Every car owner should have an automatic charger. The principle of operation of smart chargers The principle of operation of phone charging
Battery problems are not that uncommon. To restore functionality, additional charging is necessary, but normal charging costs a lot of money, and it can be done from available “trash.” The most important thing is to find a transformer with the required characteristics, and making a charger for a car battery with your own hands takes just a couple of hours (if you have all the necessary parts).
The battery charging process must follow certain rules. Moreover, the charging process depends on the type of battery. Violations of these rules lead to a decrease in capacity and service life. Therefore, the parameters of a car battery charger are selected for each specific case. This opportunity is provided by a complex charger with adjustable parameters or purchased specifically for this battery. There is a more practical option - making a charger for a car battery with your own hands. To know what parameters should be, a little theory.
Types of battery chargers
Battery charging is the process of restoring used capacity. To do this, a voltage is supplied to the battery terminals that is slightly higher than the operating parameters of the battery. Can be served:
- D.C. The charging time is at least 10 hours, during this entire time a fixed current is supplied, the voltage varies from 13.8-14.4 V at the beginning of the process to 12.8 V at the very end. With this type, the charge accumulates gradually and lasts longer. The disadvantage of this method is that it is necessary to control the process and turn off the charger in time, since when overcharging the electrolyte may boil, which will significantly reduce its working life.
- Constant pressure. When charging constant voltage, The charger produces a voltage of 14.4 V all the time, and the current varies from large values in the first hours of charging to very small values in the last. Therefore, the battery will not be recharged (unless you leave it for several days). The positive aspect of this method is that the charging time is reduced (90-95% can be reached in 7-8 hours) and the battery being charged can be left unattended. But such an “emergency” charge recovery mode has a bad effect on service life. With frequent use of constant voltage, the battery discharges faster.
In general, if there is no need to rush, it is better to use DC charging. If you need to restore battery functionality in a short time, apply constant voltage. If we talk about what is the best charger to make for a car battery with your own hands, the answer is clear - one that supplies direct current. The schemes will be simple, consisting of accessible elements.
How to determine the necessary parameters when charging with direct current
It has been experimentally established that charge car lead acid batteries(most of them) required current that does not exceed 10% of the battery capacity. If the capacity of the battery being charged is 55 A/h, the maximum charge current will be 5.5 A; with a capacity of 70 A/h - 7 A, etc. In this case, you can set a slightly lower current. The charge will continue, but more slowly. It will accumulate even if the charge current is 0.1 A. It will just take a very long time to restore the capacity.
Since the calculations assume that the charge current is 10%, we obtain a minimum charge time of 10 hours. But this is when the battery is completely discharged, and this should not be allowed. Therefore, the actual charging time depends on the “depth” of the discharge. You can determine the depth of discharge by measuring the voltage on the battery before charging:
To calculate approximate battery charging time, you need to find out the difference between the maximum battery charge (12.8 V) and its current voltage. Multiplying the number by 10 we get the time in hours. For example, the voltage on the battery before charging is 11.9 V. We find the difference: 12.8 V - 11.9 V = 0.8 V. Multiplying this figure by 10, we find that the charging time will be about 8 hours. This is provided that we supply a current that is 10% of the battery capacity.
Charger circuits for car batteries
To charge batteries, a 220 V household network is usually used, which is converted into undervoltage using a converter.
Simple circuits
The simplest and effective method- use of a step-down transformer. It is he who lowers 220 V to the required 13-15 V. Such transformers can be found in old tube TVs (TS-180-2), computer units food, found at the “ruins” of a flea market.
But at the output of the transformer it turns out AC voltage which needs to be straightened. They do this using:
The above diagrams also contain fuses (1 A) and measuring instruments. They make it possible to control the charging process. They can be excluded from the circuit, but you will have to periodically use a multimeter to monitor them. With voltage control, this is still tolerable (just attach probes to the terminals), but it is difficult to control the current - in this mode measuring device included in the open circuit. That is, you will have to turn off the power every time, put the multimeter in current measurement mode, and turn on the power. disassemble the measuring circuit in reverse order. Therefore, using at least a 10 A ammeter is very desirable.
