# How long do average 18650 batteries last?



## HEDP (Jul 21, 2015)

I think I remember hearing that 18650 batteries last about 3-4 years. Is that correct?


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## cyclesport (Jul 21, 2015)

Think more in terms of charge cycles. Li-ions like shallow discharges as well as being dormant at approx 50%/60% of charge...hence it's not unheard of to see 18650s exceeding 2000 charges for lightly used, shallow discharged batt's. On the other hand routinely deeply discharged batteries seeing heavy loads might only last 300-400 cycles.


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## markr6 (Jul 21, 2015)

Also consider they don't like being charged full and sitting without use...and at high temperatures it's even worse. Ugh, I sure wish it could be a simple charge and forget. Actually, I may stop worrying about it so much given the cost (~$8/cell) and convenience of just charging and forgetting.


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## HEDP (Jul 21, 2015)

markr6 said:


> Also consider they don't like being charged full and sitting without use...and at high temperatures it's even worse. Ugh, I sure wish it could be a simple charge and forget. Actually, I may stop worrying about it so much given the cost (~$8/cell) and convenience of just charging and forgetting.




So how long do you think they'll last with not much use?




I'm a hunter. I use mine for a few times a year (hunting season) and that's really it.



I use my work one every week though.


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## HKJ (Jul 22, 2015)

HEDP said:


> So how long do you think they'll last with not much use?
> 
> 
> I'm a hunter. I use mine for a few times a year (hunting season) and that's really it.



Depends on how you store the batteries:
Partial discharge in a cool place: Long lifetime
Fully charged in a hot place: Short lifetime

It also depends on when you consider the batteries worn out. Batteries do slowly loose capacity and increase the internal resistance, i.e. a old battery may still work, but not for as long and not on full brightness.


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## HEDP (Jul 22, 2015)

HKJ said:


> Depends on how you store the batteries:
> Partial discharge in a cool place: Long lifetime
> Fully charged in a hot place: Short lifetime
> 
> It also depends on when you consider the batteries worn out. Batteries do slowly loose capacity and increase the internal resistance, i.e. a old battery may still work, but not for as long and not on full brightness.







Why do partially discharged last longer?


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## bdogps (Jul 22, 2015)

Where are you meant to dispose these batteries once they do not longer work?


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## HKJ (Jul 22, 2015)

HEDP said:


> Why do partially discharged last longer?



That is how LiIon batteries work (Sorry, I will not get into the chemical explanation).
When manufacturers ships LiIon batteries it is always in a partial charged state and lifetime is also specified in a partial charged state.

You can also see a bit about lifetime here: http://batteryuniversity.com/learn/article/how_to_prolong_lithium_based_batteries


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## Overclocker (Jul 22, 2015)

HEDP said:


> I think I remember hearing that 18650 batteries last about 3-4 years. Is that correct?




well some li-ion chemistries last longer than others. tesla uses "NCA" 18650 cells from panasonic. actively cools them. limits max voltage. limits charge rates (but still allows supercharging at specific charge levels). etc

warranty is 8 years even if used heavily. so there, your panasonic NCR18650-XX should last quite a bit if you take care of them. other "NCA" chemistry cells include samsung 25R, 29E, etc


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## 1DaveN (Jul 22, 2015)

bdogps said:


> Where are you meant to dispose these batteries once they do not longer work?



Not sure in AU, but you could start by checking two places: you might find that a home center that sells a lot of tools will accept rechargeable batteries for recycling (here in the US, Home Depot takes them). Or, your municipal recycling facility might either accept them or know who would. Ours accepts them, but only at certain days and times.


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## markr6 (Jul 22, 2015)

HKJ said:


> Depends on how you store the batteries:
> Partial discharge in a cool place: Long lifetime
> Fully charged in a hot place: Short lifetime
> 
> It also depends on when you consider the batteries worn out. Batteries do slowly loose capacity and increase the internal resistance, i.e. a old battery may still work, but not for as long and not on full brightness.



This is key. I left a flashlight in my car for almost 2 years and I don't think I used it once. It was almost fully charged, maybe 4.15v. When I checked it on occasion, it never dropped much...in the end maybe down to 4.11v. So losing charge is no concern to me (depends on the light, though). But the killer is the internal resistance. The other battery in this "pair" was kept indoors and also not used much, but it's resistance is now a good 30-40milliohms less than the one in the car.


