How to estimate SoC (t) from the Panasonic 18650 battery cell?

How to estimate SoC (t) from the Panasonic 18650 battery cell?

t = 1369, SoC min = 0.3

SoC max =0.9

Max discharge current (A) = 11.25 (5C)

Panasonic 18650 battery cell

Rated capacity (Ah) 2.25

Nominal voltage (V) 3.7

[SALAH alatai]

@Trung Q. Nguyen Could you pls share it with me if you solve it. thanks.

Answer 1

[SAI SRUJAN]

Hi Trung,

I understand that you are facing an issue trying to estimate Soc(t) from the panasonic 18650 battery cell.

State of Charge (SoC) is a metric used to represent the remaining charge in a battery relative to its full capacity. It is expressed as a percentage, where 100% indicates a fully charged battery and 0% indicates a fully discharged battery. In this context, we are calculating the SoC of battery cell after discharging it with a specified current over a given time period.

Please go through the following code sample to proceed further. This involves converting the battery's rated capacity to Coulombs, calculating the charge discharged, and then determining the remaining charge to estimate the current SoC.

% Fine tune the Parameters as required
t = 1369; 
SoC_min = 0.3;
SoC_max = 0.9;
I_max = 11.25; 
rated_capacity_Ah = 2.25;

% Convert rated capacity to Coulombs
rated_capacity_C = rated_capacity_Ah * 3600;

Q_min = SoC_min * rated_capacity_C;
Q_max = SoC_max * rated_capacity_C;
Q_discharged = I_max * t;
Q_current = Q_max - Q_discharged;

% Calculate the current SoC
if Q_current < Q_min
    SoC_current = 0; 
elseif Q_current > Q_max
    SoC_current = 1; 
else
    SoC_current = Q_current / rated_capacity_C;
end

I hope this helps!