Some car batteries are equipped with a charge indicator, which is often called a peephole. Typically, its green color indicates that the battery is OK, red indicates the need to charge, and white or black indicates the need to top up water. Many drivers make decisions about battery maintenance based on the built-in indicator. However, its readings do not always correspond to the actual state of the battery. You can learn about what is inside the battery eye, how it works and why you cannot trust it unconditionally from this article.
Where is the battery eye located and how does it work?
The battery indicator eye looks like a transparent round window from the outside, which is located on the top cover of the battery, most often near the central banks. The battery indicator itself is a float-type liquid hydrometer. The operation and use of this device is described in detail here.
Why do you need a peephole in a battery and how does it work: video
The principle of operation of the battery charge indicator is based on measuring the density of the electrolyte. Under the eye on the lid there is a light guide tube, the tip of which is immersed in acid. The tip contains multi-colored balls made of different materials, which float up at a certain density of the acid filling the battery. Thanks to the light guide, the color of the ball is clearly visible through the window. If the eye remains black or white, this indicates a lack of electrolyte and the need to top up with distilled water, or a malfunction of the battery or indicator.
Generator faults
We began our story with the fact that the malfunction lamp on the instrument panel, which looks like a small red battery, came on and forced us to stop the car and diagnose the malfunction. We have determined when you can continue moving on your own and when you cannot do this. Now we have determined that it is the generator that is faulty. Let's consider possible options for the malfunction of this unit. Here is a complete list of what can fail in a generator:
- brush wear
- Regulator relay malfunction
- malfunction of the rectifier (diode bridge)
- rotor commutator wear
- broken stator or rotor windings
Most of these faults can be eliminated by replacing faulty parts with new ones. When carrying out repairs, it is imperative to pay attention to the condition of the generator bearings. It is better to carry out diagnostics of the generator on a special stand under load.
We have already complained more than once that today it is becoming more and more difficult for drivers to diagnose their own cars, especially while driving. The toolkit is constantly shrinking. Let's say that voltmeters have disappeared from dashboards like mammoths, and the driver learns about all problems with charging after the fact from a message from a laconic warning light. But even with the lamp, not everything is so rosy, they don’t talk about it in driving schools, in the instructions for the car there is only the phrase “contact the service center.” Most drivers roughly imagine that it is responsible for charging, but how exactly and what exactly it shows is something that not everyone understands.
Operating principle of the warning lamp
We have already written more than once about how the generator works; we would not like to repeat it. The operating principle of the control lamp is tied to the generator, although it is still a separate element. It's quite simple. Two electrical circuits are connected to the control lamp, which in a simplified form look like this:
1. The first circuit from the lamp runs through the fuse block to the ignition switch, from it to the generator and then to the battery.
2. The second circuit directly connects the generator and the test lamp.
The question arises - why are there two circuits and why are they both connected to the generator? That's the point. The control lamp depends on the current at both inputs; when the voltage is the same, the lamp goes out, when it differs, it lights up .
Imagine we turn on the ignition. In the first network, voltage came from the battery to the control lamp, but in the second it was empty, the engine did not work, the generator did not produce current, so the lamp lights up. And it will burn as long as the ignition is turned on.
But then we start the engine, the generator starts working and voltage appears in the second circuit; moreover, the first circuit also starts working from the generator. The same voltage is applied to the terminals of the control lamp, and it goes out. Some drivers believe that the warning light coming on before starting the engine is a diagnostic of the system, but in fact the car does not ring or check anything, it simply determines whether charging has started or not.
What does the color of the battery charge indicator mean?
The color of the battery charge indicator for a certain state depends on the manufacturer. And although there is no single standard, the following colors can most often be seen in the eye:
Battery charge indicator colors
- Green - the battery is 80-100% charged, the electrolyte level is normal, the electrolyte density is above 1.25 g/cm3 (∓0.01 g/cm3).
- Red - the charge level is below 60-80%, the electrolyte density has dropped below 1.23 g/cm3 (∓0.01 g/cm3), but its level is normal.
- White or black - the electrolyte level has dropped, you need to add water and charge the battery. This color can also indicate a low charge level.
Exact information about the color of the indicator and its meaning is contained in the battery passport or on the top of its label.
What does the black eye on the battery mean?
Black charging indicator eye
A black eye on a battery can appear for two reasons:
- The battery capacity has dropped. This option is suitable for batteries that do not have a red ball in the indicator. Due to the low density of the electrolyte, the green ball does not float, so you see the black color of the bottom of the light guide tube.
- The electrolyte level has decreased - due to the low acid level, none of the balls can float to the surface. If, according to the instructions, in such a situation the indicator should be white, it means it is contaminated with decay products of the battery plates.
