# Make cheap 6V battery charger circuit from a mobile charger

Is it good? we have a cheap 6V battery charger. Yes, we want it. Here is a low current 6V battery charger circuit.

We applied them from the cheapest mobile phone charger.

Inside it is a simple DC switching regulator circuit. Also, it can be a 6V 4.5Ah battery charger for 10hr charging.

It is good for battery low current no overheat, long-life battery.

This circuit we can apply in many ways.

For example, a power supply for general load and a low current battery charger circuit.

This circuit we can use for charge a 6 volts lead-acid batteries.

And also useful for others: nickel-cadmium batteries,nickel-metal hydride battery(also known as NiMH), etc.

The output current more or less depends on the voltage selected. It will discuss how to adapt later.

### How this circuit works

Look at the circuit diagram below.

First, the AC-voltage( both series AC120V or AC220V) to R1-1 ohms. It is the resistor fuse to cut off the circuit when overloaded.

While the AC220V to the diode D1-1N4007 to rectified from AC (Alternating Current) to a pulsating DC (Direct Current) about 300V.

After that, The DC300V will via the filter capacitor-2.2uF.

Then, the Q1-transistor acting together with R5, C2, D2 and coil on top of T1. Before, the Q1 has a bias at pin B via R4 and R2.

Then the feedback circuit includes D3, D4, C3, C4, and R6, will control the bias.

Finally, both D4 and C5 are a rectifier circuit. They are special because it will work at frequencies around 30KHz. But the frequency of a general transformer is 50Hz only.

The output voltage is controlled by the zener diode D3.

### Changing output voltage

Choosing the voltage of the Zener diode

In the circuit, we use number 1N5237 (8.2V 0.5W), causes the output voltage about 7.4V, for charge the 6V battery.

We will see that:

1. The output voltage of this adapter should be higher than the battery’s voltage of about 20%. If we use a 12V battery, so the output voltage is about 14 volts.

2. The breakdown voltages (Vz) of Zener Diode should also higher than the output voltage is around 20%.
Suppose, the output voltage is about 14 volts. Therefore, we should use the 18 volts Zener diode.

The Zener diode in the circuit used 0.5 watts.

Make Gel cell battery charger circuit

Parts you will need

I buy this the mobile charger in the store near my house. It is so cheap just only 0.9\$ US. Look at below!

See components list inside:

Semiconductors

• Q1: MJE13001, 600V 0.2A NPN Transistor
• D1,D2,D5: 1N4007, 1000V 1A Diodes
• D4: 1N4148_75V 150mA Diodes
• D3: 1N5237, 8.2V 0.5W Zener Diode
• LED: As you want

Electrolytic Capacitors

• C1: 2.2uF 400V
• C4: 22uF 50V
• C5: 470uF 25V

Ceramic Capacitors

• C2: 0.01uF 50V
• C3: 0.0022uF 50V

0.5 watts Resistors, tolerance 5%

• R1: 1Ω
• R2,R5: 47K
• R3: 15 ohms 1W Resistor
• R4: 1M
• R6: 390Ω
• R7: 1K
• T1: Transformer = 1 pcs

Caution
1. For the device has various polarity includes the Electrolytic capacitors,Zener diode,all diode,transistor,LED we should be careful in the assembly circuit.
2. If the output voltage is at 12V you need change C5-470uF 25V up.

While is charging, the battery is not hot. Thus, the life of a battery is a long time and can recharge several times. When the battery is full, we can use it for a longer time than the normal high current charging.

The disadvantage is it takes about 3 hours to charge because it is the low current charging.

We can easily use this adapter as the power supply circuit at about 500mA, 12V.

Sure, I want to see you grow up in electronics. Below is circuits list you may like it.

ElecCircuit – Simple Electronics Vol-03

GET UPDATE VIA EMAIL

I always try to make Electronics Learning Easy.

### 6 thoughts on “Make cheap 6V battery charger circuit from a mobile charger”

1. hallo,

die schaltung kann so nicht funktionieren. die verbindung von D3 und C3 darf nicht an den

emitter gehen. sie muss an die basis angeschlossen werden.

viele grüße

walter

2. Hi, this ckt is found to b very useful however it wud be better if u wud provide the details of the transformer T1.

3. Need a cct for charging a lead acid battery at 2.5v dc at 20 amps thanks

• Hello Alan,
Thanks for your visit to my site.
Now, I do not have that circuit as you want. If you have a new or update I will email you. Please subscribe with me.

Have a good day.

4. I would like to build this circuit. I need the details or a source for T1