li-ion cells stored at full capacity

[berry580]

Hi, I've often heard about li-ion cells ideally should be stored somewhere between full charge and minimum charge, something like 3.8V
The apparently the consequence of not doing so is permanent damage to the li-ion cell resulting in lower future maximum charge it can hold.

My question:

If I keep the li-ion at 4.2V (fully charge), what's the rate of degradation? 10% a year @ 20 degrees, 20% a year @ 20 degrees?
Also, aside from the permanent loss of capacity, would there be any other dangers (e.g. explosions)?

I'm asking this question is because I'm interested to use li-ion has back up cells due to a number of advantages IMO, including high energy density and low discharge rate.

Even if the cells suffers from permanent damage, i think its worth it. If you think about it, the L92 etc lithium cells are ~$10 a pair, that's pretty much what the 18650s cost in DX, but these li-ions can be recharged and has much greater maxiumum capacity.

 

[CaseyS]

The temperature you store them at has a bigger effect than the charge level:

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

 

[berry580]

thank you.

At 25 degrees with 100% charge, it discharges to 80% in a year. That sounds pretty OK.
But you just need to replace the batteries in every 2-3 years.

 

[CaseyS]

It doesn't discharge to 80% in 1 year, it permanently loses 20% of its capcity in one year.

 

[45/70]

At 25 degrees with 100% charge, it discharges to 80% in a year. That sounds pretty OK.
But you just need to replace the batteries in every 2-3 years.

When a LiCo Li-Ion cell charges to less than 80% of it's original capacity (ie. it is charged to 4.20 Volts (100%) and when rested, the voltage drops to < 4.00 Volts (<80%)) the cell should be discarded/recycled. The chemistry in the cell can become unstable. This is one condition where the cell could "vent with flame" during storage. As I understand it, it's pretty rare, but why take a chance? Anyway, I'd replace the cells once a year (after checking, of course) under those conditions.

I have always stored my Li-Ion cells, that were not in use, in the fridge at 2-5C/35-40F. In my early days of Li-Ion usage (2005) I stored them at 100% charge. Most of the cells I've obtained since, and the older ones as well, I now store at ~40% charge (~3.80 Volts).

This is by no means a scientific study, but I still have every Li-Ion cell I ever purchased (about 60), 4+ years later. Some will drop to 4.06 Volts when charged to 4.20 Volts and rested. These are, the older cells that were stored at 100% charge for a time, but then again, they've more than likely been used more, as well. So, from my experience, I have no reason to doubt the accuracy of the chart on BU.

I don't have any experience with storing Li-Ion cells at room temperature to compare, but as CaseyS said, I believe temperature probably does have more effect on degradation than state of charge. There seems to be little difference between 40% and 100% SOC, when the cells are kept in the fridge. Just the same, I do store them at ~40% SOC anymore.

Dave

 

[tino_ale]

Loosing permanently 20% of a battery capacity just because of storage is definetely NOT ok for me

About 3.80-3.85V (about 40% of SOC) is said to be the best bet; in a zip lock and placed in a fridge (not freezing though).

Let the pack/cell get back to room temperature before opening the zip lock.

 

[J_C]

How about just storing them in a waterproof flashlight in the fridge? That seems more convenient if reasonable, then you don't have concerns about exposing cold cells to condensation when removed from the fridge, have a flashlight ready to use in an emergency though I suppose it's a drawback that if power goes out you don't want to be unnecessarily letting heat into the fridge by opening it more than necessary.

 

[firefly101]

Hello.

I dont know about individual cells but with laptop batteries which I used and studied, Keep your Lithium Ion battery charged at 30% when not in use. this will create a much longer lifespan and have more full capacity. When you increase it or do a full charge it will lower the capacity of the battery. Its not worth it unless you have a pile you dont mind replacing?

This is why on Ebay you can get VERY OLD lithium Ion batteries that hold a great charge and newer batteries that die fast. It was all on HOW they were used and stored.

Hope this helps,

Firefly101

 

[VidPro]

This is why on Ebay you can get VERY OLD lithium Ion batteries that hold a great charge and newer batteries that die fast. It was all on HOW they were used and stored.

Firefly101

and also the original quailty of the battery. some cheap junk new batteries dont last , because they have cheap junk cells in them, and that is happening more and more.
some older stuff is still working "ok" because if it is STILL working it was built with good cell items , And as you mentined treated properly.

-----------------
you can go buy cruddy cells , and treat them like Kings, and they will still die sooner than good cells do :-(.

 

[palomino77]

How about just storing them in a waterproof flashlight in the fridge? That seems more convenient if reasonable, then you don't have concerns about exposing cold cells to condensation when removed from the fridge, have a flashlight ready to use in an emergency though I suppose it's a drawback that if power goes out you don't want to be unnecessarily letting heat into the fridge by opening it more than necessary.

I was thinking of a sealed air tight small plastic bag, inside a air tight jar inside the freezer. Would this be OK? For the extras that aren't in use :thinking:

 

[rushnrockt]

some older stuff is still working "ok" because if it is STILL working it was built with good cell items , And as you mentined treated properly.

