DIY portable phone chargers. DIY wireless phone charger. What does a standard charger consist of?
A mobile phone charger has become one of the most necessary technological little things in our lives. After all, without it, our mobile phone will be just a lifeless box. But when it breaks, the phone dies, and you’re waiting for an important call, you’ll have to experiment and try to charge it yourself.
The first design of the charger involves using a computer USB connector or a network adapter connected to an outlet. So, first you will need an old flash drive, from which you need to remove the plug, just be careful not to break the board on it. Next, take a piece of two-core cable, strip the contacts on one side and start heating the soldering iron. Now let's study the circuit that was soldered together with the plug. On it you will see four contacts, the central ones are responsible for transferring data from the computer to the memory chips of the flash drive, we are not interested in them. But the side ones are responsible for power supply, and you should carefully solder the cable that we prepared to them. Just to improve soldering, do not use acid, since the contacts are quite delicate and after a while they may deteriorate.
Of course, these options are only suitable for simple phones like Nokia, since for IPhone, new Samsung models and the like, charging is much more complex in design.
I’ve been using communicators for a long time, it’s a very convenient all-in-one thing - Notebook, calculator, flashlight, video and photo camera, Internet, video and MP3 player, navigator, safe (for information), radio, game console, and a lot more. Super gadget - what more could you dream of? And I’ll tell you something, something small nuclear reactor instead of a battery! But on this moment We break off and are happy with the li-ion battery, which, under a good load of the device, lasts for 3 hours. There is a way out: we turn down the brightness of the phone to minimum, turn off the Internet, delete live wallpapers, switch to airplane mode and turn it on only to make a call, and then the phone (as stated by the manufacturer) lasts for two days. In general, this is not an option, and I became seriously interested in alternative power sources, we will talk about an additional battery for your gadget or a “Vampire”
Let's probably start with the most basic thing - batteries, I installed two cans of li-ion bought in radio goods in Vladivostok when I was there on vacation, you can buy in principle any and in any quantities (within reasonable limits) suitable in size, the most important thing is more greed oh, containers. We increase the capacity by paralleling the jars. You can only parallelize identical batteries, ALWAYS balancing them with each other - we connect the minuses (as a rule, they are the body of the can, and we connect the pluses with a resistor with a resistance of 30 ohms.
Using a voltmeter we measure the voltage at the terminals of the resistor. We wait, sometimes for a day, sometimes immediately same values. As soon as it becomes less than a hundred millivolts, they can be connected directly, without a resistor. We solder them together and solder the ends to the controller (can be obtained from any old battery cell phone) So we have a high-capacity battery.
WHEN WORKING WITH NAKED CANS WITHOUT A CONTROLLER, BE CAREFUL, DO NOT CONFUSE THE POLARITY AND DO NOT CREATE A SHORT CIRCUIT IN ANY CASE!
We put it aside and scratch our heads with how to charge it, now, of course, charging from a cell phone. They are everywhere and always, and most of them have a USB outlet.
You can directly solder the wires to the battery and USB male and plug them into the charger; they usually go 5V 1A. But it was so boring and uninteresting that I decided to make a charge indicator. We turned on the red LED to charge, the battery was charging, the green light came on, disconnected from charging, both went out.
Transistors marked t06 - pnp PMBS3906, 100mA 40V, complementary to PMBS3904. Unsoldered from an old motherboard.
Resistors R1 and R2 marked 471 - 470 Ohm I got them from old controllers for a cellular battery
Resistor R3 can be set with a value of 1.5 Ohm, but I didn’t find this, I put two in parallel, 1 Ohm each, and it turned out to be 0.5 Ohm. I installed two because I was afraid that they would get very hot at a charge current of about 0.5A I found the 1R00 marking on the diagram hard drive from the laptop.
Diode marked SS14 Description: Diode, Schottky, 1 A, 40 V I had it lying around, I didn’t know where it came from, but if you have hardware with SMD parts, you’ll find something similar on it without any problems.
