Modern electronics dictates its own rules, and even in the automotive industry, where lead and acid ruled the roost for decades, there is a place for microcontrollers. Creation charger for Arduino - This is not just a hobby for radio amateurs, but also a real necessity for those who want to extend the life of the battery of their car or motorcycle. Standard store-bought “boilers” are often either too primitive or unreasonably expensive and do not offer flexibility in setting up charging algorithms.
Using the Arduino platform allows you to create a device that will not just supply voltage, but intelligently control the process, monitoring the slightest changes in the state of the battery. You get complete control over charging algorithms, the ability to visualize data on the display and protection against critical errors. In this article we will look at how to turn a set of electronic components into a reliable assistant for maintaining your car battery.
Operating principle and advantages of homemade chargers
The main difference between a homemade charger based on a microcontroller and a conventional transformer rectifier is the presence of feedback. If in a classical circuit the current depends only on the difference in voltage of the source and battery, then here Arduino acts as a brain that constantly polls sensors. The microcontroller reads the current voltage at the terminals and the current flowing through the circuit, and based on this data it instantly adjusts the output parameter.
This approach makes it possible to implement complex multi-stage cycles, for example, desulfation mode or asymmetric charge, which are extremely difficult to implement on an analog element base without significantly complicating the circuit. Additionally, the digital system can remember cycle history and automatically shut down when full capacity is reached, eliminating the risk recharge and electrolyte boiling.
- 🔋 Accurately maintain the specified current and voltage regardless of network surges.
- 🛡️ Availability of software protection against polarity reversal and short circuit.
- 📊 Visual control of all process parameters on an LCD or OLED display.
It is important to understand that a programmable controller allows you to adapt the same hardware for different types of batteries. By switching the mode in the menu, you can charge as a starter battery 12V, and a traction battery for an electric bicycle, simply by changing the operating logic in the code. This makes the device a versatile tool in the garage.
Required components and circuit selection
To assemble a high-quality charger, you will need to select components that can withstand the required currents. The heart of the system is, of course, the board Arduino Nano or Uno, but more powerful elements will be required to control the power part. Most often, a combination of a step-down DC-DC converter and a field-effect transistor controlled by pulse width modulation (PWM) is used.
The key element of accuracy is the current sensor. For automotive currents up to 10 Amps, a resistor-based module is perfect 0.01 Ohm and an operational amplifier, or more advanced Hall sensors such as INA219 or ACS712. It is the quality of this component that determines how accurately the device will comply with the specified charge algorithm.
Why DC-DC converter?
Using a ready-made switching power supply (DC-DC) instead of assembling the power part from scratch using transistors greatly simplifies the design. You don't need to wind transformers or assemble complex bridge circuits. You take a ready-made module, for example, based on XL4015 or LM2596, and simply control its output voltage through Arduino, sending a signal to the ADJ pin or through PWM switch control. This increases efficiency and reduces heating.
To display information, you must select a display. Most popular modules Nokia 5110, SSD1306 (OLED) or LCD1602 with module I2C. The latter are convenient because they require connecting only four wires, which simplifies installation inside the case. Don't forget about potentiometers or an encoder for entering parameters if you don't want to reflash the device every time to change the current.
Assembling the power section and connecting sensors
Installation of the power circuit requires care, since errors here can lead to failure of not only the charger, but also the battery itself. The first step is to connect the power supply to the input terminals of the DC-DC converter. The input voltage must be higher than the maximum voltage of the battery being charged, usually take power supplies to 19-24 Volts for work with 12-volt batteries.
The current sensor is connected to the open circuit between the positive output of the converter and the positive terminal of the battery. This is a critical point: if the sensor is not installed correctly or has too much resistance, it will heat up and introduce errors. To calibrate the system, an external multimeter, comparing its readings with the data produced by the Arduino.
☑️ Check before turning on
The output voltage is controlled by supplying a PWM signal from the Arduino pin to the control input of the converter or through a transistor switch. If you are using a popular op-amp, changing the duty cycle will change the effective voltage at the output. It is necessary to provide galvanic isolation or a common ground for the correct operation of the logic and power section.
Software logic and charging algorithms
Software code is the soul of your device. This is where the logic is written that turns a set of wires into a smart charger. The main program loop (loop) must be performed quickly in order to respond to changes. A typical algorithm begins by measuring the open circuit voltage and determining the type of battery connected.
