What is the specific gravity of a battery?
| Approximate state-of-charge | Average specific gravity | Open circuit voltage |
| 12V | ||
| 100% | 1.265 | 12.65 |
| 75% | 1.225 | 12.45 |
| 50% | 1.190 | 12.24 |
What is the specific gravity of a battery?
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. Secondly, how do you increase the specific gravity of a battery?
How many volts are in a 12-volt battery?
Voltages and Specific Gravity are listed for a 6-volt or 12-volt battery, and battery banks of 24 and 48 volts. The chart is listed below. But first, a few important notes and caveats…
Why is the specific gravity reading on my battery reading low?
If any specific gravity reading still registers lower than the factory specification of 1.277+/- .007 then one or more of the following conditions may exist: The battery is old and approaching the end of its life. The battery was left in a state of discharge too long.
What determines the state of charge of a 12 volt battery?
State of charge 12 volt Standard Batteries Battery state of charge is determined by reading either terminal voltage or the specific gravity of the electrolyte. The density or specific gravity of the sulphuric acid electrolyte of a lead-acid battery varies with the state of charge (see table below).
What is specific gravity of fully charged 12v battery?
The specific gravity, SG, of the electrolyte in each cell of a battery shows the battery's state of charge: Fully charged, SG = 1.280.
What is the gravity of car battery?
A lead-acid battery cell is fully charged with a specific gravity of 1.265 at 80° F. For temperature adjustments, get a specific gravity reading and adjust to temperature by adding . 004 for every 10° F above 80° F and subtracting . 004 for every 10° F below 80° F.
How do you calculate specific gravity of a battery?
In the case of battery testing, the hydrometer is measuring the specific gravity of the battery's electrolyte. The higher the acid concentration in the electrolyte, the higher the specific gravity. Based on the specific gravity, the user can determine the state of charge of the battery.
What is the specific gravity of a 6 volt battery?
12 volt – 6 volt Battery Maintenance & Charging GuideState of ChargeSpecific GravityVoltage6V100%1.2656.375%1.2256.250%1.1906.12 more rows•Oct 19, 2013
Why specific gravity is important in battery?
Specific gravity (SG) is very important because it's the most direct indicator of battery state of charge. State of charge (SoC) is directly proportional to specific gravity so if we can measure the SG we can instantly determine the SoC.
What does a specific gravity of 1.020 mean?
Ideally, urine specific gravity results will fall between 1.002 and 1.030 if your kidneys are functioning normally. Specific gravity results above 1.010 can indicate mild dehydration. The higher the number, the more dehydrated you may be.
What happens if specific gravity of battery is low?
Low battery gravity will reduce the effectiveness of the battery in terms of its charge capacity and the extent of its draining. However, you also need to understand that high gravity will result in battery wear and destruction of its plates and so you should maintain your battery gravity between 1.180-1.240.
What should a 12 volt battery read when fully charged?
about 12.6 to 12.8 voltsCheck the reading. A fully charged battery will typically display a voltmeter reading of about 12.6 to 12.8 volts. If your voltmeter is showing a voltage anywhere between 12.4 and 12.8, that means your battery is in good shape. Any voltage above 12.9 volts is a good indicator that your battery has excessive voltage.
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.
When should you check specific gravity of a battery?
The most accurate and direct way to test the state of charge of a battery cell is to determine the specific gravity of the battery electrolyte. The higher the specific gravity of the electrolyte the higher the state of charge....Temperature Correction.ChargedSpecific Gravity50%1.180-1.20025%1.155-1.1650%1.110-1.1302 more rows•Mar 25, 2021
What is gravity low in battery?
The higher the concentration of the acid, in the battery electrolyte, the higher the specific gravity of the battery. A low concentration of the acid on the electrolyte on the other hand means that the specific gravity of the battery is low. Low specific gravity of the battery is not good so something needs to be done.
When should you check specific gravity of a battery?
As this measurement provides a more accurate reading of state of charge than open circuit voltage, we recommend that you focus on specific gravity for your batteries. The battery must sit for at least 2 hours before a measurement can be made.
How accurate is a battery hydrometer?
Freas hydrometers are guaranteed to remain accurate throughout the entire life of the instrument. The 'basic' Freas No. 1 battery hydrometer measures specific gravity from 1.250–1.275 graduated in 0.002 degree. The one ounce rubber bulb and end piece are made from the highest grade acid resistant rubber.
How accurate is it to measure battery voltage?
