Today we have a very useful homemade product for car enthusiasts, especially in winter! This time we will tell you how to make a homemade charger from an old printer with your own hands!
If you have an old printer, don’t rush to throw it away; it has a power supply from which you can make a simple automatic charger for a car battery with the function of adjusting the voltage and charge current. At one time, I had a safety margin greater than that of printer print heads. In this regard, I have accumulated a couple of printers with absolutely working power supplies, quite suitable for creating low-power automatic battery chargers.
The circuit is based on 2 stabilizers:
- Current stabilizer on the LM317 chip
- Adjustable voltage stabilizer made on a microcircuit (adjustable zener diode) TL431
The device also uses another Lm7812 stabilizer chip, which powers a 12 Volt cooler (which was originally in this case).
The charger is assembled in the case, all the contents of the unit, except the cooler, are removed. Stabilizer chips Lm317 and Lm 7812 are each installed on its own radiator, which are screwed to a plastic case (ATTENTION they cannot be installed on a common radiator!).
The circuit is assembled by mounted mounting on stabilizer microcircuits. Resistors R2 and R3 with a power of 2-5 Watts in ceramic cases are responsible for limiting the charge current. They are installed so that it passes through them. Their value is calculated using the formula R=1.25(V)/I(A), you can calculate the maximum charge current you need. Since we are talking about calculations, let me remind you that we have If you need to smoothly regulate the charge current, you can install a powerful rheostat with an additional limiting resistor (so as not to exceed the maximum permissible current for Lm317)
In my case it was 24 Volts with a maximum load current of 1 Ampere. It is necessary to reserve 0.1 Ampere from this 1 Ampere for powering the cooler (the consumption current is indicated on the sticker) + I left 10% for a safety margin, respectively, for the main purpose - 0.8 Ampere remains for the charging current.
It is clear that you cannot quickly charge a car battery with a current of 800 mA. In one day, the battery can be supplied with 24 hours * 0.8 A = 19.2 Ampere hours, which is 30-45% of the capacity of a car battery (usually 45-65 Ah).
If you have a “donor” power supply with a current of 1.5 Amperes, you will be able to provide 30 Ampere hours per day, which is probably enough for a battery that has been in use for more than one year.
But, on the other hand, charging with a low current is more useful for the battery, “it is better absorbed”, just unscrew the plugs from the battery (if it is serviceable), connect the charger to the battery and that’s it! You can go about your business and not worry that the battery will be overcharged, the maximum voltage on the battery will not exceed 14.5 Volts, and the low charging current will prevent excessive overheating and boiling off of the electrolyte. Due to the fact that you don’t have to control the charging process, I think this can be safely called an automatic charger for car batteries, although there is no “tracking automation” in the circuit.
For convenience, the charger can be equipped with a Volt meter, which will make it possible to visually monitor the battery charging process. For example, like this for a couple of dollars.
The charger must be equipped with protection against polarity reversal. The role of such protection is performed by two diodes with a permissible current of 5 Amps connected to the output of the charger in combination with a 2 Ampere fuse (during installation, be careful and observe the polarity of diode connections!!!). If the charger is connected incorrectly to the battery, the battery current will flow into the charger through the fuse and “hit” the diode, when the current reaches 2 Amps, the fuse will save the world! Also, do not forget to provide the device with fuses for the 220 Volt circuit (in my case, for the 220 Volt circuit, the fuse is already inside the power supply).
We connect the charger to the car battery using special “crocodile” clips; when buying them on the Internet, pay attention to the physical size indicated in the characteristics, since you can easily buy crocodiles for a “laboratory power supply” that will be good for everyone, but will not fit on the positive one battery terminal, and reliable contact, as you yourself understand, is a must in such matters. For convenience, there are several nylon Velcro ties on the wires and the body with which you can carefully and compactly wind the wires.
I hope this printer recycling idea is useful to someone. If you have made homemade automatic chargers for car batteries (or non-automatic ones), please share with the readers of our site - send us a photo, diagram and a short description of your device by email. If you have questions about the scheme and operating principle, ask in the comments and I will answer.
Long-term use of the car leads to the fact that the generator stops charging the battery. As a result, the car will no longer start. To revive the car you need a charger. In addition, lead-acid batteries are highly sensitive to temperatures. Therefore, problems may arise with their operation if the temperature outside is sub-zero.
A car charger is not particularly technically complex. To collect it you don’t need to have any highly specialized knowledge, just perseverance and ingenuity. Of course, you will need certain parts, but they can easily be purchased on the radio market for almost nothing.
Types of chargers for cars
Science does not stand still. Technologies are developing at an incredible speed; it is not surprising that transformer chargers are gradually disappearing from the market, and they are being replaced by pulsed and automatic chargers.
The pulse charger for the car is compact in size. His easy to use, and unlike transformer type devices of this class provide a full battery charge. The charging process takes place in two stages: first at constant voltage, then at current. The design consists of similar circuits.
The automatic car charger is extremely easy to use. In fact, this is a multifunctional diagnostic center, which is extremely difficult to assemble on your own.
