Toyota

Homemade discharge plug for a car battery. Load plug for checking battery voltage. Step-by-step instructions: how to do it yourself

The load fork is used to visualize the state of charge of the battery and is an excellent measuring device for calculating possible problems during testing. In addition, the built-in voltmeter of the load plug is well suited for superficial diagnostics of the vehicle’s on-board network. In simple words, we can say that a load fork is a regular voltmeter, in parallel with which a load is connected in the form of a spiral.

There are a huge number of types of load forks. But they differ only in the voltage measurement range and load rating. You can also conditionally divide all load plugs according to the type of batteries being tested. That is, there are plugs for both acid batteries and alkaline batteries.

Examples

: voltmeter with a maximum voltage measurement range of 3-0-3 volts. Current load – 100 amperes. Used to test 1.2 volt alkaline batteries and 2 volt acid batteries.

Voltmeter up to 20 volts, load resistance 0.1 Ohm, load up to 100 amperes possible.

It contains an electronic voltmeter with a liquid crystal display. It has two 100 amp loads, with the ability to be connected separately. When connecting one load, batteries with a capacity of 15 to 100 Ah are tested. When connecting two loads, batteries with a capacity of 100 to 240 Ah are tested.

The HB-03 plug also includes some additional functions: automatic detection of the battery charge level; recording measured values into memory, etc. In addition, NV-03 has the ability to calibrate the voltmeter and the range of temporary voltage measurements. Therefore, before carrying out measuring manipulations, it is necessary to make sure that the fork is calibrated.

Load forks are available in different voltage measurement ranges. But remember that the measured voltage should not be higher than the maximum value of the load plug voltmeter. For example:

2-0-2 volts (for 1.2 V alkaline batteries)
3-0-3 volts (for alkaline batteries with a voltage of 1.2 V and acid batteries with a voltage of 2 V)
0-15
0-20 volts (for 12 V acid and alkaline batteries)
0-30 volts (for 24 V acid and alkaline batteries)

Selecting current load

When testing a battery under load, we connect the plug load to the battery, creating a discharge current in the resulting circuit.

For a better test of the battery, this current should have a maximum rating, but it should not exceed the permissible discharge current of a given battery. I advise you to focus on the following data:

for traction alkaline batteries - the current of the 3-hour discharge mode (0.33C, where C is the nominal capacity of the battery in A*h);
for traction acid batteries - 1-hour discharge current (1.0C);
for starter batteries of both types, acid and alkaline from 1.0C to 1.4C

The n-hour discharge current is the current during which the rated voltage of the battery is reduced to the permissible minimum level for a given period of time.

Checking battery voltage without load. We disconnect the load from the load plug voltmeter and measure the voltage on the battery.

Checking battery voltage under load. We connect the load and take another measurement of the battery voltage. Load fork voltmeter readings are most accurate after the fifth second of measurement. The battery charge level is determined in accordance with the table:

The measurement process should not be carried out for more than ten seconds, as the spiral loads become very hot and the measuring device may fail. If the battery's charge level is different from 100%, it must be fully charged. After this, test the battery again using a load fork.

If the percentage of battery charge without load is higher than under load, then they say that the battery “does not hold the load.” Therefore, it is urgent to take measures to restore capacity. And for this, it is advisable to understand the factors of capacity decline and the need for further operations to restore the battery.

This homemade design for testing car batteries has good accuracy due to the use of an extended scale. The built-in load resistance makes it possible to measure voltage both under load and in load fork mode. The device has a narrowed range of 0 - 10 V by a quarter of the scale, and the rest is occupied by a range of 10-15 volts, which significantly reduces the measurement error. A car battery is considered fully charged at a voltage of 14 V and completely discharged at 11 V. To be able to measure the values of individual battery cells, a three-volt scale and another terminal of the measuring device are used. The extended scale of 15 volts is obtained due to the voltage drop across the zener diode and diode. If the voltage level is higher than the zener diode's opening level, the current through the device increases. The diode also performs a protective function in case of voltage supply of the wrong polarity.

A car battery is a type of electric battery whose job is to start a car or motorcycle engine. In addition, it powers the on-board network of the vehicle when the engine is turned off. Like any rechargeable battery, at a certain moment it can fail, and a load plug is used to monitor its performance. We will talk about this device today.

What is a load fork

Let's start getting acquainted with the device with its description and purpose.

What is it for?

A load fork is a measuring device that can be used to fairly accurately determine the state of charge of a battery. Suitable for both 12-volt and 24-volt batteries. Quite easy to use.

Did you know? In the mid-50s of the last century, a transition was made from 6 V to 12 V batteries, but some cars continued to run on 6 V. These include the Volkswagen Beetle, which switched to a different type of power supply only in the mid-60s, and Citroën 2CV, which lasted until 1970.