I bought the most common SMD 3V red and green LEDs, but you can solder them in abundance from circuit boards from cell phones.
I assembled a circuit from what was more or less similar to resistors R1 and R2, which can be set to 330 Ohms
I would like to convey a huge thank you to the Electronics Forum cxem.net. The topic of indicator development, by joint efforts and especially by the Kival participant. Maybe someone will find it useful for general development.
The parts were installed on a piece of copper PCB cut from the board.
Next we mount this little wonderful device on a USB “father” I pulled out of an old data cable 
We plug it into the charger and check the functionality 
Without load, both LEDs light up; under load, the green one goes out.
In short, the principle is very simple - when the battery is charging, current flows through the circuit and does not allow the green LED to light up, as soon as the controller indicates that the battery is charged and no longer fits into it, the circuit opens, the current stops flowing and the green LED lights up as soon as you remove the diode from charging D3 does not allow current from the battery to flow to the indicator and both go out.
Well, it looks like we’ve decided on the indicator and charging, now we need to figure out how we’ll feed the phone from the battery, because our output is from 3.7v to 4.2v, and for charging a cell phone it’s gently at least 5V and for Nokia even more. Here we need a booster DC-DC converter Here I give up, I won’t draw diagrams and rant about it because the Internet is teeming with this material, and I don’t have a radio parts store in my city and so I didn’t bother with soldering this element, but stupidly (or smartly) ordered from the Internet . You can also buy a Chinese charger from one battery and pick it out from there, but I personally doubt its reliability, and we’ll be charging, not halam balam, but expensive communicators.
It would seem that everything is there and all that remains is to connect everything with wires, but some inconveniences arose during the operation of the device, so my device lies like a piece of plastic and it is not clear whether there is a charge in it or is it empty? And lithium-ion batteries really don’t like to sit discharged. I wanted a voltmeter, a small compact voltmeter, since the device was assembled and there was no room for it initially. The search for diagrams, recipes and ready-made units began. And as luck would have it, I walk into a mobile accessories store and see a miracle of Chinese engineering. 
Yes, yes, a frog with an LCD screen worth 150 rubles.
I quickly picked it apart :) As it turned out, the voltmeter circuit was made separately, from pulse transformer and is very easy to drink. The most important thing is to remember how the screen was soldered and where to solder the power wires (by the way, as it turned out, the polarity does not matter) Since my memory has long been weakened digital technologies— I decided (so as not to forget, I need to take a photo) 
After all the manipulations, we get a voltmeter with 4 divisions. With these characteristics, 4 bars 4.14V/ 3 bars 4.04v/ 2 bars 3.94V/ 1 bar 3.84V/ then an empty battery remains until the battery controller cuts off the power, which is about 3 .4 - 3.6V
Since the voltmeter also consumes a certain amount of electricity that is dear to us, we connect it through a button. Clicked, looked, let go! 
Next we are looking for a suitable box where we can put everything we have acquired through back-breaking labor, welded together with sweat and blood. In an unequal battle, I took the box of shadows from my wife (the shadows and mirror were returned) and put everything there. 
Solder according to the diagram 
I placed the USB connectors on a strip of tin to increase the area when gluing. We glue the battery with double-sided tape, the button with super glue, the USB connectors are soldered (as mentioned above) they are soldered to the tin, which in turn is glued with super glue, we cut out a rectangular hole under the LCD screen, we carry out installation and fitting carefully - the glass is very fragile. We sit on hot glue. 
Well, that's all! We decorate it to your taste and use the device!
We will tell you how to make a wireless charger for your phone with your own hands or buy a ready-made one.
The transmitting circuit has two half-windings, which are connected to the middle point.
The middle point goes through the inductor to the power supply plus. Limiting resistors that go to the bases of the transistors are also connected to the power supply plus. The diode goes from the base of one transistor to the collector of the opposite transistor. The same with the second diode.
