We need the table of li-ion battery（4.2V） voltage and battery capacity percentage
Perhaps each battery has a different percentage.
Who can share it?
Thank you very much 
I think it will depend on the individual battery, but also temperature.
HKJ is the authority here
He has done some really cool stuff:
https://lygte-info.dk/info/BatteryChargePercent%20UK.html
Thank you very much. Last time I saw this form in the forum, I didn’t expect it was the result of HKJ.
Thank you and HKJ again. :+1:
I will be able to do this type of tables much easier in the future and expect to have spare equipment to do it also.
It depends on the battery model, the temperature of the battery, the discharge rate, and the age.
All of these things will change what voltage corresponds to what percentage.
It do not really depends on discharge rate and I also doubt temperature. Do batteries change voltage if you put them the fridge?
The table is measured at zero load and after the battery has had time to recover to nearly stable voltage.
I wonder how much age affect it? If it does.
It is something like this I will be able to do soon (I hope):
The above table is generated from a fairly new high quality 21700 cell.
It need to be measured more than 5 minutes after load is removed and I have not decided if I will lose a decimal on the percent.
In things like a vape or flashlight with high drain the voltage sag from a high drain device may not even allow you to get it to 3.1V right?
You will have to check the discharge curves at specified capacity.
In the above table I have inverted the capacity scale to show how much is remaining, instead of how much is used. Calculating how much capacity is used and check the discharge chart will give your a very good idea about the voltage when loaded with some current.
Do I need to include both capacity remaing and capacity used columns?
Not real sure. I guess it depends on what the purpose of such a table is used for. It maybe too many variables to try and include more than you have already
The purpose of a “Used Ah” would be to use the value in the discharge charts and see what voltage to expect at different loads.
Bugger… I always thought it was fairly consistent. Kind of a kick in the nads to find out otherwise.
so great!!!Thanks you very much,HKJ
if you test 21700 5000mah ,3.0V-2.5V still have about 100-300mah capatity
So each battery is different.
I always thought battery voltage varies with temperature, but I was thinking of wet cell batteries. That’s why you need to trickle charge overnight or bring your car battery inside the house when it is bitter cold.
Low charge rate is because the chemical processes works slower when it is cold and a wet cell battery with frozen electrolyte is a cracked battery.
I will do a test with temperature change on a LiIon battery.
I would expect each chemistry and with fairly similar chemistries I would not expect huge differences.
With the above battery the time from current off to measurement is not that important:
I like the percent better without decimals. All 3 tables are based on the same data file, I have only moved the point where I measure the voltage.
The file used has 27800 samples, that is reduced to 46 sample points. I generate a sample point when the current is turned off, the point is offset with the specified time interval. From them I have interpolated the capacity and energy at the exact voltage point in the table.
You are the man :+1:
That’s why I use a cetek battery charger for mY car batterys ,it has temperature compensation ,it will charge at a higher rate when bellow room temperature, also a lead acid battery won’t freeze if it’s charged.
When you asked about the temperature I put a partially charged battery in my freezer.
The voltage did change, it increased 0.004V, I suspect it is recovery from an early test I used it for.
The temperature curve drops faster than the battery temperature, my sensor was already in the freezer and the battery started outside at around 25°C. Timescale is in seconds.