Thyristor chargers remain among the most reliable and easy to assemble solutions for car battery maintenance. Unlike pulsed circuits, they do not create high-frequency interference, and compared to transformer – more compact and cheaper. If you need to. charger for battery 12B or 24B With the possibility of adjusting the current, the thyristor option will be the best choice.

In this article you will find 3 working schemes (from the simplest to advanced with protection), a detailed analysis of the principle of thyristor KU202Nand step-by-step assembly instruction And that's the typical mistake. We will also analyze why many homemade charging systems fail after a month of operation – and how to avoid it.

No shortage of components will be required for assembly: all parts are available in radio stores or on the Internet. AliExpress (The list of references is at the end). If you’ve tried charging on transistors or LM317, the thyristor circuit will seem easier to use – there’s no need for fine-tuning voltages or complex bandages.

πŸ“Š What type of charger are you using now?
Factory impulse
A homemade transformer
Laptop charger.
Nothing, I'm charging from the generator.

Principle of operation of thyristor charger

The thyristor in the charger performs a role key-adjustableIt transmits current in only one direction and only when two conditions are met: the supply of voltage to the anode and the control signal to the shutter. This allows smoothly adjusting the average value of the current entering the battery, without loss of energy for heating (unlike resistor circuits).

Main stages of work:

  1. The mains voltage 220V is supplied to the downsizing transformer, where it is converted into ~15-20V AC.
  2. The diode bridge straightens the voltage, but without a smoothing capacitor – this is important for the correct operation of the thyristor!
  3. thyristor KU202N opens at certain times (phase method of adjustment), "cutting off" part of the sine wave.
  4. The later the thyristor opens, the less the average current at the output.

The key advantage of this scheme is heat-free with long work. For example, the charger on resistors at current 5A can be heated to 80Β°C, while the thyristor remains barely warm. However, there is a disadvantage: without additional chains, there is no protection against short circuit.

Why can't you use a smoothing capacitor after the bridge?

The smoothing capacitor "smears" the current pulses, and the thyristor loses the possibility of phase adjustment. As a result, the current at the output becomes uncontrolled, and the thyristor can open chaoticly, which will lead to voltage throws and damage to the battery.

3 Chargers diagrams on thyristor: from simple to advanced

We selected the circuits based on the availability of parts and reliability. All options are designed to AKB 12B, but can be adapted for 24B by changing the transformer and adding a second thyristor.

1. Simple scheme on KU202N (without protection)

Suitable for one-time charging in the garage. Current is regulated by a variable resistor R2 1-10A range. Minus - there is no protection against a pole or KZ.

Components:

  • πŸ”Ή thyristor KU202N or BT151)
  • πŸ”Ή Transformer 220V β†’ 18V, 150W
  • πŸ”Ή Diode bridge KBPC3510 (or 4 diodes) 1N5408)
  • πŸ”Ή Resistors: R1=1k, R2=10kOhm (potentiometer), R3=47 Ohm
  • πŸ”Ή Capacitor C1 = 0.1 ΞΌc

Feature: When connecting the battery current can jump to 15A - be sure to start charging from the minimum position of the potentiometer!

2. A scheme with anti-pole protection

Added relay 12B/10Awhich breaks the chain when the terminals are incorrectly connected. The current is regulated in the same way as in the first circuit, but is now safe for battery.

Additional details:

  • πŸ”Ή rela SRD-12VDC-SL-C (or analogue)
  • πŸ”Ή diode 1N4007 control circuit protection
  • πŸ”Ή LED 3mm red Indication of correct polarity

Is the transformer (primary winding to 220V) connected correctly?

Is the potentiometer in the minimum current position?

Are the terminals connected to the battery in compliance with polarity?

Is the thyristor fixed to the radiator (even at current 5A it warms up)!

3. Advanced circuit with ammeter and current stabilization

Including 75mV/10A shunt for accurate measurement of current and feedback circuit on the op-amp LM358which maintains a given current regardless of the degree of discharge of the battery.

