# mobile cellphone charger circuit

Thread Starter

#### sagivbh

Joined Jan 15, 2018
28
Hello,
i found a mobile cellphone charger circuit with 555 timer. my goal is to make the circuit charge the phone battery to 5 volts with 2 amper, and than to stop the signal from the output(3) when the battery is charged with 5 volts. i understand that i need a lower zener diode breakdown voltage, and to change the trimmers resistance value. my first question is:
when the battery is charged with 5 volts it is going to discharge the current throw R4 R6 R5 VR1 VR2, better option is to increase their value so the current would be lower when its discharge? could this effect the 555 timer output?
second quesstion: what is the role of C1?
third question:
is there a way to add a led diode when its full charged? in this circuit the led diode goes off when the battery charged.
Thanks.
https://electronicsforu.com/electronics-projects/hardware-diy/mobile-cellphone-charger

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#### wayneh

Joined Sep 9, 2010
17,498
Are you planning to charge a naked battery pack, or provide power to the phone with the battery pack inside? This circuit won’t work for the latter.

#### spinnaker

Joined Oct 29, 2009
7,830
Hello,
i found a mobile cellphone charger circuit with 555 timer. my goal is to make the circuit charge the phone battery to 5 volts with 2 amper, and than to stop the signal from the output(3) when the battery is charged with 5 volts. i understand that i need a lower zener diode breakdown voltage, and to change the trimmers resistance value. my first question is:
when the battery is charged with 5 volts it is going to discharge the current throw R4 R6 R5 VR1 VR2, better option is to increase their value so the current would be lower when its discharge? could this effect the 555 timer output?
second quesstion: what is the role of C1?
third question:
is there a way to add a led diode when its full charged? in this circuit the led diode goes off when the battery charged.
Thanks.
https://electronicsforu.com/electronics-projects/hardware-diy/mobile-cellphone-charger

Why don't you just buy a cell phone charger and save burning your house down and / or frying your phone?

Thread Starter

#### sagivbh

Joined Jan 15, 2018
28
Are you planning to charge a naked battery pack, or provide power to the phone with the battery pack inside? This circuit won’t work for the latter.
im not sure what you mean. i want it to be like any regular phone charger.

Why don't you just buy a cell phone charger and save burning your house down and / or frying your phone?
you right. i can just buy one, and it is going to be cheaper. but asking here stupid questions evantually going to teach me about electronics.

#### xanny

Joined Aug 12, 2017
1
when once voltage across pin 6 is 5.8volts, pin 3 will go low and your out put voltage will drop.........besides you will be charging your phone with about 11.5volts at the start

#### spinnaker

Joined Oct 29, 2009
7,830
you right. i can just buy one, and it is going to be cheaper. but asking here stupid questions evantually going to teach me about electronics.
There are lots of 555 timer projects that can be a lot of fun and are a lot safer. Charging lithium batteries is not one of them and no way to learn. Engineers with years of experience have started fires on board airplanes with lithium batteries and design fault. Please find another project.

#### wayneh

Joined Sep 9, 2010
17,498
im not sure what you mean. i want it to be like any regular phone charger.
There’s no such thing. Today’s chargers are able to supply higher voltage and current to devices smart enough to negotiate with the charger. The lower common denominator is plain USB, which can supply up to 100mA at 5V without any smarts. That’s a very slow charge for a smartphone. Some 5V chargers can supply 2A or more, and some devices will use that available juice, some won’t.

In all these 5V cases, the phone is controlling the charging of the battery. The charger isn’t really a “charger”, it’s a power supply with a regulated 5V and some limit to the current it can sustain. Without a charge controller (the phone), connecting it to a battery would destroy the battery, perhaps violently.

Thread Starter

#### sagivbh

Joined Jan 15, 2018
28
There are lots of 555 timer projects that can be a lot of fun and are a lot safer. Charging lithium batteries is not one of them and no way to learn. Engineers with years of experience have started fires on board airplanes with lithium batteries and design fault. Please find another project.
I understand. I wont build it. Thanks for the answer.

There’s no such thing. Today’s chargers are able to supply higher voltage and current to devices smart enough to negotiate with the charger. The lower common denominator is plain USB, which can supply up to 100mA at 5V without any smarts. That’s a very slow charge for a smartphone. Some 5V chargers can supply 2A or more, and some devices will use that available juice, some won’t.

In all these 5V cases, the phone is controlling the charging of the battery. The charger isn’t really a “charger”, it’s a power supply with a regulated 5V and some limit to the current it can sustain. Without a charge controller (the phone), connecting it to a battery would destroy the battery, perhaps violently.
Thanks for the answer! so today phone chargers is a power supply. So inside the smarphone charger there is a transformer with a rectifier?

#### wayneh

Joined Sep 9, 2010
17,498
I understand. I wont build it. Thanks for the answer.

Thanks for the answer! so today phone chargers is a power supply. So inside the smarphone charger there is a transformer with a rectifier?
No, they’re all what’s called SMPS, switch mode power supply. They’re much more efficient but also much more complicated.

#### spinnaker

Joined Oct 29, 2009
7,830
A little (big maybe) tip. If you need a switch mode supply for 12V to 5V you can use one of those cheap USB chargers for automobiles. I wish I would have thoughgt of that when I was building my solar light controller years ago.

Also depending on the chip inside your USB controller, there is a sense resistor that can be changed out to get other output voltages.

Thread Starter

#### sagivbh

Joined Jan 15, 2018
28
No, they’re all what’s called SMPS, switch mode power supply. They’re much more efficient but also much more complicated.
Thanks! I will read about that.

A little (big maybe) tip. If you need a switch mode supply for 12V to 5V you can use one of those cheap USB chargers for automobiles. I wish I would have thoughgt of that when I was building my solar light controller years ago.

Also depending on the chip inside your USB controller, there is a sense resistor that can be changed out to get other output voltages.
Thanks for the tip!

Thread Starter

#### sagivbh

Joined Jan 15, 2018
28
Very nice!