Smart battery life tester

1//Here is the code i wrote, i made it pretty basic, nothing too fancy but it does work.
2
3
4#include <Wire.h>
5#include <hd44780.h>
6#include <hd44780ioClass/hd44780_I2Cexp.h>
7
8
9
10hd44780_I2Cexp lcd;  // Create lcd object (MUST be named "lcd")
11
12float rFactor;
13int load220 = 7;
14int load100 = 5;
15int load47 = 2;
16int vPin = A0;
17int life;
18int load9v = 6;
19int vPin9 = A2;
20int bPin = 9;
21int bVal;
22
23float voltageScore;
24float voltage;
25float rint;
26float vint;
27String rating;
28int pos;
29const int NUM_SAMPLES = 50;
30const int TRIM = 5; // how many values to trim on each end
31
32int bPin220 = 3;
33int bPin100 = 4;
34int bPin47 = 8;
35int lightVal;
36int medVal;
37int heavyVal;
38
39bool pressed = 0;
40bool go;
41int battery;
42int mode;
43
44void setup() {
45  Serial.begin(9600);
46  Wire.begin();
47  lcd.begin(16,2);
48  pinMode(load220, OUTPUT);
49  pinMode(load100, OUTPUT);
50  pinMode(load47, OUTPUT);
51  pinMode(bPin,INPUT);
52  pinMode(bPin220,INPUT);
53  pinMode(bPin100,INPUT);
54  pinMode(bPin47,INPUT);
55  
56  pinMode(load9v,OUTPUT);
57  digitalWrite(bPin,HIGH);
58  digitalWrite(bPin220,HIGH);
59  digitalWrite(bPin100,HIGH);
60  digitalWrite(bPin47,HIGH);
61  pinMode(vPin, INPUT);
62  pinMode(vPin9,INPUT);
63}
64
65void loop() {
66  mode = 0;
67  pressed = 0;
68  go = 0;
69
70  lcd.clear();
71  lcd.setCursor(0, 0);
72  lcd.print("select battery");
73  Serial.print("check1");
74  //theres no difference between AA and AAA, i just wanted to use all 3 buttons. But the users doesnt know that
75  //checks which battery type
76  while(pressed == 0){
77    lightVal = digitalRead(bPin220);
78    medVal = digitalRead(bPin100);
79    heavyVal = digitalRead(bPin47);
80  
81    if(lightVal == 0){
82        battery = 9;
83  
84        Serial.println(mode);
85        lcd.clear();
86        lcd.setCursor(0,0);
87        lcd.print("9v selected");
88        lcd.setCursor(0,1);
89        lcd.print("press go ");
90        delay(1000);
91        lcd.setCursor(0,1);
92        lcd.print("to start test    ");
93        go = true;
94    }
95    if(medVal == 0){
96        battery = 1.5;
97   
98        lcd.clear();
99        lcd.setCursor(0,0);
100        lcd.print("AA selected");
101        lcd.setCursor(0,1);
102        lcd.print("press go ");
103        delay(1000);
104        lcd.setCursor(0,1);
105        lcd.print("to continue     ");
106        Serial.println(mode);
107        go = true;
108    }
109    if(heavyVal == 0){
110        battery = 1.5;
111 
112        Serial.println(mode);
113        lcd.clear();
114        lcd.setCursor(0,0);
115        lcd.print("AAA selected");
116        lcd.setCursor(0,1);
117        lcd.print("press go ");
118        delay(1000);
119        lcd.setCursor(0,1);
120        lcd.print("to continue     ");
121        go = true;
122    }
123    //escapes while loop
124    if(go == true){
125      bVal = digitalRead(bPin);
126      if(bVal == 0){
127          pressed = true;
128      }
129    } 
130  }
131
132  
133  go = 0;
134  pressed = 0;
135  //special code for 9v battery 
136  if(battery == 9){
137    pressed = 1;
138    calculate(load9v,vPin9,1000);