Measuring battery voltage is NOT the most accurate way to do this (there are variables to consider). But a good generalization. A more accurate method is to measure the specific gravity of each cell within the battery. However for many batteries this is difficult or impossible (AGM batteries, for example).
What condition does a battery have to be in to be charged?
Note: For best accuracy when measuring battery voltage, the battery must be in ‘open circuit’ condition (at rest, or ‘resting’). This means that the battery must NOT be under load and it must NOT be charging.
How to determine SOC of a battery?
There are several ways to determine a battery’s SOC. 1. Measure the battery’s chemistry (specific gravity) with a hydrometer (accurate method). 2. Measure its voltage with a volt meter while open-circuit, no load (general approximation). 3. Track the current flow in and out of the battery with a ‘shunt’ and associated metering circuit ...
What is the SOC of a battery?
The ‘State Of Charge’ (SOC) of a battery is a measurement of how much energy is remaining (percent). It’s like a fuel gauge. Measuring and knowing the SOC of a battery or battery-bank is useful when applying towards alternative energy, or any other situation where you need to know its condition.
Is battery voltage temperature dependent?
Note: Battery voltages are temperature dependent. In fact, good charger systems (alt-energy systems) have temperature compensation built-in. The voltage data in the chart below is that of manufacturer spec. sheet listings (vicinity of room temperature).
What is the effect of high or low specific gravity on a battery?
In the selection of a battery for a given application, some of the effects of high or low specific gravity to be considered are: A solution of higher specific gravity is heavier per unit volume than one of lower specific gravity. Therefore the more concentrated electrolyte created during charging sinks to the bottom ...
What is the specific gravity of an 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. However, specific gravity measurements cannot ...
When the electrolyte is near the low level mark, the specific gravity is higher than nominal?
When the electrolyte is near the low-level mark, the specific gravity is higher than nominal and drops as water is added to the cell to bring the electrolyte to the full level. The volume of electrolyte expands as temperature rises and contracts as temperature drops, therefore affecting the density or specific gravity reading.
When is a battery fully charged?
The battery is considered fully charged when specific gravity reaches it's highest possible value. Specific gravity does, of course, vary with temperature and the quantity of electrolyte in a cell. When the electrolyte is near the low-level mark, the specific gravity is higher than nominal and drops as water is added to the cell to bring ...
Can specific gravity be measured on lead acid batteries?
As mentioned earlier, specific gravity measurements cannot be taken on sealed lead-acid batteries. Measurement of the cell open-circuit voltage has been used as an indicator of the state of charge of a sealed battery.
Can specific gravity determine battery capacity?
However, specific gravity measurements cannot determine a battery's capacity. During discharge, the specific gravity decreases linearly with the ampere-hours discharged as indicated in the illustration below. Changes in voltage and specific gravity during charge and discharge. Therefore, during fully charged steady-state operation ...
Difference between specific gravity and density?
It is quite clear that these quantities are not the same from one another. Despite this, they are often used interchangeably and it is key to clearly distinguish between them.
Why measure battery acid specific gravity?
A battery produces electrical power through chemical reactions in it. The concentration levels of sulfuric acid in the electrolyte changes as the battery undergoes the cycles of charge and discharge.
How to measure battery acid specific gravity
Measuring the battery acid specific gravity will involve the following steps.
Battery acid specific gravity and temperature
The density of water maximum at 4 0 C or 39 0 F. The measure measurement of specific gravity of the sulfuric acid and the battery acid is assumed to be taken at the ideal temperatures.
What does low specific gravity indicate?
When the measured specific gravity of the battery is measured and is found to be below 1.26, it could mean any of the following:
How do you raise specific gravity of a battery?
When the specific gravity in battery acid has been low due to spillage or excess watering, one may decide to raise the gravity to the desired levels. You may achieve this by adding sulfuric acid to distilled water to achieve the desired levels.
Conclusion
Measurement of battery acid specific gravity is important to ensure that the battery is in the right condition to enhance operational efficiency. As a battery maintenance routine, always measure the specific gravity at least once a month.
How To Determine Battery Charge Levels
There are two main ways to determine the charge levels of the battery i.e voltage measurement and specific gravity measurement.
Why It Is Important To Carry Out Battery Capacity Test?
As part of the battery routine maintenance, it is always important to carry out voltage tests in the car battery. Some of these periodical tests are done so that:
Final Thoughts
Though a voltage measurement of 11.9 may seem high, it is inadequate to provide the burst of power needed to crank up the engine. The same car battery may be able to power a radio or an indicator light but does not have enough power to start the engine. It will be deemed as flat.