The assembly will require:

  • πŸ”Ή Oh. LM358 or NE5532)
  • πŸ”Ή shunt 75mV/10A (e.g., HRS10)
  • πŸ”Ή 10A ammeter (analog or digital)
  • πŸ”Ή Stabilitron 12B OC

Critical detail: the shunt should be designed for the maximum current of your circuit. For example, for the current 10A suitable shunt with a drop of 75 mV, but at 15A will require a model of 60 mV, otherwise the OU will work incorrectly.

Scheme. Max. Current, A Protection from the KZ Current stabilization Difficulty of assembly
The simplest 10 ❌ No. ❌ No (manual adjustment) ⭐⭐
With a tilt-proof 10 βœ… Yes (relay) ❌ No. ⭐⭐⭐
Advanced (with OU) 15 βœ… Yes (current restriction) βœ… Yeah (automatic) ⭐⭐⭐⭐

Step-by-step assembly of the charger at KU202N

Let's look at the assembly. second-frame (with protection against polarization), as the most balanced in terms of complexity and functionality.

Step 1. Preparation of the transformer

Use a power transformer 150-200W secondary 18-22B. If you have a transformer with multiple windings (like an old Soviet TV), connect them in series to get the desired voltage. Call the windings with a multimeter to avoid interturning.

Step 2. Diode bridge assembly

For current up to 10A fit ready bridge KBPC3510 4-diode assembly 1N5408. Install the bridge on a small radiator (a 30Γ—30 mm aluminum plate is suitable). Important: The diodes must be designed for a reverse voltage of at least 50V!

Step 3. Installation of thyristor

thyristor KU202N radiator-mounted at least 50 cm2 (current 10A). To improve heat transfer, use a thermal paste. The thyristor's conclusions:

  • πŸ”Œ Anode (A) - to the plus conclusion of the diode bridge
  • πŸ”Œ Cathode (K) - to the plus terminal of the AKB
  • πŸ”Œ Control electrode (G) - to the control circuit (resistor) R3=47 Ohm)

Step 4. Control and protection chain

Observe polarity when connecting the relay and LED:

  • πŸ”Ή The relay coil is connected to the battery plus through the diode 1N4007 (reverse current protection).
  • πŸ”Ή Normally open contacts of the relay are included in the break of the plus wire to the battery.
  • πŸ”Ή LED through resistor 1k It is connected parallel to the relay coil.
πŸ’‘

Before soldering, check all connections for short circuit with a multimeter in vertebrae mode. Pay special attention to the thyristor control circuit - if there is a KZ, the thyristor will open at full power when turned on!

Step 5. Set-up and testing

Connect the terminals to the discharged battery (voltage not lower than 10.5V!) and smoothly rotate the potentiometer. R2. The current must be adjusted in the range 1-10A. If the current is running or the thyristor is not opening:

  • πŸ”§ Check the control circuit (resistor) R3=47 Ohm It must be correct.
  • πŸ”§ Make sure that the thyristor shutter is given a pulse (check with an oscilloscope or LED).
  • πŸ”§ Replace your thyristor. KU202N It is sensitive to static electricity.
πŸ’‘

If the relay does not click when connecting the battery, check the polarity: the relay coil must be connected to the relay. plus ABB through the diode. With reverse polarity, the current will not go through the coil, and the circuit will remain open.

Calculation of components for your battery

In order for the charger to work efficiently and not damage the battery, it is necessary to choose the parameters of the components correctly. Below is the calculation for lead-acid battery 12V/60Ah.

1. Transformer.

Transformer power (P.P.) is calculated by the formula: Pt = Uzar Γ— Izar Γ— 1.3where:

  • Uzar charging voltage (14.4V for 12V batteries),
  • Isare - maximum charging current (10% of the battery capacity, i.e. 6A for 60Ah),
  • 1.3 - power reserve.

For our example: 14.4V x 6A x 1.3 = 113 W. The transformer will fit on 150W.

2. thyristor

The thyristor parameters must meet the conditions:

  • πŸ”Ή Maximum open current (>10A for our case).
  • πŸ”Ή Reverse voltage (>50V, as the peak voltage after the bridge is ~24V).
  • πŸ”Ή Control current for KU202N - 5-15mA.

