There are times, especially in winter, when car owners need to recharge car battery from an external power source. Of course, people who do not have good electrical skills will It is advisable to buy a factory charger battery , even better to buy starter-charger to start the engine with a discharged battery without wasting time on external charging.
But if you have a little knowledge in the field of electronics, you can assemble a simple charger with your own hands.
general characteristics
To properly maintain the battery and extend its service life, recharging is required when the voltage at the terminals drops below 11.2 V. At this voltage, the engine will most likely start, but if parked for a long time in winter, this will lead to sulfation of the plates and, as a result, a decrease in capacity batteries. When parked for a long time in winter, it is necessary to regularly monitor the voltage at the battery terminals. It should be 12 V. It is best to remove the battery and take it to a warm place, not forgetting monitor the charge level.
The battery is charged using constant or pulsed current. When using a constant voltage power supply, the current for proper charging should be one tenth of the battery capacity. If the battery capacity is 50 Ah, then a current of 5 amperes is required for charging.
To extend the battery life, battery plate desulfation techniques are used. The battery is discharged to a voltage of less than five volts by repeated consumption of a large current of short duration. An example of such consumption is starting the starter. After this, a slow full charge is carried out with a small current within one ampere. Repeat the process 8-9 times. The desulfation method takes a long time, but according to all studies it gives good results.
It must be remembered that when charging, it is important not to overcharge the battery. The charge is carried out to a voltage of 12.7-13.3 volts and depends on the battery model. Maximum charge indicated in the documentation for the battery, which can always be found on the Internet.
Overcharging causes boiling, increases the density of the electrolyte and, as a result, the destruction of the plates. Factory charging devices have charge monitoring and subsequent shutdown systems. Assemble such systems yourself, without having sufficient knowledge in electronics, it is quite difficult.
DIY assembly diagrams
It's worth talking about simple devices charges that can be assembled with minimal knowledge in electronics, and the charge capacity can be monitored by connecting a voltmeter or an ordinary tester.
Charging circuit for emergencies
There are times when a car that has been parked overnight near the house cannot be started in the morning due to a discharged battery. There can be many reasons for this unpleasant circumstance.
If the battery was in good condition and is a little discharged, they will help solve the problem:
Ideal as a power source laptop charger. It has an output voltage of 19 volts and a current of within two amperes, which is quite enough to complete the task. On the output connector, as a rule, the internal input is positive, the external circuit of the plug is negative.
As a limiting resistance, which is mandatory, you can use a cabin light bulb. More can be used powerful lamps, for example, from the dimensions, but this will create an extra load on the power supply, which is very undesirable.
An elementary circuit is assembled: the negative of the power supply is connected to the light bulb, the light bulb to the negative of the battery. Plus goes directly from the battery to the power supply. Within two hours the battery will receive a charge to start the engine.
From a power supply from a desktop computer
Such a device is more difficult to manufacture, but it can be assembled with minimal knowledge of electronics. The basis will be an unnecessary block from the computer system unit. The output voltages of such units are +5 and +12 volts with an output current of about two amperes. These parameters allow you to assemble a low-power charger, which, if assembled correctly will serve the owner for a long time and reliably. Fully charging the battery will take a long time and will depend on the battery capacity, but will not create the effect of desulfation of the plates. So, step-by-step assembly of the device:
- Disassemble the power supply and unsolder all wires except the green one. Remember or mark the input locations of black (GND) and yellow +12 V.
- Solder the green wire to the place where the black one was located (this is necessary to start the unit without a PC motherboard). In place of the black wire, solder a lead, which will be negative for charging the battery. In place of the yellow wire, solder the positive lead for charging the battery.
- You need to find a TL 494 chip or its equivalent. A list of analogs is easy to find on the Internet; one of them will definitely be found in the circuit. With all the variety of blocks, they are not produced without these microcircuits.
- From the first leg of this microcircuit - it is the lower left one, find the resistor that goes to the +12 volt output (yellow wire). This can be done visually along the tracks in the diagram, or using a tester by connecting the power and measuring the voltage at the input of the resistors going to the first leg. Do not forget that the primary winding of the transformer carries a voltage of 220 volts, so you need to take safety precautions when starting the unit without a housing.