The collector goes to the ends of the winding. For DIY construction there is an option without a midpoint. To do this, you need to take two chokes, parallel one of the terminals of each inductor and connect it to the power supply positive. Disconnect the free leads to the collectors of each transistor. You can assemble this option with your own hands, but the elements will get very hot.
Power depends on the elements used. A device made according to this scheme can be made both weaker and stronger. Using this scheme, you can construct a 2-amp wireless charger with your own hands.
Making your own reel
First, let's wind the outline with our own hands. It doesn't have to be very neat. You can use a piece of plastic with a diameter of 5-10 cm or your fingers.
We take one long wire. Fold it in half. Straighten it. 
We wrap 5 turns on fingers or plastic. 
Now we secure the coils themselves around the entire circumference with glue or tape. 
We are left with three tips. One with a fold. Cut off this fold. Now we have 4 tips. We clean them. 
We will need to connect either the end of the first winding to the beginning of the second, or the beginning of the first winding to the end of the second. To check what is connected to what, we use a multimeter. 
Set the multimeter to diode test mode. We connect the multimeter to each tip at both ends simultaneously. We see that when connected to some ends the multimeter reacts, but when connected to others it does not. These tips should be on different sides. We must twist them together and solder them. This midpoint. The remaining tips are two collector windings that go to the transistors. Now we are ready to assemble the charger ourselves.
Putting it all together with our own hands
To assemble the device with your own hands, we take solder, a soldering iron and a circuit board. First we solder two transistors.
After this we solder the diodes.
They have resistors. One tip goes to the diodes, the other to the board. 
Now we solder the circuit with our own hands. We wound it up earlier. Now you need to tin its two windings and connect them to the circuit. 
Receiver
As a rule, people don’t dare to make a wireless charging receiver with their own hands, since here you already need to get into the phone. A rather crude separate receiver can be made with your own hands just to check if the transmitter works. In a DIY receiver, it is advisable to use a UF diode as well.
Capacitor with a capacity of 47-100 µF. Operating voltage - 25 volts. The second capacitor can be used for 10-16 Volts. Capacity - 47 µF. The circuit of the receiver, made by hand, is also 10 turns. Wire diameter - 0.75 mm.
It is more difficult to understand the written instructions than to follow the actions shown. We have attached a video on how to make a wireless phone charger with your own hands.
Review of ready-made devices for those who do not want to assemble them with their own hands
Do Charger For a DIY phone it's not that difficult, but few people will want to mess with it. It’s much easier to buy it than to design it yourself if you have the opportunity and don’t have a particular desire to make something. For that category of users who did not want to build everything with their own hands, we offer an overview of popular wireless chargers.
RAVPower Wireless Charging Pad
The battery of this device has a capacity of 5000 mAh, thanks to which it can simultaneously charge two smartphones. But they must support the Qi standard. 
Anker Wireless Charger PowerPort Qi Wireless Charging Pad
It has a temperature sensor to monitor overheating, overcharge protection. When this charger is not in use, it enters sleep mode. Costs about $17. 
Woodpuck FAST Edition Bamboo Qi Wireless Charging Pad
This charger is more powerful and more stylish. It is made of bamboo, which in itself is a big advantage. At the same time, it charges the phone 40% faster. Price about $40. 
Samsung Fast Charge Qi Wireless Charging Pad
This option has support for fast charging, but it costs about $50. Naturally this best option for the same smartphones and tablets from Samsung, if you want to spend no more than an hour on charging. 
Tylt Vü
This wireless phone charger is different from the rest unusual shape, which causes the phone to charge in an unusual position. It looks like a regular stand. The phone or tablet is placed on it in a semi-tilt, so it becomes much more convenient to use them while charging.
Nokia DT-903
The Nokia phone charger has a backlight that changes color to match the case. Especially for the native Nokia Lumia, a missed call and SMS indicator is built-in. 
Advantages
The previous advantage is used to equip phone chargers public institutions. That is, soon you won’t have to carry a charger with you everywhere and look for a cafe with sockets (the tables next to which, as a rule, are always occupied; and for a long time). But now you have to look for a cafe with wireless chargers. Which will probably be busy too. That is life…
If your smartphone is not very new, some elements in the socket may be worn out. Because of this, problems can also arise: the contacts simply will not touch each other tightly.