The disadvantages of these schemes are obvious - there is no way to adjust the charging parameters. That is, when choosing an element base, choose the parameters so that the output current is the same 10% of the capacity of your battery (or a little less). You know the voltage - preferably within 13.2-14.4 V. What to do if the current turns out to be more than desired? Add a resistor to the circuit. It is placed at the positive output of the diode bridge in front of the ammeter. You select the resistance “locally”, focusing on the current; the power of the resistor is larger, since excess charge will be dissipated on them (10-20 W or so).
And one more thing: a do-it-yourself car battery charger made according to these schemes will most likely get very hot. Therefore, it is advisable to add a cooler. It can be inserted into the circuit after the diode bridge.
Adjustable circuits
As already mentioned, the disadvantage of all these circuits is the inability to regulate the current. The only option is to change the resistance. By the way, you can put a variable tuning resistor here. This will be the easiest way out. But manual current adjustment is more reliably implemented in a circuit with two transistors and a trimming resistor.
Charge current varies variable resistor. It is located after the composite transistor VT1-VT2, so a small current flows through it. Therefore, the power can be about 0.5-1 W. Its rating depends on the selected transistors and is selected experimentally (1-4.7 kOhm).
Transformer with a power of 250-500 W, secondary winding 15-17 V. The diode bridge is assembled on diodes with an operating current of 5A and higher.
Transistor VT1 - P210, VT2 is selected from several options: germanium P13 - P17; silicon KT814, KT 816. To remove heat, install on a metal plate or radiator (at least 300 cm2).
Fuses: at the input PR1 - 1 A, at the output PR2 - 5 A. Also in the circuit there are signal lamps - the presence of a voltage of 220 V (HI1) and a charging current (HI2). Here you can install any 24 V lamps (including LEDs).
Video on the topic
DIY car battery charger is a popular topic for car enthusiasts. Transformers are taken from everywhere - from power supplies, microwave ovens... they even wind them themselves. The schemes being implemented are not the most complex. So even without electrical engineering skills you can do it yourself.
Chargers are designed to replenish lost electricity from batteries. The principle of operation of batteries is a reversible chemical reaction.
The battery's loss of electrical energy must then be compensated by charging to restore its original capacity. The function of the charger is precisely to restore the battery capacity.
There are many methods for charging batteries. Some of them are very simple to implement and have minimal cost. Some models control the battery charging process using a built-in microcontroller and implement a complex charging algorithm.
In general terms, the principle of charging is to apply a voltage that exceeds the emf value of a discharged battery. In accordance with this, the following basic battery charging methods can be distinguished:
- direct current;
- constant voltage;
- combined methods.
Regardless of the method, the main characteristics of chargers are as follows:
- maximum charge current;
- output voltage value.
UNIVERSAL CHARGERS
We must warn you right away - completely universal chargers do not exist and, most likely, will never exist.
With a certain stretch, some types can be classified as universal, but this is only if you do not pay attention to some deviations from the recommended parameters. The validity of this statement will be discussed below.
First of all, you need to know that different types of batteries have different voltages and capacities, and if you consider that batteries are usually assembled into batteries, then this difference between these parameters increases many times over.
Different types of batteries require an individual approach to the charging process.
Initially, the first types of batteries, lead-acid, required charging with direct current throughout the entire charging time (approximately 8-12 hours). Alkaline ones were charged in the same way, but with different current values.
This technique is simple, but had a serious drawback - at the end of the charge there was intense gas evolution from the electrolyte (boiling), which required constant monitoring of the charging process, especially at the end.
Charging with constant voltage is free from this disadvantage, but requires a longer time. It is used mainly to restore batteries that have lost their initial capacity for various reasons.
More advanced models use a combined technique. At the beginning of the charge, the battery is charged with the rated charging current, and when the voltage at its terminals reaches a level close to the maximum value, the voltage at the output of the charger is reduced to such an extent that it is only slightly higher than the battery voltage.
The charging current drops and the battery continues to charge at a minimum current. Thus, the electrolyte does not boil, and the charging time is only slightly longer than the time at constant current.
The first two types can be called universal in relation to car starter batteries. Such devices are still widespread, especially among hobbyists, due to their simplicity, reliability and minimal cost.
Improvements in battery manufacturing technology have led, on the one hand, to an increase in specific capacity, and on the other, increased requirements for the parameters of equipment for recharging them.