- Unsolder the found resistor and measure its resistance with a tester. Select a variable resistor that is close in value. Set it to the desired resistance value and solder it in place of the removed circuit element with flexible wires.
- By starting the power supply by adjusting the variable resistor, get a voltage of 14 V, ideally 14.3 V. The main thing is not to overdo it, remembering that 15 V is usually the limit for working out the protection and, as a result, shutting down.
- Unsolder the variable resistor without changing its setting, and measure the resulting resistance. Select the required or closest resistance value from several resistors and solder it into the circuit.
- Check the unit, the output should have the required voltage. If desired, you can connect a voltmeter to the outputs on the plus and minus circuit, placing it on the case for clarity. Subsequent assembly occurs in reverse order. The device is ready for use.
The unit will perfectly replace an inexpensive factory charger and is quite reliable. But you MUST remember that the device has overload protection, but this will not save you from polarity errors. Simply put, if you confuse the plus and minus when connecting to the battery, The charger will instantly fail.
Charger circuit from an old transformer
If you don’t have an old computer power supply at hand, and your radio engineering experience allows you to install simple circuits yourself, then you can use the following rather interesting battery charging circuit with control and regulation of the supplied voltage.
To assemble the device, you can use transformers from old uninterruptible power supplies or TVs Soviet made
. Any powerful step-down transformer with a total voltage set on the secondary windings of approximately 25 volts will do.
The diode rectifier is assembled on two KD 213A diodes (VD 1, VD 2), which must be installed on the radiator and can be replaced with any imported analogues. There are many analogues, and they can be easily selected from reference books on the Internet. Surely the necessary diodes can be found at home in old unnecessary equipment.
The same method can be used to replace the control transistor KT 827A (VT 1) and zener diode D 814 A (VD 3). The transistor is installed on the radiator.
The supply voltage is adjusted by variable resistor R2. The scheme is simple and obviously working. It can be assembled by a person with minimal knowledge of electronics.
Pulse charging for batteries
The circuit is difficult to assemble, but this is the only drawback. It is unlikely that you will be able to find a simple circuit for a pulse charging unit. This is compensated by the advantages: such blocks hardly heat up, at the same time they have serious power and high efficiency, and are compact in size. The proposed circuit, mounted on a board, fits into a container measuring 160*50*40 mm. To assemble the device, you need to understand the operating principle of PWM ( Pulse width modulation) generator. In the proposed version, it is implemented using the common and inexpensive IR 2153 controller.
With capacitors used, the power of the device is 190 watts. This is enough to charge any light car battery with a capacity of up to 100 Ah. By installing 470 µF capacitors, the power will double. It will be possible to charge batteries with a capacity of up to two hundred amperes/hours.
When using devices without automatic battery charge control, you can use a simple network, daily relay made in China. This will eliminate the need to monitor the time the unit is disconnected from the network.
The cost of such a device is about 200 rubles. Knowing the approximate charging time of your battery, you can set the desired shutdown time. This ensures that the electricity supply is cut off in a timely manner. You can get distracted by business and forget about the battery, which can lead to boiling, destruction of the plates and failure of the battery. New battery will cost much more
Precautionary measures
When using self-assembled devices, the following safety precautions should be observed:
- All devices, including the battery, must be on a fire-resistant surface.
- When using the manufactured device for the first time, it is necessary to ensure full control of all charging parameters. It is imperative to control the heating temperature of all charging elements and the battery; the electrolyte should not be allowed to boil. The voltage and current parameters are controlled by a tester. Primary control will help determine the time fully charged battery, which will be useful in the future.
Assembling a battery charger is easy even for a beginner. The main thing is to do everything carefully and follow safety measures, since you will have to deal with an open voltage of 220 volts.
Even with a fully serviceable car, sooner or later a situation may arise when you need an external source - long parking, accidentally left on parking lights and so on. Owners of old equipment are well aware of the need to regularly recharge the battery - this is due to the self-discharge of a “tired” battery and increased leakage currents in electrical circuits, primarily in the diode bridge of the generator.
You can purchase a ready-made charger: they Available in many variants and are easily accessible. But some may think that making a charger for a car battery with their own hands will be more interesting, while for others the ability to make a charger literally from scrap material will help them out.