Design

Load fork design may vary depending on model. But the only difference between the options will be additional elements that expand the list of device capabilities. The main components are the same everywhere:

voltmeter (shows voltage, which is used to determine the battery charge level using tables);
resistor (spiral made of sheet steel);
two probes (with their help the device is connected to the battery);
protective casing (covers the spiral).

Features of the device

The operating principle of the measuring device is quite simple, so every car owner can easily master it. But to get the correct battery level data, It is necessary to take into account some measurement features:

The load fork shows accurate data only if measurements are taken at an ambient temperature of 20 to 25 °C;
the pole of the plug is connected to the plus of the battery, the minus to the minus;
the contact probe of the device tends to heat up during operation, so you need to work very carefully so as not to get burned;
measurements should not last more than 6–8 seconds, and there should be a 5-minute pause between each measurement;
if it is found that the battery is discharged, then fully charge it and repeat the measurements;
If the battery is serviceable, then when taking measurements it is necessary to unscrew the plugs.

Why check the battery with a fork?

Checking the condition of the battery is very important, especially if you get a used vehicle rather than a new one.

This method of determining battery charge is the most accurate of all existing ones. Simple measurements with a tester will not display a complete picture of the condition of the battery.
For example, when checking the voltage with a tester, the device showed that the battery was charged, but the car did not start or started poorly. In order to understand the cause of the battery malfunction, measurements must be carried out with a load. It is extremely difficult to simulate the necessary conditions that reflect the operation of a car in a garage.

The starter reduces the time for measurements to a minimum, as it produces a high current. Starting the engine at intervals several times in a row can have a bad effect on the condition of the battery. Therefore, it is the load fork that will help most accurately determine the condition of the battery.

Important! When taking measurements with the device, the voltage on the battery should first drop and then gradually rise. If the performance continues to decline, it can be assumed that the battery has failed.

How to check correctly

There are 2 ways to check the condition of the battery using a load plug. Below we will describe each of them in detail.

Without load

The essence of this method is to measure capacity without connecting an additional load. Measurements can only be taken when at least 7 hours have passed since the engine was turned off. During this time, the battery should not work either. The longer the period of time, the better.

Let's start measuring:

Before you begin testing the battery, it must be completely disconnected from the vehicle.
The plug must be connected to the battery terminals (plus to plus, minus to minus).
We look at the voltmeter and remember the readings.

To understand how much the voltmeter should show if the battery is working properly, you need to look at the table below.

Under load

This testing method is rarely used, as it can harm the battery, and is used only when the maximum charge data was obtained in the first case.

Measurements are carried out as follows:

Connect an additional load to the plug that corresponds to the parameters specified in the instructions.
Disconnect the battery from the car's electrical system.
Apply the probes of the plug to the battery terminals of the corresponding polarity. Use the button to apply additional load.
At the 5th second of measurement, remember the voltmeter readings and immediately turn off the device.

You can compare the obtained data with the battery capacity using the table.

Video: checking the battery with a load fork When working with a load, it is necessary to take into account the following nuances:

when contacts with a minus sign come into contact, sparks may appear (no need to be alarmed, this is a normal phenomenon);
repeated measurements can be carried out only after 5 minutes;
Do not apply a load for longer than 5 seconds;
If, even after recharging the battery, the voltage on it drops under load, then the battery is considered unsuitable for use.

Important! When the voltmeter shows a voltage of 9 V or more, this means that the battery is working. If the indicators are lower, then repeated measurements must be taken. If they did not provide data that corresponds to the standard, then the battery is no longer suitable for use.

Popular models for checking car batteries

Models of the most commonly used load forks for battery testing.

Model	Operating voltage	Load current, A	*Battery capacity, Ah**	Operating temperature range, °C
VN-1	0–15	100	15–190	+1...+35
NV-01	0–15	100/200	15–190	–30...+60
NV-02	0–15	100/200	15–240	–20...+60
NV-03	0–16	100/200	15–240	–30...+60
NV-04	0–32	at 12 V - 50, at 24 and 3 V - 100	15–240	–20...+60
NV-B	3–0–3	100	up to 500	no data

A double current value (100/200) indicates that the device has two spirals that can be turned on either in turn or simultaneously.

Scheme for manufacturing

The standard load fork diagram looks like this:

V - voltmeter;
S - key;
arrows - contact legs.

A resistor is connected in parallel to the voltmeter with a switch connected to it in series. When the key is open, the voltmeter shows the voltage on the battery without load. When the circuit is closed with the key, a load is applied to the battery, and data under load is taken from the voltmeter.

Did you know?The sealed car battery, which does not require refilling, was invented in 1971.

As you can see, the load fork is very easy to use and has a simple design. You can easily do it yourself. Every car owner should always have this device at hand.

