Tesla battery automatic charging principle - 3 circuit diagrams to understand

火辣西米秀

Tesla battery automatic charging principle - 3 circuit diagrams to understand [Copy link]

>>>> Battery automatic charger circuit schematic (I)

The circuit is shown in Figure 4-8. FU is a short-circuit protection tube, LED I is a power supply indicator, adjusting RP1 can change the output voltage of IC1, the center end of RP2 provides a reference voltage for the positive input end of the voltage comparator IC?, R3 is a charging current sampling resistor, VD can prevent the battery from discharging. LED2 is a charging current indicator, and C2 is used to prevent r pulse interference.

The control principle of automatic stop charging is: the charging current gradually decreases as the charging progresses, and the voltage drop on R3 also decreases. If it is less than the set value on RP2, the relationship between the level of IC2's pin ② and pin ③ changes from higher than the check to lower than the pin ⑥ output high level.

It jumps to a low level, VD is reverse biased, and the charging current drops to zero. At this time, since there is no voltage drop on R3, the pin of IC& remains at a low level, and LED2 lights up to indicate that the battery is fully charged and ready for use.

　　

Components can be selected with reference to Figure 4-8. A heat sink should be installed on 1CI. 1C2 does not necessarily have to use LM741, other types of single op amps or a unit of multi-op amps can also be used.

The debugging process is as follows: first, do not install IC2, do not connect the battery, adjust RP1, make the output voltage of ICl be B.5V. Disconnect the power supply, install IC2, and connect two fully charged battery packs. Restore the power supply, adjust RF to make the LED start to emit, and fix RP1 and RP2.

>>>> Battery automatic charger circuit schematic (II)

Figure 4-9 is the electrical schematic diagram of the automatic charger. The 220V mains is stepped down by transformer T to obtain the secondary voltage U2, which is rectified in the format of VD1~VD4 to output a DC pulsating voltage. From the positive pole point A, it passes through the normally closed contacts of the relay K1-2, R4, ammeter PA, VT1, and the battery GB and VT2 to the negative pole point B to charge GB. The size of RP1 is adjusted, that is, the base potential of VT1 and VT2 is adjusted, thereby adjusting the Icb of VT2, that is, the charging current. Since the terminal voltage of the battery can reflect its charging status, taking a battery with a nominal voltage of 12V as an example, when the battery voltage rises to (12/2)*2.5=15V, VT3 is saturated and turned on, K1 is energized and attracted, the normally closed contact K1-2 is disconnected, the charging circuit is cut off, and the charger stops charging.

Adjust RP2 to set the upper limit of the battery full stop. LED1 is the power indicator, LED2 is the charging indicator. The greater the charging current, the brighter LED2, and vice versa. The charging current of the battery is the product of the battery's ampere-hour value and the charging rate. For example, if there is a 24V, 6Ah battery, then its charging current is approximately = (6/10) x (1 + 20%) = 0.72A. The full rate automatic stop limit is (24/2) x 2.5 = 30V.

　　

>>>> Battery automatic charger circuit schematic (III)

Common automatic battery chargers detect the battery voltage while charging to achieve automatic control. However, when charging current flows, the voltage across the battery will be high, so it is difficult to accurately judge the charging level based on the battery voltage. The automatic battery charger introduced in this article compares the charging voltage with the reference voltage during a period of time when no charging current flows, which can more accurately reflect the battery charging level. When the battery is charged to the specified voltage value, the charger will automatically stop charging to prevent the battery from overcharging.

The circuit is shown in Figure 4-10. This is an automatic charger with thyristor as the core. When the charger is connected to a fully discharged battery, the thyristor VS is turned on at the beginning of each positive half cycle to charge the battery. At the end of the positive half cycle, when the charging voltage is lower than the battery voltage, the thyristor VS is turned off. As the charging progresses, the battery voltage increases, and the moment of thyristor conduction is gradually delayed. At the beginning of the positive half cycle, VS is in the off state. At this time, the charging voltage is compared with the reference voltage to determine whether VS is turned on. When the voltage across the battery reaches a certain value (about 13.5V), due to the voltage limiting effect of VD3, VT no longer has current passing through it, VS is cut off, and charging stops automatically.

　　

　　

The voltage stabilization value of VD3 determines the reference voltage. If the final voltage of the battery does not reach the required value, a voltage regulator with a larger voltage stabilization value can be selected. For the convenience of adjustment, a potentiometer of tens of kilo-ohms can be connected to both ends of VD3, and the base of VT in the figure can be connected to the sliding end of the potentiometer.

R1 and neon bulb HL form a power indicator. It is not advisable to use a light-emitting diode connected to the rectifier output end for power indication, because this will form a circuit for the battery to discharge to the emitter junction of VT and the control electrode of VS, which is easy to cause damage to the emitter junction of VT and the control electrode of VS.

According to the values of the rectifier diodes VD1, VD2 (1N5401) and VS (6A) in the figure, the charging current of the charger can reach 3A. The size of the charging current and whether the charging is completed can be displayed by the ammeter.