Unused Li-ion battery pack
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From: Jeff Liebermann on 1 Oct 2009 23:22 On Fri, 02 Oct 2009 09:15:31 +0800, who where <noone(a)home.net> wrote: >On Thu, 01 Oct 2009 09:34:43 -0700, Jeff Liebermann <jeffl(a)cruzio.com> >wrote: > >>On Thu, 1 Oct 2009 14:29:37 +0100, "N_Cook" <diverse(a)tcp.co.uk> wrote: >> >>>How to store to retain it for possible future use? >> >><http://en.wikipedia.org/wiki/Lithium-ion_battery#Shelf_life> >>Store at about 50% charge in the coldest place you can find. Warm to >>room temperatures before using. >> >>"At a 100% charge level, a typical Li-ion laptop battery that is full >>most of the time at 25 �C or 77 �F will irreversibly lose >>approximately 20% capacity per year...." > >that's seriously dated and extremely inaccurate. It doesn't explain >the packs that are ten years older (or more) and still can demonstrate >2/3rds of original capacity. Unfortunately some of these references >seem to never track reality. How recent a web page would you consider to be adequately up to date? More pages that say basically the same thing: <http://www.batteryuniversity.com/parttwo-34.htm> <http://powerelectronics.com/portable_power_management/battery_charger_ics/proper_care_extends-li-ion-battery-0425/> <http://www.apple.com/batteries/> If you use your iPod, iPhone, or notebook in temperatures higher than 95� F (or 35� C), you may permanently damage your battery�s capacity. That is, your battery won�t power your device as long on any given charge. You may damage it even more if you charge the device in these temperatures. Even storing a battery in a hot environment can damage it irreversibly. <http://www.centralhobbies.com/instructional/lithium.html> 3. Don't charge up the battery pack just to store it away. When storing for long periods of time, keep the battery at a 40% charge level. More if you want them.... Google for "Li-Ion battery care". >>>deliberately discharged and then unattended outside of pc >> >>That will blow up the battery. > >That's also an extreme view, assuming discharge to the "normal" >end-point and *not* to zero volts per cell (which is geberally >precluded by the pack protection module anyway). Agreed. However, the OP didn't specify how he plans to discharge the battery. I had visions of discharging the battery pack outside of the laptop (or whatever). >Have you ever witnessed that occur? The normal decomposition of cells >allowed to deteriorate from EOD is non-spectacular, just a quiet >process without the leakage that say an alkaline primary would >exhibit. Witnessed what? Having a Li-Ion battery die from excessive discharge? Yep, but with LiPo batteries in model airplanes. They don't have the protection found in most laptops and cell phones. The motor is fully able to fly the battery into the ground. Two to perhaps five such cycles is all that's required to kill the battery. >>>charged up in pc and then unattended outside of pc >> >>Full charge will eventually self-deteriorate the battery. > >The things that determine the rate of loss_of_usable_capacity are >temperature and state-of-charge. Also simple choices (not generally >available to the user of consumer appliances) play a big part in cycle >life. Lowering the end-of-charge voltage from 4.20 to 4.10 returns a >trebling of cycle life in return for a small reduction in usable >capacity. I had the opportunity to verify part of that on a small scale. Four identical LiPo batteries. 1. 100% charge refreshed every two weeks at room temperature. 2. 100% charge refreshed every two weeks in my fridge. 3. 50% charge refreshed every two weeks at room temperature. 4. 50% charge refreshed every two weeks in my fridge. Unfortunately, 50% charge was largely a guess and my not have been accurate. The 2 week interval was also not exact. None of the batteries were discharged with any load other than self-discharge. At the end of 6 months, I used a West Mtn Radio battery analyzer to see what was left. <http://www.westmountainradio.com/CBA.htm> I returned all the batteries to room temperature, let them stabilize for a day, and charged them all to 100%. I then tested them and generated discharge graphs at rated Amp-Hr capacity. 1. 60% of rated capacity 2. 85% of rated capacity 3. 98% of rated capacity 4. 98% of rated capacity. The above numbers are from my fading memory and may not be exact. I think I can post the corresponding graphs, if I can find the data. The laptop I was using for testing crashed and I'm not sure if I had backed up the data. >>>charged via otherwise unused pc once a month? 6 monthly ? yearly ? and then >>>removed from pc >> >>Nope. Lifetime is measured in charge cycles. That would just >>decriment the number of charge cycles available. > >It isn't that simple. True. It never is that simple. >>>stored in a fridge? or just a cool dry place or a warm place >> >>Cool. Cold is better, but don't freeze. Optionally store in sealed >>plastic bag to prevent condensation when removed from fridge. So, since you indicate that everything I posted is wrong, how should one store a Li-Ion battery? -- # Jeff Liebermann 150 Felker St #D Santa Cruz CA 95060 # 831-336-2558 # http://802.11junk.com jeffl(a)cruzio.com # http://www.LearnByDestroying.com AE6KS