Alternatives KU202N:

  • πŸ”Ή BT151-600R (15A, 600B)
  • πŸ”Ή TIC226D (25A, 400B)
  • πŸ”Ή SCR S6025L (25A, 600B)

3. Diode bridge

The current of the diodes of the bridge should be at least the maximum charging current (6A in our case), and the reverse voltage is not less than 50V. For example:

  • πŸ”Ή KBPC3510 (35A, 1000B) - with a large margin.
  • πŸ”Ή BY229 (5A, 1000V) - for currents up to 5A.
  • πŸ”Ή 4-diode assembly 1N5408 (3A, 1000B).

4. Resistors and capacitors

Resistor denominations R1 and R3 They are selected experimentally for smooth regulation of current. Capacitor C1 = 0.1 ΞΌc It is used to filter interference in the control circuit. When increasing its capacity to 0.47 ΞΌF, the current adjustment will become more smooth, but there may be a delay in the response to a change in the position of the potentiometer.

πŸ’‘

For accurate resistor calculation R3 Use the formula: R3 = (Uppre - 0.7B) / Iuprewhere Upr. voltage at the control electrode (usually 1-3V), and ipre - Thyristor control current (taken from datashite).

Common Mistakes and How to Avoid Them

Even experienced radio amateurs make mistakes when assembling thyristor chargers. Here. Top 5 Problems with Top 5 Problems and their decisions:

⚠️ Attention: If after assembly the thyristor immediately opens to full capacity and is not regulated - most likely, the capacitor is broken. C1 or closed-circuit R3. Turn off the power and check the multimeter control circuit!

1. The thyristor is warming or punching

Reasons:

  • πŸ”₯ There is no radiator or it is too small (for 10A you need a radiator from the radiator). TIP41C or similar).
  • πŸ”₯ Exceeded the maximum current (for example, with CZ at the output).
  • πŸ”₯ The reverse voltage on the thyristor exceeds the permissible (check the transformer!).

Decision: Set the thyristor on the heatpast radiator, add a safety lock on 10A to the break of the plus wire.

2. Current is unregulated.

Possible problems:

  • πŸ”§ Potentiometer malfunctioned. R2 (check multimeter).
  • πŸ”§ Break in the control circuit (resistor) R3 capacitor C1).
  • πŸ”§ The thyristor opens from tips (add a 10nF capacitor parallel to the control electrode).

3. Charging is off.

Checklist for diagnosis:

  • πŸ”Œ Check the fuse on the primary winding of the transformer.
  • πŸ”Œ Make sure there is a voltage (~18V) on the secondary winding of the transformer.
  • πŸ”Œ Call the diode bridge – all diodes must pass current in only one direction.

4. Protection against overpooling works with the correct connection

The reason is the wrong connection of the relay coil. Relay must be. open-ended, and the coil is connected to the plus of the battery through the diode. If you confuse the contacts, the relay will work at any polarity.

5. The voltage at the output is too high (more than 15V)

It's dangerous for the BAC! Reasons:

  • πŸ”‹ The transformer (interturn circuit) is defective.
  • πŸ”‹ The thyristor does not close completely (check the control circuit).
  • πŸ”‹ No load (plug the battery before measuring!).
⚠️ Attention: If the idling voltage (without battery) exceeds 20V, immediately disable the circuit! This is a sign of a transformer or diode bridge malfunction, which can cause the battery to explode when connected.

Modernization of the scheme: adding useful functions

The basic scheme on the thyristor can be modified to improve convenience and safety. Let's see. 3 popular upgrades:

1. Automatic shutdown at full charge

Add a comparator to LM358It tracks the voltage on the battery. When it reaches 14.4BThe comparator breaks the thyristor control circuit.

Additional details:

  • πŸ”Ή Oh. LM358
  • πŸ”Ή Stress divider resistors (VR)10k and 3.3k)
  • πŸ”Ή rela 12B chain-break

2. Digital Voltmeter and Ammeter

Connect the module. DSN-VC288 (or similar) to the shunt and terminals of the AKB. The module is powered by a stabilized 5V voltage (can be taken from USB charging).