Semiconductor diode + light bulb
It is not known who first came up with the idea of charging the battery in this way, but this is exactly the case when you can charge the battery literally with improvised means. In this circuit, the current source is a 220V electrical network; a diode is needed for conversion alternating current into a pulsating constant, and the light bulb serves as a current-limiting resistor.
The calculation of this charger is as simple as its circuit:
- The current flowing through the lamp is determined based on its power as I=P/U, Where U– network voltage, P– lamp power. That is, for a 60 W lamp, the current in the circuit will be 0.27 A.
- Since the diode cuts off every second half-wave of the sinusoid, the real average load current, taking this into account, will be equal to 0.318*I.
As you can see, even when using a powerful lamp, the load current is small, which will allow the use of any common diode, for example 1N4004 (these usually come with alarm systems, are found in power supplies for low-power equipment, and so on). All you need to know to assemble such a device is that the stripe on the diode body indicates its cathode. Connect this contact to the positive terminal of the battery.
Do not connect this device to the battery unless it is removed from the vehicle to avoid damage to the on-board electronics. high voltage!A similar manufacturing option is shown in the video
Rectifier
This memory is somewhat more complicated. This scheme is used in the cheapest factory devices:
To make a charger, you will need a mains transformer with an output voltage of at least 12.5 V, but not more than 14. Often a Soviet transformer of the TS-180 type is taken from tube TVs, which has two filament windings for a voltage of 6.3 V. When they are connected in series (the purpose of the terminals is indicated on the transformer body) we get exactly 12.6 V. A diode bridge (full-wave rectifier) is used to rectify the alternating current from the secondary winding. It can either be assembled from individual diodes (for example, D242A from the same TV), or you can buy a ready-made assembly (KBPC10005 or its analogues).
The rectifier diodes will heat up noticeably, and you will have to make a radiator for them from a suitable aluminum plate. In this regard, using a diode assembly is much more convenient - the plate is attached with a screw to its central hole using thermal paste.
Below is a pin assignment diagram for the most common pulse blocks power supply for TL494 chip:
We are interested in the circuit connected to pin 1. Looking through the traces connected to it on the board, find the resistor connecting this leg to the +12 V output. It is this that sets the output voltage of the 12-volt power supply circuit.
How often do car owners fail to start a four-wheeled pet due to lack of charge in the battery? Of course, if this incident happened in the garage near the charging unit or there is a friend with a car nearby who is ready to help start the starter, no special problems are expected.
The situation is much worse if you cannot implement either the first or second option, especially motorists who do not have the opportunity to purchase an expensive factory-made charger suffer from this. But even in this case, you can find a solution if you make a charger for a car battery with your own hands.
Advantages and disadvantages of a homemade device
The main advantage of a homemade charger is its low cost, even if you do not have all the necessary parts, the savings will be noticeable. Also a significant advantage is the ability to use unnecessary instruments and devices as a source of materials for a homemade memory.
The disadvantages of homemade battery charging include imperfection in operation. Alas, the model cannot turn off on its own when the maximum charge is reached, so you will have to control this process or supplement the invention with homemade automation, which is possible for experienced radio amateurs.
Device Settings
As you well know, the entire network in the car is powered low voltage 12V direct current, but the charge level of the car battery should be in the range from 13 to 15V. The charge current at the device output should be about 10% of the power source capacity. If the current is less, the charge will still occur, but the procedure will last much longer. Therefore, the choice of elements for the charger should be based on the operating parameters of the specific model of lead-acid battery and the network to which it will be connected.
What is needed for the memory?
Structurally, the charger includes the following elements:
Rice. 2: Example of setting the adjustment resistor If you are going to charge the battery once, you can use only the first three elements; for constant use it will be more convenient to have at least control devices. But before you put it all together, you need to make sure that the charger's parameters after assembly will meet your needs. The first thing that needs to match is the charger transformer.
If the transformer is not suitable
Not always in a garage or at home you will find just such a transformer that will be powered by 220V and output 13 - 15V at the output terminals. Most models used in everyday life do have a 220V primary coil, but the output can be of any value. To fix this you will need to make a new secondary.
First, recalculate the transformation ratio using the formula: U 1 / U 2 = N 1 / N 2,
N 1 and N 2 – the number of turns in the primary and secondary, respectively.
