What counts as a cycle for Li-Ions?

[eyeeatingfish]

The rechargeable lithium ion batteries are often rated at 500 charges or so. Some brands claim 1000.
Its also said that lithium ion batteries do well with being put into the charger often.
With this im wondering what counts as 1 cycle? If you use 25 percent of the battery then recharge it then 50 percent then recharge it does this count as 2 cycles?
Reason why im asking is that im rating possible police flashlights. And if a police officer working at night uses his light 10 separate times for 5 minutes each and throws it into the car charger between each time than has he just used up roughly 10 cycles in one day? This would mean that the battery would only last a few months.

Thoughts?

 

[offroadcmpr]

I am curious too, partly because I was wondering something similar with my cell phone. Would the battery last longer if I charged it every night, or only when it died?

 

[mdocod]

It's tough to nail down for various reasons.

Lets think of the cycle life in terms of how much energy is cycled through the cell through it's life.

A routine discharge depth in the 60-80% range (approximated)(20-40% remaining), should result in the highest possible quantity of energy that can be cycled through the cell before the cell is worn to the point of needing to be replaced.

In either direction away from this target range, the cells total "energy cycled" before recycle time, would be reduced by some amount. But the number of total shallow cycle possible should increase.

Shallower cycles would be considered less of a "full" cycle than deep discharges against the cells life. But it would not be a direct conversion I don't think.

Very deep discharges, like repeatedly pushing the cell to ~3V or less, would most likely result in even less cycle life than advertised on most cells.

As I understand, most Li-Ion cells, are manufacture rated based on 80% depth of discharge for cycle life. So routinely discharging below 20% capacity will reduce cycle life of the cell below the manufactures suggested cycle life...

Here's something to consider for a shallow cycled setup:
LiCo is least self-destructive when stored around 3.8-4.0V. I would assume, with great confidence, that if one were to somehow shift their shallow cycles into this voltage range, then the cycle life of the cell would likely be improved as compared with cycling at the top of the cells capacity in the 4.0-4.2V range. This would be a way to really maximize the total energy that could be cycled through a cell in it's lifetime for people who shallow cycle a lot....

I am going to throw out some TOTAL GUESSES:

Li-ion cell rated for 500 cycles to 80% original capacity.

20% cycle depth: 1500 cycles
50% cycle depth: 750 cycles
80% cycle depth: 500 cycles
90% cycle depth: 300 cycles
100% cycle depth: 150 cycles (this might be optimistic)

If one were to perform "20%" cycle depths but keeping the cell in the 3.8-4.0V range under a light load the entire time, the cycle life would probably grow in excess of 2000 cycles.

 

[HarryJames]

Yes its depend of the battery if the battery goes 5 hours then you recharged the battery after 4 hour then its OK , best of luck

 

[SemiMan]

Yes its depend of the battery if the battery goes 5 hours then you recharged the battery after 4 hour then its OK , best of luck

Posting on 7 year old topics with no information to get your post count up is in bad form .....

 

[Eneloops]

Posting on 7 year old topics with no information to get your post count up is in bad form .....

Doing the exact same thing, only to whine and complain about things that are out of your control is worse. If the thread is open for responses, who are you to make up fake rules to the contrary? Get over yourself and let people post as they wish. You're not a moderator, so stop bossing people around with your ideals that only clutter up the thread, hypocrite.

 

[ChrisGarrett]

 

[TinderBox (UK)]

Battery Universality`s seems to show much better cycle life, Do you know something they do not know.

Or are you adding high temps into the mixture.

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

John.

EDIT: I only charge to 80% and never discharge below 20% on my devices with built in battery`s like my android phones and tablets, I use the App, GSam Battery Monitor to sound an alarm, when any of these values are reached.

It's tough to nail down for various reasons.

Lets think of the cycle life in terms of how much energy is cycled through the cell through it's life.

A routine discharge depth in the 60-80% range (approximated)(20-40% remaining), should result in the highest possible quantity of energy that can be cycled through the cell before the cell is worn to the point of needing to be replaced.

In either direction away from this target range, the cells total "energy cycled" before recycle time, would be reduced by some amount. But the number of total shallow cycle possible should increase.

Shallower cycles would be considered less of a "full" cycle than deep discharges against the cells life. But it would not be a direct conversion I don't think.

Very deep discharges, like repeatedly pushing the cell to ~3V or less, would most likely result in even less cycle life than advertised on most cells.

As I understand, most Li-Ion cells, are manufacture rated based on 80% depth of discharge for cycle life. So routinely discharging below 20% capacity will reduce cycle life of the cell below the manufactures suggested cycle life...

Here's something to consider for a shallow cycled setup:
LiCo is least self-destructive when stored around 3.8-4.0V. I would assume, with great confidence, that if one were to somehow shift their shallow cycles into this voltage range, then the cycle life of the cell would likely be improved as compared with cycling at the top of the cells capacity in the 4.0-4.2V range. This would be a way to really maximize the total energy that could be cycled through a cell in it's lifetime for people who shallow cycle a lot....

