Each lead-acid battery loses its maximum capacity and performance properties over time; a deposit of lead sulphate salts forms on the plates - sulfation. The amount of acid per percentage of electrolyte becomes less and naturally the density of the electrolyte decreases.
How can I check my battery?
- Electrolyte density is the oldest and most popular method, but modern sealed batteries do not have holes for checking in this way. With this method you can only learn a little about the general condition of the battery and its immediate future.
- Using a load fork. It is a handle with two probe terminals that last for 1 sec. connected to the battery contacts. The device contains a voltmeter scale and a load that is designed for a certain battery capacity (car battery). The device shows the voltage under load and, depending on the readings of its arrow, one could judge the health of the battery.
- A lead-acid battery tester is an electronic device that can show many battery parameters in a few seconds (up to 3 seconds), the main ones being: current, voltage, capacity, forecast for battery life.
- Test discharge - well, the drawback is that the battery must be fully charged and its operation (discharge) must be checked for a long time against a known load. This takes a lot of time and wastes battery life.
Checking the battery using improvised means
Before checking, the battery must be fully charged.To test, you need a load corresponding to half the battery capacity(in ampere hours)
For example: we have a sealed 12 volt 7A/h battery - which means we need a load of 3.5 amperes. At 12 volts (3.5 * 12 = 42) this is 42 watts
On some models, an even lower current parameter is indicated (for example, this inscription - Initial current less than - 2.1A) based on this, we take this figure 2.1 * 12 volts = 25 Watt - this is the operating load power of the battery.
Now we need a load average between the operating one and half of the maximum capacity, this is approximately 35 Watt; if the operating current is not specified, we can take 40 Watt.
As a load a light bulb is best(but another similar current load is also possible) at 12 volts and a power of 35-40 W.
So, we connect the light bulb to the battery terminals for a period of 2 minutes and see if the light bulb changes brightness; if the light dims during this time, then the battery is faulty.
If everything remains unchanged, then after reaching 2 minutes of glow, connect a voltmeter (multimeter) to the glowing bulb and check the voltage:
- more than 12.4 volts - the battery has retained its nominal capacity and is fully operational.
- 12-12.4 volts - the battery is serviceable but already tired
- less than 12 volts - the battery has already lost 50% of its rated capacity and it is better to replace it.
You should be sure that the battery is fully charged; it is best to charge it over the course of a day or at least 6 hours with an appropriate current.
The most important parameter of each battery is its battery capacity. It determines the amount of energy given to them for each period of time. This applies to all batteries from car to telephone. Knowing about them and understanding the device is important because using the wrong battery capacity can cause serious problems in starting these devices.
The units of measurement for this quantity are Amperes or Milliamps/hour. Based on this parameter, the battery for the equipment is selected, guided by the recommended values. If the recommendations are violated, for example, the car may not start in winter.
What is the capacity of a battery or accumulator
All batteries are usually decorated with inscriptions like 55, 70 Ah or 1800mAh. This designation indicates that the capacity of this battery is, respectively, 55 Amperes or fractions of Amperes per hour, only translated into English - A/hour. It must be distinguished from another parameter - voltage, which is written in Volts.
Standard battery
The Ah indicator shows how long the battery will work for an hour at a load of 60 Amps and a voltage of 12.7V. In other words, capacity is the amount of energy that a battery can hold.
And if there is less than 60A load, the battery will last longer than 60 minutes.
How to quickly check the capacity of any battery
Most often, battery capacity is measured using a tester. This is a device for quick measurements. It works automatically and does not require any additional knowledge to use it. The time required is no more than 15 seconds. All that is required is to connect the tester to a power source and press a single button, after which it begins to determine the capacity of the connected batteries.
It is used when choosing a battery, comparing the residual and nominal capacity, which is officially indicated on the device. If the difference is more than 50%, then the battery cannot be used.
Which device to use to accurately measure the capacity of any battery
The capacity indicator determines the density of electrolytes; it is determined using a special device - a hydrometer. New batteries always indicate the basic parameters. However, this value is determined independently.
Small battery
The simplest way is with ordinary testers like “Pendant”. This device is used to measure the capacity and voltage of the battery in a car. This requires minimal effort and time while achieving reliable results.
To use the “Pendant”, you need to connect it to the battery terminals, after which it will begin to determine the voltage and capacity.
