# How long do 18650's stay charged?



## Chippy_boy (Oct 8, 2013)

Hello folks, newbie here so please be gentle with me;-)

I have searched for an answer to this but no joy, hence me registering here. But I am new to LED torches and have bought a couple of Fenix torches to keep in the cars. I honestly don't think I will use them often, so 2x CR123A's may well do for both. But I am interested in. Trying 16850's instead for lower cost and longer output.

But this will be no use if when I come to use a flashlight in a few weeks/months, I find the battery is flat. I know the shelf life of Lithium primaries is excellent, but how about rechargeables? If I can rely on them holding their charge (unused) for say 3 to 6 months, that would fine. But if it's shorter than that, maybe I should stick to 123a's?

Thanks for your advice.


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## TEEJ (Oct 8, 2013)

The good ones seem to hold full charge for many months...6 months is about as long as I've let any sit though before using/cycling them....but at 6 months they are still at full charge.


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## LilKevin715 (Oct 8, 2013)

http://batteryuniversity.com/learn/article/elevating_self_discharge/

Id say 3 to 4 months would be fine. Any longer than that I'd recommend using CR123's. Also for any type of light that is stored for many months (e.g. 6+) its preferable to not have a light with parasitic drain (e.g. electronic switches). Tailcap lockout (if possible) should be done for storing lights with parasitic drain and to prevent accidental activation.


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## Chippy_boy (Oct 9, 2013)

Thanks guys - appreciate the guidance. I have to confess I am undecided on CR123A's vs 18650's. I like the idea of the rechargeables, but since I don't plan on using these torches day to day, not sure it would be worth it.

What I want to avoid is some emergency situation happening with my wife alone in her car, she reaches for the flashlight in the glovebox and finds that it doesnt work, or that she has to fiddle with it in the dark to get it to work.

Regards parasitic drain, is this bad for a li-ion rechargeable? Or does it just mean it goes flat over time. If the latter, I can live with that because periodically I can just take them out and recharge. But if it's going to impair the batteries' performance, then clearly the end cap lockout is needed.


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## markr6 (Oct 9, 2013)

Good question. I had the same concerns recently; here's what I've decided to do.

I leave a PD32UE in my car but don't find myself using it often. But I leave an 18650 in it because WHEN I use it, I want to be able to recharge it afterwards instead of throwing $5 worth of batteries back in. Plus, I want to KNOW I'm going out with a 90%-100% charge the next time I use it instead of using half-dead CR123s, wondering when I'll need to replace them, again.

But just to be safe, I do keep an unopened package of CR123a in my car as well. This way, I'm covered if my 18650 fails of if I simply use it all up.

The 18650 that has been in my car all summer seems fine. If the heat ends up shortening it's life, no big deal - I'll be replacing it after awhile anyway.


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## Chippy_boy (Oct 9, 2013)

markr6 said:


> Good question. I had the same concerns recently; here's what I've decided to do.
> 
> I leave a PD32UE in my car but don't find myself using it often. But I leave an 18650 in it because WHEN I use it, I want to be able to recharge it afterwards instead of throwing $5 worth of batteries back in. Plus, I want to KNOW I'm going out with a 90%-100% charge the next time I use it instead of using half-dead CR123s, wondering when I'll need to replace them, again.
> 
> ...



Hmmm, thanks Mark - I really like that idea. Go with 18650 and charge it immediately after use. Plus CR123A's as back up just in case - they are sure small enough aren't they.

I will do just what you recommend!


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## tonkem (Oct 9, 2013)

markr6 said:


> Good question. I had the same concerns recently; here's what I've decided to do.
> 
> I leave a PD32UE in my car but don't find myself using it often. But I leave an 18650 in it because WHEN I use it, I want to be able to recharge it afterwards instead of throwing $5 worth of batteries back in. Plus, I want to KNOW I'm going out with a 90%-100% charge the next time I use it instead of using half-dead CR123s, wondering when I'll need to replace them, again.
> 
> ...



I am also considering an 18650 light for my wife to keep in her car.. I currently have a 2 x 123 light in her car, and have kept it in the glove box in hot Texas summers, without issue(as I do the same with my lights that I keep in my car). Can the 18650 batteries (assuming good ones, like zebralight, eagletac, etc) take the heat of texas summers, or should she keep the 18650 in her purse and leave the 123 lights in the car?

Thanks, and sorry if this has already been addressed in another forum.


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## markr6 (Oct 9, 2013)

tonkem said:


> I am also considering an 18650 light for my wife to keep in her car.. I currently have a 2 x 123 light in her car, and have kept it in the glove box in hot Texas summers, without issue(as I do the same with my lights that I keep in my car). Can the 18650 batteries (assuming good ones, like zebralight, eagletac, etc) take the heat of texas summers, or should she keep the 18650 in her purse and leave the 123 lights in the car?
> 
> Thanks, and sorry if this has already been addressed in another forum.



No problem. This question gets kicked around every so often.