For example, an electric machine is used as a 42V power supply, but you want to get 14V for the charger. Therefore, you need to make 31 turns on the charger secondary with 480 turns in the primary. This can be achieved either by reducing the number of turns, removing unnecessary ones, or by winding a new one. But the first option is not always suitable, since the cross-section of the transformer winding may not withstand the current with a smaller number of turns.
U 1 *I 1 = U 2 *I 2 ,
Where U 1 and U 2 are the voltage on the primary and secondary windings, I 1 and I 2 are the current flowing in the primary and secondary.
As you can see, with a decrease in the number of turns and voltage on the secondary winding, the current strength in it will increase proportionally. As a rule, the cross-sectional margin is not enough, so after determining the current strength, a new conductor is selected for it from the data in the table:
Table: selection of cross section, depending on the flowing current
| Copper conductor | Aluminum conductor | ||
| Section
lived mm 2 |
Current, A | Section of veins. mm 2 | Current, A |
| 0,5 | 11 | — | — |
| 0,75 | 15 | — | — |
| 1 | 17 | — | — |
| 1.5 | 19 | 2,5 | 22 |
| 2.5 | 27 | 4 | 28 |
| 4 | 38 | 6 | 36 |
| 6 | 46 | 10 | 50 |
| 10 | 70 | 16 | 60 |
| 16 | 80 | 25 | 85 |
If the calculated current value at the output of the charger exceeds the required 10% of the battery capacity, a current-limiting resistor must be included in the circuit, the value of which is selected in proportion to the excess current.
The procedure for assembling a charger for a car battery
Depending on the components you have and the battery parameters, the charger assembly will vary significantly. In this example, the manufacturing technology includes the following steps:
But you must build on the parameters of your electric machine. Therefore, if necessary, remove excess windings or insulate their terminals (if any), wind a secondary (if the existing one does not provide the required voltage level in the memory).
Rice. 5: Rewind the windings 
and on the secondary there are pins 9 and 9′.
Rice. 7: connect pins 9 - Solder the power cord leads to terminals 2 and 2′.
Rice. 8: Connect the power cord - Assemble the diode assembly on a textolite plate, as shown in the diagram. Due to intense heat generation due to high charging currents, semiconductor devices are installed on a radiator.
Rice. 9: diode assembly - Connect the bridge to the 12V terminals, in this example these are terminals 10 and 10′. The main elements of the charger are assembled.
Rice. 10: connect pins 10 to the diode bridge - Install an ammeter with a measurement limit of up to 15 A between the diode bridge terminal and the battery terminals.
Rice. 11: connect the ammeter - Connect a current-limiting block of resistors or a switch with a resistance adjustment function to the ammeter circuit; they will allow you to change the value of the charger current. Rice. 13: Connect the voltmeter
To protect the charger, both on the mains side and on the lead battery side, you need to install two fuses. In this example, a 0.5A fuse is used on the high side of the charger, and in the charging circuit lead battery 10A.
If you have a charger current regulator, you should start charging from the minimum value on the ammeter and gradually increase it to the required value. When a sufficient amount of charge has accumulated in the battery, the ammeter will show about 1A, after which you can safely disconnect the charger from the network and use the battery for its intended purpose.
Rice. 14: dependence of values on charging time Video on the topic
Sometimes it happens that the battery in the car runs out and it is no longer possible to start it, since the starter does not have enough voltage and, accordingly, current to crank the engine shaft. In this case, you can “light it” from another car owner so that the engine starts and the battery starts charging from the generator, but this requires special wires and a person willing to help you. You can also charge the battery yourself using a specialized charger, but they are quite expensive and you don’t have to use them very often. Therefore, in this article we will take a detailed look at the homemade device, as well as instructions on how to make a charger for a car battery with your own hands.
Homemade device
Normal battery voltage when disconnected from the vehicle is between 12.5 V and 15 V. Therefore, the charger must output the same voltage. The charge current should be approximately 0.1 of the capacity, it can be less, but this will increase the charging time. For a standard battery with a capacity of 70-80 Ah, the current should be 5-10 amperes, depending on the specific battery. Our homemade battery charger must meet these parameters. To assemble a charger for a car battery, we need the following elements:
Transformer. Any old electrical appliance or one purchased on the market with an overall power of about 150 watts is suitable for us, more is possible, but not less, otherwise it will get very hot and may fail. It’s great if the voltage of its output windings is 12.5-15 V and the current is about 5-10 amperes. You can view these parameters in the documentation for your part. If the required secondary winding is not available, then it will be necessary to rewind the transformer to a different output voltage. For this:
Thus, we found or assembled the ideal transformer to make our own battery charger.