For beginners, creating a load fork with your own hands is not too difficult. However, some knowledge of its collection process and application is required. It is indispensable when inspecting the battery.

This device can easily measure how charged the battery itself is. It is a unique element belonging to an electrical circuit of considerable power. The simplest plug is equipped with a pair of clamps and a special voltmeter. As for more complex models, their elements also include an ammeter and other devices for measuring a wide variety of vehicle parameters.

Of course, the load type of forks can be found in any specialized store, but if you have the desire and ingenuity in the process of creating it, you can limit yourself solely to your own efforts.

How to use it correctly

A homemade plug is great for measuring the amount of energy in 12-watt batteries.
However, it is also suitable for batteries with large capacities. The only difference is that the more powerful version requires a pair of load springs, while the less capacious version requires only one. To conduct a full test using this device you need:

Measure the voltage at the terminals themselves, without resorting to the use of load resistances, but this action is most appropriate to perform at least six hours after the motor has been turned off;
The “positive” clamp is connected to the corresponding terminal, but without a spring;
The “negative” clamp is connected to the terminal and only after this the voltmeter should show the battery voltage with an open circuit;
The information obtained must be compared with that described in the instruction manual, and only after this can a confident conclusion be made about how discharged the battery is;
If there is a full charge, the battery is checked under load, or more precisely, using a lower load. Such a check also includes all of the above repeated actions;
After five seconds of active testing, you can take reliable readings, which are displayed by a homemade device.

If, while connecting the “negative” terminal to the corresponding terminal, sparks suddenly begin to appear, it’s okay, there’s no harm in this and this is normal. However, you should not forget to tighten the battery plugs themselves during the testing process. Since the clamps tend to heat up due to the energy passing through them, it is better not to touch them after taking all the necessary readings.

Nine W is considered an acceptable charge indicator, since other values literally “scream” about the need for either recharging or complete replacement. You should understand and remember that such a check puts a certain load on the car’s battery, therefore such an overly frequent loading procedure has an extremely negative impact on the process of its operation.

Do it yourself

Before directly creating the load device, first measure the voltage value of one fully charged battery jar. In addition, each such jar must be freely accessible individually. The data obtained from such a measurement should be used as a starting point in drawing up a special scale, which in the future will show the charge of the car battery in the required range. However, if there is an instruction for it, then you can find out, thus, the minimum permissible and maximum permissible charge values. This is also important.

The load plug itself must not be connected to the battery being charged. This is just as unacceptable as storing it next to similar devices. Therefore, the scheme for creating such a device also requires the presence of certain knowledge of physics. First of all, the resistance of the load element of the electrical circuit is calculated, which is done using the following formula:

The R value is resistance, measured in "ohms". Accordingly, U is the voltage itself, which is measured in “V”. The last value, the I value, is the direct current, which is measured in “A”.

As for the power (P) of such a circuit, it can be found by multiplying the voltage (U) by the current (I).

It is clear that the clamps themselves must have enormous endurance, because high current flows will flow through them. They are attached to the circuit element manually - using high-quality wires that can withstand heavy loads. All parts at the joints must be perfectly soldered using an appropriate soldering apparatus. All that remains is to connect a voltmeter to the finished device.

For greater ease of use, it is advisable to place all these elements on a frame with a handle that does not bend. In addition, the material of such a frame cannot be wood or any other material that has flammable properties. After the inspection procedure, the room in which it took place is also fully ventilated.

Video “Checking the battery with a load fork”

The recording shows one method of testing a battery using a load fork.

All car owners understand that the main element of any car is the battery, which ensures the operation of all electrical systems and devices. But, like any power source, the device can fail. In this case, maintenance will be required. One of the effective diagnostic methods is to check with a load fork.

Basic Concepts

A load fork is a device that analyzes the operation of car batteries. The device monitors the open circuit voltage, the batteries under load at the output points, and the overall performance of the battery. The device includes a voltmeter, resistance coils, and in some cases an ammeter. The scope of application of the device is not limited to car batteries; it can be used to take readings from any part electrical circuit.

This is a small device in a metal case with several resistances and a voltmeter. On one side, a thick wire is connected to the voltmeter, on the other there is a clamp for connecting the positive electrode of the device to the battery. The negative terminal is connected to a metal pin. The resistance coils are connected with two nuts. The load on each spiral is calculated at 100 A of electric current. Clips on the wires are necessary to connect them to the battery terminals.

There are quite a few types into which the load fork is divided. The device diagram is the same for everyone and is nothing complicated. An important difference between the devices is the voltage measurement range and load rating. For alkaline batteries and acid batteries use different plugs.

How to use the load fork?