Now in production batteries various types A huge number of manufacturers are involved, but most of them do not make publicly available the necessary charging technology, which is optimal for a particular battery model.
Therefore, consumers have to either purchase an expensive branded product or select an inexpensive one that matches the average parameters of rechargeable batteries of comparable production technologies.
Manufacturers of mobile phones and other small gadgets have taken a different route. Charge control is carried out by a microcontroller built into the “charging”, as well as directly into the battery.
This approach has led to the emergence of truly universal chargers that are equally suitable for charging any battery that meets a single standard.
The most striking example is smartphones and tablets running Android OS. All these gadgets have a charging input made according to the Micro USB standard.
A separate class of products for car batteries make up the start-up charging device. As the name suggests, they can start the car, and powerful devices are able to do this even without a battery.
As is known, the starting current of a starter, especially in winter on a frozen engine, reaches several hundred amperes. Thus, the output parameters of the starting-charger are very close to the characteristics of welding machines.
The dimensions and weight of a starter-charger with traditional transformer power supply are large, but when using the inverter method of energy conversion they are reduced many times.
AUTOMATIC CHARGER
The charging process can be simplified by using automatic chargers. The simplest charging machines monitor the voltage at the battery terminals and stop the charging process when a certain value is reached.
The disadvantage of such devices is that the battery does not reach full capacity or, conversely, it is overcharged.
Both options lead to a reduction in battery life.
More advanced designs, when the threshold voltage is reached, transfer the battery charge to a buffer mode, when the output current only slightly exceeds the self-discharge current of the battery. Such chargers can be left unattended for a long time without the risk of damaging the battery being charged.
A certain type of device allows not only to charge batteries, but also, in some way, to restore lost capacity. In this case, the charging process alternates with periods of zero charging current or with a small discharge.
This training technique shows satisfactory results when restoring lead-acid batteries due to the reduced effect of plate sulfation.
Chargers for small-sized batteries and batteries today also overwhelmingly operate in automatic mode.
This became possible thanks to the built-in microcontroller, which not only automates the charging process, but also performs it according to a specially designed algorithm. Such products are usually produced by battery manufacturers, so they are optimal for a specific type of battery.
Nowadays, electronics manufacturers more often use batteries based on lithium technology for power supply: lithium polymer ( Li-Po), lithium ion ( Li-ion). The advantage of such batteries is that they have a large specific capacity, low self-discharge, the ability to deliver high currents when discharged, and such batteries are manufactured in any shape and size. To charge such batteries, special chargers are needed.
Note that such chargers are often used to recharge various electrical tools used by housing and communal services employees. Products for housing and communal services, by the way, can be purchased at a relatively low price from the ZHKH-MARKET company, which has been supplying housing and communal services in Moscow and the Moscow region for more than 10 years.
Standard batteries
Consumers often purchase devices that run on standard AA or AAA batteries. They can be replaced with regular batteries and no special charger is required. People who used NiMH batteries are appearing less and less often. They have a capacity of 40% more than NiCD batteries. NiMH batteries are improving every day. For example, if previously their self-discharge was high, now some batteries have minimal self-discharge.
Battery charging methods
When a battery is charged, chemical changes occur in it. The energy that comes during charging, part of it is spent on these transformations, and part of it turns into heat. NiMH batteries get hotter when charging than NicD batteries because the chemical reactions that occur when charging are exothermic.
The battery charging speed depends on the charging current. The charging current will be measured in units of C - the numerical value of the battery capacity. There are several types of charging:
trickle charge – current 0.1 C
fast charging ( quick charge) – current 0.3 C
accelerated charging (fast charge) – current 0.5-1.0 C
Drip charging
With trickle charging, a small current is chosen because charging continues even if the battery is charged. With such a low current, the battery does not heat up as much. It is impossible to accurately determine the end of the charging process here.
Fast battery charging
Such charging with a current of 1C is not recommended for all batteries, because the battery ventilation hole may open at high ambient temperatures (up to +40). When fast charging, you need to stop the charging process during the charging process.
