whatever method they choose to do.

 

A full discharge helps the battery calibration. However, while the on-battery electronics stop the voltage dropping to a dangerously low level, the wisdom is that frequent deep discharges aren't good for the battery health. Many notebooks have a battery calibration option in the BIOS which puts the computer through a full discharge. Without the calibration you can't be confident that the shutdown with 3% remaining is actually 3% and not 5% or 1%.

A few days back I did a full discharge on my Dell E6400's battery which is now 4 months old. This restored about 2% to the reported fully charged capacity.

John

 

Over the past week I've noticed my battery power is getting lower while I've got it constantly plugged into mains. It first dropped to 97, then 95, 92 and is now on 90%. I've got a Dell Inspiron 1525 which is about 10 months old.

 

You may not have been around long enough. Almost every car manual from the 60's to the 90's and perhaps beyond recommend oil service at 6k or over. Conventional oil, not syn.

It is pertinent since we're talking about manuals, ALL manuals, with regard to their recommendations, not specifications.

The point is that mfg's don't even know, they're just speculating. Regarding your li-ion experience... well there are far too many converse experiences.

The mobile power supply industry is changing too quickly. Their goal is stability and ubiquity. This discussion is precisely an indication of an infant industry that clearly needs a lot more development.

 

hmm i just did the very same. Hp has what they claim the smart battery feature. to calibrate the battery you´d have to completely charge the battery, then completely discharge it and charge it again. i do hope they know what they are doing.
i did what they recommended to calibrate my battery. ( first time since 14 months of use)

officially the notebook batteries have a lifecycle of 1 up to 1.5 years or approximatly 300-350 charging cycles, before they start going to hell. mine is now 14 months old , and it still is at 98% of the full capacity.

 

Oh darn, i'm from europe and i read it as 60000km to 90000km, which was really high in my eyes But now i see, 6k-9k mile s is 10000km to 15000km, which is correct yes. Even for syntethic oil.

And i didn't mean it in that way, that i didn't understand the relevance, between your "car manual vs pc manual" thingy.

Those converse experiences may be due to older Li-Ion technology? The fact is still that what i've experienced works (and another user here in this thread), and if the converse works too for others, then i guess it's different type of Li-Ion batteries, or something those users forgot to tell about their experience that may be critical to whatever fact they told. Can't see any other explaination. As apparently vice versa works?