It just depends on your usage really. If it's not getting used much, and even when it does if it's only for a minute here or there, then I would say CR123 since they handle the extreme temps and the shelf life is LONG. The 18650s don't like to sit charged for a long period of time, and the heat isn't great for them, but I continue to use them since I'm addicted to rechargeables  If you're talking about two lights (purse and car), I would recommend the situation you mentioned above (123=car, 18650 purse)


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## hunterblue (Oct 21, 2013)

Hi,

For all lithium-ion batteries or secondary rechargeable cells, the storage temperatures and state of charge make all the difference.

Most lithium-ion cell manufacturers recommend a storage temperature of between 0°C and 45°C and base the storage numbers on state of charge (SOC) or degree of discharge (DOD) in that range.
A fully charged (100% SOC or 0% DOD) bare cell will lose around 5% charge and 2% recoverable capacity in 12 months. 
A fully discharge (0% SOC or 100% DOD) bare cell will lose <1% charge and <1% recoverable capacity in 12 months.

Any circuitry attached to the cell will also cause a slight drain on the cell (protection circuitry or if its in a flashlight) which can affect the storage time as well.

Chemistry of the lithium-ion cell will also make a difference. ICR or cobalt based cells tend to store better than the other chemistries like IMR or Manganese based cells.

Extremes of temperature will also cause some storage issues, most notably increasing the internal resistance of the cell and an increase in capacity loss. (both retained and recovered.)

Age of the cell will also make a difference, cells that have a considerable amount of cycles on them will also age faster than fresh new cells.

I would say that if you are using this for an emergency light, top up the cells every six months and you will be fine.

HB.


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## Gauss163 (Oct 21, 2013)

@hunterblue Those numbers differ greatly from most sources. Compare for example the table at http://batteryuniversity.com/learn/article/how_to_store_batteries, which estimates the recoverable capacity of LiCo stored for one year at 100% charge, as 94% (at 0C), 80% (at 25C), 65% (at 40C), and when stored for one year at 40% charge as 98% (at 0C), 96% (at 25C), 85% (at 40C), viz.


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## hunterblue (Oct 21, 2013)

@Gauss163, you are correct that my numbers are different than those of battery university, but that data is pretty old, cobalt cells have come along way since those numbers were put on the internet. Also the chart shows recoverable capacity, not charge lost, i've seen data that shows the major manufacturers cobalt cells to perform much better than the chart describes, but again, everything is not absolute and there are many factors that can affect individual cell performance and storage, including temperature, state of charge, manufacturer and so on.

I think it is easy enough to agree that lithium-ion cells store very well and if they are bare cells you could easily store them for six months and not worry about them too much.

HB.


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## markr6 (Oct 22, 2013)

hunterblue said:


> @Gauss163, you are correct that my numbers are different than those of battery university, but that data is pretty old, cobalt cells have come along way since those numbers were put on the internet. Also the chart shows recoverable capacity, not charge lost, i've seen data that shows the major manufacturers cobalt cells to perform much better than the chart describes, but again, everything is not absolute and there are many factors that can affect individual cell performance and storage, including temperature, state of charge, manufacturer and so on.
> 
> I think it is easy enough to agree that lithium-ion cells store very well and if they are bare cells you could easily store them for six months and not worry about them too much.
> 
> HB.



Yeah I don't trust that chart anymore. I recovered two 18650s from an external cell phone battery pack. Something about the circuity made it stop working but the batteries were still good. This left me with two batteries I really didn't need (more batteries than lights). So I decided to charge them up and let them sit, measuring the voltage every few days or weeks as a test. It's been at least 4 months and they're still nearly 100% charged. These were stored around 71°F (21°C).

I've also had a torch with an 18650 in my Jeep's door pocket over the summer - easily 120°F+ in there in the parking lot all day long. I only used it a few minutes here and there. It's still well over the 60%-65% the chart suggests.


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## Gauss163 (Oct 22, 2013)

@hunterblue I'm not aware of any studies that report only a 2% capacity loss after storing for one year a fully-charged Li-ion battery between 0°C and 40°C. It would be difficult to attain that even in the best possible case: _a constant_ storage temperature of 0°C. At 40°C, most studies report much higher irrecoverable capacity loss - similar to the 35% capacity loss quoted in said table from BatteryUnversity. See for example the extensive studies at JPL etc for the NASA Mars missions (which make very interesting reading). And see any support forum for a major laptop manufacturer for many thousands of complaints from users whose batteries have died in around a year's time after being stored at *full *charge in* hot* laptops, i.e. with both major governing *parameters* at their worst possible values (this has been partly alleviated in the past few years, not primarily by improvements in battery technology but, rather, by improvements in laptop technology - generally they now run cooler and, further, they are now often configured with "battery saver" software that allows the user to specify charge termination levels lower than 100%).


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## hunterblue (Oct 22, 2013)

% State of charge23°C Constant Temperature
28 Days3 Months6 months12 months100%%Retained97.6%95.9%94.6%92.5%100%
%Recovered99.2%99.1%98.4%97.9%50% (ship state)%Recovered99.9%99.7%99.2%99.4%0%%Recovered100%100%100%99.9%


Here's a slide from a presentation that I have on a major manufacturer's 2.6Ah cobalt cell storage capability. (Tried to copy and paste but realized that dosent work so I recreated the table, not as colorful as the original but the data is the same.)