The most advanced devices of this class will notify you with a signal if the poles are connected incorrectly. Moreover, the power supply will not even start. You cannot ignore the diagnostic functions of the device. It is able to measure battery capacity and even charge level.
Electrical circuits have a timer. Therefore, an automatic car charger allows for various types of charging:
- complete,
- fast,
- restorative.
Once the automatic car charger has finished charging, a beep will sound and the current will automatically stop flowing.
Three ways to make a car charger with your own hands
How to make a charger from a computer block
Old computers are not uncommon. Some people leave them out of a sense of nostalgia, while others hope to use serviceable components somewhere. If you don’t have an old desktop computer at home, it’s okay. Second-hand The power supply can be purchased for 200-300 rubles.
Power supplies from desktop computers are ideal for creating any chargers. The controller used here is the TL494 chip or a similar KA7500 chip.
The power supply for the charger must be 150 W or higher. All wires from sources -5, -12, +5, +12 V are soldered off. The same is done with resistor R1. It needs to be replaced with a trim resistor. In this case, the value of the latter should be 27 Ohms.
The operating diagram of a car charger from a power supply is extremely simple. The voltage from the bus marked at +12 V is transmitted to the upper pin. In this case, pins 14 and 15 are simply cut off due to their uselessness.
Important! The only pin that needs to be left is the sixteenth one. It is adjacent to the main wire. But at the same time it needs to be turned off.
A potentiometer-regulator R10 should be installed on the rear wall of the power supply. You also need to run two cords: one for connecting the terminals, the other for the network. Additionally, you need to prepare a block of resistors. It will allow for adjustments.
To make the block described above, you will need two current measuring resistors. It is best to use 5W8R2J. A power of 5 W is quite enough. The block resistance will be 0.1 Ohm, and the total power will be 10 W.
To configure, you will need a trim resistor. It is attached to the same board. Part of the print track is first removed. This will eliminate the possibility of communication between the case and the main circuit, and will also significantly increase the safety of the car charger.
Before as solder pins 1, 14-16, they must first be tinned. Multi-core thin wires are soldered. Full charge is determined by the open circuit voltage. The standard range is 13.8-14.2 V.
The full charge is set by a variable resistor. It is important that potentiometer R10 is in the middle position. To connect the output to the terminals, special clamps are installed at the ends. It is best to use the crocodile type.
The insulating tubes of the clamps must be made in different colors. Traditionally, red is a plus, blue is a minus. But you can choose any colors you like. This is not important.
Important! If you mix up the wires, it will damage the device.
To save time and money when assembling a charger for a car, you can eliminate the volt and ammeter from the design. The initial current can be set using potentiometer R10. Recommended value is 5.5 and 6.5 A.
Charger from adapter
The best option for creating a car charger is a 12-volt adapter. But when choosing a voltage, you must first consider the battery parameters.
The adapter wire must be cut at the end and exposed. About 5-7 centimeters will be enough for comfortable work. Wires with opposite charges must be laid at a distance of 40 centimeters from each other. A “crocodile” is put on the end of each one.
The clamps are connected to the battery in sequential order. Plus to plus, minus to minus. After that, all you need to do is turn on the adapter. This is one of the simplest schemes for creating a charger for a car with your own hands.
Important! During the charging process, you need to ensure that the battery does not overheat. If this happens, the process must be interrupted immediately to avoid damage to the battery.
Everything ingenious is simple or a car charger made from a light bulb and a diode
Everything you need to create this charger can be found at home. The main element of the design will be an ordinary light bulb. Moreover, its power should not be higher than 200 W.
Important! The more power, the faster the battery will charge.
When charging, some care must be taken. You should not charge a low-capacity battery with a 200-watt light bulb. Most likely this will lead to it simply boiling. There is a simple calculation formula that will help you choose the optimal light bulb power for your battery.
You will also need a semiconductor diode that will conduct electricity in only one direction. It can be made from a regular laptop charger. The final element of the design will be a wire with terminals and a plug.
It is very important to follow safety rules when creating a charger for a car. First, always unplug the circuit before touching any of the elements with your hand. Secondly, all contacts must be carefully isolated. There should be no exposed wires.
When assembling the circuit, all elements are connected in series: lamp, diode, battery. It is important to know the polarity of the diode in order to connect everything correctly. For greater safety, use rubber gloves.
When assembling the circuit, pay special attention to the diode. There is usually an arrow on it that points to the plus. Since it only allows electricity to pass in one direction, this is extremely important. You can use a tester to check the polarity of the terminals.
If everything is configured and connected correctly, the light will light at half a channel. If there is no light, it means you did something wrong or the battery is completely discharged.
The charging process itself takes about 6-8 hours. After this time period, the car charger must be disconnected from the network to avoid overheating of the battery.
If you urgently need to recharge the battery, the process can be accelerated. The main thing is that the diode is powerful enough. You will also need a heater. All elements are connected into one circuit. The efficiency of this charging method is only 1%, but the speed is many times higher.
Results
The simplest car charger can be assembled with your own hands in a few hours. At the same time, a set of necessary materials can be found in every home. More complex devices require more time to create, but they have increased reliability and a good level of security.