Next, the system switches to constant current mode (CC - Constant Current). Arduino reads the readings from the sensor, compares them with a user-specified value and adjusts the PWM signal. If the current drops below the set value, the controller increases the duty cycle; if it increases, it decreases it. This process occurs hundreds of times per second, ensuring stability.
| Parameter | Description | Typical value for 12V battery |
|---|---|---|
| Charge current | Current strength in the main phase | 10% of capacity (for example 5A for 50Ah) |
| Cut-off voltage | Maximum voltage in phase CV | 14.4 - 14.8 V |
| Cut-off current | Current at which the charge is considered complete | 0.5 - 1.0 A |
| Desulfation voltage | Peak Pulse Voltage | 16.0 - 16.5 V |
When the terminal voltage reaches the specified threshold (phase CV — Constant Voltage), the algorithm switches to maintaining voltage. The current begins to gradually drop as the battery plates become saturated. The task of the program is to prevent excess voltage and turn off the charge when the current drops to a minimum value indicating 100% charge.
Measuring system calibration
No circuit is perfect, and components have tolerances. Resistors can have an error of 1-5%, and op-amps have their own bias voltage. Therefore, the calibration step is mandatory to obtain an accurate charger. Without calibration, the readings on the display may differ from real values by 10-20%, which is unacceptable for delicate chemistry batteries.
The calibration process usually involves two steps: voltage calibration and current calibration. To begin, connect the device to a reference voltage source or a fully charged battery measured with an accurate multimeter. In the device menu (or in the code), select the conversion factor so that the display readings coincide with the standard readings.
⚠️ Attention: When calibrating the current, be sure to use a load resistor or a real battery. Never turn on the charger without a load in current calibration mode, as the readings may be incorrect due to the characteristics of the Hall sensor or shunt.
To calibrate the current, run a known current (measured with an external ammeter) through the system and record the raw data from the Arduino's analog input. By dividing the real value by the resulting number, you will get a coefficient that needs to be included in the calculation formula in the sketch. The accuracy of the calibration directly affects the safety and efficiency of the charge.
Improvements and device protection
The basic version of the device is already functional, but for use in garage conditions it could use additional protection. First of all, you should think about protection against polarity reversal. Although many DC-DC converters have built-in protection, it is better to play it safe by installing a diode assembly or relay at the input that will only complete the circuit if the terminals are connected with the correct polarity.
Heat dissipation is also critical. Power elements such as transistors and diodes generate a significant amount of heat at currents of 5-10 Amps. Installing a radiator with active cooling (cooler), which is turned on by a temperature sensor or when charging starts, will extend the life of your creation. Arduino can control the temperature and reduce the current if the sensor indicates overheating.
- 🌡️ Installation of a DS18B20 temperature sensor to monitor case heating.
- 🔌 Use of high-quality XT60 or XT90 connectors for connecting to the battery.
- 🔇 Adding a sound alarm (beeper) when a cycle is completed or an error occurs.
Use ferrite beads on the wires going to the battery. This will reduce the level of high-frequency interference from the PWM converter, which can interfere with the controller itself or interfere with radio reception in the car.
Don't forget about software improvements. You can add the “Battery Training” function, where the device first discharges the battery to a certain level and then charges it. This helps combat sulfation of the lead plates, returning some of the lost capacity to the battery. Implementing such a loop on Arduino is quite simple by adding a load resistor or lamp to the circuit.
Frequently asked questions (FAQ)
Can lithium-ion batteries be charged with this device?
Yes, but you need to change the algorithm in the code. Lithium-ion batteries (Li-Ion) require strict voltage control (4.2V per cell) and cannot be overcharged. For them, the CC/CV mode with more stringent limits is often used. It is also important to add balancing if the battery is multi-cell, which will require modification of the circuit.
What is the maximum current that can be obtained with such a circuit?
The maximum current is limited by the capabilities of the selected DC-DC converter, transistor and current sensor. Standard modules like XL4015 hold up to 5A, more powerful ones (XL4016, LM2596 with modifications) - up to 10-15A. For high currents, you need to change the power components to more powerful analogues.
Do I need to remove the battery from the car to charge it?
Preferable, but not always required. If you disconnect the terminals, you are guaranteed not to damage the car's sensitive electronics (ECU, radio) due to voltage surges that may occur when the pulse charger is operating. If you can't turn it off, make sure your device has very low ripple.
Where can I get firmware for Arduino?
Basic sketches can be found on official Arduino resources, forums like Arduino.ru, or in GitHub repositories by searching for "Arduino Battery Charger". However, in order to fully work for your specific circuit, the code will have to be adapted by changing the calibration coefficients and connection pins.
A homemade Arduino charger is a great project that combines practical benefits with a deep understanding of electrochemistry and electronics. It allows you to charge batteries more carefully and efficiently than many cheap store-bought analogues.