How to diagnose the capacity of a car battery?

A car battery has a number of parameters by which it can be selected for a particular car. And these are not only dimensions, weight, pin layout, but also electrical characteristics by which one can judge the purpose of the battery. Today in stores you can find batteries for motorcycles, cars, trucks and special equipment, which differ in their performance. If you choose the wrong battery, then problems may arise during subsequent operation.

One of the key characteristics of a battery is its capacity. For car batteries, this value is measured in ampere-hours (Ah). Typically, this battery parameter is selected according to the volume of the internal combustion engine. Below is a table depending on the volume of the internal combustion engine of the vehicle.

As you can see, for passenger cars, batteries with a capacity of 50-65 Ah are the most common (for SUVs, they are usually set at 70-90 Ah).

The amount of energy a battery can hold gradually decreases as it is used. This is an important factor for the operation of the car, so you need to control it and measure it periodically. There is a set of methods for this:

• check digit;
• calculation with a multimeter;
• using special technology.

Although the first two methods are quite complicated, they allow you to determine the battery capacity at home. The latter requires special equipment, which is often available at service stations. If you find such equipment, then self-diagnosis of the capacity is greatly simplified.

An important nuance is that checks are carried out only on a fully charged battery. Otherwise, the result will be incorrect.

How to diagnose the capacity of a car battery with a multimeter?

The method of checking the capacitance through is rather complicated, although fast. To measure this indicator, you will need the following equipment: a multimeter, and also a device that will consume approximately half of the declared capacity of the device. In other words, with a capacity of 7 A / h, the consumption should be about 3,5 A.

In this case, it is worth considering the voltage at which the device operates. It should be 12 V. For such tasks, an ordinary lamp from a car headlight is suitable, but still the consumption should be selected according to your battery.

The disadvantage of this method is that it cannot be used to tell the exact capacity of the battery. You can only find out the current percentage of capacity from the original. In other words, such a test determines the wear of the device.

After connecting a certain device, you need to wait a couple of minutes, and then measure the voltage at the terminals. After that, you need to check against the following parameters, which determine the percentage of the original capacity:

• more than 12,4 V - 90-100%;
• between 12 and 12,4 V — 50-90%;
• between 11 and 12 V — 20-50%;
• less than 11 V - up to 20%.

However, even with an indicator of less than 50% of the capacity, it is impossible to drive with such a battery. This damages the entire car.

**If a lamp was connected as a powered device, then it can be used to determine the battery failure. If it shines dimly or blinks, then such a battery is definitely defective.

The result obtained must be compared with the percentage, and then compared with the declared capacity. This will allow you to approximately determine the current capacity and make an appropriate decision about the further operation of the device.

It is much easier to determine the battery capacity by means of a control discharge or special testers. Using the second option will allow you to get a quick result, so they are used in various services and workshops. The first method is to measure the battery discharge rate based on the current strength.

The capacity of a car battery is an important factor that should be taken into account and regularly diagnosed, since over time the resource of the device decreases, the capacity is rapidly declining. A significant decrease affects the operation of the car's electronics, so you should carefully monitor this.

Is it possible to put a larger capacity battery in a car?

When the need arises to change the battery, many people want to install a battery with a larger capacity. This seems like a good idea in terms of starting energy and subsequent battery life. But here everything is not so clear.

Choosing a battery for a car should be primarily based on the requirements of the automaker. That is, you need to look at the battery that has already been installed on the car, or refer to the technical documentation of the car. However, we all understand that the amount of additional equipment on board is increasing, which means that the load on the electrical system as a whole and on the battery in particular. Therefore, the establishment of a battery with a larger capacity under such circumstances may be justified.

In total, we note a number of points when you should take a battery with a slightly larger capacity:

• if a large number of consumers work in the vehicle's on-board network (navigation, registrar, security system, TV, various types of heating, etc.);
• if you have a car with a diesel engine (they need a larger battery to start).

A small supply will help out in the cold season. According to the empirical dependence, starting from plus 20 degrees Celsius, when the temperature drops by one degree, the capacity of the car battery decreases by 1 Ah. So, with a larger capacity, you will have a small margin of safety in the cold season. But, remember that too high a value is also "not good." There are two reasons for this:

• The on-board network of the car, including the generator, is designed for certain characteristics of the battery. Therefore, they may not fully charge a car battery of a larger capacity. As a result of operating in this mode, the battery will lose the advantage of additional capacity;
• The car's starter will function at a more intense rhythm. This will affect the wear of the brushes and the commutator. After all, the starter is also calculated for certain parameters (starting current, etc.).

An important point is the mode of operation of the car. If the car is often driven short distances, a larger capacity battery simply won't have time to charge. Conversely, if the daily runs are long enough, the generator will have enough time to fully recharge the battery. In any case, a slight deviation of the capacity indicator from the manufacturer's recommended value may be acceptable. And it is better to deviate towards increasing capacity.