Flaws
The minimum cost of such charging is about 700 rubles. Quite inexpensive, you say. But keep in mind that the speed is much lower than that of the standard model. Behind high speed you have to pay extra. As a result, one wireless phone charger will cost at least 2.5 thousand.
In addition to the fact that energy efficiency is less, part of it will simply go away in the form of heat.
However, this method is not suitable for all phones. The same iPhones, for example, need additional devices.
FAQ
Above we told you how to do the exercises yourself and which one is better to buy. Now it remains to clarify some points. This technology is quite new, so not everyone knows what it is and how to use wireless charging. Here we answer the most popular questions.
What is the name of wireless phone charging?
Wireless charger- this, of course, is a name “for the masses”. Few people know what wireless phone charging is called. And its name is this: Qi standard induction coil. The name reflects the principle of its operation. Phone chargers of this type contain an inductive current transmitter, which charges the phone. And the little word Qi also has its own history, a very ancient one - it is the energy of Qi, so it is written in Latin. The concept is taken from traditional Chinese medicine.
How does wireless charging work?
The basic operating principle of wireless phone charging is magnetic induction. Electricity creates a magnetic field in the charger, which transfers voltage to the battery in the phone or tablet. The Wireless Electronic Energy Consortium has developed its own Qi standard specifically for such devices, which can be used to evaluate devices regardless of the manufacturer. The standard determines the current power supplied to the coil - 5 Watts.
How does wireless charging work? The magnetic field operates at a distance of 4 cm. It begins to form when a signal is given - a compatible device has appeared in the coverage area. Most often, this signal is given by the smartphone itself. The NFC function helps them with this. It stands for Near Field Communication. Under the influence of the voltage of this field, a current also appears in the coil built into the phone, which is supplied to the battery.
Which phones support wireless charging?
In the previous paragraph, we described the principle of wireless phone charging. After reading it, we understand that according to the Qi standard, wireless charging will work if a receiver-receiver is built into the smartphone. This receiver will be able to receive energy from that magnetic field, which is created in the charger coil. Which phones support wireless charging? Almost all modern smartphones and tablets are created taking into account this technology. These are companies such as Yota, Sony, Nokia, Samsung, Kyosera, Motorola, LG, Asus, Google, HTC and Blackerry. 
How do you know if your phone supports wireless charging or not?
How do you know if your phone supports wireless charging? This depends on the specific model. For example, Samsung Galaxy Note Edge supports it, but Sasung Galaxy Note 3 does not. You can ask your sales consultant or look on the Consortium website. There is a form on this page. By entering the brand name in the Brand name line and the phone name in the Product name line, you will find out whether your device is on the list or not. If not, don't worry. For those models that are not equipped with the necessary technology, special adapters are produced. And it would be a good idea to buy them, because wireless chargers are gradually appearing in in public places like coffee shops or airports. They are even going to build them into IKEA furniture.
How to charge wirelessly
How to charge wireless charger? Paradoxically, this must be done using a wire. If voltage is supplied to the phone through the air, then current flows into the charger itself in the standard way. First, assemble the power adapter and connect it to the device. Then we connect the adapter to the outlet. Some models have micro-USB cables, which allows you to charge them from laptops, for example.
How to connect and charge your phone with wireless charging
How to connect and charge your phone with wireless charging? As easy as pie. After connecting the device to an energy source, you need to place it on a flat surface and place the phone on top. It must be positioned so that the battery is within the coverage area, that is, in the middle of the backrest.
Hello dear friends!
Today I will tell you how to make a “Portable USB charger” with your own hands.
For this we need:
1. Car USB charger in the cigarette lighter.
2. Four wires.
3. Small on/off switch. I took it from an old table lamp. But it turned out to be impractical and I replaced it with a light switch.