Before using the device, the engine must be idle for at least 6 hours; you can check it after overnight parking. The procedure is carried out in two stages. It should be taken into account that 12-volt batteries can be tested using one spiral, and for larger capacities two are used.

A device with an unconnected load is connected to each terminal of the element. The positive terminal is connected to the same charge of the battery terminal, after which they work with the negative elements. The voltmeter readings are recorded.

Meaning of indicators and action plan

The battery is 100% charged - 13 W.
Battery malfunction or discharge - 11.5-11.8 W.
75% charge - 12.3-12.6 W.
At 50% the data will be between 12.1 and 12.3 watts.
25% (almost complete discharge) - 11.8-12.1 W.

If after checking it turns out that the battery is fully charged, you need to perform the same actions as additional measurements, only you need to turn on the load connections.

Sequence of work:

the terminal is cleaned;
the load plug is connected with the correct polarity;
voltage is measured;
The resistance is set according to the battery volume.

The load fork is pressed against the battery terminal until it stops for a short time (up to 5 seconds). The battery plugs must be wrapped when performing these steps. If sparks start when you touch the negative terminal, it’s okay - this is normal. However, the heated pin should not be touched with your hands between measurements.

Identifying indicators

About serviceability and completeness charging the battery The 9 W mark indicates. Indicators less than this figure indicate that the battery is incomplete or broken. In this case, it is necessary to charge and repeat the measurement procedure.

If the battery is working properly, the indicators should return to normal; if this does not happen, detailed diagnostics or battery replacement is required. You should not use the load fork for preventive purposes and very often - such actions can damage the battery.

Making a device yourself

So, the load fork is a powerful tool with a DC voltmeter and two test leads. Of course, this type of device can be found in any specialized store, but with desire and ingenuity, a self-created load fork will become an equally useful device.

A homemade plug is good for measuring energy in 12-watt batteries. Before you start creating the device, you need to measure the voltage value of one fully charged battery jar. Each such jar must have free access. The data obtained is necessary to compile a scale that will show the car’s battery charge in the desired range in the future.

Next, you will need to turn on the microammeter together with the resistor. It is necessary to monitor the resistance; it should be slightly greater than the voltage of one of the battery banks. The scale of the device is changed by applying an alternating direct current voltage to the voltmeter in the required polarity, which is controlled by a reference device.

Formulas for calculations

The instructions for the battery indicate information about the minimum and maximum permissible charge values, you need to know them. The design of the device requires some knowledge of physics, namely the formula for the resistance of the load element of an electrical circuit. It is determined by the formula: R=U/I.

Here R is defined as the resistance value (Ohm), U stands for voltage (V), and current stands for I (A). The power (P) of such a circuit can be found by multiplying the voltage (U) by the current (I). The clamps must have a long endurance, because a large current will pass through them. They are manually connected to the resistor with high-quality wires that can withstand heavy loads.

All parts at the joints must be well soldered using a soldering apparatus. Now you need to connect a voltmeter to the homemade load plug (you can use a microammeter with a small resistor as it). The terminals are marked with the same polarity as on a working voltmeter. The connection points are isolated.

You can build a frame to mount the device on it for ease of use. The materials used for this are exclusively non-flammable; metal is best suited. In this way, a do-it-yourself load fork is created.

Installation Rules

When installing, it is important to follow the basic rules:

the device is connected to the battery only in the disconnected state;
It is prohibited to store the plug near other battery devices;
after work, the room is thoroughly ventilated;
connection to each jar is carried out separately;
it is necessary to monitor the current power so as not to damage the elements;
steel or nichrome is used for clamping;
The equipment does not connect for long, especially homemade ones.

The task performed by a digital load fork is no different from a conventional device. However, its important feature is the ultra-precise measurement results displayed on the equipment display.

Features and disadvantages of the device

For many years, the heavy load method has been used to test the performance of lead batteries. Devices capable of taking hundreds of amperes of current from a battery and measuring voltage under such a load are still being produced. The voltmeter scale is painted in several colors. When the arrow is in the green area, the battery is considered to be in good condition, red is a sign that the battery needs to be replaced.

The popularity of the fork is due to the qualitative identification of indicators. However, check Battery capacity impossible. Therefore, it is extremely difficult to predict the service life of a product in this way. Another fact that needs to be taken into account: the plug takes a significant percentage of the charge from the battery, so it cannot be used often.

Effectively, such devices help to identify a defective individual bank from the overall assembly, and also make it possible to check the battery’s charge to a certain voltage and the ability to withstand the operating current of the battery.

The most accurate data is obtained when diagnosing new battery devices. It is recommended to carry out testing at a time when the electrolyte temperature is positive from +10 to +25 °C. It is not at all necessary to throw away spoiled batteries; there are enough recycling points for such devices. The replacement resistance must match the capacity and type of battery.