The fast charger operating algorithm consists of several phases:
1. Determining the presence of a battery
2. Battery qualification
3. Pre-charge
4. Transition to fast charging (Ramp)
5. Fast charge
6. Top-of Tcharge
7. Maintenance charge
Battery detection phase. Here the voltage at the battery terminals is checked with the charging current generator turned on, approximately 0.1C. If the voltage is 1.8 V, the battery is missing or damaged. If the voltage is high, charging should not start as soon as it is detected low voltage, charging will begin. In the remaining phases, the presence of the battery must be checked, because in any phase the battery can be removed and the charger must return to the first phase.
Battery qualification phase. This phase begins charging the battery. This phase is needed to estimate the initial battery charge. Judging by the voltage on the battery, you need to determine whether pre-charging is needed or not.
Pre-charge phase. This phase should not last more than 30 minutes. A pre-charge phase is required for deeply discharged batteries. For all long phases, temperature control is required; it should not exceed 60 degrees during charging.
Transition phase to fast charging. It is not advisable to immediately turn on the fast current; it is better to gradually increase it over 2 minutes. Fast charging can begin if the battery voltage is above 0.8 V.
Fast charge phase. The most important thing in this phase is to stop charging in time, otherwise the battery will be destroyed. To stop charging in time, you can use several methods to determine the charge.
For NiCd batteries The dV method is used - this is the fastest method for determining charge; towards the end of charging, the voltage on the battery decreases.
For NiMH batteries The dV method doesn't work as well. And they use the dV=0 method. Here the constant voltage on the battery is detected. If the voltage remains the same for 10 minutes, then it’s time to turn off charging.
Also, the end of charging can be determined by the temperature, since towards the end of charging the pressure inside the battery increases and the temperature rises. Some chargers use pulse instead of DC. Current pulses last 1 second. The advantage of this method is that it better equalizes the concentration of active substances throughout the entire volume, reduces the likelihood of the formation of large crystalline formations on the electrodes and their passivation.
Recharging phase. In this phase, the charging current should be 0.1-0.3 C. The duration of recharging is 30 minutes, then there will be a recharge. After a quick charge, it is better to cool the battery and then begin the charging process.
Maintenance charging phase. Direct current is harmful to the battery, as the battery will constantly be at a high temperature. After charging is complete, NiCd batteries go into trickle mode to maintain the charge. But NiMH batteries do not tolerate overcharging and therefore maintaining a charge will do them little good. In principle, you can do without this phase.
Ultra-fast charge
You can use current up to 3C. When the battery is 70% charged, the charge should be reduced and continued as usual. If this is not done, the ultra-high heating of the battery will destroy it or even explode.
Smart charger
Batteries of the same form factor. For example, AA size NiMH batteries have a capacity of 1900-2850 mAh, and AAA size batteries have a capacity of 750-1100 mAh. The charging current must be proportional to the battery capacity. When charging a battery with a small capacity with a high current, there will be heating. When charging with a small current, the charging time will be long. In general, the charger should control the current, that is, use a high current for batteries with a large capacity and a small current for a smaller capacity. This is the meaning of a smart charger.
Charger power off problem
If the charger power is turned off during the charging process, then when the power is turned on, a transition to the phase of determining the presence of a battery should occur. In this case, charging starts from the beginning and recharging will be completed completely. The disadvantage of frequent recharging is that it can develop into overcharging. A “smart” Li+ battery contains a controller that measures the amount of charge.
Primary current sources
Primary sources of current are batteries (alkaline and manganese-zinc). The difference between primary sources and batteries is the internal resistance, which is higher for primary sources. If the internal resistance is greater than normal, the charging process will be interrupted.
Memory and battery recovery effect
The memory effect appears in NiCd batteries. The meaning of the effect is that large crystalline formations form on the electrodes, as a result of which part of the volume of the active substance of the battery ceases to be used. To eliminate the memory effect, a complete discharge is recommended. This complete discharge is recommended for NiMH batteries before charging them. It will be better if you have a charger with a discharge function.
Interaction of batteries in the assembly
Separate batteries into batteries may have different characteristics. Batteries that have smaller capacity, will be destroyed during the discharge process of the assembly. And each battery in the battery must be charged separately, but in ready-made assemblies there are only two terminals and only joint charging is possible. In this case, alignment is needed.
