Calculate the discharge time of a capacitor under constant resistive load.
costLoadDischargeTime(
	1.4F, // capacitance
	2V, // carged voltage
	1.0V, // discharged voltage
 50Ohm, // load resistor value
	1.5Ohm // ESR of the cap
)
| C | The capacitance of the capacitor. | 
| Umax | The carged voltage of the capacitor. Discharging beginns from here. | 
| Umin | The discarged voltage of the capacitor. Discharging ends here (for example the buck-boost converter shuts down at this voltage level). | 
| R | The value of the load resistor. | 
| ESR | The equivalent series resistance of the capacitor. Optional. If not given, 0 is assumed. | 
| return value | The discharge time of the capacitor. |