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Below is the LTspice sim of a basic constant-current circuit for the battery discharge;
The TLV9152 is a low-cost CMOS op amp with a low offset voltage, which is important when the maximum input signal is only 100mV.
The circuit's negative feedback means the battery current value equals the PWM input voltage divided by R1.
The PWM signal simulates the average (LP filtered) voltage from your PWM control (0-100mV here).
The sim was done for battery voltages, V(Vb) of 1V, 2V, 3V, and 4.1V.
This give a constant current from the battery -I(Batt) that goes from 0 to 5A for the 0-100mV PWM signal, V(pwm).
Note that the current is independent of the battery voltage (the current plot is actually 4 curves, one for each battery voltage simulated, superimposed on each other).
The TLV9152 is a low-cost CMOS op amp with a low offset voltage, which is important when the maximum input signal is only 100mV.
The circuit's negative feedback means the battery current value equals the PWM input voltage divided by R1.
The PWM signal simulates the average (LP filtered) voltage from your PWM control (0-100mV here).
The sim was done for battery voltages, V(Vb) of 1V, 2V, 3V, and 4.1V.
This give a constant current from the battery -I(Batt) that goes from 0 to 5A for the 0-100mV PWM signal, V(pwm).
Note that the current is independent of the battery voltage (the current plot is actually 4 curves, one for each battery voltage simulated, superimposed on each other).
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