AW Protected Cells and Cold Weather

[Curious_character]

Right after buying some AW protected Li-Ion cells, I put some of them into the freezer. Judging by the terminal voltage, they were roughly half charged. I figured the combination of cold temperature and partial charge would maximize the lifetime of cells I'm not actively using.

About a week after storing them, I took out an 18650 cell and found a very low voltage, around 0.2 volts, and erratic. The cell would charge for less than a minute (after warming to room temperature), then stopped. I could get very little energy out of it before it would open again. After trying several charge cycles with the same result, I put it aside. Later, I saw that part of the white rim around the positive terminal had been stained brown. Considering this a bad sign, I got rid of it.

Now I've found two others, an 18650 and 18500 (AW protected), both put into the freezer brand new and checked after a couple of weeks. These showed the same low voltage. When I put them on the charger, they showed a charge for a few seconds, then stopped. After taking off the charger, they're completely open, zero volts, and won't charge at all. I do have a number of other cells of various sizes which fortunately survived. It's apparent that the first cell wasn't a fluke, and that these cells simply can't reliably survive storage at around 0 F.

Sanyo shows a permitted minimum storage temperature of -20C for their Li-Ion cells, and my freezer is above this. From my experience, it looks like simply leaving a flashlight in a car on a cold night has a good chance of permanently ruining these protected AW cells. When camping on a cold night, it would be necessary to keep the flashlight inside your sleeping bag if you want to have a working battery in the morning.

So what's the coldest temperature it's safe to store these cells at? Are there any readily available Li-Ion cells which can handle temperatures around zero degrees F without destruction?

c_c

 

[VidPro]

when you put them in the freeser were they kept from getting moisture in them ?
does your freeser have a "defrost" cycle?
did you wait till they changed temperature, before removing them from the moisture barrier? because Condensation will form around them.

do you know the self discharge rate of the cells WHEN they have the protection curcuit on them? (some people mentioned that Packs and protected, that the curcuit might have a tiny draw)

it SOUNDS like they expanded in the freeser and popped, which should not happen with normal li-ion electrolytes. dont make much sence what has happened.

i would wanta remove the protection curcuit, and see if the CELL itself was effected or if the protection curcuit itself broke. but seeing one poped open, it is likly that the others did also.

 

[Curious_character]

when you put them in the freeser were they kept from getting moisture in them ?

They were in a sealed ZipLoc bag. Some were in a second bag inside that.

does your freeser have a "defrost" cycle?

No.

did you wait till they changed temperature, before removing them from the moisture barrier? because Condensation will form around them.

No. Should I expect a small amount of condensation to permanently destroy these batteries? If so, they're pretty useless.

do you know the self discharge rate of the cells WHEN they have the protection curcuit on them? (some people mentioned that Packs and protected, that the curcuit might have a tiny draw)

I haven't a clue. If it's enough to discharge a half-charged 1.5 - 2 Ah cell in a week at zero F, they're not very useful batteries.

it SOUNDS like they expanded in the freeser and popped, which should not happen with normal li-ion electrolytes. dont make much sence what has happened.

Popped? There's no evidence of "popping" or other physical changes or damage, except that first cell (with the discolored ring). And that happened several days after it was taken out of the freezer. I don't believe that anything in the cell should freeze at zero F, so the cell and components should have shrunk, not expanded, with the cold.

i would wanta remove the protection curcuit, and see if the CELL itself was effected or if the protection curcuit itself broke. but seeing one poped open, it is likly that the others did also.

What's a safe way to open a cell to remove the protection circuit?

c_c

 

[DM51]

Your freezer is probably colder than you think. It is a very bad idea to store batteries in a freezer anyway.

 

[Curious_character]

Your freezer is probably colder than you think.

I think it's what a thermocouple measures it as -- -14C. What makes you think it's probably colder than the thermocouple measurement?

This is, by the way, the freezing compartment in an old refrigerator, and not used for storing food.

It is a very bad idea to store batteries in a freezer anyway.

I've been doing it for around 20 years now, and every battery (except the AW Li-Ions) come out as good as new, verified by many discharge tests on primary cells. The only battery type I don't store in the freezer is sealed lead-acid, on the off chance that one might become discharged enough for the electrolyte to freeze. So what is it that makes this a very bad idea? What experiences have you had? I do agree that it's a bad idea to store AW protected Li-Ion cells in a freezer and, by extension, to allow them to get very cold at any time.

c_c

 

[LuxLuthor]

That's a very interesting and well documented experiment. When you say you have been freezing batteries for years, has that included other Li-Ion cells, such as Pilas ? That would be an interesting test. I also have an infrared thermometer coming that I'm going to use to get an accurate freezer temp.

