At the moment, the mechanism for switching between saturation and float is relatively simple. A counter ticks steadily upwards or downwards depending on whether the PWM duty cycle is at 100% or not. At each end of the range of this counter, the mode (saturation or float) is changed.
This technique works reasonably well and is simple to implement, but it doesn’t very accurately model what is happening inside the battery. We need to model the charging process more closely to determine when to switch between saturation and float charge modes.
Let’s assume that the battery is at equilibrium between 13.0 and 13.5 volts. Within this band it is neither charging nor discharging. Above this range, the battery is taking in charge and we must let our timer migrate toward the point where we switch to the float charge phase. At higher voltages, the timer can count more quickly.
Tags: battery voltage measurement, deadband, float charge, saturation charge