Learn how to check battery capacity with Arduino, including essential techniques for temperature monitoring and selecting the right battery type, in my detailed article:
This guide is a valuable resource for anyone interested in Arduino-based battery management and monitoring systems.
Battery capacity tester. With this device you can check the 18650 battery capacity. For safe I added with thermistor the temperature of power resistance and battery to prevent explosion. I'm doing some change from original project: v0.1
- VCC of Arduino now It's automatically calculated;
- Added variable to change setting in more confortable way.
- Added percentage of discharging
- Added temperature of battery and power resistor
v0.2
- Added possiblity of battery selection
- Created prototype board (Look the schema), screen, button and speaker is out of board because in the future I'd like to create a package. - Added manage of temperature limit for power resistor.to block when raise 70°.
In v0.2 to support various type of battery I created a struct that must be filled with battery name, min voltage, e max voltage (I need help to fill :P).
// Structure of battery type
struct BatteryType {
char name[10];
float maxVolt;
float minVolt;
};
#define BATTERY_TYPE_NUMBER 4
BatteryType batteryTipes[BATTERY_TYPE_NUMBER] = {
{ "18650", 4.3, 2.9 },
{ "17550", 4.3, 2.9 },
{ "14500", 4.3, 2.75 },
{ "6v Acid", 7.2, 6.44 }
};Now I use 10k resistor for voltage read, if you want change voltage support you must change this value (explain better next):
// Battery voltage resistance
#define BAT_RES_VALUE_GND 10.0
#define BAT_RES_VALUE_VCC 10.0
// Power resistor voltage resistance
#define RES_RES_VALUE_GND 10.0
#define RES_RES_VALUE_VCC 10.0If you don't use thermistor set to false this:
#define USING_BATTERY_TERMISTOR true
#define USING_RESISTO_TERMISTOR trueIf you use a different i2c display you must rewrite this method:
void draw(void);In project you can find fritzing, schema, photo and other.
I use generic character display, and I build the i2c controller and use It with my custom library, but if you want You can take a normal i2c controller (less than 1€) with standard library, the code remain the same. All code of display is in draw function so you can change that without change other.
Created from an idea of OpenGreenEnergy.
To measuring voltage we use the principle of Voltage divider, more information on: Wikipedia or Blog, in simple word this code
batVolt = (sample1 / (1023.0 - ((batResValueGnd / (batResValueVolt + batResValueGnd)) * 1023.0))) * vcc;measure battery voltage,
batResValueGnd / (batResValueVolt + batResValueGnd) this is the multipler factor of the reading voltage, I inserted 2 resistance of batResValueVolt and batResValueGnd ohom after and before the analog read wire;
sample1 --> is the average analog readings;
vcc --> reference arduino voltage;
1023.0 --> is the reference maximun value of analog read (arduino analog read go from 0 to 1023)
The principle is that we measure the voltage afther and before the power resistor and so we can calculate milliampere that consumes the battery.
The MOSFET is used to stard and stop battery drain from power resistor. I'm pretty scary, so I inserted 2 thermistors to monitorage battery and power resistor temperature.
On prototype board:
I create a prototype board very extendible, but for now I use only minimal set of pin (in future led and other button).
If you want support voltage greater than 10v you must change the resistor value of Battery and Resistance in according to the formula
(BAT_RES_VALUE_GND / (BAT_RES_VALUE_VCC + BAT_RES_VALUE_GND) in the schema Resistor power voltage GND 1/2 / (Resistor power voltage 2/2 + Resistor power voltage GND 1/2).
Shopping List
| Amount | Part Type | Properties |
|---|---|---|
| 2 | 5mm Screw TermInal eBay | pin spacing 0.2in (5.08mm); 2 Pole 5mm Pitch PCB Mount Screw TermInal Block 8A 250V LW SZUS |
| 1 | Arduino Pro Mini clone (compatible Nano) eBay | tipo Arduino Pro Mini (Clone comp Nano); variant variant 1 |
| 1 | Basic FET P-Channel IRF744N or IRLZ44N eBay | package TO220 [THT]; tipo p-channel |
| 11 | 10kΩ Resistor | bands 4; pin spacing 400 mil; tolerance ±5%; package THT; resistenza 10kΩ |
| 1 | Temperature Sensor (Thermistor) eBay | package THT; thermistor type NTC; resistance at 25° 10kΩ; tipo thermistor |
| * | Generic male header | form ♂ (male); pin spacing 0.1in (2.54mm); package THT; row single; hole size 1.0mm,0.508mm; pins 2 |