TMS device panel
This device is best suited for those owners who have a second battery built into their car. The device looks like an aluminum panel with a special voltmeter and a toggle switch for switching between batteries. The place of production is considered to be China, the cost reaches 1,500 rubles.
In stores you can find car battery indicators with a 12-volt charge level from the manufacturer Faria, located in the USA. But the cost for such devices is very high and ranges from four to five thousand rubles. For that kind of money it will be much easier to buy a new battery.
Why does the battery eye show incorrectly?
Even among conventional hydrometers, float-type devices are considered the least accurate. This also applies to the built-in battery indicators. Below are options and reasons why the color of the battery eye does not reflect its actual condition.
How the battery indicators work
- The eye on a discharged battery may remain green in cold weather. The density of the battery electrolyte increases with decreasing temperature. At +25°C and a density of 1.21 g/cm3, corresponding to a 60% charge, the indicator eye would be red. But at -20°C, the electrolyte density increases by 0.04 g/cm³, so the indicator remains green even if the battery is half discharged.
- The indicator reflects the state of the electrolyte only in the jar in which it is installed. The level and density of the liquid in others may be different.
- After adding electrolyte to the required level, the indicator readings may be incorrect. The water will mix with the acid naturally after 6-8 hours.
- The indicator may become cloudy, and the balls in it may become deformed or stuck in one position.
- The peephole will not allow you to find out the condition of the plates. Even if they have crumbled, shorted or become covered with sulfate, the density will be normal, but the battery will not actually hold a charge.
For the reasons described above, you should not rely solely on the built-in indication. To reliably assess the condition of the battery being serviced, it is necessary to measure the level and density of the electrolyte in all banks. The charge and wear of a maintenance-free battery can be checked using a multimeter, load plug or diagnostic tool.
Why doesn't the eye on the battery show green after charging?
Battery charge indicator design
A situation often arises when, after charging the battery, the eye does not turn green. This happens for the following reasons:
- The balls are stuck. To release it, you need to knock on the window or, if possible, unscrew the hydrometer and shake it.
- The destruction of the plates led to contamination of the indicator and electrolyte, so the ball is not visible.
- During charging, the electrolyte boiled away and its level dropped below normal.
Possible errors
You should not rely 100% on the accuracy of the indicator eye in the design of a car battery. Motorists often note that this system for determining the condition of the battery has errors. This does not always accurately reflect the current state of affairs.
There are several reasons for errors:
- The density of the liquid inside the battery is affected by temperature. In extreme cold, the density increases. Because of this, a green ball may be observed in the eye, although in fact there is a strong discharge.
- High temperatures can affect the status of the indicator. The design usually involves the use of plastic and glass. The materials are quite fragile and can become deformed due to cold and heat.
- The battery usually has 6 sections or cans. But the indicator is located in only one of them, and the general condition of the battery is determined by only one bank. It is unknown how things stand in all other sections. The parameters may differ significantly and thereby negatively affect the condition of the power supply.
The only task facing the motorist is to open the hood and look through the peephole. If what you see clearly does not suit you, you need to take measures to normalize the condition of the battery.
FAQ
What does the peephole on the battery show?
The color of the eye on the battery indicates the current condition of the battery depending on the electrolyte level and its density.
What color should the battery indicator light up?
If the electrolyte level and density are normal, the battery indicator should light green. Please note that sometimes, for example in cold weather, this may not reflect the actual condition of the battery.
How does the battery charge indicator work?
The charging indicator works on the principle of a float hydrometer. Depending on the density of the electrolyte, multi-colored balls float to the surface, the color of which is visible through the window thanks to the light guide tube.
Why doesn't the green light on the battery light up?
People usually become confused after reproducing a full charging cycle or adding water. First of all, it is worth noting that the indicator should not immediately appear green - this is not a light bulb.
But most often the problem of the green ball not floating up is simple:
- you need to wait - the electrolyte has not had time to mix - this may take several days, while the battery itself will work;
- the ball is stuck - try shaking the battery a little;
- color distortion - over time, the battery plates crumble somewhat and make the electrolyte cloudy;
- The battery life has expired and it is time to replace it.
Battery indicators Beast and Tyumen
Is it possible to fix the problem?
The main thing is not to miss messages issued by the operating system , which also monitors battery performance. When problems arise with the battery, the OS sends a message about its damage - as a rule, it “crawls out” on the right. If the system does not produce such a message and “believes” that everything is fine with the battery pack, most likely there is a problem with the charger itself.
It is important to keep in mind that if the battery is damaged, it is no longer possible to repair it. In the best case, it will have to be either completely changed or a partial replacement of elements. About laptop battery repair →
The charger can simply be disassembled into parts and tested using a multimeter. Most likely, the wiring has frayed or the contacts have come loose - this problem can be fixed with your own hands. However, if the capacitor burns out, you will have to look for a new, suitable charger.
