How long do 18650s last if always charged at 4.20v?

How long do 18650s last before they degrade if always charged at 4.20v?

For example, I have a new Thrunite TN30 Mini, I use it often but I end up keeping the 4x18650 cells inside fully charged at 4.20v. In the case I need it, or when I go out and need the max life, which is pretty much daily.

I wouldn't mind getting new cells yearly, but don't want any premature wear.

Any help, opinions, suggestions, and I'd be deeply grateful.

Years from my experiences and have many lights and cells . If I am not using a light for a while or plan on not using, cells will be stored at 3.6/3.7v . Lights that get use within a week are fully charged.

As you use the light often it's a none issue, by charging them after use due to it being regular, they are not full charge cycles. For example a deep charge cycle maybe bellow or around 3v back up to 4.2v, from say 3.7v it's a part cycle. 3 part cycle may = a full cycle what the battery is rated for. (Rough example).

My work lights are used daily and topped up pretty much most days.....for years! Still using same cells, still charging to 4:18-4.20v (slight variation on charger used).

Maybe another matching 4 cells if not already and rotate them, fresh in and top the other set up and repeat, this way never without the light.

Enjoy!

I agree with ven. Use em! If you want a little peace of mind you could always charge up to 4.15v, but that's only if you're going to let the light sit for longer periods. For your use, I say charge them full. I bet the only way you would KNOW that you were not getting 100% out of them would be comparing them in a test with a new set.

300-500 cycles according to the guide in the link below.

But as the battery`s are easily replaceable and not built-in, just use them and don't worry about how many cycles you will get.

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

John.

I always keep my batteries fully charged. I recently bought an Opus 3100 charger and did a charge test on a 4 year old protected AW 3100mAh 18650. One of my first batteries. It had a result of 2909mAh. Not bad for a 4 year old cell with many dozen cycles always stored fully charged.

msim said:

I always keep my batteries fully charged. I recently bought an Opus 3100 charger and did a charge test on a 4 year old protected AW 3100mAh 18650. One of my first batteries. It had a result of 2909mAh. Not bad for a 4 year old cell with many dozen cycles always stored fully charged.

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That's pretty good. You also have to consider the internal resistance as well. It could be really high, but the affect that has depends on what you're using the cell in. A 1x18650 light pulling 300mA = not a big deal. But in a highly driven light pulling 6A, not a good application.

TinderBox (UK) said:

300-500 cycles according to the guide in the link below.

But as the battery`s are easily replaceable and not built-in, just use them and don't worry about how many cycles you will get.

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

John.

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That's one of the rare cases where BatteryUniversity backs up their often dubious claims with a link to the research literature. But the study cited is so old (2002 Choi et al) that's its relevance to modern cells is questionable. Ditto for the old NASA studies that are often cited here.

Generally if you seek data like this on modern cells then you will have to do your own tests, because few if any such test results are currently in the public domain.

Again, Battery University is not a good place to look for accurate, up-to-date knowledge on Li-ion battery technology. It's a collection of random excerpts that the author has culled from all over the web, most of it not vetted against current research literature.

markr6 said:

That's pretty good. You also have to consider the internal resistance as well. It could be really high, but the affect that has depends on what you're using the cell in. A 1x18650 light pulling 300mA = not a big deal. But in a highly driven light pulling 6A, not a good application.

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Very true! If I had to guess, this cell was usually run about 50% of the time at a ~700ma medium and the rest of the time between 1.5a and 3a, rarely higher than that.

Gauss163 said:

That's one of the rare cases where BatteryUniversity backs up their often dubious claims with a link to the research literature. But the study cited is so old (2002 Choi et al) that's its relevance to modern cells is questionable. Ditto for the old NASA studies that are often cited here.

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Thank you! I always hated seeing people reference that site. And the military research that was older than dirt, among others.

You right it is old, but a lot of it is still useful to no pro cell users, and i don't see anybody else posting any newer information, please provide some links i would love to read them, and others might find them interesting as well.

thanks

John.

Gauss163 said:

That's one of the rare cases where BatteryUniversity backs up their often dubious claims with a link to the research literature. But the study cited is so old (2002 Choi et al) that's its relevance to modern cells is questionable. Ditto for the old NASA studies that are often cited here.

Generally if you seek data like this on modern cells then you will have to do your own tests, because few if any such test results are currently in the public domain.

Again, Battery University is not a good place to look for accurate, up-to-date knowledge on Li-ion battery technology. It's a collection of random excerpts that the author has culled from all over the web, most of it not vetted against current research literature.

Click to expand...

TinderBox (UK) said:

You right it is old, but a lot of it is still useful to no pro cell users, and i don't see anybody else posting any newer information, please provide some links i would love to read them, and others might find them interesting as well.

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I'm not aware of any newer studies in the public domain that incorporate the many advances since then. Qualitatively the results still hold because generally the same degradation mechanisms are work - governed by basic electrochemistry. But quantitatively the old studies may be way off due to recent improvements, so it doesn't make sense to attempt to apply the same numbers to recent cells.

Further, the studies may not apply if your use does not closely match the test protocol, e.g. are the cells discharged immediately after they are charged or are they stored for some nontrivial amount time before use? This and many other parameters play a large role in calendar/cycle life. One can accurately extrapolate from such studies only when all of the relevant parameters are properly taken into account.

A few years ago I saw a reference to (IIRC) Lenovo, who claimed that charging to 95% capacity greatly increased overall battery life. The article mentioned an option to charge to 95%. Don't have more details, it's been a while.