There are many other ways to calculate these parameters. The classic method is to measure a car battery using a multimeter. In order to do this, it must be fully charged and connected to the consumer (an ordinary 60W light bulb is sufficient). However, even this does not guarantee absolute accuracy of the readings.
Multimeter device
The first step after assembling the circuit from the battery itself, a multimeter, or a light bulb is to apply voltage. If the light does not go out within 2 minutes (if this does not happen, the battery cannot be restored), take the “Coulomb” readings. As soon as the readings drop below battery voltage standards, the battery begins to discharge. Having measured the time required for the final consumption of energy and the load current of the consumer, you need to multiply these readings by each other. The resulting number is the battery capacity.
If the result differs from the official value, the battery must be replaced. A multimeter allows you to calculate the capacity of any battery. The disadvantage of this method is that it takes a lot of time.
In the second measurement method, the battery is discharged using a resistor according to a special circuit. Using a stopwatch, the discharge time is determined. However, it is important not to completely discharge the battery, protecting against this using a relay.
How to make a device with your own hands
If you don’t have the necessary equipment at hand, you can implement the device yourself. Load forks will do. There are always a lot of them on sale, but they are also collected independently. This option is discussed below.
Plug diagram
This fork has an expanded scale, which allows you to achieve the highest accuracy of readings. Load resistance is built in. The scale ranges are divided in half, thereby reducing the reading error. The device is equipped with a 3-volt scale. This makes it possible to test individual battery banks. Scales of 15V are achieved by lowering the voltage on diodes and zener diodes.
The current reading of the device will increase as soon as the voltage values become greater than the opening level of the zener diode. When a voltage of the wrong polarity is applied, diodes provide protection. In the picture: SB1 is a toggle switch, R1 is a transmitter of the required current, R2 and R3 are resistors intended for M3240, R4 are determinants of the width of narrow scale ranges, R5 is a load resistance.
How to find out the capacity of a telephone battery at home
When using a cell phone, its battery is subject to constant degradation. This process cannot be avoided; it is natural. This happens regardless of the model, price, or features of the phone. To accurately understand how long the battery in your device will last, you need to measure its current capacity. This will allow you to replace the battery in time before it starts to turn off at the most inopportune times.
Swollen battery
First of all, you need to inspect the battery. Dangerous problems in a lithium battery are immediately visible: the case may swell, be full of traces of corrosion, and greenish and white spots.
If signs of swelling are detected, it is dangerous to continue using such a battery. This can cause short circuits in the phone's electrical circuits. The swelling may begin from a small bulge to serious deformation. Another worrying factor is the rapid loss of charge in the phone.
Today, there are many applications to measure the current capacity of a phone.
To accurately determine the battery capacity, the advanced charger method is used. The battery is completely discharged, then connected to this device. It, in turn, calculates the battery capacity taking into account time and current value.
Load differences
The parameters of each car are different. Their engine sizes and battery capacities differ. In a passenger car, a battery usually has a capacity of 40-45A, and in a large car it is about 60-75A.
The reasons for this lie in the starting current - the smaller the battery, the less electrolytes, lead, etc. it contains. The larger it is, the greater the amount of energy that can be given off at one moment. Based on this, large batteries can work successfully in a small car, but small ones cannot be inserted into a large car.
Case dependency
Batteries of different sizes
Capacity is directly related to the number of electrolytes and lead in the battery. Because of this, small capacity batteries will be much smaller in volume and weight than larger batteries. For these reasons, large batteries are never installed on a small car, since this does not make sense - these cars have little space under the hood. And the small battery does an excellent job of starting the engine.
Capacity reduction
Any battery is subject to depreciation and its capacity decreases over time. Conventional batteries last about 3-5 years. The highest quality specimens remain in good condition for up to 7 years.
As capacity drops, the battery loses its ability to provide sufficient starting current. Then it's time to replace it. The main reasons for the drop in capacity include:
- Accumulation of sulfuric acid on the positive plate. It can completely cover all surfaces, contact with electrolytes deteriorates, and capacity decreases.
- The plate crumbles due to overcharging, then there is a lack of electrolytes. This leads to an immediate decrease in battery capacity.
- When the bank is short-circuited and the negative and positive plates are connected to each other, the battery capacity decreases. However, it is being restored.
What determines the current battery capacity?
Throughout the life of a battery, its capacity changes. At the beginning of their work, they have the highest capacity, since the plates are actively being developed. Then there is a period of stable operation, and capacity remains at the same level. Then the capacity begins to decline due to wear of the plates.
