Unused Li-ion battery pack
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From: Jeff Liebermann on 3 Oct 2009 03:10 On Fri, 02 Oct 2009 14:03:46 +0800, who where <noone(a)home.net> wrote: >><http://www.batteryuniversity.com/parttwo-34.htm> >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. Guilty as charged and you're correct, but not for commodity Li-Ion laptop batteries as the OP apparently is using. According to: <http://www.batteryuniversity.com/parttwo-34.htm> Temp 40% storage charge 100% storage charge 0C 96% after 1 yr 94% after 1 yr 25C 96% after 1 yr 80% after 1 yr 40C 85% after 1 yr 65% after 1 yr 60C 75% after 1 yr 60% after 3 months Kinda looks like about 20%/yr loss with 100% charge at room temp. My abbreviated test showed a 40% loss with 100% charge at room temp in 6 months. I'll agree with the Wikipedia numbers until someone specified a specific chemistry and testing method (that I can perform with my West Mtn Radio CBA II tester). However, you are correct that there are new and improved chemistries that do not have anywhere near the self discharge and self-deterioration rate of commodity laptop batteries. Eagle Picher makes Lithium-CFX batteries, that claim a self discharge rate of less than 1%/year at room temperature. <http://www.edn.com/article/CA6672104.html> These batteries are made to operate at body temperature (37C) and must therefore not suffer from self-deterioration at elevated storage temperatures. >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. True. The battery pack has enough electronics inside to protect itself from excessive discharge. Under Windoze, one can set an alarm and a shutdown point based on battery capacity. The default threshold is about 10%. I've never tested this to determine if it works. Presumably, if you don't want to run the battery down to below perhaps 25% capacity, setting a shutdown threshold below this point is wasted effort. Similarly, if there's a protection threshold inside the battery pack, it's certainly not labeled or easily determined. >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. Yep. Model airplanes and helicopters are even worse. All the protection electronics is in the external battery charger. It protects against fatal overcharge, but does nothing for excessive discharge. >No protection means all bets are off. Yep. >No need. I've seen numbers on these before, and Evgenij Barsukov has >posted comment on this previously in sci.chem.electrochem.battery. (...) >I never suggested that everything you posted is wrong, far from it. >But several points were amiss and they attracted specific comment. No problem. However, I'll stand on the Wikipedia 20%/year loss at 100% charge at room temperature for commodity laptop batteries. My results were even worse. I'll concede that there are new chemistries that offer substantial improvements in self-discharge and self-deterioration, but I haven't seen any in laptops. >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. Same here. That's also my recommended storage condition. >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. Well, of course. I mentioned (twice) that one should let the battery warm to room temperature before using. I don't know what will happen if the battery is either charged or discharge at near freezing temperatures, but it probably will not do anything useful. >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. The user can set the Windoze low battery warning to trip at a much higher level than the ridiculously low default value of 10%. That will prevent excessive discharge. >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). The Acernote Light 370 was delivered with NiMH batteries, but later LiIon batteries were made available. Why do you discharge the battery before charging? As I understand it, LiIon doesn't have a memory problem. >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. Agreed. 3.92v is the highest voltage that a LiIon-Cobalt cells will deliver. You did something right because my 6 month experiment showed deterioration in both room temperature batteries. -- 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
From: AZ Nomad on 3 Oct 2009 04:47 On Fri, 02 Oct 2009 23:22:02 -0700, Jeff Liebermann <jeffl(a)cruzio.com> wrote: >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. only if the battery uses pure water as it's electrolyte.
From: Jeff Liebermann on 3 Oct 2009 08:47 On Sat, 03 Oct 2009 03:47:36 -0500, AZ Nomad <aznomad.3(a)PremoveOBthisOX.COM> wrote: >On Fri, 02 Oct 2009 23:22:02 -0700, Jeff Liebermann <jeffl(a)cruzio.com> wrote: >>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. >only if the battery uses pure water as it's electrolyte. Sigh... I guess I have to do the necessary Google searching. <http://www.nationmaster.com/encyclopedia/Lithium-ion-battery%23External-links> Many authors suggest that freezing Li-ion batteries may be detrimental. However, most Li-ion battery electrolytes freeze at approximately -40 �C. Household freezers rarely reach below -20�C. Published experiments demonstrate that freezing (even below -40�C) is unharmful if the battery is fully warmed to room temperature before use. More details are given in the book "Characteristics and Behavior of 1M LiPF6 1EC:1DMC Electrolyte at Low Temperatures" by L.M. Cristo, T. B. Atwater, U.S. Army Research, Fort Monmouth, NJ. Seems that it's safe to put a Li-Ion battery in the freezer. However, many web pages suggest the proper storage conditions are 0C to 20C at 40% charge. For example: <http://www.idxtek.com/pdf/tech_info/T-004.pdf> (camera battery) Incidentally, I just received ten RAZR cell phone batteries from a vendor in China. All arrived charged to about 30-40%. -- 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
From: Jeff Liebermann on 3 Oct 2009 09:35 On Sat, 03 Oct 2009 08:26:56 -0400, Meat Plow <meat(a)petitmorte.net> wrote: >On Sat, 03 Oct 2009 00:10:54 -0700, Jeff Liebermann ><jeffl(a)cruzio.com>wrote: > ><snip> >>No problem. However, I'll stand on the Wikipedia 20%/year loss at >>100% charge at room temperature for commodity laptop batteries. >My Asus model MNB600's battery has lived at pretty much full charge >and at room and above temperature for 5 years with not a significant >loss of capacity. It still goes around 2.5 hours speed stepped down to >800 mhz and about 1 hour at full speed 1.8 ghz. If the battery lived INSIDE your laptop, it's not at room temperature. Laptops run hot. One of my enrolled agent customers used IBM A31/A31p laptops as their main computahs. The grand plan was to make it easy to take them on interviews at clients homes, but that rarely happened. The batteries were at 100% charge, inside a hot laptop, for 24x7x365. After 2.5 years, all the batteries were essentially dead with perhaps 10 minutes runtime. Rhetorical question: Why don't UPS manufacturers use Li-Ion batteries? -- 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
From: AZ Nomad on 3 Oct 2009 13:00
On Sat, 03 Oct 2009 05:47:19 -0700, Jeff Liebermann <jeffl(a)cruzio.com> wrote: >On Sat, 03 Oct 2009 03:47:36 -0500, AZ Nomad ><aznomad.3(a)PremoveOBthisOX.COM> wrote: >>On Fri, 02 Oct 2009 23:22:02 -0700, Jeff Liebermann <jeffl(a)cruzio.com> wrote: >>>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. >>only if the battery uses pure water as it's electrolyte. >Sigh... I guess I have to do the necessary Google searching. ><http://www.nationmaster.com/encyclopedia/Lithium-ion-battery%23External-links> > Many authors suggest that freezing Li-ion batteries may be > detrimental. However, most Li-ion battery electrolytes freeze > at approximately -40 ?C. Household freezers rarely reach below Thanks you for verifying that the phrase "freezing is 0C" was complete bullshit. |