TABLE 1. State of charge as related to specific gravity and open circuit voltage

Percentage of Charge Specific Gravity Corrected to 80° F Open-Circuit Voltage
12V
100 1.277 12.73
90 1.258 12.62
80 1.238 12.50

What is the specific gravity of a fully charged 12v battery?

The specific gravity of the electrolyte in a fully charged cell should be from 1.280 to 1.300. If it varies more than 10 points above or below these values, adjust it by drawing off some of the electrolyte with a hydrometer and adding water to lower the gravity, or 1.400 acid to raise the gravity.

What is the specific gravity of battery?

Since the electrolyte of a lead-acid battery consists of a mixture of water and sulfuric acid, the specific gravity of the electrolyte will fall between 1.000 and 1.835. Normally, the electrolyte for a battery is mixed such that the specific gravity is less than 1.350. Specific gravity is measured with a hydrometer.

How do you find the specific gravity of a battery?

To check the specific gravity of the electrolyte, it is possible to use a hydrometer (also called an “aerometer”) or a digital density meter (also called a “digital hydrometer”). A lead acid battery hydrometer is a special type of hydrometer which looks like a syringe with a bulb.

How do you calculate specific gravity?

The formula for specific gravity, given that the reference substance is water, is the density of the object divided by the density of the water.

Why specific gravity test is done for battery?

One of the key parameters of battery operation is the specific gravity of the electrolyte. Specific gravity is the ratio of the weight of a solution to the weight of an equal volume of water at a specified temperature. Specific gravity is used as an indicator of the state of charge of a cell or battery.

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What is specific gravity of fully discharged battery?

The specific gravity of a fully-charged battery is 1.265 at a temperature of 80 degrees Fahrenheit (F).

What is a good battery hydrometer reading?

A hydrometer reading of 1.265 indicates a fully charged battery. A 75% charge is 1.225. Approximately 1.190 is half-charged, 25% is 1.155 and 1.120 indicates complete discharge. Each cell of the battery should be checked.

How do you measure specific gravity of a battery using a hydrometer?

Insert the Hydrometer Press on the bulb that acts as a syringe. You should see fluid filling the hydrometer. Continue to squeeze the bulb until the battery electrolyte solution fills the device to the maximum level. This device tests each cell by measuring the specific gravity of the fluid.

What voltage is too low for a 12 volt battery?

12.0 volts or below – At 12.0 volts your battery is considered to be fully discharged or ‘flat’ and should be recharged as soon as possible. The lifespan of your battery will be severely affected if it remains within this voltage range for extended periods of time.

What should a 12 volt battery read when fully charged?

Fully charged automotive batteries should measure at 12.6 volts or above. When the engine is running, this measurement should be 13.7 to 14.7 volts.

How much water should be in a battery?

While a battery should only be filled after it is completely charged, you should also check the water level before charging to make sure there is just enough water to cover any exposed plates. After charging, add enough water to bring the level to the bottom of the vent, about ¾ below the top of the cell.

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What unit is specific gravity?

Specific gravity is a dimensionless quantity; that is, it is not expressed in units. To find the sp gr of a solid or liquid, you must know its density in kilograms per meter cubed (kg/m3) or in grams per centimeter cubed (g/cm3). Then, divide this density by the density of pure water in the same units.

What does a battery hydrometer tell you?

Hydrometers (density meters) measure the specific gravity of a battery’s electrolyte. Based on the specific gravity, the user can determine the state of charge of the battery. Retaining these hydrometer readings and data over time is recommended by IEEE as part of any Battery Maintenance Program.