At first glance, it does look like there is something related to the AW cells.

 

[DM51]

Maybe you should try measuring it with an accurate thermometer. The gauge on an old domestic freezer is very unlikely to be accurate.

The best temperature range for storing most batteries is 5-10 degC. Obviously they will survive colder temperatures than that (depending on type) but routinely freezing them is not a good idea at all.

Since you ask, I have had plenty of experience of using battery-powered equipment in extreme cold conditions, in both the Arctic and Antarctic.

 

[LuxLuthor]

Again the question here besides verifying the temp, is about Lithium cells. Did you use those in more recent Arctic trips?

 

[VidPro]

What's a safe way to open a cell to remove the protection circuit?

the protection is usually on the top or the bottom, you just remove the insulation around the battery, and you will see the chip thing, and be able to easily access the cell itself. watch out for the metal strip that runs from the other pole, as it can incurr a short.

popped meaning anode disconnected, which they should do , but ONLY apon expansion of the internal contents.

condensation , i mention only because a backpacking trip in the cold, would not have that as a occurance very often, as the temp changes are gradual. any liquids could increase the rate of self discharge, also some CHEAP stuff will rust, quick, and cause unexpected issues.

i am with you on the idea that the cells might not be the best in the world, but you dont have any controls, or original discharge rates, prior to putting them partly DISCHARGED into a extreeme environment.

 

[DM51]

Yes. No problem with them, but I was very careful not to let them freeze.

 

[Curious_character]

Maybe you should try measuring it with an accurate thermometer. The gauge on an old domestic freezer is very unlikely to be accurate.

I'm sorry, the thermocouple with Fluke 80TK thermocouple module is the most accurate thermometer I have. It correlates very well with other reasonably accurate thermometers, and -14C is entirely within reason for a freezer temperature. But even if it's grossly in error, should I expect the batteries to be destroyed if exposed to, say, -20C, or -25? If so, why?

The best temperature range for storing most batteries is 5-10 degC. Obviously they will survive colder temperatures than that (depending on type) but routinely freezing them is not a good idea at all.

Is that true for all types of batteries? Should batteries fail if exposed to lower temperatures? And what in a battery (of any kind except discharged lead-acid) freezes at -14C?

Since you ask, I have had plenty of experience of using battery-powered equipment in extreme cold conditions, in both the Arctic and Antarctic.

I didn't, but that's very interesting. Do you expect your batteries to permanently fail if they get down to -20C? I assume you're familiar with the discovery of some 1939 vintage carbon-zinc cells found at Little America after having been there for 7-1/2 years. (Temperature was 0 degrees F when they were found but had been lower.) They were tested with the standard tests of the time, a "heavy intermittent test" and "railroad lantern test". The cells ran 70 hours in the first test vs 66 hours nominal for new cells; in the second test they ran 34 hours vs 42 for new cells. (Ref. NBS Letter Circular LC 965, Nov. 15, 1949.) In contrast, the AW Li-Ions ran for zero time after storage for one week at 7 degrees F.

c_c

 

[VidPro]

And what in a battery (of any kind except discharged lead-acid) freezes at -14C?

the electrolyte in the li-ions should not be freesing at say around -20*F
I thought it was a volitile solvent type of electrolyte.

BUT, remember they have been "improving the safety" of the cells, take out more volitile flamable solvents, and you get "safer".

also, they say that the electrolyte in a Lead acid (only for example) freeses Much faster when the battery is discharged. i have no idea if that applies.

dum notes: lithium chemisty cant be "wet" because lithium reacts with water.

 

[Curious_character]

That's a very interesting and well documented experiment. When you say you have been freezing batteries for years, has that included other Li-Ion cells, such as Pilas ? That would be an interesting test.

No. I'm new to Li-Ion cells -- it came with my recently acquired descent into flashaholism. I've stored only alkaline, NiMH, NiCd, and e2 litium primary cells in the freezer until recently.

I also have an infrared thermometer coming that I'm going to use to get an accurate freezer temp.

That should work reasonably well, but if you really want an accurate measurement you need to pay attention to the emmissivity of what you're looking at. Best is to have something flat black at the temperature you're measuring. I just took a quick sweep of several measurements with an Alltrade brand IR thermometer I picked up at Costco some years ago. It measured 3 - 9 F at various points, vs the 7 F reading from the thermocouple.[/QUOTE]

At first glance, it does look like there is something related to the AW cells.

