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Battery indicator: principle of operation, connection diagram, device

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Battery indicator: principle of operation, connection diagram, device
Battery indicator: principle of operation, connection diagram, device

A permanently charged battery (battery) will not only ensure a reliable start of the car engine, but also maintain its uptime for a long time. Hence the need to constantly monitor the battery charge level. There are different methods - operational, which do not require removal of the battery from the vehicle, and verification work using additional control devices. The article describes operational control methods that should be used periodically.

Types of car battery charge indicators

Not many car enthusiasts know the digital values ​​​​of the battery voltage, sufficient to confidently start the car engine. This problem is especially relevant for beginners. On-board computers of modern cars provide the consumer with a large amount of necessary information, among which there is also open circuit voltage.battery. Old car analog voltmeters have a scale that gives information about battery voltage.

Therefore, there is a need for indicators that can assess the readiness of the battery to start the engine and report the results to the driver in the form of a visual message. The following varieties of such indicators can be distinguished:

  • built-in, showing the status of the battery, located directly on the battery case;
  • Battery charging indicators produced by third-party manufacturers, having a scale of acceptable and prohibited battery voltage values ​​​​to start starting, charge level, expressed as a percentage of its full value.
Electronic indicator

Built-in batteries are of medium and high price scale, mostly maintenance-free type. To use indicators from third-party manufacturers, it is necessary to carry out additional work to install them in the vehicle interior (in a visible place) and connect the automotive electrical wiring to the battery bus.

Built-in charge indicator

This battery indicator, referred to as a "warning light" by many motorists, is a hydrometer. Its round signal window is located on the top cover of the battery case. The main sensitive element of the float device is a green ball moving along a profile-tube built into the fittings and having the shape of a triangle. Its angle is directed vertically upward along the axis of the battery case. Ballmoves in an electrolyte environment that fills the internal cavities of the battery compartments.

Built-in peephole

From the eye (window) of the battery indicator, a light guide tube is laid. Its lower part ends with a conical prism opposite the upper corner of the profile tube, along which the signal ball moves. The light guide is designed for visual control of its position.

The tube-profile built into the armature, the light guide, the lens of the indicator eye make up a single structure, which is mounted on the battery case by means of a screw connection in the eye area. In case of emergency, it can be taken outside (which is highly undesirable).

The principle of operation of the built-in indicator

The green ball is made of a material with a density of (1, 26-1.27) g/cm3. The electrolyte density of a fully charged battery under normal conditions is 1.27g/cm3. The sensor is subjected to a buoyancy force proportional to the density of the liquid it is in.

The density of the electrolyte in the battery depends on the degree of its charge. With a discharged battery, sufficient buoyant force is not created, and the ball "rolls" under the action of gravity to the lowest point of the profile along which it moves. The peephole is painted in black - the color of the material from which the profile is made.

Battery peephole

As the battery charges, the density of the electrolyte increases. Starting from a charge level of 65 percent of the maximum value, the buoyancy of the electrolyteovercomes the component of gravity acting on the ball, and it begins to move along the profile to its highest point. In it, with sufficient lighting, you can see the green color of the eye. "The battery indicator is on" - such an expression can sometimes be heard from the lips of unfortunate experts in car batteries.

battery with eye

There may be a situation where the battery indicator is white. In this case, the surface of the electrolyte can be observed through the eye. In this case, the operation of the battery must be stopped - topping up with distilled water is required.

Some battery manufacturers put a second red indicator ball in the profile tube. The density of the material from which it is made allows it to occupy the upper position in the profile tube at a reduced electrolyte density (1, 23-1, 25) g/cm3. In case of insufficient battery charge with this technology, the battery indicator eye will turn red.

Industrial charging indicators

Third party products are electronic devices that evaluate the readiness of the battery to start the engine by measuring the open circuit voltage on the battery bars. Analog or digital voltmeters display measurement results on graphic indicators in the form of sectors of different colors - green / red.

Electronic charge indicator

They do not measure, like hydrometers, the level of electrolyte density. It is problematic to measure it in sealed battery compartments.vehicle preparing to travel.

DIY battery indicators

The unreasonably high price of industrial battery voltage level devices forces motorists who are familiar with the basics of radio engineering and have soldering skills to make these devices on their own. Especially for them, a popular designer (DC-12 V) is produced with a set of radio components, on the basis of which you can independently assemble a battery discharge indicator.

The device informs the user that the measured voltage has reached one of the three levels determined by the ratings of the circuit elements. If the battery indicator lights up, the corresponding voltage level has been reached.


The battery indicator only signals the user about the state of critical values ​​of his indicators. For the cells built into the battery, such an indicator is the density of the electrolyte and its level in the battery cell (bank) in which it is installed.

This does not take into account the ambient temperature. The electronic indicators give an estimate of the vehicle's battery bus voltage thresholds, which gives a very rough indication of the state of charge of the battery. Only complete diagnostics with special devices will give a complete picture of the state of the battery.

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