4. Three Krona batteries.
5. A box of "Fort" coffee, or something else. You need either iron or plastic.
6. Glue gun.
And so: We take our car USB charger into the cigarette lighter, disassemble it, and take out the board. This is the most important part of our portable charging. On one side of this board you will see a spring and a small piece of iron plate. The spring in the middle is always a plus, and the iron plate on the side is always a minus. The spring can simply be soldered to the board or to the wiring and the wiring to the board. It’s the same with this piece of hardware on the side.. If the spring is soldered to the board, then we carefully unsolder it and solder the wires in its place. Then it’s the same with this piece of iron. If the spring is soldered to the wiring, then simply unsolder the spring from the wiring. It’s the same with this piece of hardware. After soldering the wiring to the board, let’s debug it to the side for now. Let's start making the terminal that we will need to connect the battery. The finished terminal can be removed from old children's toys or from anything where a Kron-type battery was attached. Or you can make it yourself. To do this, take one Kron battery, remove the plug from it, turn it over, take soldering flux, soak a cotton swab in it and degrease the contacts. Then we take the wires and solder them to the contacts. After soldering we take glue gun and apply glue to the place where the wires were soldered. So we're just doing isolation. Then we take our terminal and connect the battery to it. We do this in order to make sure where we have a plus and where we have a minus. When we are sure where the plus and where the minus are, we take our board to which we soldered wires instead of a spring with a piece of iron, and twist the wires minus with minus and carefully insulate the wires that we twisted with electrical tape. And we will let the plus through the switch. To do this, we take our switch; it has two contacts; to one we solder the wiring that comes from our board, and to the other we solder the wiring that comes from the terminal. Now our charger is almost ready. All that remains is to place it all in the case. 
To do this, we take our box; in my case, it’s the “Workstation First Aid Kit” box for repairing pneumatic tires.. We make a hole for USB. 
Then we make a hole for our switch.
Now let's take our insides. And this is our board, switch, and terminal. And we install it all inside the box. We attach the board to the bottom of the box using glue gun just like our switch. We also attach it to the box using a glue gun. 
Now we connect our battery and close the box. We connect the phone, turn on the charger and our phone charges. P.S. The input power of car USB chargers into the cigarette lighter is only 12V, so in no case do not connect it to power sources above 12V, otherwise it will simply burn out. The power of the Kron battery that I used for this portable charger is only 9V, which is quite enough to charge a phone, iPhone, camera, tablet, etc. approximately 2-3 times depending on the power of your battery... after which you will have to change the battery. I have a 3000 mAh battery in my phone, so the Kron battery is enough to maintain the battery charge and not fully charge it. Therefore, I replaced the Kron battery with a 12V battery, which is quite enough to charge the phone. To do this, we simply make 2 terminals from Kron batteries, solder one of them to the battery and that’s it, simply connect it to our portable charger. But in order not to buy a new battery every time, I would advise you to buy a charger for Kron batteries and when one battery runs out, you put it on charge and put the other in your portable charger. Or you can make a charger for Kron batteries yourself. But as? I will tell you about this in the next issue. Bye everyone, all the best. If you have any questions, write to my mailbox.
Prologue
The idea to build this design was inspired by a flight on an Airbus A380 aircraft, in which there is a USB connector under the armrest of each seat, designed to power USB-compatible devices. But such luxury is not available on all planes, and even more so it cannot be found on trains and buses. And I have long dreamed of rewatching the series “Friends” from beginning to end. So why not kill two birds with one stone - watch the series and brighten up your travel time.
An additional incentive to build this device was the discovery.
Technical task
The Portable Charger must provide the following capabilities.
- Battery operating time under rated load is at least 10 hours. High-capacity lithium-ion batteries are ideal for this purpose.
- Automatic switching on and off of the charger depending on the presence of load.
- Automatic shutdown of the charger when the battery is critically discharged.
- The ability to force the charger to turn on when the battery is critically discharged, if necessary. I believe that on the road a situation may arise when the battery of a portable charger is already discharged to a critical level, but the phone needs to be recharged for an emergency call. In this case, you need to provide an “Emergency power-on” button to use the energy still available in the battery.
