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The best chargers for car batteries. Every car enthusiast should have an automatic charger. Circuit diagram of a charger with automatic shutdown.

For those who don’t have time to “bother” with all the nuances of charging a car battery, monitoring the charging current, turning it off in time so as not to overcharge, etc., we can recommend a simple car battery charging scheme with automatic shutdown when the battery is fully charged. This circuit uses one low-power transistor to determine the voltage on the battery.

Scheme of a simple automatic car battery charger

List of required parts:

  • R1 = 4.7 kOhm;
  • P1 = 10K trimmer;
  • T1 = BC547B, KT815, KT817;
  • Relay = 12V, 400 Ohm, (can be automotive, for example: 90.3747);
  • TR1 = secondary winding voltage 13.5-14.5 V, current 1/10 of the battery capacity (for example: battery 60A/h - current 6A);
  • Diode bridge D1-D4 = for a current equal to the rated current of the transformer = at least 6A (for example D242, KD213, KD2997, KD2999...), installed on the radiator;
  • Diodes D1 (in parallel with the relay), D5.6 = 1N4007, KD105, KD522...;
  • C1 = 100uF/25V.
  • R2, R3 - 3 kOhm
  • HL1 - AL307G
  • HL2 - AL307B

The circuit lacks a charging indicator, current control (ammeter) and charging current limitation. If desired, you can put an ammeter at the output at the break of any of the wires. LEDs (HL1 and HL2) with limiting resistances (R2 and R3 - 1 kOhm) or light bulbs in parallel with C1 “mains”, and to the free contact RL1 “end of charge”.

Changed scheme

A current equal to 1/10 of the battery capacity is selected by the number of turns of the secondary winding of the transformer. When winding the transformer secondary, it is necessary to make several taps to select the optimal charging current option.

The charge of a car (12-volt) battery is considered complete when the voltage at its terminals reaches 14.4 volts.

The shutdown threshold (14.4 volts) is set by trimming resistor P1 when the battery is connected and fully charged.

When charging a discharged battery, the voltage on it will be about 13V; during charging, the current will drop and the voltage will increase. When the voltage on the battery reaches 14.4 volts, transistor T1 turns off relay RL1, the charging circuit will be broken and the battery will be disconnected from the charging voltage from diodes D1-4.

When the voltage drops to 11.4 volts, charging resumes again; this hysteresis is provided by diodes D5-6 in the emitter of the transistor. The circuit's response threshold becomes 10 + 1.4 = 11.4 volts, which can be considered to automatically restart the charging process.

This homemade simple automatic car charger will help you control the charging process, not track the end of charging and not overcharge your battery!

Website materials used: homemade-circuits.com

Another version of the charger circuit for a 12-volt car battery with automatic shutdown at the end of charging

The scheme is a little more complicated than the previous one, but with clearer operation.

Table of voltages and percentage of battery discharge not connected to the charger


P O P U L A R N O E:

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If such devices had appeared on stage forty years ago, they would have been booed. Because everyone knew: a real charger is a heavy box with a huge transformer inside, various kinds of twisters, a voltmeter and an ammeter outside. Everything else is not serious.

A modern charger is, as a rule, a rather nice automatic box with a minimum of controls. Or even without them at all. At the same time, for some reason many are very similar to each other. But are they the same at work?

We tested eight devices taken for testing at two temperatures: -10 and +20 ºС. Let us say right away that you should not believe the statements of individual manufacturers regarding performance in severe frosts. Firstly, the intensity of the charging process in the cold drops very much: at -25 ºС, the charging current of the 55th battery will be only 4–6% of the value at plus twenty-five. And attempts to increase the charge voltage are fraught with destruction of the active mass and corrosion of down conductors. Secondly, at lower temperatures the insulation of the power wires of the presented devices hardens and breaks. Thirdly... However, two reasons are quite enough.

We compiled kilograms, millimeters and volts with amperes into a table, and supplemented the photo gallery with comments for each instance. In general, we can say that the devices honestly issue the stated charging programs. The reasons for quibbling were the fuses instead of electronic protection, the lack of clear inscriptions on the body and the overpriced compared to “colleagues” with approximately equal talents.

8th place

Sweden

Approximate price, rub. 4950 It looks very nice. Everything is intuitively clear, except for the term RECOND: you can’t figure it out without instructions. However, you can do without this mode to restore discharged batteries. There are no complaints about automation and circuitry. In general, everything is excellent, except for the price. Well, no way!

