Maintenance free battery
The maintenance-free battery does not have plugs on the top side. The need to measure the level and density of the electrolyte is eliminated, since it is not lost or evaporated.
Maintenance-free batteries are often equipped with an optical status indicator. This indicator shows the electrolyte level and the state of charge of the battery in a color way. To assess the condition of the battery, you need to shine a flashlight on the optical indicator.
- Indicator green: the battery is in good condition.
- Indicator black: The battery needs to be charged.
- Other colors: critical state of the electrolyte. The maintenance-free battery must be replaced.
Note: The latest generation batteries are equipped with a backflash protection, the so-called Fritte device. Gases generated during charging exit through the hole on the top side of the cover where this unit is installed. The device is made up of small round balls of fiberglass and works like a valve.
Conventional battery
A conventional battery is recognized by the plugs on the top side or by the blanking plate. Such a battery requires regular monitoring of the electrolyte level.
Checking the electrolyte level
The electrolyte level in each cell should be approximately 5mm above the cell plates. If for some batteries the electrolyte level can be determined from the outside, then it should be between the upper MAX mark and the lower MIN·mark. For batteries with a plastic protrusion in the filling holes, the electrolyte level in all cells must be flush with this protrusion. Shine a flashlight into the filling holes from above.
Using a wide screwdriver, unscrew the plugs or, respectively, carefully press out the blanking plate.
If necessary, add distilled water through the filling holes using a funnel. Repeat the operation until the elements are filled correctly.
Screw in the plugs or press in the sealing strip accordingly.
Charge the battery and test it under load, see the relevant chapter below.
Electrolyte Density Check
The density of the electrolyte, along with the measurement of voltage, allows an accurate conclusion about the state of charge of the battery. To check the density of the electrolyte, a densimeter with a pipette is used, for example, HAZET 4650-1. The temperature of the electrolyte in the battery during the test must be at least +10°C.
Switch off the ignition.
Using a wide screwdriver, unscrew the plugs or, respectively, carefully press out the blanking plate.
Immerse the densimeter in each battery cell and suck in the electrolyte until the float of the densimeter floats freely in the electrolyte.
The greater the specific gravity (density) of the absorbed electrolyte, the more the float floats.
On the densimeter scale, you can determine the density of the electrolyte in g / ml or in degrees Baume (+°Be). The density of the electrolyte must be at least 1.24 g/ml. If the density is less than the specified value, the battery must be charged.
Consistently check each battery cell, all cells must have the same electrolyte density. The maximum permissible difference in electrolyte density in individual cells is 0.04 g/ml. Otherwise, it is concluded that the battery is defective.
Screw in the plugs or press in the sealing strip accordingly.
The battery is conventional and maintenance-free
Battery test under load
Connect a voltmeter to the battery terminals. Do not disconnect battery cables.
Start the engine and read the voltmeter reading.
When starting the engine, the voltage with a fully charged battery should not fall below 10 volts (at an electrolyte temperature of approximately +20°С).
If the voltage immediately drops and, moreover, a different density of the electrolyte was found in the cells of the battery, then it is necessary to conclude that it is defective.
Open circuit voltage test
The condition of the battery can be checked by measuring the voltage by connecting a voltmeter to its poles.
Disconnect battery, see chapter «Removing and installing the battery».
Before testing, the battery must be disconnected for at least two hours.
Connect a voltmeter to the battery terminals and measure the voltage.
Conclusions based on the measurement results:
- 12.7 volts or more - battery in good condition:
- less than 12.7 volts - the battery is in poor condition, it needs to be charged or replaced.
Connect the wires to the battery.
positive wire (+) and ground wire (-) connect to the battery with the ignition off.
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