Battery test process
The capacity of the battery varies depending on the presence of active materials and the design of the electrodes, electrolytes, their temperatures and concentrations, the magnitude of the discharge current, the depreciation of the battery, the concentration of additional deposits in the electrolytes and many other factors.
As the discharge current increases, the battery capacity decreases. With a rapid, specially provoked discharge, batteries lose less capacity than in smoother modes with low current values. Based on this, indicators for 4, 15, 100 hours of discharge are recorded on the case. The capacities of the same batteries vary extremely greatly. The capacity is least at 4 hours of discharge, and most of all other things are at large periods of time.
Also, the capacity indicators change with increasing temperature of the electrolytes, however, with an increase in the maximum permissible standards, the service life decreases. The reasons for this lie in the fact that at elevated temperatures, electrolytes penetrate into the active mass, because their viscosity decreases, and on the contrary, their resistance increases. Because of this, there is more active mass in discharge reactions than during charging at a lower temperature.
At particularly low temperatures, the capacity of the battery is reduced as well as its useful effect.
As the concentration of electrolytes increases, the battery capacity also increases. However, the battery deteriorates faster, as the active mass of the battery is loosened.
Thus, checking the battery capacity is necessary at all stages of its life.
A device with which you can check the capacity of lithium-ion AA batteries. Quite often, laptop batteries become unusable due to the fact that one or more batteries lose their capacity. As a result, you have to buy a new battery when you can get by with little expense and replace these unusable batteries.
What you will need for the device:
Arduino Uno or any other compatible.
16X2 LCD display using Hitachi HD44780 driver
Solid State Relay OPTO 22
10 MΩ resistor at 0.25 W
18650 battery holder
Resistor 4 Ohm 6W
One button and power supply from 6 to 10V at 600 mA
Theory and operation
The voltage on a fully charged Li-Ion battery with no load is 4.2V. When a load is connected, the voltage quickly drops to 3.9V, and then slowly decreases as the battery operates. A cell is considered discharged when the voltage across it drops below 3V.
In this device, the battery is connected to one of the analog pins of the Arduino. The voltage on the battery without load is measured and the controller waits for the “Start” button to be pressed. If the battery voltage is higher than 3V. , pressing the button will start the test. To do this, a 4 Ohm resistor is connected to the battery via a solid state relay, which will act as a load. The voltage is read by the controller every half second. Using Ohm's law you can find out the current supplied to the load. I=U/R, U-read by analog input of the controller, R=4 Ohm. Since measurements are taken every half second, there are 7200 measurements in every hour. The author simply multiplies 1/7200 hour by the current value, and adds the resulting numbers until the battery discharges below 3V. At this moment the relay switches and the measurement result in mAh is displayed on the display
LCD pinout
PIN Purpose
1 GND
2 +5V
3 GND
4 Digital PIN 2
5 Digital PIN 3
6,7,8,9,10 No connected
11 Digital PIN 5
12 Digital PIN 6
13 Digital PIN 7
14 Digital PIN 8
15 +5V
16 GND
The author did not use a potentiometer to adjust the brightness of the display; instead, he connected pin 3 to ground. The battery holder is connected with the minus to ground, and the plus to analog input 0. A 10 MΩ resistor is connected between the plus of the holder and the analog input, which acts as a pull-up. The solid-state relay is turned on with a minus to ground, and a plus to digital output 1. One of the contact pins of the relay is connected to the plus of the holder; a 4 Ohm resistor is placed between the second pin and ground, which acts as a load when the battery is discharged. Keep in mind that it will get quite hot. The button and switch are connected according to the diagram in the photo.
Since the circuit uses PIN 0 and PIN 1, they must be disabled before loading the program into the controller.
After you connect everything, upload the firmware attached below, you can try to test the battery.
The photo shows the voltage value that the controller calculated.
The voltage on it must be higher than 3V
Recently, I began to notice that my smartphone began to discharge faster. The search for a software “energy eater” did not bear fruit, so I began to wonder if it was time to replace the battery. But there was no absolute certainty that the battery was the cause. Therefore, before ordering a new battery, I decided to try to measure the real capacity of the old one. To do this, it was decided to assemble a simple battery capacity meter, especially since this idea had been incubated for a long time - there are a lot of batteries and accumulators that surround us in everyday life, and it would be nice to be able to test them from time to time.