I have seen lots of laptops used as desktops (always plugged in) and the packs do lose capacity over time. I got a couple packs at work, cells in one were about 1 amp-hour, the other was 200 mah. We cycle laptops every few years so these weren't real old packs.

I only charge my Samsung Tab S1 10.5" to 80% and dont discharge below 20% i have only charged it to 100% 3 times in 18 months just to calibrate the battery gauge and i use my tablet every day, my brother-in-law bought the same tablet a month after me and his battery just died, luckly it was still in warranty.

I do the same with my HTC M7 as the built in battery is the worst in the world to replace without the correct tools.

John.

TinderBox (UK) said:

I only charge my Samsung Tab S1 10.5" to 80% and dont discharge below 20% i have only charged it to 100% 3 times in 18 months just to calibrate the battery gauge and i use my tablet every day, my brother-in-law bought the same tablet a month after me and his battery just died, luckly it was still in warranty.

I do the same with my HTC M7 as the built in battery is the worst in the world to replace without the correct tools.

John.

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I have a 6 year old Samsung netbook, which have a function to charge up to 80%, and almost never discharge to 0 and when not in use or plugged in, I store the battery charged from 30-40%, and it's still as good as new, lasting as always (4-5 hours more or less).The battery reports 21% wear level but I still think is a bogus value.

Meanwhile, my father has a slightly older (also Samsung) Laptop, always charged to 100% and never used (always plugged in) and now barely lasts 30 minutes on battery with 70% wear level. Maybe it was bad from beginning, I don't know.

And I always try to avoid to charge my Huawei Y6 to 100%, even if it has a removable battery, as well as my portable chargers

derek10 said:

I have a 6 year old Samsung netbook, which have a function to charge up to 80%, and almost never discharge to 0 and when not in use or plugged in, I store the battery charged from 30-40%, and it's still as good as new, lasting as always (4-5 hours more or less).The battery reports 21% wear level but I still think is a bogus value.

Meanwhile, my father has a slightly older (also Samsung) Laptop, always charged to 100% and never used (always plugged in) and now barely lasts 30 minutes on battery with 70% wear level. Maybe it was bad from beginning, I don't know.

And I always try to avoid to charge my Huawei Y6 to 100%, even if it has a removable battery, as well as my portable chargers

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That's why I love Lenovo thinkpads. You can set custom start an stop charging thresholds to preserve the battery. I set my 8 years old W500 (used mainly on AC power) to start charge the battery only if <40% and stop at 70%. After 8 years and 88cycles the (panasonic) battery report still 70% of the original charge capacity.

I have had an few notebook with the battery saver, I just wish phones and tablets with built in battery`s had this feature, I use an app to sound an alarm at 80% when charging, but i have to manually remove the charging cable.

John.

kappa7 said:

That's why I love Lenovo thinkpads. You can set custom start an stop charging thresholds to preserve the battery. I set my 8 years old W500 (used mainly on AC power) to start charge the battery only if <40% and stop at 70%. After 8 years and 88cycles the (panasonic) battery report still 70% of the original charge capacity.

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kappa7 said:

That's why I love Lenovo thinkpads. You can set custom start an stop charging thresholds to preserve the battery. I set my 8 years old W500 (used mainly on AC power) to start charge the battery only if <40% and stop at 70%. After 8 years and 88cycles the (panasonic) battery report still 70% of the original charge capacity.

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Mine is not as customizable (only the 80% option, no way to change the max charging nor set a minimum threshold to start charging) but when I expect not to use the battery anytime soon, I discharge it to 40% or sometimes less and take out of the netbook and use it only on mains, to keep it away from heat and self-discharge (even when off, laptops tend to draw power, most likely due to CMOS or USB ports). Twice the battery overdischarged because I left it empty, and the netbook refused to charge it, charging led blinking red/green and saying 0 plugged it not charging, but eventually started charging it, phew

I have had a few Lenovo notebooks and i like them, though i don't like how when you clone the hdd to ssd or larger hdd the recovery partition no longer works, I have had all brands of notebooks and Lenovo is the only one that has this problem.

Also Lenovo is a Chinese company a couple of years ago it was discovered they had put spyware on the notebooks at the factory transmitting data back to Lenovo what about i don't know, they had to apologise when they were found out and release a tool to remove it.

John.

kappa7 said:

That's why I love Lenovo thinkpads. You can set custom start an stop charging thresholds to preserve the battery. I set my 8 years old W500 (used mainly on AC power) to start charge the battery only if <40% and stop at 70%. After 8 years and 88cycles the (panasonic) battery report still 70% of the original charge capacity.

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TinderBox (UK) said:

Also Lenovo is a Chinese company a couple of years ago it was discovered they had put spyware on the notebooks at the factory transmitting data back to Lenovo what about i don't know, they had to apologise when they were found out and release a tool to remove it.

John.

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Lenovo is the computer division that IBM sold off 5-6 years back. You can't trust anyone in the computing world not to spy on you. Samsung got caught spying using net connected smart TV's.

I am glad my 3D 55" Samsung was the last generation that came without the webcam and microphone, it still does not stop Samsung knowing what tv programs you are watching if you are internet connected (though in my case it`s mp4 movies) as i have not seen live tv in quite a few years.

John.

NoNotAgain said:

Lenovo is the computer division that IBM sold off 5-6 years back. You can't trust anyone in the computing world not to spy on you. Samsung got caught spying using net connected smart TV's.

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