From: who where on 2 Oct 2009 02:03 On Thu, 01 Oct 2009 20:22:26 -0700, Jeff Liebermann <jeffl(a)cruzio.com> wrote: >On Fri, 02 Oct 2009 09:15:31 +0800, who where <noone(a)home.net> wrote: > >>On Thu, 01 Oct 2009 09:34:43 -0700, Jeff Liebermann <jeffl(a)cruzio.com> >>wrote: >> >>>On Thu, 1 Oct 2009 14:29:37 +0100, "N_Cook" <diverse(a)tcp.co.uk> wrote: >>> >>>>How to store to retain it for possible future use? >>> >>><http://en.wikipedia.org/wiki/Lithium-ion_battery#Shelf_life> >>>Store at about 50% charge in the coldest place you can find. Warm to >>>room temperatures before using. >>> >>>"At a 100% charge level, a typical Li-ion laptop battery that is full >>>most of the time at 25 �C or 77 �F will irreversibly lose >>>approximately 20% capacity per year...." >> >>that's seriously dated and extremely inaccurate. It doesn't explain >>the packs that are ten years older (or more) and still can demonstrate >>2/3rds of original capacity. Unfortunately some of these references >>seem to never track reality. > >How recent a web page would you consider to be adequately up to date? > >More pages that say basically the same thing: ><http://www.batteryuniversity.com/parttwo-34.htm> ><http://powerelectronics.com/portable_power_management/battery_charger_ics/proper_care_extends-li-ion-battery-0425/> > ><http://www.apple.com/batteries/> > If you use your iPod, iPhone, or notebook in temperatures higher > than 95� F (or 35� C), you may permanently damage your battery�s > capacity. That is, your battery won�t power your device as long on > any given charge. You may damage it even more if you charge the > device in these temperatures. Even storing a battery in a hot > environment can damage it irreversibly. > ><http://www.centralhobbies.com/instructional/lithium.html> > 3. Don't charge up the battery pack just to store it away. When > storing for long periods of time, keep the battery at a 40% charge > level. > >More if you want them.... Google for "Li-Ion battery care". You've rolled a number of points into one. I was referring speciically to their 20% p.a. loss of capacity claim, which is a crock. >>>>deliberately discharged and then unattended outside of pc >>> >>>That will blow up the battery. >> >>That's also an extreme view, assuming discharge to the "normal" >>end-point and *not* to zero volts per cell (which is geberally >>precluded by the pack protection module anyway). > >Agreed. However, the OP didn't specify how he plans to discharge the >battery. I had visions of discharging the battery pack outside of the >laptop (or whatever). If it is a laptop pack recent enough to care about, it will contain a pack protection module which will preclude discharge beyond a LVCO point, typically 3.0v, and will also preclude excessive discharge current. Nothing unsafe about a DYI discharge on that pack. If it is a single cell from a cellphone or similar, different story. these tend to have minimal inbuilt protection (if any) and rely heavily on the host device for the customary protective functions. >>Have you ever witnessed that occur? The normal decomposition of cells >>allowed to deteriorate from EOD is non-spectacular, just a quiet >>process without the leakage that say an alkaline primary would >>exhibit. > >Witnessed what? Having a Li-Ion battery die from excessive discharge? >Yep, but with LiPo batteries in model airplanes. They don't have the >protection found in most laptops and cell phones. The motor is fully >able to fly the battery into the ground. Two to perhaps five such >cycles is all that's required to kill the battery. No protection means all bets are off. >>>>charged up in pc and then unattended outside of pc >>> >>>Full charge will eventually self-deteriorate the battery. >> >>The things that determine the rate of loss_of_usable_capacity are >>temperature and state-of-charge. Also simple choices (not generally >>available to the user of consumer appliances) play a big part in cycle >>life. Lowering the end-of-charge voltage from 4.20 to 4.10 returns a >>trebling of cycle life in return for a small reduction in usable >>capacity. > >I had the opportunity to verify part of that on a small scale. Four >identical LiPo batteries. >1. 100% charge refreshed every two weeks at room temperature. >2. 100% charge refreshed every two weeks in my fridge. >3. 50% charge refreshed every two weeks at room temperature. >4. 50% charge refreshed every two weeks in my fridge. >Unfortunately, 50% charge was largely a guess and my not have been >accurate. The 2 week interval was also not exact. None of the >batteries were discharged with any load other than self-discharge. > >At the end of 6 months, I used a West Mtn Radio battery analyzer to >see what was left. ><http://www.westmountainradio.com/CBA.htm> >I returned all the batteries to room temperature, let them stabilize >for a day, and charged them all to 100%. I then tested them and >generated discharge graphs at rated Amp-Hr capacity. >1. 