I am going to throw out some TOTAL GUESSES:

Li-ion cell rated for 500 cycles to 80% original capacity.

20% cycle depth: 1500 cycles
50% cycle depth: 750 cycles
80% cycle depth: 500 cycles
90% cycle depth: 300 cycles
100% cycle depth: 150 cycles (this might be optimistic)

If one were to perform "20%" cycle depths but keeping the cell in the 3.8-4.0V range under a light load the entire time, the cycle life would probably grow in excess of 2000 cycles.

 

[markr6]

LOL!! Life is hard! I was starting to think I wouldn't laugh at all today.

I don't have much room to talk though...half my posts are me bishing about bad tints

 

[SemiMan]

Doing the exact same thing, only to whine and complain about things that are out of your control is worse. If the thread is open for responses, who are you to make up fake rules to the contrary? Get over yourself and let people post as they wish. You're not a moderator, so stop bossing people around with your ideals that only clutter up the thread, hypocrite.

So tell me ..... Have you been told lately .... Cause if not ... Now you have. When you have something valuable to add ....please do. If you had anything valuable to say perhaps you would comment on the grossly inaccurate data previously posted on this thread .... But no one was paying attention ....

 

[mdocod]

Battery Universality`s seems to show much better cycle life, Do you know something they do not know.

Or are you adding high temps into the mixture.

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

John.

EDIT: I only charge to 80% and never discharge below 20% on my devices with built in battery`s like my android phones and tablets, I use the App, GSam Battery Monitor to sound an alarm, when any of these values are reached.

Maybe things have changed over the last 7 years.

 

[thedoc007]

Maybe things have changed over the last 7 years.

I'm sure they have. Now the accepted ideal storage charge is 3.6-3.7 volts. (Roughly 40% state of charge.) If you go lower for prolonged periods, it is not good for the cell. If you keep it constantly topped up (near 100% SOC), and especially if you combine that with high heat (many lights will get cells quite warm on higher modes) you will lose MUCH more capacity in a given amount of time.

I found this thread helpful in determining state of charge.

Depth of discharge​	Discharge cycles​	Table 2: Cycle life as a function of depth of discharge A partial discharge reduces stress and prolongs battery life. Elevated temperature and high currents also affect cycle life.
100% DoD​ 50% DoD​ 25% DoD​ 10% DoD​	300 – 500​ 1,200 – 1,500​ 2,000 – 2,500​ 3,750 – 4,700​

Temperature​	40% charge​	100% charge​	Table 3: Estimated recoverable capacity when storing Li-ion for one year at various temperatures Elevated temperature hastens permanent capacity loss. Not all Li-ion systems behave the same.
0°C​ 25°C​ 40°C​ 60°C​	98%​ 96%​ 85%​ 75%​	94%​ 80%​ 65%​ 60% (after 3 months)​

And these charts from Battery University make it pretty clear that high voltage and high heat are a bad combination when it comes to preserving capacity over the long term. If you are running a lot of cycles in a short time, depth of discharge makes a large difference too, but I doubt that matters as much for most people. Lithium-ion cells have so much capacity, and modern LEDs are so efficient, that unless you are running on turbo all the time, you are more likely to lose more capacity simply through time then you are through running too many cycles on a cell.

 

[IonicBond]

Our cells would be immortal if it wasn't for the secondary reactions. They are exacerbated by heat, time, and of course overcharge and undercharge. Staying away from both the top and bottom ends of SOC would be ideal, but practical concerns usually means we always charge to full. Not ideal, but a balance for practicality in our application.

If one really wants to dig into it, this class from Prof Jeffrey Dahn at Dalhousie University gives the best details I have ever found. While the intro first appears to deal with EV's, the physics get down to the size of cells we use:

https://www.youtube.com/watch?v=9qi03QawZEk

Needs quality time for viewing. And maybe pad and paper.

 

[HKJ]

And these charts from Battery University make it pretty clear that high voltage and high heat are a bad combination when it comes to preserving capacity over the long term.

That is also very obvious from the datasheet for a LiIon cell, look at this specification:

Storage Temperature: 1 year : -20~25°C, 3 months : -20~45°C, 1 month : -20~60°C

I usual leave out the conditions, they say something about cell voltage (about 3.6 volt) and how much recoverable capacity is left after the storage time.

 

[MidnightDistortions]

I always keep the percentage around 60-80% range and in some cases if it's around 70% i'll just top it off to 80%. If i need the phone for an extended period of time i'll just charge it to full and try to keep it around 60-70%. One thing i do fail to remember is to check the temperature from time to time and i got one for battery defender which lets me know the temps. It's rough sometimes though when you need to use the phone and it's just building up more heat to the battery.

 

[SemiMan]

Way too much effort. Just easier to replace the battery once in the life of the phone.