Connection diagram:

  • πŸ”Ή + module - to plus battery through the diode 1N4007.
  • πŸ”Ή - Module to minus battery.
  • πŸ”Ή Shunt plugs in to conclusions IN+ and IN- Ammeter.

3. Protection against short circuit

Add to the chain safety-guard at 10A and relay with normally closed contacts, which opens at a current of more than 12A (use a current relay). DZ-47 Or a homemade circuit on a shunt and comparator.

Example of a diagram: 



AUC +


β”‚


β–Ό


[Relay 12B (NZ)] β€” [Fuse 10A] β€” [Tyristor]


β”‚


β–Ό


Shunt 75mV/10A β†’ Comparator β†’ Transistor Base β†’ Relay

Where to buy the details and how much it costs

All components are available in radio stores or on AliExpress. Below is the approximate cost for a tilting-proof scheme (as of 2026):

Component Model/nominal Number of Cost, rubles Reference (AliExpress)
thyristor KU202N or BT151-600R 1 80–150 Reference
Transformer. 220V β†’ 18V, 150W 1 500–800 Reference
Diode bridge KBPC3510 1 120–200 Reference
rela SRD-12VDC-SL-C 1 90–150 Reference
Radiator For TO-22050Γ—50 mm 1 50–100 Reference

Total: ~1000-1500 rubles (excluding delivery). For comparison, a factory charger with similar characteristics will cost 2500-4000 rubles.

If you want to save money, look for used transformers from old power supplies or Soviet equipment (for example, from TVs). horizon tape-record vega). Diode bridges and thyristors can be soldered out of faulty welding machines or UPS.

FAQ: Frequent questions about thyristor chargers

Can I use a thyristor charger for Li-ion batteries?

Nope! Thyristor schemes are not suitable for Li-ion or LiPo batteries for two reasons:

  1. They require precise voltage stabilization (usually 4.2V per jar), whereas thyristor charging produces a β€œdirty” voltage with pulsations.
  2. Li-ion needs a balancer that aligns the charge between banks – it is not in thyristor schemes.

For lithium batteries, use circuits on TP4056 (for one bank) or BMS fees (for assemblies).

How to calculate the charging time of the battery?

Charging time (T) is approximately calculated by the formula: T = (Capacity of battery Γ— 1.2) / Charging current

Example: for 60Ah battery and current 6A: T = (60 Γ— 1.2) / 6 = 12 hours.

Coefficient 1.2 takes into account the efficiency of charging (not all energy goes to restore the capacity).

Important: If the battery is severely discharged (voltage below 11V), start charging with a current of 1-2A to avoid sulfation.

Why does the thyristor charger "squeak" when working?

This is a normal phenomenon caused by phase-control. The thyristor β€œcuts” the sinusoid of the network, which leads to acoustic vibrations in the transformer and throttles. To reduce noise:

  • πŸ”‡ Fix the transformer on shock absorbing legs (such as rubber pads).
  • πŸ”‡ Add a 0.1 ΞΌF capacitor parallel to the primary winding of the transformer.
  • πŸ”‡ Use a transformer with a closed magnetic circuit (torrhoidal).

If the "squeak" is accompanied by sparking or smell of burning - immediately turn off the circuit and check the thyristor for a break!

Can I charge a gel battery with a thyristor charger?

Yes, but with reservations:

  • πŸ”‹ The maximum voltage shall not exceed 14.1B (for 12B batteries).
  • πŸ”‹ Charging current - no more 0.1C (e.g. 6A for 60Ah).
  • πŸ”‹ Be sure to use the scheme with stress-stabilization (for example, on OU).

The gel batteries are sensitive to overvoltage - without limiting the voltage, they quickly degrade.

What is the difference between the KU202H and the BT151?

Major differences:

Parameter KU202N BT151-600R
Max. Current, A 10 15
Max. tension
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