60% of rated capacity >2. 85% of rated capacity >3. 98% of rated capacity >4. 98% of rated capacity. >The above numbers are from my fading memory and may not be exact. I >think I can post the corresponding graphs, if I can find the data. The >laptop I was using for testing crashed and I'm not sure if I had >backed up the data. No need. I've seen numbers on these before, and Evgenij Barsukov has posted comment on this previously in sci.chem.electrochem.battery. >>>>charged via otherwise unused pc once a month? 6 monthly ? yearly ? and then >>>>removed from pc >>> >>>Nope. Lifetime is measured in charge cycles. That would just >>>decriment the number of charge cycles available. >> >>It isn't that simple. > >True. It never is that simple. > >>>>stored in a fridge? or just a cool dry place or a warm place >>> >>>Cool. Cold is better, but don't freeze. Optionally store in sealed >>>plastic bag to prevent condensation when removed from fridge. > >So, since you indicate that everything I posted is wrong, how should >one store a Li-Ion battery? I never suggested that everything you posted is wrong, far from it. But several points were amiss and they attracted specific comment. I have seen numerous manufacturer-derived articles recommending 50-60% SOC and cool/cold but not freezing as the optimum storage condition for maximised life. I see nothing at all wrong with this approach *if* maximum life is the sole objective. If OTOH the user wants to be able to pull the cell/battery out of storage and into service without an intervening warm-up or recharge, maybe a higher SOC is warranted. Like many things relating to Li-XX cells, it is a tradeoff. The extra life obtained by reducing the EOC voltage is well documented and well worth it in laptop applications BUT the end user doesn't get to choose. The manufacturer is out to deliver (well, promise) the maximum discharge runtime he can, and he doesn't give a rats how long the pack lasts in service. I have a pack from an olde Acernote Lite 370 series dated 9637, so it is just over 13 years old. It is stored with, but not *in*, the machine. About once every year or so I pull that out and run it until the machine shuts down, then recharge it to 100% (sic). It delivers about 1.3 hours, compared to 2.5+ when new. That is stored at 100% and room temperature (32S/116E). I also have several test packs of 18650 cells left over from a project about five years ago when I designed a commercial Li-XX charger. They were shelved at 4.20v and currently all are above 3.9v. I haven't bothered to measure their storage capacity because I have no reason, but I can assure you that they wouldn't show that sort of cell voltage if they had lost 20% of original capacity per year.
From: JW on 2 Oct 2009 05:23 On Thu, 1 Oct 2009 07:12:28 -0700 "William Sommerwerck" <grizzledgeezer(a)comcast.net> wrote in Message id: <ha2dej$ato$1(a)news.eternal-september.org>: >Anti-static bags are conductive. Not like metal, but they conduct. Especially the cheap ones that motherboards and such come in with the crosshatch patterns on the outside of the bag. Never put a motherboard down on the outside of one or you can discharge the CMOS battery if left long enough.
From: Joe on 2 Oct 2009 18:36 In article <5bm9c5hqdi8mpthbu7kuvutfi02aj8qmob(a)4ax.com>, Jeff Liebermann <jeffl(a)cruzio.com> wrote: <http://en.wikipedia.org/wiki/Lithium-ion_battery#Shelf_life> > Store at about 50% charge in the coldest place you can find. Warm to > room temperatures before using. <SNIP> > Cool. Cold is better, but don't freeze. Optionally store in sealed > plastic bag to prevent condensation when removed from fridge. Jeff, "coldest place you can find" versus "don't freeze". Which is it? --- Joe
From: Jeff Liebermann on 3 Oct 2009 02:22
On Fri, 02 Oct 2009 15:36:03 -0700, Not(a)this.address (Joe) wrote: >In article <5bm9c5hqdi8mpthbu7kuvutfi02aj8qmob(a)4ax.com>, Jeff Liebermann ><jeffl(a)cruzio.com> wrote: > > <http://en.wikipedia.org/wiki/Lithium-ion_battery#Shelf_life> >> Store at about 50% charge in the coldest place you can find. Warm to >> room temperatures before using. > >> Cool. Cold is better, but don't freeze. Optionally store in sealed >> plastic bag to prevent condensation when removed from fridge. >"coldest place you can find" versus "don't freeze". >Which is it? The coldest place you can find that doesn't freeze the battery. I would think you could decode that from what I wrote. Freezing is 0C so anything between that and somewhat below room temperature is a good target. The fridge at 5 to 8C is about as cold as I would think necessary. Any colder runs the risk of freezing the battery. If that's too difficult, room temperature is fine. Just don't let the battery get hot. Before using the battery, let it warm up to room temperature. -- Jeff Liebermann jeffl(a)cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |