This means that the battery must NOT be under load, and it must NOT be charging. Measure Battery While “At Rest” “Open Circuit” For best accuracy when measuring battery voltage, the battery must be in ‘open circuit’ condition (at rest, or ‘resting’). Many (most) alt-energy systems incorporate a DC-shunt which keeps track of SOC by monitoring the current flow in and out of the battery or battery bank, which is a very accurate way to track state-of-charge. However for many batteries this is difficult or impossible (AGM batteries, for example). A more accurate method is to measure the specific gravity of each cell within the battery. Measuring battery voltage is NOT the most accurate way to do this (there are variables to consider). Note: Voltage measurements are only approximate to determine SOC. Battery Voltage Measurements Are Just Approximation However I averaged all of them together to come up with a chart which represents what I believe to be a good GENERAL indication. Some were slightly different from each other with regards to their SOC values. I researched as many battery manufacturers that I could find regarding their own published SOC data. But first, a few important notes and caveats… How I Made The Battery State of Charge Chart Voltages and Specific Gravity are listed for a 6-volt or 12-volt battery, and battery banks of 24 and 48 volts. I put together the following battery state of charge chart which indicates the state-of-charge (percent) as it relates to battery voltage or specific gravity. The most popular hydrometer on amzn used for measuring specific gravity of a lead acid battery with access to its chemistry. Track the current flow in and out of the battery with a ‘shunt’ and associated metering circuit (common with alt-energy systems). Measure its voltage with a volt meter while open-circuit, no load (general approximation).ģ. Measure the battery’s chemistry (specific gravity) with a hydrometer (accurate method).Ģ. There are several ways to determine a battery’s SOC.ġ. 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. The ‘State Of Charge’ (SOC) of a battery is a measurement of how much energy is remaining (percent). There are important caveats to this type of measurement (listed below) regarding measuring battery voltage to determine how charged it is.

Actually I have voltages for 6v, 12v, 24v, and 48v.

I have researched 12v lead acid battery voltage readings versus percent charge (state of charge) which you may find useful or helpful. Battery voltage, (chart below) can help determine its state-of-charge.

6 and 12 volt battery charger