The very idea underlying the operation of the device is extremely simple: there is a charged battery and a load in the form of a resistor, you just need to measure the current, voltage and time during the battery discharge, and based on the data obtained, calculate its capacity. In principle, you can get by with a voltmeter and an ammeter, but sitting at instruments for several hours is a dubious pleasure, so you can do this much easier and more accurately using a data logger. I used the Arduino Uno platform as such a recorder.
1. Scheme
There are no problems with measuring voltage and time in Arduino - there is an ADC, but to measure current you need a shunt. I had the idea to use the load resistor itself as a shunt. That is, knowing the voltage on it and having previously measured the resistance, we can always calculate the current. Therefore, the simplest version of the circuit will consist only of a load and a battery, connected to the analog input of the Arduino. But it would be nice to provide for turning off the load when the threshold voltage on the battery is reached (for Li-Ion this is usually 2.5-3V). Therefore, I included a relay in the circuit, controlled by digital pin 7 through a transistor. The final version of the circuit is shown in the figure below.
I placed all the elements of the circuit on a piece of breadboard, which is installed directly on the Uno. As a load I used a spiral of nichrome wire 0.5 mm thick, having a resistance of about 3 Ohms. This gives a calculated discharge current of 0.9-1.2A.
2. Current measurement
As mentioned above, the current is calculated based on the voltage on the spiral and its resistance. But it is worth considering that the spiral heats up, and the resistance of nichrome depends quite strongly on temperature. To compensate for the error, I simply took the current-voltage characteristic of the coil using a laboratory power supply and letting it warm up before each measurement. Next, I generated the trend line equation in Excel (graph below), which gives a fairly accurate dependence i(u) taking into account heating. It can be seen that the line is not straight.
3. Voltage measurement
Since the accuracy of this tester directly depends on the accuracy of the voltage measurement, I decided to pay special attention to this. Other articles have already repeatedly mentioned a method that allows you to most accurately measure voltage with Atmega controllers. I will repeat only briefly - the essence is to determine the internal reference voltage using the controller itself. I used the materials in this article.
4. Program
The code is not anything complicated:
Program text
#define A_PIN 1 #define NUM_READS 100 #define pinRelay 7 const float typVbg = 1.095; // 1.0 -- 1.2 float Voff = 2.5; // shutdown voltage float I; float cap = 0; float V; float Vcc; floatWh = 0; unsigned long prevMillis; unsigned long testStart; void setup() ( Serial.begin(9600); pinMode(pinRelay, OUTPUT); Serial.println("Press any key to start the test..."); while (Serial.available() == 0) ( ) Serial.println("Test is launched..."); Serial.print("s"); Serial.print(" "); Serial.print("V"); Serial.print(" "); Serial. print("mA"); Serial.print(" "); Serial.print("mAh"); Serial.print(" "); Serial.print("Wh"); Serial.print(" "); Serial .println("Vcc"); digitalWrite(pinRelay, HIGH); testStart = millis(); prevMillis = millis(); ) void loop() ( Vcc = readVcc(); //read reference voltage V = (readAnalog(A_PIN ) * Vcc) / 1023.000; //reading the battery voltage if (V > 0.01) I = -13.1 * V * V + 344.3 * V + 23.2; //calculating the current using the I-V characteristic of the spiral else I=0; cap += (I * (millis() - prevMillis) / 3600000); //calculation of battery capacity in mAh Wh += I * V * (millis() - prevMillis) / 3600000000; //calculation of battery capacity in Wh prevMillis = millis(); sendData (); // send data to the serial port if (V< Voff) { //выключение нагрузки при достижении порогового напряжения
digitalWrite(pinRelay, LOW);
Serial.println("Test is done");
while (2 >1) ( ) ) ) void sendData() ( Serial.print((millis() - testStart) / 1000); Serial.print(" "); Serial.print(V, 3); Serial.print(" ") ; Serial.print(I, 1); Serial.print(" "); Serial.print(cap, 0); Serial.print(" "); Serial.print(Wh, 2); Serial.print(" " ); Serial.println(Vcc, 3); ) float readAnalog(int pin) ( // read multiple values and sort them to take the mode int sortedValues; for (int i = 0; i< NUM_READS; i++) {
delay(25);
int value = analogRead(pin);
int j;
if (value < sortedValues || i == 0) {
j = 0; //insert at first position
}
else {
for (j = 1; j < i; j++) {
