18650 charging curve?

Hey guys, this has probably been asked a million times before, but does anyone know of a good spreadsheet and/or graph that can show the input voltage and amperage of a18650 battery in comparison to SoC? I want to understand the relationship between voltage and amperage while charging so I can make my Electric Bike/Scooter calculator programme more accurate.
Thanks.
(This category seems like the best place to ask this question to me, if there's a better place, do let me know!)

THEWHITEBOY503 said:

Hey guys, this has probably been asked a million times before, but does anyone know of a good spreadsheet and/or graph that can show the input voltage and amperage of a18650 battery in comparison to SoC? I want to understand the relationship between voltage and amperage while charging so I can make my Electric Bike/Scooter calculator programme more accurate.
Thanks.
(This category seems like the best place to ask this question to me, if there's a better place, do let me know!)

Click to expand...

This is a bit custom to each cell. Further, if you are talking battery made up of cells - it will be even more custom.
Many cells have specs you can find online - this may be a good enough guide for you. For example -here's a charge curve for NCR18650A(s) that I found online - this shows what you are asking:




Depending on how 'precise' you want to to get - youlocal cells/battery/IR/load - e.g.situation - will vary. Forthis the best suggestion I can make is to get an iCharger X6/X8 (or something like it) and log charge sequences to your computer and discover your ownsituation.

For SoC, it's better to have a meter that counts amps in/out over time eg via a shunt resistor.
Using cell voltages for SoC will only be approximate & will change with load.

Redpacket said:

For SoC, it's better to have a meter that counts amps in/out over time eg via a shunt resistor.
Using cell voltages for SoC will only be approximate & will change with load.

Click to expand...

Good to know, I'll keep that in mind!

OffGridInTheCity said:

This is a bit custom to each cell. Further, if you are talking battery made up of cells - it will be even more custom.
Many cells have specs you can find online - this may be a good enough guide for you. For example -here's a charge curve for NCR18650A(s) that I found online - this shows what you are asking:




Depending on how 'precise' you want to to get - youlocal cells/battery/IR/load - e.g.situation - will vary. Forthis the best suggestion I can make is to get an iCharger X6/X8 (or something like it) and log charge sequences to your computer and discover your ownsituation.

Click to expand...

Looks good, thank you!

Though capacity vs voltage is not that straight.... Its more of a curve in middle at 3.6-3.7V. Can be seen in al wolf work he have done and int discharge curves from all manufactures. Therefore SOC from Voltage is hard and especially it can only be done after resting atleast 5min or more.

In top and bottom its easier but in middle hard. Best to meassure soc is colloumb counter aka shunt with electronics.