Add 0.004 for each 10⁰F the electrolyte temperature is above 80⁰F Look on your hydrometer (or its instructions) and it should tell you. acid. Figure 1 reveals the flat voltage profile of Li-phosphate (LiFePO) batteries. Battery state-of-charge can also be estimated with impedance spectroscopy using the Spectro™ complex modeling method. Prior to charging it has 12.42V. 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. I do off grid solar for a living, 25 years now and I sent a customer the link to this chart to give him an extra tool to keep tabs of his system. The Trojan sounds like it is getting old, and needs more frequent watering and equalizing to keep it functioning. Temperature is another variable that alters the specific gravity reading. This approach has the unintended benefit of prolonging battery bank life. In other words a heavier load for shorter periods. 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. If this is not a typo, I’d like to understand it a bit better. Some innovative BMS (battery management systems) use the rest periods to adjust the SoC readings as part of a “learn” function. the health of each cell. Lead acid comes with different plate compositions that must be considered when measuring SoC by voltage. You get what you pay for and you reap what you sow, so take good care of your batteries and they will take good care of you longer. On April 15, 2018 at 2:58am I really wonder how AH-counting process works? If they told you 75AH is good for a 30 miles of rolling on a street, you can make rule of three: if 75->30, then 55-> 22miles, 90->36miles, 115->46miles. The capacity that geometrically decays is the “AVAILABLE” capacity, and not the overall capacity. has sufficient electrolyte to permit hydrometer float to rise freely. A very highly rated ‘smart’ 12-volt battery charger:(( Most Reviewed Battery Charger on amzn )), Open circuit voltage, or specific gravity per cell, Download full size PDF (Battery State Of Charge). This one works. In the PDF the method is explained. electrolyte from. High acid concentration artificially raises the open circuit voltage, which can fool SoC estimations through false SG and voltage indication. Can anyone spare a clue? This allows taking SoC readings with a steady parasitic load of 30A. if the battery was neglected, often charging with a current limited high voltage can restore some life Click on the different category headings to find out more.