if (sortedValues <= value && sortedValues[j] >= value) ( // j is insert position break; ) ) ) for (int k = i; k >< (NUM_READS / 2 + 5); i++) {
returnval += sortedValues[i];
}
return returnval / 10;
}
float readVcc() {
// read multiple values and sort them to take the mode
float sortedValues;
for (int i = 0; i < NUM_READS; i++) {
float tmp = 0.0;
ADMUX = _BV(REFS0) | _BV(MUX3) | _BV(MUX2) | _BV(MUX1);
ADCSRA |= _BV(ADSC); // Start conversion
delay(25);
while (bit_is_set(ADCSRA, ADSC)); // measuring
uint8_t low = ADCL; // must read ADCL first - it then locks ADCH
uint8_t high = ADCH; // unlocks both
tmp = (high << 8) | low;
float value = (typVbg * 1023.0) / tmp;
int j;
if (value < sortedValues || i == 0) {
j = 0; //insert at first position
}
else {
for (j = 1; j < i; j++) {
if (sortedValues <= value && sortedValues[j] >= value) ( // j is insert position break; ) ) ) for (int k = i; k > j; k--) ( // move all values higher than current reading up one position sortedValues[k] = sortedValues; ) sortedValues[j] = value; //insert current reading ) //return scaled mode of 10 values float returnval = 0; for (int i = NUM_READS / 2 - 5; i< (NUM_READS / 2 + 5); i++) {
returnval += sortedValues[i];
}
return returnval / 10;
}
Every 5 seconds, data on time, battery voltage, discharge current, current capacity in mAh and Wh, and supply voltage are transmitted to the serial port. The current is calculated using the function obtained in step 2. When the threshold voltage Voff is reached, the test stops.
In my opinion, the only interesting point in the code is the use of a digital filter. The fact is that when reading voltage, the values inevitably “dance” up and down. At first I tried to reduce this effect by simply taking 100 measurements in 5 seconds and taking the average. But the result still did not satisfy me. During my searches, I came across such a software filter. It works in a similar way, but instead of averaging, it sorts all 100 measurement values in ascending order, selects the central 10, and calculates the average of them. The result impressed me - measurement fluctuations stopped completely. I decided to use it to measure the internal reference voltage (readVcc function in the code).
5. Results
Data from the serial port monitor is imported into Excel in a few clicks and looks like this:
In the case of my Nexus 5, the declared capacity of the BL-T9 battery is 2300 mAh. The one I measured is 2040 mAh with a discharge of up to 2.5 V. In reality, the controller is unlikely to allow the battery to drain to such a low voltage, most likely the threshold value is 3V. The capacity in this case is 1960 mAh. A year and a half of phone service led to a loss of capacity by about 15%. It was decided to hold off on purchasing a new battery.
Using this tester, several other Li-Ion batteries have already been discharged. The results look very realistic. The measured capacity of new batteries coincides with the declared capacity with a deviation of less than 2%.
This tester is also suitable for metal hydride AA batteries. The discharge current in this case will be about 400 mA.
Hello. In today's short review I want to look at a tester for lead and lithium batteries. Let's figure out what is actually hidden under this big name and where it can be applied. If you are interested, welcome to cat.
The order was made on January 8, 2016 using a coupon of 5 out of 10 received for points on the New Year's socks promotion. Therefore, the product cost me only $3.03. I will tell you what was added to the basket up to $10 in the next review. The tester was promptly sent on the same day.
Inside, in a blue plastic bag, there was the tester itself, wires and 4 screws. Although the tester has only 2 mounting holes:
Let's look at the tester device:
The inscription on the microcircuit body is carefully ground off. There is one button to select the battery type.
The battery types are switched like this. With the tester turned off, hold down the button, connect the tester to the battery, and then release the button. The tester proceeds to selecting the battery type. Briefly press the button to select the desired mode.
For example, 2S lithium:
Or a 12 volt lead battery:
After selecting the desired value, turn off the tester. The settings will be saved and in the future the tester will always turn on for this type of battery. To change the type, repeat the above steps.
Here are the mode values from the store website:
P1: Pb12V lead-acid battery
P2: Pb24V lead-acid battery
P3: not working
P4: not working
C2: 2 pcs lithium batteries
C3: 3 pcs lithium batteries
C4: 4 pcs lithium batteries
C5: 5 pcs lithium batteries
C6: 6 pcs lithium batteries
C7: 7 pcs lithium batteries
C8: not working
C15: not working.