They might have been charged to lower voltages (4.1V vs. 4.2V) which would also increase the lifespan of a battery.

 

[Justintoxicated]

I have never worried about this. I charge my laptop to 100% because when I need to grab it to go I don't have time to sit and let the battery charge. That defeats 1/2 the purpose in having a battery! I'm also not about to unplug it every time it reaches 80% or unplug the battery and plug in the power cable.

100% charge here if the battery goes bad I will Just replace it. it has been going strong for 2 years now and shows no signs of decay.

I have SEVERAL Pila 150A 18500 lithium cells that I have never worried about storing them at a certain temperature or charge capacity. Charge them up and use them as needed. They are several years old now.

I don't plan on rechargeable batteries for my emergency flashlights, mostly put them in lights I use at least somewhat frequently. Otherwise whats the point in using rechargeable batteries? I guess its good to know that if you have a ton of cells to store them at 80% or 30% or whatever if possibble. But I don't think I would ever be bored enough to sit and discharge each one of them to 80% after fully charging them.

 

[Nite]

20% loss of capacity? not just charge? wow

I hadnt realized that I would lose 1/5th my power forever by storing at room temp for a year...at 100%

Refrigerator huh?

 

[Julian Holtz]

Hi!

I converted my RC transmitter to LiIon cells in 2006. I always store it fully charged. The capacity has gone down from 2000 to 1600 mAh by now. However, I only charge the cells to 4.1V, and I never drain them completely.

 

[45/70]

I was thinking of a sealed air tight small plastic bag, inside a air tight jar inside the freezer. Would this be OK? For the extras that aren't in use :thinking:

I'm not sure about some of the other chemistries, but LiCo cells really shouldn't freeze. Some of them, if exposed to temperatures below 4 F, can damage the separator. So, I guess it would depend on your freezer, but I wouldn't do it. I store my Li-Ion cells (LiCo and LiFe) that are not in service, in my fridge @ 35-40 F.

Dave

 

[palomino77]

I'm not sure about some of the other chemistries, but LiCo cells really shouldn't freeze. Some of them, if exposed to temperatures below 4 F, can damage the separator. So, I guess it would depend on your freezer, but I wouldn't do it. I store my Li-Ion cells (LiCo and LiFe) that are not in service, in my fridge @ 35-40 F.

Dave

Thank you. :thanks:
I have a whole bunch of air-tight containers. I will charge to 3.85 v and store in fridge. :thumbsup:

After taking out of fridge do you have to let them reach room temp before opening up container to avoid condensation?

 

[45/70]

After taking out of fridge do you have to let them reach room temp before opening up container to avoid condensation?

I store my cells in Ziploc bags. I don't know how humid it is in Guadalajara, but here, it's always humid enough to cause condensation, especially in the Summer. What I do is take the cells out of the bag and put them in my pants pocket for a few minutes. If I take more than a few cells out, I spread them out on a terrycloth towel and roll them around a bit, until they're warmed up.

Ultimately, I suppose if you put a desiccant in with the cells, you could do as you say, and just let them warm up in the bag/container. The problem for me is, I never have any around. The "pocket method" seems to work well for me, and if your in a hurry, it's also somewhat faster.

Dave

 

[J_C]

There is no need for a desiccant in the bag if you leave the bag sealed till they warm up. That way, the only moisture present is the little bit that was already in the bag (assuming bag mostly evacuated of excess air before sealing).

It doesn't take long for them to warm up enough, wrapping a bare hand around each it'd be less than a minute.

 

[45/70]

There is no need for a desiccant in the bag if you leave the bag sealed till they warm up.

That's for the most part probably true. In my own experience however, no matter how hard I try to get all the air out, if I let them warm up in the Ziploc, moisture usually condenses on the inside. Again, it's humid here.

If I used a solid container the problem, I'm sure, would be worse, as there is no way to get any of the air out. I'd say in this case, a desiccant would be a really good idea. If you live in Arizona, well, I wouldn't be to concerned about moisture. It may very well be that in Guadalajara, the situation is the same. I have no idea.

Dave

 

[palomino77]

That's for the most part probably true. In my own experience however, no matter how hard I try to get all the air out, if I let them warm up in the Ziploc, moisture usually condenses on the inside. Again, it's humid here.

If I used a solid container the problem, I'm sure, would be worse, as there is no way to get any of the air out. I'd say in this case, a desiccant would be a really good idea. If you live in Arizona, well, I wouldn't be to concerned about moisture. It may very well be that in Guadalajara, the situation is the same. I have no idea.

Dave

I was thinking of wrapping in dry paper towel before putting in container to absorb moister after taking out of fridge. Moister in Guadalajara is about normal right now it is 33% http://weather.yahoo.com/mexico/jalisco/guadalajara-124162/

these are the containers: http://www.lighthound.com/Lighthoun...batteries-or-4-x-CR-123-batteries_p_2803.html


Thanks