7th place

Denmark

Approximate price, rub. 4200 Let us immediately blame you for the lack of inscriptions in Russian. But there is an LED to illuminate the space. The entire process is automatic and does not require intervention. Charging is provided through the cigarette lighter socket. By the way, the product can be hung on the wall if desired. Overall not bad, but the price ruined everything.

6th place

Taiwan

Again they offended the Russian language: all the inscriptions on the device are not ours. However, there is nothing to read: I connected it and forgot it. There is protection against polarity reversal, sparking, overcharging and short circuit. But its authors should be ashamed of the shameful unit of measurement of capacity “A/h” in the instructions. That's right: Ah!

5th place

, China

Approximate price, rub. 3000 There is a heavy transformer inside. Just don’t believe the inscription on the box: the device is not a launcher at all. Look at the thin wires with “crocodiles” - what a start with them! It’s not for nothing that it is sold on the Internet as a regular charger. It works fine, but I'm not happy with the fuse. And it looks like someone adapted a suitable case for a different filling.

4th place

, Russia

Approximate price, rub. 1070 The product is the simplest in appearance and technically uncomplicated. A fuse as protection against incorrect connection is not the most user-friendly solution. There is no recharging mode during storage. But, based on the principle “it couldn’t be simpler,” many will be attracted by the complete lack of bells and whistles. The price, which is several times lower than others, is also an important factor.

3rd place

, China

Approximate price, rub. 3220 Perhaps the most presentable look. At least put it under the tree! The pictograms are clear and do not require translation. Works with 6- and 12-volt batteries. “Crocodiles” without wires look funny: the consumer must screw them on himself. There is a “hanger” on the wall for ease of use. But the fuse as “foolproof” is outdated and inconvenient.

2nd place

Universal charger device "SOROKIN" 12.94, “made for Russia”

Approximate price, rub. 2000 The cute, foolproof device can work with both 12- and 6-volt batteries. The charge is carried out cyclically, in several stages, and a “desulfation” mode is provided for almost dead batteries. The kit includes various connecting wires, including those for plugging into the cigarette lighter socket. In general, not bad.

1 place

Berkut Smart Power SP-8N, China

Approximate price, rub. 2650 The Chinese "Berkut" has become quite comfortable in Russia: even the inscriptions are in Cyrillic. It's simple: turn it on and use it. There is protection, the current is solid, the automation works, there are modes to choose from, the price is average, the appearance is modern. No comments, everything is fine.

A very simple charger circuit that uses only one transistor to determine the voltage to automatically disconnect the battery from the network when it is fully charged.

Description of the car battery charger circuit

In the figure we see a simple circuit where one transistor is turned on in its standard operating mode.

The principle of operation of the circuit can be understood from the following points:

  1. The battery charge is considered complete when the voltage at its terminals reaches 13.5 - 14 volts.
  2. The shutdown threshold (13.5 - 14 volts) is set by trimming resistor R2 with a connected, fully charged battery. When the voltage at the battery terminals is about 14 volts, transistor T1 will turn on the relay and the charging circuit will be broken.

This automatic car charger is not only easy to make, but also smart enough to take care of the battery's condition and charge it very efficiently.

Parts List:

  • R1 = 4.7 kOhm;
  • R2 = 10K trimmer;
  • T1 = ;
  • Relay = 12V, 400 Ohm, SPDT;
  • TR1 = secondary winding voltage 14 V, current 1/10 of the battery capacity;
  • Diode bridge = for a current equal to the rated current of the transformer;
  • Diodes D2 and D3 = 1N4007;
  • C1 = 100uF/25V.

From the site administrator

The article is theoretical in nature, in practice I didn't put this diagram together. I recommend paying attention to the following important points:

  1. The battery is disconnected from the charger when the charging voltage reaches 13.5 - 14 volts. This voltage threshold (tuning resistor R2) must be set with a connected, fully charged battery. If there is no charged battery, then you need to set R2 to the lower (according to the diagram) position, that is, “plant” the base of the transistor on the ground. Then connect the battery and plug in the charger. Next, you need to constantly monitor the charging voltage; when it reaches 13.5 - 14 volts, you need to set R2 to such a position that the relay opens its contacts.
  2. When the voltage at the battery terminals reaches 13.5 - 14 volts, the device is disconnected from the battery. Then, when the voltage drops to 11.4 volts, charging resumes again. The original article says that such hysteresis is provided by diodes in the emitter of the transistor.
  3. In the scheme no charging current limitation, therefore, when making this charger, I recommend using a transformer with a power of at least 150 watts, the secondary winding of which is designed for a current of at least 10 amperes. The diode bridge must also correspond to the specified current.