We will also need:
Having prepared all the materials, you can proceed to the process of assembling the car charger itself.
Assembly technology
To make a charger for a car battery with your own hands, you need to follow the step-by-step instructions:
- We create a homemade battery charging circuit. In our case it will look like this:
- We use transformer TS-180-2. It has several primary and secondary windings. To work with it, you need to connect two primary and two secondary windings in series to obtain the desired voltage and current at the output.
- Using a copper wire, we connect pins 9 and 9’ to each other.
- On a fiberglass plate we assemble a diode bridge from diodes and radiators (as shown in the photo).
- We connect pins 10 and 10’ to the diode bridge.
- We install a jumper between pins 1 and 1’.
- Using a soldering iron, attach a power cord with a plug to pins 2 and 2’.
- We connect a 0.5 A fuse to the primary circuit, and a 10-amp fuse to the secondary circuit, respectively.
- We connect an ammeter and a piece of nichrome wire into the gap between the diode bridge and the battery. One end of which is fixed, and the other must provide a moving contact, thus the resistance will change and the current supplied to the battery will be limited.
- We insulate all connections with heat shrink or electrical tape and place the device in the housing. This is necessary to avoid electric shock.
- We install a moving contact at the end of the wire so that its length and, accordingly, the resistance are maximum. And connect the battery. By decreasing or increasing the length of the wire, you need to set the desired current value for your battery (0.1 of its capacity).
- During the charging process, the current supplied to the battery will itself decrease and when it reaches 1 ampere, we can say that the battery is charged. It is also advisable to directly monitor the voltage on the battery, but to do this it must be disconnected from the charger, since when charging it will be slightly higher than the actual values.
First start assembled circuit any power source or charger is always produced through an incandescent lamp, if it lights up at full intensity - either there is an error somewhere, or the primary winding is short-circuited! An incandescent lamp is installed in the gap of the phase or neutral wire feeding the primary winding.
This circuit of a homemade battery charger has one big drawback - it does not know how to independently disconnect the battery from charging after reaching the required voltage. Therefore, you will have to constantly monitor the voltmeter and ammeter readings. There is a design that does not have this drawback, but its assembly will require additional parts and more effort.
A visual example of the finished product
Operating rules
The disadvantage of a homemade charger for a 12V battery is that after the battery is fully charged, the device does not automatically turn off. That is why you will have to periodically glance at the scoreboard in order to turn it off in time. Another important nuance is that checking the charger for spark is strictly prohibited.
Additional precautions to take include:
- when connecting the terminals, make sure not to confuse “+” and “-”, otherwise a simple homemade battery charger will fail;
- connection to the terminals should only be made in the off position;
- the multimeter must have a measurement scale greater than 10 A;
- When charging, you should unscrew the plugs on the battery to avoid its explosion due to boiling of the electrolyte.
Master class on creating a more complex model
That, in fact, is all I wanted to tell you about how to properly make a charger for a car battery with your own hands. We hope that the instructions were clear and useful for you, because... This option is one of the simplest types of homemade battery charging!
Also read:
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Today we will look at 3 simple circuits chargers that can be used to charge a wide variety of batteries.
The first 2 circuits operate in linear mode, and linear mode primarily means high heat. But the charger is a stationary thing, and not portable, so that efficiency is a decisive factor, so the only disadvantage of the presented circuits is that they need a large cooling radiator, but otherwise everything is fine. Such schemes have always been used and will be used, as they have undeniable advantages: simplicity, low cost, do not “crap” the network (as in the case of pulsed circuits) and high repeatability.
Let's look at the first diagram:
This circuit consists of just a pair of resistors (with the help of which the end of charge voltage or the output voltage of the circuit as a whole is set) and a current sensor that sets the maximum output current of the circuit.
