Check of operation for Battery charger

After confirming that there is no mistake in the wiring, confirm in the operation.
A to C of the following figure shows checkpoints.

Check of the voltage control circuit operation

I checked operation of the voltage control circuit and current control circuit using

stabilised-power-supply equipment

, before inputting AC.

If there should be faulty wiring, there is a possibility of breaking equipment.

Connect the output of stabilised-power-supply to point A, and connect a circuit tester to point B in voltage measurement mode.
Make VR1 into the minimum voltage side (full of left). Then, raise the voltage of a stabilised-power-supply gradually to 30V.
The voltage displayed on a circuit tester should be stabilized in about 8V. If it becomes high more, the voltage control circuit may not be operating normally. Check wiring once again.
In my case, when the voltage of 30V was applied from a stabilised-power-supply, the range of 7.9V to 29V has been controlled by changing VR1. This is a value as a design mostly.

Check of the current control circuit operation

Next, operation of a current control circuit is checked.
Stop a stabilised-power-supply. Connection of a stabilised-power-supply is still point A.
Make a circuit tester into current measurement mode, and connect with the output terminal of a charger. Because the ammeter is attached to the charger, you may short-circuit the plus terminal and minus terminal of an output, without using a circuit tester.
Make VR2 into the minimum current side (full of left). Then, raise the voltage of a stabilised-power-supply gradually to 30V.
A circuit tester's current should be stabilized in about 85mA. When flowing more, the current control circuit may not be operating normally. Check wiring once again.
In my case, when the voltage of 30V was applied from a stabilised-power-supply, it has controlled in 85.6mA to 500mA by changing VR2. This is a value as a design mostly. Even if it changes VR1 for voltage control, current does not change. This is also as a design. The voltmeter of a charger shows about 1 V in this condition. This is the voltage applied to the reverse current prevention diode (about 0.6V), the ammeter of a charger and circuit tester. Because they have some resistance, the voltmeter of a charger is not set to 0V even if it short-circuits an output.

Check of the rectifier circuit operation

Finally operation of a rectifier circuit is checked.
A voltage of RMS (Root Mean Squared) is used for alternating voltage. This voltage is not the maximum of voltage (peak voltage).

Why is RMS used for alternating voltage? Because, calculation of electric power is easy. As for alternating voltage, peak voltage is not held but voltage is changing with time. Therefore, peak voltage cannot be used when calculating electric power (quantity which electricity works). RMS voltage is

of peak voltage. W = Vrms x I rms (When the phase of voltage and current is the same)
Because the outputs of the transformer used this time are 24Vrms, peak voltage is about 33.6V. Actually, there was 35.0V voltage at point A. This error is caused by the error of AC input voltage and accuracy of transformer. Normal operation of a rectifier circuit was also checked.

Calculation of power consumption

If a battery is charged by the 500mA charging current, the portion of the bottom of a charger will get warm. It is not hot.
Calculation of the power consumption of IC for voltage control and current control is shown below.
The premise of calculation is the following.
Charge voltage is 14V. Charging current is 500mA. And voltage of voltage control is 23V.

Power consumption of IC for voltage control

Potential difference of input and output of IC	= Input voltage - Output voltage = 35V - 23V = 12V
Current which passes IC	= 500mA ( IC itself uses current, but it's small so ignored. )
Power consumption in IC	= 12V x 0.5A = 6W

Power consumption of IC for current control

Potential difference of input and output of IC	= Input voltage - Voltage for current control - Output voltage = 23V - 5V - 14V = 4V
Current which passes IC	= 500mA ( IC itself uses current, but it's small so ignored. )
Power consumption in IC	= 4V x 0.5A = 2W

If voltage for voltage control is made high, the power consumption of IC for voltage control will decrease, and the power consumption of IC for current control will increase.
Conversely, if voltage for voltage control is made low, the power consumption of IC for voltage control will increase, and the power consumption of IC for current control will decrease.
Total power consumption seldom changes. Because voltage control is for over charge prevention of a battery, it is the above values generally.

As a charger, the power consumption of R3 and VR2 (about 3 W) is added to the above-mentioned value. So, it can be regarded as about 10W power consumption.
If the charging current is reduced, power consumption will decrease more.

The performance of this equipment is summarized as follows.

Voltage control range	7.9V to 32.5V
Current control range	85.6mA to 500mA

The maximum voltage is high from the value previously explained at Check of the voltage control circuit operation.
This is because it applied only to 30V in Check of the voltage control circuit operation.