Probably every car enthusiast has at least once encountered the problem of a dead car battery. Even the highest quality and most modern power sources discharge from time to time and require recharging. When purchasing an automatic charger for a car battery, you must carefully study the characteristics of the battery that you plan to charge, and also understand the meaning of the parameters of the device itself.

From the characteristics of a car battery, you need to know the capacity, voltage and type. The vast majority of rechargeable batteries are of the lead-acid type. The exact parameters of the power supply can be found in the documentation for it or directly on the case or label.

Types of devices for charging car batteries

There are two types of chargers on the market: simple pre-chargers (otherwise called “trickle chargers”) and complex pre-chargers. The first are distinguished by the fact that the recharging process takes quite a long time, however, due to the slow rate of recovery of battery energy, it practically does not lose its properties. The latter, as a rule, have a higher price and may have a number of additional features. The device allows recharging in both normal smooth and significantly accelerated modes. Very useful functions of units of this type are: the ability to restore the charge of an almost completely depleted car battery, as well as start the car engine without a battery at all.

Fast charging, available when using jump chargers, by the way, has a rather unfavorable effect on the condition of the car battery and its durability. In view of this, it is not recommended to use the accelerated mode on an ongoing basis unless there is a specific justified need. Under normal conditions, experts recommend recharging with a pre-start device or a start-charging device in low current mode. The slow mode, by the way, provides for automatic regulation of the incoming charging current when the battery is restored. For greater safety, the process occurs as follows: at the beginning of the procedure, the battery is charged with a weak current, which gradually increases and decreases again towards the end of the cycle.

Modern chargers can be programmed to take into account the exact indicators of the battery being charged, eliminating both over- and under-charging of the battery, both options have a detrimental effect on the performance of the devices.

In addition, there are chargers that operate at constant voltage, constant current, and combined. The first two allow you to restore the charge of a car battery quite quickly, however, as already noted, this reduces the resource of the power source. The latter allows you to carry out the procedure without damaging the battery. Rather, this is why almost all modern charging units use combined parameters.

Operating principle of the charger

The operating principle of all devices that are designed to recharge batteries is almost the same. When connected to the network, the device receives 220 V. The voltage and current are adjusted by the device to the proper values, the current is rectified and supplied to the charging power source.

For each type of battery, a certain order and charging method is preferred. For example, experts believe that it is better to recharge lead-acid batteries more often, without allowing them to discharge. Alkaline batteries, due to the fact that they have a “memory effect,” are recommended to be completely discharged. However, both need to be charged to maximum.

Automatic charger

An automatic charger is the best choice for beginners and car enthusiasts who do not want to delve too deeply into the theory of electricity. Devices of this type do not require human intervention; everything happens automatically. Simply connect the unit to the power supply and place the clamps on the terminals of the car battery that needs recharging.

The automatic device independently controls the entire process: it takes into account the charge level, builds a cycle, and controls the course of the procedure. When the charge reaches one hundred percent, the device turns off automatically. Further, if the charger is not disconnected, it continues to monitor the condition of the battery. If its charge drops (due to self-discharge), the sensors will detect this and the automation will turn on again to recharge. Thus, the charge level of the power supply will be constantly maintained at 100%.

Five-stage chargers in automatic mode are capable of:

  • recharge to 80% charge level;
  • bring charging to the maximum with a decreasing current;
  • maintain the battery charge level at 95–100%;
  • using the pulse mode of operation to eliminate sulfation of the plates;
  • Diagnose the condition of the power supply.

The eight-stage device has wider functionality:

  • the charge-discharge method combats sulfation;
  • diagnostics;
  • recharging up to 80%;
  • full recharging with reducing current;
  • checking battery self-discharge;
  • elimination of electrolyte separation when fully charged;
  • maintaining maximum available capacity;
  • preventive charging at 95% and above.

Thus, an automatic charger for a car battery has a number of advantages. It is very simple and convenient to use, and does not require special skills and knowledge from the car enthusiast.