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## Timothybil (Jul 22, 2015)

Does it really matter? If you are a heavy user and recharge every day, 500 charge cycles will mean a year and a half of use. Considering one 18650 is replacing two CR123 cells, at $0.75 each (large bulk purchase), one will have saved roughly $750 over that time, say $700 after subtracting the cost of the charger and the cell. If you are like me and recharge once every two weeks, then 500 cycles will last 20 years, at which time they will be long obsolete and have been replaced by something smaller, cheaper, and with a much higher energy density. Just sit back and enjoy the free lumens!


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## StorminMatt (Jul 22, 2015)

Timothybil said:


> If you are like me and recharge once every two weeks, then 500 cycles will last 20 years, at which time they will be long obsolete and have been replaced by something smaller, cheaper, and with a much higher energy density. Just sit back and enjoy the free lumens!



The calendar life of an 18650 is FAR shorter than 20 years. If you don't charge it much, it will die on you LONG before that.


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## Timothybil (Jul 22, 2015)

StorminMatt said:


> The calendar life of an 18650 is FAR shorter than 20 years. If you don't charge it much, it will die on you LONG before that.


I realize that. I was just trying to make the point that all this dithering about how long doesn't really mean anything. Pick up a Nitecore i2 charger and two 3100 mAh cells for under $40 USD, recharge them 25 times and you have recovered all your expenses. Everything after that is gravy. I wonder how many people actually reach 500 cycles, let alone 2000.


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## markr6 (Jul 22, 2015)

Timothybil said:


> I realize that. I was just trying to make the point that all this dithering about how long doesn't really mean anything. Pick up a Nitecore i2 charger and two 3100 mAh cells for under $40 USD, recharge them 25 times and you have recovered all your expenses. Everything after that is gravy. I wonder how many people actually reach 500 cycles, let alone 2000.



I'm OK with the math, but the OP, and myself, seem to let (some) lights sit for long periods of time which is the problem. They're just basically self-destructing.

Fully charge and have it ready to go? Charge to 4.05v and call it a compromise? Or keep stored at 3.6-3.8v and recharge before you know you'll need it? All a bit of a hassle to me, so I just try to stop caring and shoot for 4.10-4.15v and call it a day.

I didn't think it was a big deal until I used my external battery pack one day. I noticed it was only charging my cell phone about half as much as it used to. The two 2600mAh cells inside were getting pretty weak only after 18 months or so. I didn't RTFM so I missed the part where the manufacturer said to use it at least once monthly and keep it half charged when not in use.


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## 1DaveN (Jul 22, 2015)

markr6 said:


> I'm OK with the math, but the OP, and myself, seem to let (some) lights sit for long periods of time which is the problem. They're just basically self-destructing.



I've been thinking a lot about this. My normal practice would be to have a battery in the light, and another one fully charged and ready to go. But given the amount of time it would take me to deplete an 18650, the charged "on deck" cell would be getting trashed if stored fully charged.

So this is my current thought (no pun intended): Fully charge a cell and put it in the light. Charge another one to 60%. When the first one is ready to be swapped out, either bring the second one to full charge, or if necessary, use it until there is time to charge it fully. The depleted one would then get charged to 60% and become the "on deck" backup.

For the worst case scenario - low charge, backup at 60%, zombie apocalypse - I always keep some lithium primaries around.

Given the length of time it takes me to go through batteries, I've been perfectly happy using CR123As. What's got me considering 18650s is more disaster preparedness than budget, particularly considering 880 hours of run time for the CL25R lantern (with a 3400 mAh cell in moonlight mode). Between that and the PD35, with 150 and 38 hours at the two lowest settings, three or four 18650s gets me a pretty good run before I have to fall back to primaries.


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## WarRaven (Jul 22, 2015)

I'll charge whether seriously needed or barely needed every two days, and rotate last charged into lights for two days.
Rinse and repeat this only applies to edc.
Special lights an cells are a once a week or more if needed.

I Charge my phone every night, tablets and laptops, I get three good years, I'm OK with that.
None are drained, all top off's usually, there always high use time now and then.


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## Overclocker (Jul 23, 2015)

Timothybil said:


> I realize that. I was just trying to make the point that all this dithering about how long doesn't really mean anything. Pick up a Nitecore i2 charger and two 3100 mAh cells for under $40 USD, recharge them 25 times and you have recovered all your expenses. Everything after that is gravy. I wonder how many people actually reach 500 cycles, let alone 2000.




well i use hundreds of cells so making them last is a big deal


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