Battery capacity: how it is measured, how to measure it with your own hands

The most important parameter of each battery is its battery capacity. It determines the amount of energy given to them for each length of time. This applies to all batteries from automobile to telephone. It is important to know about them and understand the device, because when using the battery of the wrong capacity, serious problems can arise when starting these devices.

The units of this value are Amperes or Milliamperes / hour. According to this parameter, the battery for the equipment is selected, guided by the recommended values. If you violate the recommendations, for example, the car may not start in the winter.

What is battery or battery capacity

All batteries are usually decorated with labels like 55, 70 Ah or 1800mAh. This designation indicates that the capacity of this battery is 55 Amperes or Amperes per hour, respectively, only in English - A / hour. It must be distinguished from another parameter - the voltage, which is written in Volts.

Standard battery

The Ah indicator shows how much the battery will last for an hour at a load of 60 Amps and a voltage of 12.7V. In other words, capacity is the supply of energy that a battery can hold in itself.

And if there is less than 60A of the load, then 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, for its application no additional knowledge is needed. Time costs are no more than 15 seconds. All that is required is to connect the tester to a power source and push on a single button, after which it begins to determine the capacities 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 operated.

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. On new batteries, the main parameters are always indicated. However, this value is determined independently.

Small battery

The easiest way is to use ordinary testers like the Coulomb. With this device, the capacity and voltage of the battery in a car are measured. This requires minimal effort and time to achieve 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 the capacity value.

Many other methods are used to calculate these parameters. A classic is the measurement with a multimeter auto battery. In order to do this, it must have a full charge and connection to the consumer (a regular 60W light bulb is sufficient). However, even this does not guarantee the absolute accuracy of the readings.

Multimeter device

The first step after collecting the circuit from the battery itself, a multimeter, a light bulb will be applying voltage.If the lamp does not go out within 2 minutes (if this is not so, the battery cannot be restored), take the testimony of the "Coulomb". As soon as the readings fall below the battery voltage standards, it begins to discharge. Having measured the time required for the final consumption of energy and the load current of the consumer, it is necessary 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 inconvenience of this method is time consuming.

In the second measurement method, the battery is discharged using a resistor according to a special scheme. Using a stopwatch determines the discharge time. However, it is important not to discharge the battery completely, being protected from this by means of 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 collected on their own. Below we consider such an option.

Fork scheme

This fork has an extended scale, which allows to achieve the highest accuracy of the reading. The built-in load resistance. The ranges of the scale are divided in half, thereby reducing the error of readings. The device is equipped with a 3-volt scale. This makes it possible to check individual battery banks. Scales of 15V are achieved by lowering the voltage on the diodes and zener diodes.

The current reading of the device will increase as soon as the voltage values ​​become greater than the zener diode opening level. During the supply of the wrong polarity, the diodes provide protection. In the picture: SB1 is the toggle switch, R1 is the transmitter of the required current, R2 and R3 are the resistors designed for M3240, R4 is the determinant of the width of the narrow ranges of the scales, R5 is the load resistance.

How to find out the capacity of a telephone battery at home

When using a cell phone, its battery undergoes continuous degradation. This process cannot be avoided; it is natural. This happens regardless of the model, price, or phone features. To accurately understand how long the battery will last in the device, 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 time.

Swollen battery

First of all, you need to inspect the battery. Dangerous problems in a lithium battery are immediately visible: the case can swell, be full of corrosion, stains of greenish and white shades.

If signs of bloating are detected, it is dangerous to use such a battery further. This can cause a short circuit in the telephone. Perhaps the beginning of swelling with a small bulge up to serious deformations. A worrying factor is the rapid drop in the charge in the phone.

Today, there are many applications for measuring the current capacity of the phone.

To accurately determine the battery capacity, use the advanced charger method. The battery is completely discharged, then connected to this unit. It, in turn, calculates the capacity of the battery, taking into account the time and current value.

Load differences

The parameters of each car are different. Their engine volumes and battery capacity vary. In a passenger car, usually a battery with a capacity of 40-45A, and in a large car about 60-75A.

The reasons for this lie in the starting current - the smaller the battery, the less electrolytes, lead, etc. in it. The larger it is, the greater the amount of energy that can give out at one moment. On this basis, large batteries are able to successfully operate in a subcompact, and small batteries cannot be inserted into a large car.

Case Dependence

Different size batteries

Capacity is directly related to the number of electrolytes and battery lead.Because of this, small capacity batteries will be much smaller in volume and weight than larger batteries. For these reasons, large batteries are never put on a subcompact, as this does not make sense - in these cars there is little space under the hood. A small battery does an excellent job of starting the engine.

Capacity reduction

Any battery is subject to depreciation, its capacity becomes less with time. Ordinary batteries serve about 3-5 years. The highest quality specimens are kept in good condition for up to 7 years.

When the capacity drops, the battery loses its ability to give enough inrush current. Then it comes time to replace it. The main reasons for the drop in capacity include:

• Accumulation of sulfuric acid on a positive plate. It can completely cover all surfaces, contact with electrolytes deteriorates, capacity drops.
• The plate crumbles due to overcharges, then there is a lack of electrolytes. This leads to an instantaneous decrease in battery capacity.
• When the banks are closed 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 the battery, its capacity changes. At the beginning of their work, they have the greatest capacity, since the plates are actively being developed. Then comes the period of stable operation, and the capacity is kept at the same level. Further, the decline in capacity begins due to wear of the plates.

Battery Testing Process

Battery capacity varies depending on the availability of active materials and the design of electrodes, electrolytes, their temperatures and concentrations, discharge current values, battery amortization, the concentration of additional deposits in electrolytes and many other factors.

With increasing discharge current, the battery capacity decreases. With fast, specially provoked discharge, batteries lose less capacity than in more smooth modes with low currents. Based on this, indicators for 4, 15, 100 hours of discharge are recorded on the case. At the same time, the capacities of the same batteries vary tremendously. The smallest capacity at 4 hours of discharge, and most of all - with large periods of time.

Also, the capacity indicators change with increasing temperature of the electrolytes, however, with an increase in the maximum permissible norms, the service life decreases. The reasons for this lie in the fact that, at an elevated temperature, electrolytes penetrate the active mass, because their viscosity decreases, and resistance, on the contrary, increases. Because of this, there is more active mass discharge in the reactions than during a charge with a low temperature.

At a particularly low temperature, the battery capacity decreases in the same way as its beneficial effect.

With increasing concentration of electrolytes, the battery capacity also increases. However, the battery deteriorates faster, since the active mass of the battery is loosening.

Thus, checking the battery capacity is necessary at all stages of its life.