This is a very simple attachment circuit for your existing charger. Which will control the battery charge voltage and, when the set level is reached, disconnect it from the charger, thereby preventing the battery from overcharging.
This device has absolutely no scarce parts. The entire circuit is built on just one transistor. It has LED indicators that indicate the status: charging in progress or the battery is charged.
Who will benefit from this device?
This device will definitely come in handy for motorists. For those who do not have an automatic charger. This device will turn your regular charger into a fully automatic charger. You no longer have to constantly monitor the charging of your battery. All you need to do is put the battery on charge, and it will turn off automatically only after it is fully charged.Automatic charger circuit
Here is the actual circuit diagram of the machine. In fact, it is a threshold relay that is activated when a certain voltage is exceeded. The response threshold is set by variable resistor R2. For a fully charged car battery, it is usually equal to - 14.4 V.
You can download the diagram here -
Printed circuit board
How to make a printed circuit board is up to you. It is not complicated and therefore can easily be laid out on a breadboard. Well, or you can get confused and make it on textolite with etching.
Settings
If all the parts are in good working order, setting up the machine is reduced only to setting the threshold voltage with resistor R2. To do this, we connect the circuit to the charger, but do not connect the battery yet. We move resistor R2 to the lowest position according to the diagram. We set the output voltage on the charger to 14.4 V. Then slowly rotate the variable resistor until the relay operates. Everything is set.Let's play with the voltage to make sure that the console works reliably at 14.4 V. After this, your automatic charger is ready for use.
In this video you can watch in detail the process of all assembly, adjustment and testing in operation.
Today, there are quite a lot of different battery-powered devices. And it’s even more annoying when, at the most inopportune moment, our device stops working, because the batteries are simply dead, and their charge is not enough for the normal functioning of the device.
Buying new batteries every time is quite expensive, but trying to make a homemade device for charging finger batteries with your own hands is quite worth it.Many craftsmen note that it is preferable to charge such batteries (AA or AAA) using direct current, because this mode is most beneficial in terms of safety for the batteries themselves. In general, the transferred charge power from the network is about 1.2-1.6 times the capacity of the battery itself. For example, a nickel-cadmium battery with a capacity of 1A/h will be charged with a current of 1.6A/h. Moreover, the lower the given power, the better for the charging process.
In the modern world, there are quite a lot of household appliances equipped with a special timer that counts down a certain period, then signaling its end. When making your own device for charging AA batteries, You can also use this technology, which will notify you when the battery charging process is complete.
AA is a device that generates direct current, charging with a power of up to 3 A/h. During production, the most common, even classic, scheme was used, which you see below. The basis, in this case, is the transistor VT1.
The voltage on this transistor is indicated by a red LED VD5, which acts as an indicator when the device is connected to the network. Resistor R1 sets a certain power of currents passing through this LED, as a result of which the voltage in it fluctuates. The value of the collector current is formed by the resistance from R2 to R5, which are included in VT2 - the so-called “emitter circuit”. At the same time, by changing the resistance values, you can control the degree of charging. R2 is constantly connected to VT1, setting a constant current with a minimum value of 70 mA. To increase the charging power, it is necessary to connect the remaining resistors, i.e. R3,R4 and R5.
Read also: Making a simple 12V - 220V converter with your own hands
It is worth noting that The charger only functions when the batteries are connected.After connecting the device to the network, a certain voltage appears on resistor R2, which is transmitted to transistor VT2. Then, the current flows further, as a result of which the VD7 LED begins to burn intensely.
A story about a homemade device
Charging from USB port
You can make a charger for nickel-cadmium batteries based on a regular USB port. At the same time, they will be charged with a current of approximately 100 mA. The scheme, in this case, will be as follows:
At the moment, there are quite a lot of different chargers sold in stores, but their cost can be quite high. Considering that the main point of various homemade products is precisely to save money, self-assembly is even more advisable in this case.
This circuit can be modified by adding an additional circuit to charge a pair of AA batteries. Here's what we ended up with:
To make it more clear, here are the components that were used during the assembly process:
It is clear that we cannot do without basic tools, so before starting assembly you need to make sure that you have everything you need:
- soldering iron;
- solder;
- flux;
- tester;
- tweezers;
- various screwdrivers and knife.
Read also: Let's learn everything about step-down transformers 220-12 volts
Interesting material about making it yourself, we recommend viewing it
A tester is necessary to check the performance of our radio components. To do this, you need to compare their resistance, and then check it with the nominal value.
For assembly we will also need a case and a battery compartment. The latter can be taken from the children's Tetris simulator, and the body can be made from an ordinary plastic case (6.5cm/4.5cm/2cm).
We attach the battery compartment to the case using screws. The board from the Dandy console, which needs to be cut out, is perfect as a basis for the circuit. We remove all unnecessary components, leaving only the power socket. The next step is to solder all the parts based on our diagram.
The power cord for the device can be taken from a regular computer mouse cord with a USB input, as well as part of the power cord with a plug. When soldering, polarity must be strictly observed, i.e. solder plus to plus, etc. We connect the cord to USB, checking the voltage supplied to the plug. The tester should show 5V.
