Unused Li-ion battery pack

How to store to retain it for possible future use?

deliberately discharged and then unattended outside of pc charged up in pc and then unattended outside of pc charged via otherwise unused pc once a month? 6 monthly ? yearly ? and then removed from pc stored in a fridge? or just a cool dry place or a warm place

Reply to
N_Cook
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Will destroy it.

Yes.

If you have an antistatic bag and a moisture abosrber, put them in it and seal it. Keep cool, but do not freeze (as the UNIX fortune program used to say).

In case any one wonders, the cells themselves are not affected by static, but the electronics inside the battery pack are.

If you are the cautious type, place the anti static bag inside a sealed zip lock bag. If the cells leak, the electrolyte is extremely corrosive.

I have no proof, just a feeling, but I would not place them in bag and seal it using a vacuum food sealing system. The cells are designed to not leak at seal level air pressure, not a vacuum.

Geoff.

--
Geoffrey S. Mendelson, Jerusalem, Israel gsm@mendelson.com  N3OWJ/4X1GM
Reply to
Geoffrey S. Mendelson

Anti-static bags are conductive. Not like metal, but they conduct. Make sure the battery's contacts are covered.

Reply to
William Sommerwerck

I heard charge to half then store in the fridge in a Ziploc bag. Might want to toss a silica gel bag in as a desiccant.

This will retard the battery's natural decay rate.

Reply to
Meat Plow

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 will blow up the battery.

Full charge will eventually self-deteriorate the battery.

Nope. Lifetime is measured in charge cycles. That would just decriment the number of charge cycles available.

Cool. Cold is better, but don't freeze. Optionally store in sealed plastic bag to prevent condensation when removed from fridge.

--
Jeff Liebermann     jeffl@cruzio.com
150 Felker St #D    http://www.LearnByDestroying.com
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Reply to
Jeff Liebermann

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.

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).

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.

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.

It isn't that simple.

Reply to
who where

How recent a web page would you consider to be adequately up to date?

More pages that say basically the same thing:

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.

  1. 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".

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).

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.

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.

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.

True. It never is that simple.

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
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Reply to
Jeff Liebermann

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.

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.

No protection means all bets are off.

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.

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.

Reply to
who where

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.

Reply to
JW

Jeff,

"coldest place you can find" versus "don't freeze".

Which is it?

--- Joe

Reply to
Joe

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@cruzio.com
150 Felker St #D    http://www.LearnByDestroying.com
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Reply to
Jeff Liebermann

Guilty as charged and you're correct, but not for commodity Li-Ion laptop batteries as the OP apparently is using. According to:

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.

These batteries are made to operate at body temperature (37C) and must therefore not suffer from self-deterioration at elevated storage temperatures.

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.

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.

Yep.

(...)

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.

Same here. That's also my recommended storage condition.

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 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.

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.

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@cruzio.com
150 Felker St #D    http://www.LearnByDestroying.com
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Reply to
Jeff Liebermann

only if the battery uses pure water as it's electrolyte.

Reply to
AZ Nomad

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.
Reply to
Meat Plow

Sigh... I guess I have to do the necessary Google searching.

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: (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@cruzio.com
150 Felker St #D    http://www.LearnByDestroying.com
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Reply to
Jeff Liebermann

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@cruzio.com
150 Felker St #D    http://www.LearnByDestroying.com
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Reply to
Jeff Liebermann

"room and above temperature" The battery pack is on the front ledge it does not get hot from the laptop but gets "above" room temperature. Just how much "above room temperature" I don't know never measured it but it's surly not warm to the touch as the rear end is where the fans and heat sink are located.

I've seen many including HP batteries go belly up in a short time.

Reply to
Meat Plow

Thanks you for verifying that the phrase "freezing is 0C" was complete bullshit.

Reply to
AZ Nomad

Laptop monitor software to display battery temperature.

It would be interesting if the protection circuit in the battery pack also logged temperature. That would be sufficient to estimate battery life and alert the user that the battery is too hot.

Yep. Seen any Li-Ion battery chargers that have a settable EOC (end of charge) adjustment? I haven't. One could program it to stop charging at perhaps 80% of charge, and somewhat extend the life of batteries that are in 7x24x365 laptops. Also useful for the spare batteries that I carry in the bag. Left fully charged, they also tend to die early.

Aw, you're no fun...

Still waiting for fuel cell laptop batteries. Polyfuel died in August. Ultracell is selling mostly to the military.

Most of the major Japanese manufacturers have announced and even demonstrated products, but nothing I can buy, yet. Grumble...

--
Jeff Liebermann     jeffl@cruzio.com
150 Felker St #D    http://www.LearnByDestroying.com
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Reply to
Jeff Liebermann

The Windoze setting is purely for functionality - so the user can bail before the pack pulls the plug and causes that "You didn't shut Windoze down properly, so I'm doing a disc scan" screen on restart.

The pack protection modules we used were preset to open the series FET switch at 3v0. If you look at the discharge curve of Li-Ions at constant current (or with a constant load impedance) you will notice a distinct droop below about (from memory here) 3v3. While cell deterioration starts at/below 2v5 there is very little useful capacity gained by proceeding below 3v0.

Cost. Commodity chemistries have been around for over a decade and are cheaper than newer solutions that aren't into the same part of the volume/cost curve yet. Remember that the laptop manufacturer generally sees the battery pack as a non-warranted item (wear and tear), and even when it IS warranted it only has to function for that period without any capacity guarantee. So cheap is good for them.

Yes (see earlier) but I was referring to end-of-charge setpoint.

Yep, I have both here (two 370's) and the NiMH is thoroughly rooted.

It doesn't, but the only way I can sensibly evaluate it's usable capacity is by measuring runtime.

These are cheap (Chinese) 18650 commodity cells which my client imports. Far from special. To evaluate the prototype charger I set the EOC to 4v20 and did cyclical testing on packs of 1/2/3/4 cells. There were some interesting points to emerge from this, but somewhat O/T for this thread.

Reply to
who where

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