Battery State Of Charge

Solar Battery State Of Charge Check

When using the solar battery in different modules, many a time, it so happens, that one needs to determine the state of charge. Ideally, a hydrometer still remains the quickest and the safest way for the sake of determining the state of charge of lead-acid batteries that have been flooded in the solar battery system. Let us explore further and find the finer details to determine the state of charge for solar batteries.

The need to determine the state of charge

Owing to fluctuating solar exposure and even aging with time, the batteries may develop changes which would prevent them from charging up fully. This ends up deteriorating the net performance level too. Hence, determining the state of charge is important for optimal performance of the solar powered system.

The different ways

While a hydrometer is the best and the most efficient way to check, there are load testers and even electronic battery checkers which are available. They too can offer valuable information. As most batteries come with removable vent caps, using a hydrometer becomes remarkably easy. It measures the specific gravity of the electrolyte which in turns helps in determining the state of charge of the batteries.

The reaction of electrolyte specific gravity with charge

The electrolyte specific gravity is known to have a direct relation with the state of charge of the battery. In cases when the battery is completely charged, the specific gravity of the electrolyte will increase as the available sulfates all bind to the sulphuric acid electrolyte.When the battery discharges, the same sulfate now moves back to the plate. This is going to decrease the specific gravity. This is how a hydrometer accurately determines the state of charge of the batteries.

The precautions and method to measure

When using a hydrometer for determining the SOC, the following are some of the details you need to be wary of.
  • Make sure to remove the battery vent caps as per the details and recommendation offered by the manufacturer
  • Take the hydrometer and place it in one of the cells of the battery. Slowly, draw in some electrolyte from it and then make sure to squirt it back to the cell. This is an important step as it mixes the electrolyte. This makes sure that you get an accurate reading.
  • You then need to draw the electrolyte again and wait for a few moments so that the float can settle. This will help you get a stable and accurate reading.
  • Note down the readings and you need to note that corrections have to be added for accuracy.
Listed below are the corrections.
  1. Add 0.004 for each 10⁰F above 80⁰F; add 0.005 for each 7⁰C above 27⁰C
  2. Subtract 0.004 for each 10⁰F below 80⁰F; subtract 0.005 for each 7⁰C below 27⁰C
  3. Some hydrometers automatically correct for temperature and do not require correction.
So, now that you are acquainted with the details follow these steps and determine the SOC.
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