| * | Generic female header | form ♀ (female); pin spacing 0.1in (2.54mm); package THT; row single; hole size 1.0mm,0.508mm; pins 2 |
| PerfBoard board | Prototype board eBay | 24x18 |
Soldering prototype:
Display
On breadboard:
Serial output for debug:
Volt: 2.94V - B Volt: 2.94V - Res Volt: 0.00V - Curr: 292mA - mAh: 219.4 - DISCHARGING: 1 - Battery temp: 19.47 - Resistance temp: 32.28
Volt: 2.94V - B Volt: 2.94V - Res Volt: 0.00V - Curr: 292mA - mAh: 219.4 - DISCHARGING: 1 - Battery temp: 19.47 - Resistance temp: 32.24
Volt: 2.94V - B Volt: 2.94V - Res Volt: 0.00V - Curr: 292mA - mAh: 219.4 - DISCHARGING: 1 - Battery temp: 19.44 - Resistance temp: 32.28
Volt: 2.92V - B Volt: 2.92V - Res Volt: 0.00V - Curr: 292mA - mAh: 219.7 - DISCHARGING: 1 - Battery temp: 19.49 - Resistance temp: 32.28
Volt: 2.94V - B Volt: 2.94V - Res Volt: 0.00V - Curr: 292mA - mAh: 219.7 - DISCHARGING: 1 - Battery temp: 19.46 - Resistance temp: 32.26
Volt: 2.94V - B Volt: 2.94V - Res Volt: 0.00V - Curr: 292mA - mAh: 219.7 - DISCHARGING: 1 - Battery temp: 19.42 - Resistance temp: 32.28
Volt: 2.92V - B Volt: 2.92V - Res Volt: 0.00V - Curr: 292mA - mAh: 219.7 - DISCHARGING: 1 - Battery temp: 19.46 - Resistance temp: 32.22
Volt: 2.94V - B Volt: 2.94V - Res Volt: 0.00V - Curr: 294mA - mAh: 220.0 - DISCHARGING: 1 - Battery temp: 19.46 - Resistance temp: 32.26
| Label | Part Type | Properties |
|---|---|---|
| (LCD bb) Display* | LCD screen | pins 16; tipo Character |
| (LCD bb) i2c controller* | PCF8574 | tipo PCF8574; package DIP16 [THT] |
| (LCD bb) 10K Trimmer potentiometer* | TRIMPOT | variant variant 2; package trimpot_pth_s3_lock_3386P |
| (LCD bb) 2N2222* | NPN-Transistor | tipo NPN (EBC); package TO92 [THT]; part number 2N2222 |
| 18650 Battery | LIPO-1000mAh | variant 1000mAh; package lipo-1000 |
| Beeper | Piezo Speaker | |
| For battery | Screw terminal - 2 pins | pin spacing 0.1in (2.54mm); pins 2; hole size 1.0mm,0.508mm; package THT |
| For power resistor | Screw terminal - 2 pins | pin spacing 0.1in (2.54mm); pins 2; hole size 1.0mm,0.508mm; package THT |
| IRF744N | Basic FET N-Channel | tipo n-channel; package TO220 [THT] |
| MF58 | Temperature Sensor (Thermistor) | resistance at 25° 10kΩ; tipo thermistor; package THT; thermistor type NTC |
| MF58 | Temperature Sensor (Thermistor) | resistance at 25° 10kΩ; tipo thermistor; package THT; thermistor type NTC |
| Microcontroller | Arduino Pro Mini clone (compatible Nano) eBay | variant variant 1; tipo Arduino Pro Mini (Clone comp Nano) |
| Power resistor | 10kΩ Resistor | pin spacing 400 mil; bands 5; resistenza 10kΩ; tolerance ±5%; package THT; part number Power resistor |
| Resistance of battery volt. 1/2 | 10kΩ Resistor | pin spacing 400 mil; bands 4; resistenza 10kΩ; tolerance ±5%; package THT |
| Resistance of battery volt. 2/2 | 10kΩ Resistor | pin spacing 400 mil; bands 4; resistenza 10kΩ; tolerance ±5%; package THT |
| Resistance of power res. volt. 1/2 | 10kΩ Resistor | pin spacing 400 mil; bands 4; resistenza 10kΩ; tolerance ±5%; package THT |
| Resistance of power res. volt. 2/2 | 10kΩ Resistor | pin spacing 400 mil; bands 4; resistenza 10kΩ; tolerance ±5%; package THT |
| Thermistor battery resistance | 10kΩ Resistor | pin spacing 400 mil; bands 4; resistenza 10kΩ; tolerance ±5%; package THT |
| Thermistor power res. resistance | 10kΩ Resistor | pin spacing 400 mil; bands 4; resistenza 10kΩ; tolerance ±5%; package THT |
| Amount | Part Type | Properties |
|---|---|---|
| 1* | LCD screen | pins 16; tipo Character |
| 1* | PCF8574 | tipo PCF8574; package DIP16 [THT] |
| 1* | TRIMPOT | variant variant 2; package trimpot_pth_s3_lock_3386P |
| 1* | NPN-Transistor | tipo NPN (EBC); package TO92 [THT]; part number 2N2222 |
| 1 | LIPO-1000mAh | variant 1000mAh; package lipo-1000 |
| 1 | Piezo Speaker | |
| 2 | Screw terminal - 2 pins | pin spacing 0.1in (2.54mm); pins 2; hole size 1.0mm,0.508mm; package THT |
| 1 | Basic FET N-Channel | tipo n-channel; package TO220 [THT] |
| 2 | Temperature Sensor (Thermistor) | resistance at 25° 10kΩ; tipo thermistor; package THT; thermistor type NTC |
| 1 | Arduino Pro Mini clone (compatible Nano) | variant variant 1; tipo Arduino Pro Mini (Clone comp Nano) |
| 1 | 10kΩ Resistor | pin spacing 400 mil; bands 5; resistenza 10kΩ; tolerance ±5%; package THT; part number Power resistor |
| 6 | 10kΩ Resistor | pin spacing 400 mil; bands 4; resistenza 10kΩ; tolerance ±5%; package THT |
* Only if you want assembly LCD i2c character controller
Breadboard
Thermistor on power resistor (heat shrink sleeve to hold).
Thermistor on battery.