- The ability to charge the batteries of a portable charger from a network charger with a Mini USB interface. Since you always take a phone charger with you on the road, you can also use it to charge the batteries of a portable power supply before the return trip.
- Simultaneous charging of charger batteries and recharging of a mobile phone from the same mains charger. Since the network charger from a mobile phone cannot provide sufficient current to quickly charge the battery of a portable charger, the charge can take a day or more. Therefore, it should be possible to connect the phone to charge directly while the battery of the portable power supply is charging.
Based on this technical specification, a portable charger using lithium-ion batteries was built.
Block diagram
The portable memory consists of the following components.
- Converter 5 → 14 Volt.
- A comparator that turns off the charge converter when the voltage on the lithium-ion battery reaches 12.8 Volts.
- Charge indicator – LED.
- Converter 12.6 → 5 Volts.
- 7.5 Volt comparator that turns off the charger when deep discharge batteries.
- A timer that determines the operating time of the converter when the battery is critically discharged.
- Converter operation indicator 12.6 → 5 Volts - LED.
Switching voltage converter MC34063
It didn’t take long to choose a driver for the voltage converter, since there wasn’t much to choose from. At the local radio market, at a reasonable price ($0.4), I found only the popular MC34063 chip. I immediately bought a couple to find out if it was possible to somehow forcibly turn off the converter, since the datasheet for this chip does not provide for such a function. It turned out that this can be done by applying supply voltage to pin 3, intended for connecting the frequency-setting circuit.
The picture shows a typical circuit of a step-down pulse converter. The forced shutdown circuit, which may be needed for automation, is marked in red.
In principle, having assembled such a circuit, you can already power your phone or player if, for example, the power is supplied from ordinary batteries (batteries).
I will not describe in detail the operation of this microcircuit, but from " Additional materials» you can download and detailed description in Russian, and a small portable program for quickly calculating the elements of a step-up or step-down converter assembled on this chip.
Lithium-ion battery charge and discharge control units
When using lithium-ion batteries, it is advisable to limit their discharge and charge. For this purpose, I used comparators based on cheap CMOS chips. These microcircuits are extremely economical, as they operate on microcurrents. At the entrance they have field effect transistors with an insulated gate, which makes it possible to use a microcurrent Reference Voltage Source (VNS). I don’t know where to get such a source, so I took advantage of the fact that in microcurrent mode, the stabilization voltage of conventional zener diodes decreases. This allows you to control the stabilization voltage within certain limits. Since this is not a documented inclusion of a zener diode, it is possible that in order to provide a certain stabilization current, the zener diode will have to be selected.
To provide a stabilization current of, say, 10-20 µA, the ballast resistance should be in the region of 1-2 MOhm. But, when adjusting the stabilization voltage, the resistance of the ballast resistor may turn out to be either too small (several kiloohms) or too large (tens of megaohms). Then you will have to select not only the resistance of the ballast resistor, but also a copy of the zener diode.
The digital CMOS chip switches when the input signal level reaches half the supply voltage. Therefore, if you power the ION and the microcircuit from a source whose voltage you want to measure, then a control signal can be obtained at the output of the circuit. Well, this same control signal can be applied to the third pin of the MC34063 chip.
The drawing shows a comparator circuit using two elements of the K561LA7 microcircuit.
Resistor R1 determines the value reference voltage, and resistors R2 and R3 are comparator hysteresis.
Charger switching and identification unit
In order for a phone or player to start charging from a USB connector, it needs to be made clear that this is a USB connector, and not some kind of surrogate. To do this, you can apply a positive potential to contact “-D”. In any case, this is enough for Blackberry and iPod. But, my branded charger also supplies positive potential to the “+D” contact, so I did the same.
Another purpose of this node is to control the switching on and off of the 12.6 → 5 Volt converter when a load is connected. This function is performed by transistors VT2 and VT3.
