I thought of doing smart discharge for AA batteries using a board Arduino. Therefore, I had a need to break the discharge circuit when a certain voltage on the battery was reached. After reading books and articles, I determined that for this task there are two options for solving the problem: the first is to break the discharge circuit using a relay controlled by 5 volts; the second - using a powerful MOSFET field effect transistor.
Designation scheme:
I have selected the IRFZ44N Induced-Channel Field-Effect Transistor (MOSFET) IRFZ44N.
Documentation for IRFZ44N - IRFZ44N_en.PDF
View online file:
To open it (reducing the voltage between the terminals “source” and “drain” will greatly decrease), it is necessary to apply a voltage to the terminal “gate”, which is called a “threshold voltage at the gate”.
For the IRFZ44N transistor, the “gate gate voltage” is normalized from 2 volts to 4 volts.
From the documentation (see photo above), we can determine what resistance the transistor will have between the source and the drain at the gate voltage relative to the source of 4.5 Volts and the voltage applied to the source and drain (discharge circuit). From the diagram we see that at Uc = 4.5 V, Uc = 1.5 V, the current through the transistor is Ic = 7 A. Now we calculate the resistance between the source-drain terminals using Ohm's law: Ric = 1.5 / 7 = 0.214 ohms. From the documentation we know that the resistance of a fully open transistor is Rds (on) = 0.0175 ohms. I am going to discharge the battery with a current of no more than 0.5 amperes. We determine what power will be released on the transistor at a current of 0.5 A: P = 0.5 * 0.5 * 0.214 = 0.0535 W. I think that the transistor heats up slightly.
I received 10 IRFZ44N transistors bought on Aliexpress, I decided to check everything and take a picture. Checked Lcr-t4 - meter.
Vt in the photographs corresponds to the threshold voltage at the shutter.
Cost: ~ 8