I cannot say who's cell this is, but I see that all the major cell manufacturer's data to be about the same.

Now I'm not saying this is concrete proof, I would take this with a grain of salt as it is the cell companies own data and marketing material but it is marked confidential so even if the retained and recovered were twice as bad its still not the 35% that you quote.

HB.


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## Gauss163 (Oct 23, 2013)

@HB Those are quite impressive claims for recoverable capacity. I confess I am a bit skeptical since these numbers are about an order of magnitude improvement over widely reported figures. I'm more inclined to believe that these figures are marketing hype - inflated in the same manner that many Chinese manufacturers inflate capacity ratings. But I'd love to be proved wrong. Do you know any references to publicly accessible documents supporting these claims?


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## markr6 (Oct 23, 2013)

hunterblue said:


> % State of charge
> 23°C Constant Temperature
> 28 Days
> 3 Months
> ...



Those seem to be closer to the results on the two 18650s I currently have testing on my shelf. I'll try to continue the test through a year to see how they hold up. I have more 18650s than I really need, so I don't mind if I need to junk them later on.


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## Timothybil (Dec 29, 2013)

*How long will an 18650 stay charged?*

I've been using primaries in my TM11, which I don't use that much. But once in a while #1 son borrows it, with the usual result of dead batteries. Since I'm getting tired of spending $15+ every time I replace the batteries, I'm seriously considering switching to 18650s. My big question is, how long will an 18650 hold a charge when it is not in use?

Thanks in advance for any advice you can give!


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## Max Ohms (Dec 29, 2013)

*Re: How long will an 18650 stay charged?*

Here is a testimony to how well the older Panasonics hold a charge:

I purchased a case of CGR18650 CG's made in 2008.

Every single one I took out of the box so far (about 15) are at 3.66 volts.

I do not yet know what they left the factory at 5 years ago.

I have cycled several of them through lights with single and triple XM-L T6 LED's and they are getting very close to the 3100 run times, especially considering the cost difference.


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## Norm (Dec 29, 2013)

*Re: How long will an 18650 stay charged?*



Max Ohms said:


> Every single one I took out of the box so far (about 15) are at 3.66 volts.
> 
> I do not yet know what they left the factory at 5 years ago.


Should have been somewhere around 3.8V.

Norm


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## Max Ohms (Dec 29, 2013)

*Re: How long will an 18650 stay charged?*



Norm said:


> Should have been somewhere around 3.8V.
> 
> Norm



So..........a loss of about .14 volts in about 5 years.

.......or about a 3.6842105263% loss

........or .7368421053% per year

........power when you need it!


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## torukmakto4 (Dec 29, 2013)

*Re: How long will an 18650 stay charged?*

Actually, CGR18650CG is not a LiCo. That is the PTC equipped version of the CGR18650CH which is used in high current apps up to 10A continuous (no PTC). It's a hybrid cell, NMC, I forget what Pana document mentioned that but it's out there somewhere.

Storage charge for Li-ion is 40-50% SOC and for nickel based hybrids that is around the range of the 3.66V you mentioned, not 3.8V, which is for LiCo (and I assume IMR which has similar voltage behavior). New NCRs and power tool cells (also non-LiCo chems) are always coming at similar voltages in my experience, regardless of age. Most likely Pana shipped those cells under 3.7V. I would bet money it was 3.67.

So I think you have an even better result here.

Runtime result is expected if the light is one of those that can't use the NCR cells' capacity at low voltages (half of that 3100 is below circa 3.4V at 3A and linear/buck lights with many emitters are thus going to start dimming when the NCR is half empty, and if there is a PCB it's potentially worse by significant margin because of how little voltage you have to spare). The CH/CG cell is 2250mAh and has a flatter/more favorable discharge curve than the NCR, and a low IR.


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## Max Ohms (Jan 7, 2014)

*Re: How long will an 18650 stay charged?*



torukmakto4 said:


> Actually, CGR18650CG is not a LiCo. That is the PTC equipped version of the CGR18650CH which is used in high current apps up to 10A continuous (no PTC). It's a hybrid cell, NMC, I forget what Pana document mentioned that but it's out there somewhere.
> 
> Storage charge for Li-ion is 40-50% SOC and for nickel based hybrids that is around the range of the 3.66V you mentioned, not 3.8V, which is for LiCo (and I assume IMR which has similar voltage behavior). New NCRs and power tool cells (also non-LiCo chems) are always coming at similar voltages in my experience, regardless of age. Most likely Pana shipped those cells under 3.7V. I would bet money it was 3.67.
> 
> ...



Do you know the difference between the CGR18650CG's with the 5 rows of dots (inked) around rim and the CGR18650CG's with just the single bar?

Thanks!
Russell (Max).....or Justin Case!


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