The design of the portable charger also includes a mechanical power switch, but its purpose is more likely to correspond to the “mass switch” of the battery in a car.
Electrical circuit of a portable power supply
The figure shows a diagram of a mobile power supply.
C1, C3 = 1000µF
C2, C6, C10, C11, C13 = 0.1µF
C14 = 20µF (tantalum)
IC1, IC2 – MC34063
| DD1 = K176LA7 | R3, R12 = 1k | R27 = 44M |
| DD2 = K561LE5 | R4, R7 = 300k | R28 = 3k |
| FU=1A | R5 = 30k | VD1, VD2 = 1N5819 |
| HL1 = Green | R6 = 0.2 Ohm | VD3, VD6 = KD510A |
| HL2 = Red | R8, R15, R23, R29 = 100k | VT1, VT2, VT3 = KT3107 |
| L1 = 50mkH | R10, R11, R13, R26 = 1M | VT4 = KT3102 |
| L2 = 100mkH | R16, R24 = 22M | Are being selected |
| R0, R21 = 10k | R17, R19, R25 = 15k | R14* = 2M |
| R1 = 180Ohm | R18 = 5.1M | R22* = 510k |
| R2 = 0.3Ohm | R20 = 680Ohm | VD4*, VD5* = KS168A |
Purpose of circuit nodes.
IC1 – step-up voltage converter 5 → 14 Volts, which serves to charge the built-in battery. The converter limits the input current to 0.7 Amps.
DD1.1, DD1.2 – battery charge comparator. Interrupts the charge when the battery reaches 12.8 Volts.
DD1.3, DD1.4 – indication generator. Makes the LED flash while charging. The indication is made by analogy with Nikon chargers. While charging is in progress, the LED flashes. The charge is complete - the LED lights up constantly.
IC2 – step-down converter 12.6 → 5 Volts. Limits output current to 0.7 Ampere.
DD2.1, DD2.2 – battery discharge comparator. Interrupts battery discharge when the voltage drops to 7.5 Volts.
DD2.3, DD2.4 – timer for emergency switching on of the converter. Turns on the converter for 12 minutes, even if the battery voltage drops to 7.5 Volts.
Here the question may arise, why such a low threshold voltage was chosen if some manufacturers do not recommend allowing it to drop below 3.0 or even 3.2 Volts on the bank?
I reasoned like this. Traveling does not happen as often as we would like, so the battery is unlikely to have to go through many charge-discharge cycles. Meanwhile, in some sources describing the operation of lithium-ion batteries, a voltage of 2.5 Volts is called critical.
But, you can limit the discharge limit to more high level voltage if you plan to use such a charger frequently.
Construction and details
I express my gratitude to Sergei Sokolov for his help in finding the design components!
Printed circuit boards (PCBs) are made of foil-coated fiberglass laminate with a thickness of 1 mm. The dimensions of the PP were selected based on the dimensions of the purchased case.
All elements of the circuit, except the battery, are placed on two printed circuit boards Oh. Moreover, on the smaller one there is only a Mini USB connector for connecting an external charger.
The power supply units were placed in a standard Z-34 polystyrene housing. This is the most expensive part of the design, for which we had to pay $2.5.
The power switch pos. 2 and the forced power button pos. 3 are hidden flush with the outer surface of the case to avoid accidental pressing.
The Mini USB connector is located on the rear wall of the case, and the USB connector pos. 4 together with indicators pos. 5 and pos.6 to the front.
The size of the printed circuit boards is designed to fix the batteries in the body of the portable power supply. Between the batteries and other structural elements, a 0.5 mm thick electrical cardboard gasket, bent in the shape of a box, is inserted.
This movie requires Flash Player 9 |
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And this is a portable power supply unit in assembled form. Drag the image with the mouse to view the power supply from different angles.
Settings
Setting up a portable charger came down to selecting instances of zener diodes and ballast resistors for each of the two comparators.
How it works? Video illustration.
The three-minute video shows how this homemade product works and what is inside. Video format – Full HD.