139    voltage = voltage * (10000.0 + 6800.0)/6800.0;
140    vint = vint * (10000.0 + 6800.0)/6800.0;
141    rint = calcR(vint, 1000, voltage);
142    Serial.println(voltage);
143    Serial.println(vint);
144    Serial.println(rint);
145    mode = 3;
146    voltageScore = constrain((voltage - 7.0) / (9.4 - 7.0), 0.0, 1.0) * 100.0;
147    rFactor = getRFactor(rint);
148    life = (voltageScore * rFactor) / 100.0;
149    pos = 8;
150  }
151  if(pressed == 0){
152      lcd.clear(); 
153      lcd.setCursor(0, 0);
154      lcd.print("Select load");
155  }
156  // chooses the load value
157  while(pressed == 0){
158    lightVal = digitalRead(bPin220);
159    medVal = digitalRead(bPin100);
160    heavyVal = digitalRead(bPin47);
161    if(lightVal == 0){
162      mode = 0;
163      Serial.println(mode);
164      lcd.clear();
165      lcd.setCursor(0,0);
166      lcd.print("light load");
167      lcd.setCursor(0,1);
168      lcd.print("press go ");
169      delay(1000);
170      lcd.setCursor(0,1);
171      lcd.print("to start test");
172      go = true;
173    }
174    if(medVal == 0){
175      mode = 1;
176      lcd.clear();
177      lcd.setCursor(0,0);
178      lcd.print("medium load");
179      lcd.setCursor(0,1);
180      lcd.print("press go ");
181      delay(1000);
182      lcd.setCursor(0,1);
183      lcd.print("to start test     ");
184      Serial.println(mode);
185      go = true;
186    }
187    if(heavyVal == 0){
188      mode = 2;
189      Serial.println(mode);
190      lcd.clear();
191      lcd.setCursor(0,0);
192      lcd.print("heavy load");
193      lcd.setCursor(0,1);
194      lcd.print("press go ");
195      delay(1000);
196      lcd.setCursor(0,1);
197      lcd.print("to start test");
198      go = true;
199    }
200    if(go == true){
201      bVal = digitalRead(bPin);
202      if(bVal == 0){
203      pressed = true;
204      }
205    }
206
207  }
208  if(mode == 0){
209    calculate(load220,vPin,220);
210    if(voltage - vint <0.005){
211      rint = -1;
212      life = -1;
213      rating = "pls read again";
214    }
215    
216  }
217  if(mode == 1){
218    calculate(load100,vPin,100);
219  }
220  if(mode == 2){
221    calculate(load47,vPin,47);
222  }
223  lcd.clear();
224
225  
226  //ratings
227  if (rint < 0) {
228    rating = "error try again";
229    life = 0;
230  } else if (life >= 85) {
231    rating = "Excellent";
232  } else if (life >= 60) {
233    rating = "Good";
234  } else if (life >= 35) {
235    rating = "Weak";
236  } else if (life >= 15) {
237    rating = "Poor";
238  } else {
239    rating = "Throw it out";
240  }
241
242
243  
244  // Final average
245  
246  Serial.print("Average Internal Resistance: ");
247
248  Serial.println(" Ω");
249  lcd.clear();
250  lcd.setCursor(0,0);
251  lcd.print("voltage:");
252  lcd.setCursor(8,0);
253  lcd.print(voltage);
254  lcd.setCursor(0,1);
255  lcd.print("Rint:");
256  lcd.setCursor(7,1);
257  lcd.print(rint);
258  delay(5000);
259  lcd.clear();
260  lcd.setCursor(0,0);
261  lcd.print("life:");
262  lcd.setCursor(6,0);
263  lcd.print(life);
264  lcd.setCursor(pos,0);
265  lcd.print("%");
266  lcd.setCursor(0,1);
267  lcd.print(rating);
268  
269
270  delay(5000);
271  lcd.setCursor(0,0);