That's how it looks to me, too. I have a smattering of other brands and a few unprotected cells, but not enough to come to any kind of statistical conclusion. My guess at this point is that there's some sort of mechanical failure -- solder connection, component end cap, or something like that -- in the protection circuit. I've seen plenty of temperature-related failures like that in my career.

c_c

 

[65535]

Maybe send them to someone who can do more accurate tests? :shrug:

 

[Curious_character]

And what in a battery (of any kind except discharged lead-acid) freezes at -14C?

the electrolyte in the li-ions should not be freesing at say around -20*F
I thought it was a volitile solvent type of electrolyte.

BUT, remember they have been "improving the safety" of the cells, take out more volitile flamable solvents, and you get "safer".

also, they say that the electrolyte in a Lead acid (only for example) freeses Much faster when the battery is discharged. i have no idea if that applies.

dum notes: lithium chemisty cant be "wet" because lithium reacts with water.

I don't know anything, really, about the chemistry of Li-Ion cells. But Sanyo says their cells can be stored down to -20C. There are a lot of places in the country where you can expect the inside of your car to get a lot colder than that on a winter night, so any cell that won't take it wouldn't be too useful.

The electolyte in a lead-acid battery is dilute sulfuric acid when the battery is fully charged, and it has a very low freezing temperature. I don't know what it is, but cars in Alaska do just fine. But the electrolyte gets more and more dilute as the battery discharges, becoming plain water when fully discharged. So the freezing point rises as the battery discharges. I recall a friend in Denver having his car battery freeze solid one winter -- it was an older car with a generator and he took more energy out of the battery each morning starting the car than got put back on the short drive to work. Eventually the combination of a cold night and discharged battery did the deed.

c_c

 

[Curious_character]

Maybe send them to someone who can do more accurate tests? :shrug:

I'll bet my thermocouple is easily good to one degree C. What level of accuracy do you think we need? What conclusion would you reach if the cells failed at precisely -14.3 degrees C rather than -14.0?

c_c

 

[SilverFox]

Hello Curious Character,

Based on what you have related to us, it is my wild guess that the circuit board, or a component on it, failed.

The cell should be fine.

If you are up to some testing, remove the shrink wrap and remove the protection circuit and wiring. Wrap some tape around the bare cell and try charging and discharging it again.

I have a couple of protected cells that acted the same way (however I did not have a brown stain). The cells were good, but the protection circuit was not.

Tom

 

[Tom M]

Late last year, I discovered had an AW protected 18650 fail that caused the white area around the + contact turn a brown red color. There was residue on the adjacent 18650 as well, and on the inside of the flashlight. I tossed both both batteries, and cleaned the light thoroughly. Although I did not think I drained these dead, they were in a light, so I couldn't rule out the possibility that it had turned on and drained them completely - which I would not do myself. I didn't know if the protection circuit would be expected to cut out at low voltage, or just protect against overcharge. In any case I assumed that I had expereinced a rare occurance that I had possibly caused myself, although I replaced the cells with PILAs, at a higher cost, but I've never had one leak.

At the time I did not make the connection, but the light with the cells in it was left in the car in December, and while the winter here has been relatively mild, it is likely that they were exposed to temps at or near the temp of your freezer. I wish I had investigated further at the time.

-Tom M

 

[Curious_character]

Hello Curious Character,

Based on what you have related to us, it is my wild guess that the circuit board, or a component on it, failed.

The cell should be fine.

If you are up to some testing, remove the shrink wrap and remove the protection circuit and wiring. Wrap some tape around the bare cell and try charging and discharging it again.

I have a couple of protected cells that acted the same way (however I did not have a brown stain). The cells were good, but the protection circuit was not.

Tom

Thanks! I didn't realize that the protection circuit was entirely outside the cell and under the shrink wrap. I disassembled one of the failed cells and removed the protection circuitry. As you (and I) suspected, the cell itself seems fine -- at least, it's charging normally now.

So all the comments about damaging the cell itself by putting it into the freezer are beside the point.

I took a look at the protection circuit board with an inspection microscope, and it's very noticeably corroded. I took a couple of pictures with a digital camera looking down the eyepiece -- here's what it looks like:

The circuit should be designed to take just a tiny amount of current to operate, so it probably wouldn't take much of a conductive path to make it malfunction. The combination of that crud and a little condensation or just humidity from the air could well be enough. I'll put the other malfunctioning cell in a warm spot for a day or two and see if it recovers. But even if it does, I won't be able to trust it anywhere but inside a warm house.

c_c

 

[Curious_character]

I've emailed AW the picture with the suggestion that he look into this.

c_c