I wonder what the Siemens charger (power supply) consists of and whether it is possible to repair it yourself in the event of a breakdown.
First, the block needs to be disassembled. Judging by the seams on the body, this unit is not intended for disassembly, therefore it is a disposable item and you don’t have to place much hope in the event of a breakdown.
I literally had to tear apart the body of the charger; it consists of two tightly glued parts.
Inside is a primitive circuit board and several parts. The interesting thing is that the board is not soldered to the 220V plug, but is attached to it using a pair of contacts. In rare cases, these contacts may oxidize and lose contact, leaving you thinking the unit is broken. But the thickness of the wires going to the connector on mobile phone, I was pleasantly pleased, you don’t often see a normal wire in disposable devices, usually it is so thin that it’s scary to even touch it).
There were several parts on the back of the board; the circuit turned out to be not so simple, but still not so complicated that you couldn’t fix it yourself.
Below in the photo are the contacts of the inside of the case.
There is no step-down transformer in the charger circuit; its role is played by an ordinary resistor. Next, as usual, a couple of rectifying diodes, a pair of capacitors for rectifying the current, then comes a choke and finally a zener diode with a capacitor completes the chain and outputs the reduced voltage to a wire with a connector to the mobile phone.
The connector has only two contacts.
Your new ones iPhone smartphones 8/8 Plus and iPhone X, Apple called support for the function almost the main feature of the devices wireless charging Qi standard. Also introduced was the Air Power wireless charging mat, which allows you to simultaneously charge your smartphone, Apple Watch And wireless headphones AirPods. Wireless charging is slowly becoming standard function for A-brand flagships and more.
But is Apple's solution so revolutionary? How does wireless charging work in practice? This will be discussed in the article.
How wireless charging works
Most wireless chargers use magnetic induction and magnetic resonance. They suggest placing the gadget on a special surface for automatic charging, without the need to connect a cable to the device.
Of course, wireless charging isn't truly wireless. Your phone, smart watch, tablet does not need to be connected to the charger, but the wireless charger itself still needs to be connected by cable to the power adapter or USB port.
How Apple's opinion on wireless charging has changed
When Apple introduced the iPhone 5 without support for wireless charging, at the same time in smartphones on competing Android platforms and Windows modules have been built into many flagship models. But Apple's Phil Schiller that "creating a separate charger that you have to plug into an outlet is actually, for most situations, more complicated." That is, in Cupertino they didn’t even think about wireless charging, dismissing this possibility in the bud.
Five years later, Apple changed its mind. With iPhone 8, iPhone 8 Plus, and iPhone X, Apple includes support for wireless charging using the open standard Qi (pronounced "shi" because it's a Chinese word that refers to the "life energy" in living things.).
Qi wireless charging
Wireless chargers in this moment use the phenomenon of magnetic induction. Simply put, they use magnetism to transfer energy. First, you place a device, such as a smartphone, on a wireless charger. Current from the wall outlet passes through a coil in the wireless charging module, creating a magnetic field. The magnetic field creates a current in a coil inside the smartphone. This magnetic energy is converted into electrical energy, which is then used to charge the battery. Devices must have the appropriate hardware to support wireless charging. That is, a device without the necessary coil inside the case cannot be charged wirelessly. 
While the range of the Qi standard was initially limited to a short range magnetic field, it now also supports the use of magnetic resonance phenomenon. It works in a similar way, but the gadget being charged can be located up to 45 mm from the surface of the wireless charger, and not touch it, as was before. This method is less efficient than the magnetic induction method, but there are some advantages - for example, the wireless charger can be installed under the surface of the table, and you can place the gadget with the receiver on the table to charge it. It also allows you to place multiple devices on one charging pad and each of them will be charged in parallel.
A little about the system's power consumption. When gadgets are not charging, the Qi charger does not consume a large amount of electricity. A special low-power module monitors this moment and turns off the current to the coil, but when it detects that a gadget that requires charging is placed on the charger pad, it increases the output power of the magnetic field.
Competitors of the Qi standard
Wireless charging is becoming more common and more thoroughly standardized. And this time Apple didn't create its own wireless standard. Instead he decided to support existing standard Qi, which also supports many third-party devices.
