LithiumIon Wear rate, how to calculate

Hi,

Wikipedia has a great table showing how charge level and heat affect long term maximum capacity of li-ion batteries.

The table shows as example that at 40% charge rate for 12 months at 0c would result in around 2% capacity loss.

Does anyone know how this is calculated.

Thanks

 

A great place to ask this is CPF , see link below.

They use the li-ion batterys used in our laptop batterys to power their flashlight and have lots of info on charging/storage ect.

Flashlight Electronics - Batteries Included - CandlePowerForums

 

If you just want to know the current max capacity of your battery vs its designed capacity you can use HWMonitor from CPUID right here.

 

Hi,

I want to calculate the long term effects of storage on the battery, not the actual current capacity.

Also that form wont let me register... doh

 

There are too many variables to give you a one size fits all answer. What temps, what is your discharge/charge usage? Your question is impossible to answer.

 

"lithium wear rates" are dependent on many things including day to day environmentals (heat & cold & humidity).

Anyone who says that they can predict future wear rates is telling tall tales.

The best you can do is to look at the original capacity and the current capacity and then keep track.

 

It's calculated by doing an experiment. Then do the following calculation 100-(current capacity/previous capacity).

 

Stored lithium ion cells maximum capacity reduces over time, the two main factors that affect the loss of maximum capacity are heat and charge level while stored.

By stored I mean in an unused state.

"A unit that is full most of the time at 25 °C (77 °F) irreversibly loses approximately 20% capacity per year. Poor ventilation may increase temperatures, further shortening battery life. Loss rates vary by temperature: 6% loss at 0 °C (32 °F), 20% at 25 °C (77 °F), and 35% at 40 °C (104 °F). When stored at 40%–60% charge level, the capacity loss is reduced to 2%, 4%, and 15%, respectively"

What I am seeking is the formula or table used to create the above numbers.

Thanks.

 

Data from here

Storing and priming of batteries

 

That data came from BatteryUniversity. The numbers are a result of experimentation. The tested a series of batteries and came to the conclusions shown. So, there is no formula.

 

Thanks for the info

 

From the data you can create a formula, but either they didn't publish it or didn't do it, but you could if you wanted to.

 

such a formula would be useful ONLY if the battery drain between cells from individual manufacturers and between production lots were the same.

It isn't.

'Guessing' battery drain/wear is nothing more than a guess. There are far too many variables between the factory that makes the cells, their storage conditions, their use and charge conditions, and user discharge/use patterns.

 

Of course there are general rules for Lithium-ion wear. I once heard 300 cycles before significant deterioration, but that might be an urban legend, and it probably depends tremendously on the quality of manufacturing and how "smart" its charger is.