It is no secret that over time, the capacity of rechargeable batteries becomes smaller, and they can no longer supply the device with the amount of current that they could supply before. In this regard, many users often have a question about how to measure the battery capacity, or more precisely, how to find out the indicator of its residual potential, with which you can understand whether the battery will need to be replaced in the near future.
If you start from the concept that the capacity indicator is the amount of energy or current given by the battery over a certain period of time, it simply will not work. If we are talking about how to find out the real capacity of a battery in the form of AA batteries, you will have to first measure the current, and then use some simple calculations so that the indicator is as accurate as possible. As for any Android-based mobile phone, using a small USB tester.
A simple test of battery capacity with a USB tester and subsequent clarification
The USB tester for measuring battery capacity has very rich functionality - it can be used to measure the battery capacity of a tablet, smartphone, etc. Based on what this device shows, you can get an idea about the wear of the batteries: is it worth changing the battery, or do you need to purchase a new device.
With just one control button, you can measure various indicators, including the battery capacity of a particular device. The button switches tester memory cells and operating modes. If there is a sufficient voltage level in the connected device, the tester turns on.
The meter usually displays the battery capacity indicator in the lower left corner. The measurement accuracy of the tester is not 100% , and therefore it is recommended to use a simple mathematical formula based on the following example.
Let's say you have a certain device (phone, power bank or tablet), which, being completely discharged, charged in a period of time equal to 3 hours. If, out of curiosity, you measured the current using a tester, and its value was, for example, 1.15 A, the actual battery capacity of your device is calculated by multiplying these two numbers together. 1.15 amperes is 1150 milliamps, multiply this number by 3 and get 3450 mAh. This is how real capacitance is measured. If the current “capacity” on your device indicated by the manufacturer is several times greater than the actual one, this is just a standard advertising ploy that should not be trusted.
How to determine battery capacity using a multimeter
It is impossible to determine the battery capacity itself with a multimeter. To be more precise, this device will help in determining the actual capacity indicators.
In order to find out the capacity of an 18650 battery, as well as other batteries, so-called “smart chargers” are used. But their cost is quite high. It’s not worth buying such chargers simply to determine the capacity of a couple of batteries. This indicator will easily determine the usual calculation method with the preliminary use of a multimeter. However, when making calculations, certain subtleties must be observed.
Checking the battery capacity indicator with a multimeter is not just measuring its real indicator, the calculations of which are made using basic mathematical calculations. It is necessary to measure the current level supplied by the battery (any battery) and calculate the exact amount of time during which the battery could continuously and efficiently produce electrochemical energy. It is important to remember that all measurements will not be 100% accurate. But they are the ones that best reflect the true essence of the matter.
They have their own scale of ranks. It shows how much U depends on the charge rate. This is necessary to know: the current flow through the resistance depends on the voltage level. To ensure that this dependence does not affect the measurements, an additional device should be assembled - linear current stabilizer (2.7-3 volts).
Using a linear stabilizer
Using this stabilizer, set the current indicator, calculating it from a 2.7 volt U battery. Then, using the U stabilizer, connect any resistor device (it can be made independently or purchased from an online store). Measure the current that passes through the circuit and set a stopwatch. Next, we periodically check and monitor the voltage at the battery terminals. When it reaches the number 2.7 volts, the stopwatch will need to be quickly turned off and the time obtained recorded.
So, how to measure the capacity of a 18650 battery and other chemical current sources? Real indicator mwe deduce by doing multiplying the current flowing through the circuit through resistance by the same time (in hours) that was originally spent . This is the most accurate measurement of capacitance. In the absence of technical capabilities, it will be more difficult to design a voltage stabilizer, carry out calculations and measurements. Try to find a way out of the situation using a variable resistor.
Using a Variable Resistor
In order to conduct a high-quality capacity test, you can use a smaller battery. For example, 14500, the actual capacity of which is 300 mAh. Let's take a variable resistor of 100 Ohms. Important point: if a direct current resistor is used, the process will be complicated by the fact that it will be necessary to frequently record the results of its readings and carry out calculations of the spent capacitance for certain sections of the scale .
It is possible to average the indicators as much as possible, focusing the calculation on the “arithmetic average” number of the current. In order to understand how to measure the battery capacity, it is recommended to use a variable resistor with a dosed decrease in the resistance value throughout the entire time the battery is being discharged. It is important that the current level is approximately the same throughout the entire process.