This plate looks strange compared to the description of the tester:
Specification:
Input voltage:8-30V
Input current:5-12mA
Fit for Battery Type: lead-acid/Pb-Acid battery and Lithium battery
LI 1S/2S/3S/4S/5S/6S/7S Lead-acid 12V/24V
Where did lithium go from table 1S, since it is stated in the description? This interested not only me, but also one of the buyers. And he asked this question to the store representative on the product page. And they received the answer:
Thank you for asking!
1. Battery code C1 1 pcs lithium batteries.
Did you find anything strange in the answer? What if you look at the description again?
This tester simply physically cannot work with 1S lithium! After all, for the most part, a fully charged 1S lithium has a voltage of 4.2 volts. And the tester, as it turned out from real tests, turns on only when a voltage of 4.65 volts is applied to it. The first, but not the last secret is revealed.
The tester has a pleasant, uniform green backlight:
When 5% is reached, the bars on the battery disappear, the battery outline begins to flash, and the backlight turns off:
Let's measure 2 lithium 18650 batteries. This is my most accurate tester; when checking it with ION, it measures accurately to the hundredth. This accuracy is quite enough for me. And this is what we see:
And lithium polymer battery:
And one question remains: how does this tester actually test the battery? One of the buyers also asked a question on the product page. He was interested in how the battery is actually tested? Does the tester measure internal resistance? Does it put a strain on the battery? How it works?
And here, drum roll, is the response from the store representative in Google Translate. The original can be found on the product page:
Battery capacity tester can test battery voltage, load voltage (pressure difference), internal resistance, short circuit protection, short circuit recovery time protection function, discharge current, charging function, resistance detection (R1, R2), read test code and power (including charge and discharge test).To extend battery life and use the battery correctly
Isn't it cool for such and such a price? This tester is simply the dream of all battery workers, motorists and modellers in the world.
But what kind of short circuit and discharge test can there be if the tester consumes during operation:
But in reality even less. 2 times. Myth debunked? It would be more correct to call it not a tester, but a charge indicator. Most likely, the voltage values and charge percentages corresponding to them are stored in the indicator’s memory. This is what we will do now. Let's see what voltage corresponds to what percentage. For this purpose, a test bench was assembled:
If the tester measures battery parameters, it should not be powered by a power supply. But we won’t check the tester, we’ll check the indicator.)))
Since the existing power supply produces a maximum of 15 volts, I will limit myself to only measuring the 3 indicator modes. This is a 12 volt lead battery, and 2S and 3S lithium.
Let's see how the indicator behaves in this operating mode. I don't want to overload the review with unnecessary photos, so I'll just give the conformity plates. If anyone needs photos confirming this, I will provide them. But I don’t see the point in this, it’s absolutely the same on them.
So, turn on the 1P mode on the indicator:
13.01V – 100%
12.50V – 75%
12.20V – 50%
11.80V – 25%
11.01V – 0%
Well, quite a good result.
Lithium batteries are generally 4.2 volts when fully charged. 4.35V is not yet widespread. And it is not recommended to discharge lithium below 3 volts. For 2S this needs to be multiplied by 2. And for 3S - accordingly, by 3.
Now let's check the 2S lithium by turning on the 2c mode:
8.30V – 100%
7.75V – 75%
7.37V – 50%
7.00V – 25%
6.00V – 0%
And 3S lithium. Mode 3c:
12.49V – 100%
11.65V – 75%
11.13V – 50%
10.53V – 25%
9.05V – 0%
And again a good result! Despite the inaccuracies in the description, this indicator exists. It looks beautiful and can be used in cars, UPS, modeling and many other crafts that use batteries for power. Moreover, it has quite modest weight and dimensions.
The degree of charge in percentage is more visual than voltage in volts. Especially for people who are far from this. Like on a mobile phone. Anyone will understand that, for example, the battery will soon run out or, on the contrary, will charge. For me, this is a necessary and useful thing that will soon be used for its intended purpose. In principle, I expected to receive a charge indicator, and not a mythical super-duper tester, having analyzed the description and technical characteristics before purchasing.
It's definitely worth 3 dollars.
I'm planning to buy +67 Add to favorites I liked the review +87 +138