If you need a universal charger, the circuit will look like this:
Rotation trim resistor you can set any output voltage from 3 to 30 V. In theory, up to 37V is possible, but in this case 40V must be supplied to the input, which the author (AKA KASYAN) does not recommend doing. The maximum output current depends on the resistance of the current sensor and cannot be higher than 1.5A. The output current of the circuit can be calculated using the following formula:
Where 1.25 is the voltage of the reference source of the lm317 microcircuit, Rs is the resistance of the current sensor. To obtain a maximum current of 1.5A, the resistance of this resistor should be 0.8 Ohm, but in the circuit it is 0.2 Ohm.
The fact is that even without a resistor, the maximum current at the output of the microcircuit will be limited to the specified value; the resistor here is mostly for insurance, and its resistance is reduced to minimize losses. The greater the resistance, the more the voltage across it will drop, and this will lead to strong heating of the resistor.
The microcircuit must be installed on a massive radiator; an unstabilized voltage of up to 30-35V is supplied to the input, this is slightly less than the maximum permissible input voltage for the lm317 microcircuit. It must be remembered that the lm317 chip can dissipate a maximum of 15-20W of power, be sure to take this into account. You also need to take into account that the maximum output voltage of the circuit will be 2-3 volts less than the input.
Charging occurs at a stable voltage, and the current cannot exceed the set threshold. This circuit can even be used for charging lithium-ion batteries. If there is a short circuit at the output, nothing bad will happen, the current will simply be limited, and if the cooling of the microcircuit is good and the difference between the input and output voltages is small, the circuit can operate in this mode for an infinitely long time.
Everything is assembled on a small printed circuit board.
You can find it, as well as the printed circuit boards for the two subsequent circuits, along with the general archive of the project.
Second scheme is a powerful stabilized power supply with a maximum output current of up to 10A, it was built on the basis of the first option.
It differs from the first circuit in that an additional direct conduction power transistor is added here.
The maximum output current of the circuit depends on the resistance of the current sensors and the collector current of the transistor used. In this case, the current is limited at 7A.
The output voltage of the circuit is adjustable in the range from 3 to 30V, which will allow you to charge almost any battery. The output voltage is regulated using the same trimming resistor.
This option is great for charging car batteries; the maximum charge current with the components indicated in the diagram is 10A.
Now let's look at the principle of operation of the circuit. At low current values, the power transistor is closed. As the output current increases, the voltage drop across the specified resistor becomes sufficient and the transistor begins to open, and all the current will flow through the open junction of the transistor.
Naturally, due to the linear operating mode, the circuit will heat up, the power transistor and current sensors will heat up especially harshly. The transistor with the lm317 chip is screwed onto a common massive aluminum radiator. There is no need to insulate the heat sink substrates, since they are common.
It is highly desirable and even mandatory to use an additional fan if the circuit will be operated at high currents.
To charge batteries, you need to set the end-of-charge voltage by rotating the trimming resistor and that’s it. Maximum current The charge is limited to 10 amperes; as the batteries charge, the current will drop. Scheme short circuits Don't be afraid, in case of a short circuit the current will be limited. As in the case of the first scheme, if there is good cooling, the device will be able to tolerate this operating mode for a long time.
Well, now some tests:
As you can see, the stabilization is working, so everything is fine. And finally third scheme:
It is a system automatic shutdown battery at fully charged, that is, it is not really a charger. The initial circuit underwent some modifications, and the board was refined during testing.
Let's look at the diagram.
As you can see, it is painfully simple, it contains only 1 transistor, an electromagnetic relay and small things. The author also has a diode bridge at the input and primitive protection against polarity reversal on the board; these components are not shown on the diagram.
The circuit input is supplied constant pressure from a charger or any other power source.
It is important to note here that the charging current should not exceed the permissible current through the relay contacts and the fuse tripping current.
When power is supplied to the input of the circuit, the battery is charged. The circuit contains a voltage divider, which monitors the voltage directly on the battery.
As it charges, the voltage on the battery will increase. As soon as it becomes equal to the operating voltage of the circuit, which can be set by rotating the trimming resistor, the zener diode will operate, sending a signal to the base of the low-power transistor and it will operate.
Since an electromagnetic relay coil is connected to the collector circuit of the transistor, the latter will also work and the indicated contacts will open, and further power supply to the battery will stop, at the same time the second LED will work, notifying that charging is complete.