Now switch the multimeter to the voltmeter position (measure U) and measure U at the terminals of your battery. Let's say it has an incomplete charge level, say 4 volts. Next, discharge it by applying a current of 450-500 milliamps, lowering the resistance level from time to time and controlling the voltage. When it drops to 2.7 volts, turn off the stopwatch. To completely discharge the battery using 500 mA current , it takes about half an hour, more precisely, 25 minutes. Now let's multiply this current by the amount of time measured in hours. So, the real capacity indicator is 200 mAh.
Thus, it becomes clear how to find out the battery capacity using the most accurate method - not just by measurements, but by mathematical calculations that can most accurately reflect the actual state of the battery and help the user navigate what its potential is in reality.
Today, batteries of various types are used in a wide variety of equipment. This ensures autonomy and comfort when working with equipment. The functioning of the equipment depends on the correct operation of the battery, so users strive to monitor the main indicators of the batteries.
Owners of vehicles, devices, mechanisms, tools that run on electricity may have a question: This simple process is carried out according to specific instructions. It will be interesting for every user to study in detail how to take measurements themselves.
What is a multimeter
It is performed using a special device. It combines the functions of an ohmmeter. Therefore, the multimeter is considered a universal device.
Using the presented equipment, you can check the wire for a break, the voltage in the socket, the performance of household electrical appliances, and also evaluate the charge level of various types of batteries (car, laptop, phone, household appliances, etc.).
The device allows you to measure direct and alternating current and its continuity in the network. It also provides information about the resistance of a circuit element. This is a useful device that every home craftsman will find useful in everyday life.
Types of Multimeters
Wondering Is it possible to measure battery capacity with a multimeter? car, smartphone, laptop or any other household appliance, you need to consider the types of devices presented.
There are analog and digital multimeters. In the first case, the measurement result is shown by an arrow on a special scale. This is one of the cheapest types of devices. However, for those who have never used such devices, it is better to give preference to digital varieties. Also, analog multimeters have a small measurement error.
Digital multimeters display the measurement result on the display. This distinguishes them from the previous group of devices. The information on the screen is highly accurate and understandable to any user.
Device structure
Delving into the question how to determine battery capacity with a multimeter, you also need to understand how the device works. The design of the device has a dial. Test information is displayed on it. If an analog type of device is used, it is necessary to study the meaning of the divisions before use.
The device also has a button or function switch. This design element allows you to switch modes and the scale of the counter. When storing the device, the handle is set to the off position. To start working with the multimeter, turn the lever into the desired mode.
The housing must have holes for probes. The probe with the red wire has a positive polarity, and the one with the black wire has a negative polarity. These are the main points that a novice user should know.
Existing battery types
When using household appliances, the user may be interested in How to measure the capacity of a 18650 battery with a multimeter. This one is popularly called finger-shaped.
It is most often used in various remote controls, flashlights, and household appliances. To examine the performance of each battery, the charge of such batteries is measured.
The user may also be interested in how to check the functional qualities of such varieties as a battery for a laptop, smartphone or any other gadget. If, after fully charging the device, the multimeter shows a capacity different from that declared by the manufacturer, the battery will soon have to be changed.
Various power tools may use a battery that requires the correct charging approach. If this manufacturer's requirement is not met, the battery capacity is gradually reduced. You can determine such problems using a multimeter.
One of the main areas of application of the measuring device is assessing the capacity of a car battery. In this case, a special measurement technology is used.
Battery charge measurement
Considering how to measure phone battery capacity with a multimeter, as well as other types of household batteries, the technology of this process should be studied. First of all, you need to turn it on. Its mode switching lever is set to the “DC” position.
The maximum range when measuring these types of batteries should be from 10 to 20 MA. Next, the probes are brought to the battery contacts. In this case, the “minus” must be connected to the “plus” and vice versa. If the action is performed correctly, a test reading will appear on the screen. For example, for a AA battery the value can range from 0 to 1.5 V.
After measurements, the electrical circuit is quickly disconnected. For all batteries that are tested using the presented method, the result obtained should be compared with the indicators on the box. If there are deviations, you need to draw conclusions about the further use of the battery.
Car battery
Car owners may also be interested in: How to measure battery capacity with a multimeter. Instructions This process contains a number of features. Batteries may have a sensor that allows you to determine their capacity and charge changes. However, not every car battery has such a function. In this case, a multimeter will help to evaluate the indicators.