Power Matters Alliance (PMA)
However, Qi run by the Wireless Power consortium, the most widespread at the moment, but it is not alone. In second place -Power Matters Alliance, or PMA standard. It uses magnetic induction, just like Qi. However, these two standards are incompatible. New iPhones and other Apple products cannot be charged using the PMA wireless charger.
But some devices on the market are compatible with both standards. Modern smartphones, such as Galaxy Note 8, Galaxy S8 and Galaxy S7, in fact, support both Qi and PMA, so they can be charged from any charger. Starbucks company (global cafe chain)previously relied on PMA, but now there is an option that it can rethink the situation, since the iPhone only supports Qi.
Apple is confident that in the near future many airports, hotels and other public places will also rely on Qi. That is, most likely there will be devices from other manufacturers that support wireless charging of this standard. As practice shows, this will probably actually happen.
Alliance for Wireless Power (A4WP)
There is a third competitor to the Qi standard. This Alliance for Wireless Power (A4WP), which uses Rezence technology in its work. The essence of the operating principle of the standard is to use the magnetic resonance effect, which will expand the charging area for several devices. You can place multiple gadgets on one charger, move them around, and even charge them through an object such as a book. Rezence technology requires a Bluetooth connection to your device to work.
AirFuel Alliance
Realizing that the Qi standard is the most popular on the market, the competitors decided to unite. This is how a new education appeared AirFuel Alliance, which has been promoting its wireless charging technologies since 2015. The consortium included 195 companies. The most interesting thing is that the AirFuel Alliance has secured the support of Intel, which suggests that everything is serious and here to stay. Well, competition is always good for users, because it is the engine of progress.
What devices can you use wireless charging with today?
I am sure that many users ask themselves this question. After all, everyone wants to try how wireless charging actually works, and whether it is as convenient as the developers say.
I have quite a lot of experience using wireless charging. You will be surprised, but it’s been almost 5 years. My good old Nokia Lumia 820 supports wireless charging. Back in December 2012, when I purchased a smartphone, I received an additional accessory that made it possible to use wireless charging for this smartphone.
True, in order for the Nokia Lumia 820 to be charged wirelessly, it was necessary to buy a special back cover. From personal experience I can say that using wireless charging is very convenient and practical. Place your smartphone on a special surface and it will begin to receive energy to charge the battery. It is worth noting that there are also unpleasant sides to using wireless charging from Nokia. Let's start with the fact that in this case the smartphone body heats up quite noticeably, and the charging process itself is much slower than when charging via a cable.
Unfortunately, the story of Microsoft smartphones seems to be over. But you still have the opportunity to try wireless charging.
Over the past few years, Android smartphone manufacturers have been increasingly installing wireless charging in their devices. For example, Google does not offer it on its Pixel smartphone, although some Nexus devices previously supported this function. Of the A-brands, only Samsung has retained wireless charging capabilities in its latest flagship models.
But with Apple's move to give the Qi standard a vote of confidence, wireless charging may become more common, including on Android devices.
However, you can already buy a smartphone that supports wireless charging. This Samsung Galaxy Note8 and Galaxy Note 5,Galaxy S8, S8+, S8 Active, S7, S7 Edge, S7 Active,LG G6 (US and Canada version only) and LG V30,Motorola Moto Z, Moto Z Play, Moto Z2 Force, Moto Z2 Play (only with wireless charging module), and of course the new iPhone 8, 8 Plus, X (10). As you can see, there is quite a large selection, from different brands and on different platforms.
Even if your smartphone does not support wireless charging, you can add support for this function using a special case. Also in some cases it is possible to use wireless adapter charger, which is attached to the back of the gadget and connects to the power port.
And now the most important thing. In order to charge your smartphone using wireless charging, of course, you first need to purchase a charger that will support the Qi standard. You can find such devices in various online stores such as Amazon, Aliexpress, eBay and others. After purchasing a device in a store, connect it to a power outlet and place your smartphone on a special platform. Now it will charge wirelessly, just like you wanted.
Results
Something tells me that the appearance in new iPhones wireless charging functions will give impetus to the development of this segment of the IT industry. Very soon we will observe a situation where everything flagship smartphones will begin to support wireless charging technology by default. And then it may come to budget devices. So we're in for some interesting times.