272  lcd.print("let battery rest");
273  lcd.setCursor(0,1);
274  lcd.print("before reTesting");
275  delay(2000);
276}
277
278
279// read voltage
280int readVoltage(int pin) {
281  int readings[NUM_SAMPLES];
282
283  // Collect readings
284  for (int i = 0; i < NUM_SAMPLES; i++) {
285    readings[i] = analogRead(pin);
286    delayMicroseconds(500); // short delay to stabilize readings
287  }
288
289  for (int i = 0; i < NUM_SAMPLES - 1; i++) {
290    for (int j = i + 1; j < NUM_SAMPLES; j++) {
291      if (readings[j] < readings[i]) {
292        int temp = readings[i];
293        readings[i] = readings[j];
294        readings[j] = temp;
295      }
296    }
297  }
298  // Step 3: Average the middle values
299  long sum = 0;
300  for (int i = TRIM; i < NUM_SAMPLES - TRIM; i++) {
301    sum += readings[i];
302  }
303
304  int trimmedAverage = sum / (NUM_SAMPLES - 2 * TRIM);
305  return trimmedAverage;
306}
307//calculate internal resistance
308float calcR(float vload, int rload, float vOpen) {
309  float rInt = rload * ((vOpen - vload) / vload);
310  Serial.print("→ rInt: ");
311  Serial.print(rInt, 3);
312  Serial.println(" Ω");
313  return rInt;
314}
315//gets arduino reference voltage
316long readVcc() {
317  // Measures Vcc using the 1.1V internal reference
318  ADMUX = _BV(REFS0) | _BV(MUX3) | _BV(MUX2) | _BV(MUX1);
319  delay(2); // Wait for Vref to settle
320  ADCSRA |= _BV(ADSC);
321  while (bit_is_set(ADCSRA, ADSC));
322  uint16_t result = ADC;
323  long vcc = 1125300L / result; // 1.1V * 1023 * 1000
324  return vcc; // in millivolts
325}
326//turns analog reading into actual voltage
327void calculate(int load,int pin,int rload){
328  float Vref = readVcc() / 1000.0;
329  voltage = readVoltage(pin) * (Vref / 1023.0);
330  Serial.print("Open : ");
331  Serial.println(voltage, 3);
332  lcd.clear();
333  lcd.setCursor(0,0);
334  lcd.print("getting voltage");
335  
336  delay(200);
337
338  digitalWrite(load, HIGH);
339  delay(500);
340  vint = readVoltage(pin)* (Vref / 1023.0);
341  Serial.print("Load Voltage: ");
342  Serial.println(vint, 3);
343  rint = calcR(vint, rload, voltage);
344  digitalWrite(load, LOW);
345  delay(500);
346
347  
348  
349 if(pin == vPin){
350   if (voltage >= 1.6) voltageScore = 100;
351  else if (voltage >= 1.5) voltageScore = 95;
352  else if (voltage >= 1.4) voltageScore = 80;
353  else if (voltage >= 1.3) voltageScore = 60;
354  else if (voltage >= 1.2) voltageScore = 35;
355  else if (voltage >= 1.1) voltageScore = 15;
356  else voltageScore = 5;
357
358  
359  if (rint <= 0.3) rFactor = 100;
360  else if (rint <= 0.4) rFactor = 90;
361  else if (rint <= 0.6) rFactor = 75;
362  else if (rint <= 1.0) rFactor = 50;
363  else if (rint <= 1.5) rFactor = 30;
364  else rFactor = 10;
365   life = (voltageScore * rFactor) / 100.0;
366  if(life == 100){
367    pos = 9;
368  }else{
369    pos = 8;
370  }
371 }
372
373}
374// gets the rFactor for life expectanty
375float getRFactor(float rint) {
376  if (rint < 5.0)       return 100.0;
377  else if (rint < 10.0) return 90.0;
378  else if (rint < 15.0) return 70.0;
379  else if (rint < 25.0) return 50.0;
380  else if (rint < 35.0) return 30.0;
381  else                  return 15.0;
382}