During the test, the voltage at the terminals is measured. A fully charged battery will have a reading of 12.6 V. If the reading drops to 12.2 V, this indicates a battery. In this case, the car owner must recharge the battery.
If without load on the battery the multimeter shows a figure less than 12 V, this means that the device is completely discharged. Device readings less than 11 V are considered critical. In this case, the battery can no longer be used. Also, the battery cannot be charged, so you will have to purchase new equipment.
How to check the battery?
Studying how to measure battery capacity with a multimeter, you need to consider the procedure for the vehicle battery. A full check of the autonomous power source will allow you to avoid problems in the vehicle’s electrical network and extend the life of the battery.
First, the battery must be disconnected from the machine system. It is allowed to disconnect only the “minus” contact. Next you need to turn on the multimeter. The test mode is set to the range from 0 to 20 V.
The multimeter probes are connected to the battery contacts. The red wire is connected to the positive terminal, and the black wire is connected to the negative terminal. If this procedure is performed correctly, the measurement result will appear on the device screen.
Measuring capacitance with a multimeter
Studying how to measure battery capacity with a multimeter, the main features of this process should be considered. There are several ways to do it. Less commonly used is the approach of measuring capacitance using a control discharge. Capacity measurement occurs at a load that is capable of taking half the battery current.
When carrying out this process, the vehicle owner must take into account the density of the electrolyte. If the battery is fully charged, this figure will be 1.24 g/cm³. If the battery is one-fourth discharged, the reading will be 1.2 g/cm³. Accordingly, a half-discharged power source will show 1.16 g/cm³.
The check is performed if the car does not start well. The capacity and charge of the battery must be within the limits established by the manufacturer, otherwise the operation of the equipment will be defective.
Capacity measurement
Knowing how to measure battery capacity with a multimeter, you can perform the procedure yourself. To do this, you need to prepare a multimeter. When measuring, the battery must be subject to a load that takes half the battery current. For example, if the battery capacity is 7 Ah, then the load should be 3.5 V. You will need a car headlight bulb (35-40 V).
If the light shines brightly, you can take measurements. A voltage at the terminals of 12.4 V indicates that the battery is in good condition and has full capacity. If there are certain starting problems, the problem is not with the battery. If the capacity is less than 12.4 V, you should think about purchasing a new battery soon.
If the equipment parameters during measurements do not correspond to those indicated by the manufacturer in the instructions, the car, telephone, or power tools will not be able to work correctly. This will cause them to quickly break down and lead to the need to purchase new expensive equipment.
Having considered how to measure battery capacity with a multimeter, You can evaluate the functionality of any type of battery. This will avoid the malfunction of any electrical equipment powered from an autonomous source of electricity.
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 through 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
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.
Every year the number of auxiliary equipment and tools used in service centers and large ATPs increases. Not only new tools are appearing, but also electronics that significantly facilitate diagnostics. Developed by talented engineers, the battery tester allows you to determine the performance of the power source and the remaining resource in a matter of seconds. The devices are in steady demand, because with their help the process of checking batteries is noticeably accelerated.
Features of measuring equipment
Note that the devices are compact and do not take up much space. Manufacturers provide detailed instructions, thanks to which it is easy to understand the operation algorithm of the product. A capacity tester equipped with options deserves a more careful study; the information presented will certainly help you make a quicker choice:
- Let's start with the most common areas of application. When shipments from the manufacturer arrive at warehouse sites and stores, it becomes possible to instantly identify defective items. Regular recording of operating parameters during battery operation allows timely detection of deviations from optimal characteristics and determination of the approximate remaining life.
- The equipment is equipped with USB, which makes it possible to create a large database. Processing the received signal takes only three seconds. This time is enough to remove information.
- A modern, advanced battery capacity tester is capable of taking readings from the battery in different temperature conditions with minimal error. In this case, the capacity assessment is as accurate as possible, regardless of the temperature of the energy source.
- The designers took care to create reliable protection against interference, so the degree of error in any conditions is minimal.
Justified expenses
This is not the first year that devices capable of quickly checking batteries have been sold. During this time, it was possible to collect user data indicating the undoubted benefits of electronics. Even in a small enterprise, a battery tester will pay for itself in six months. The product is indispensable if you have at least a dozen pieces of equipment in your garage.
