Despite making goodness how many observations I have not been able to establish a relationship between battery volts and state of charge. The battery is reckoned to be full at just over 60V and empty at about 51.5V. But I can be showing 60 V but battery SOC can be anything between 80 and 100 %. Equally at bottom end and be showing 52V and be 40% full then take some juice then drops to zero. Was once told BSM was controlling the charging and sometimes needed to know what was empty like, and what full was like. Akin to knowing how much a bucket will hold is to empty it and measure how much it takes to fill it. But am no wiser to what is going on. Today after being empty this morning reached 80% at 60V then started discharging to grid and later charging again presumably equalising the cells within the battery. Anyone understands what is going on.?
Battery Volts / SOC relationship
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It would help to know how big your bucket was in the first place .
12v 24v 48v etc
Just stating a voltage and % is meaningless
12v 24v 48v etc
Just stating a voltage and % is meaningless
Ignore the voltages, they don't mean much. At top and bottom ends of soc, the charge rates reduce to protect the battery cells.
Start slowly.
Are these 5 12V batteries or a single 50 V.
The voltages you quote suggest lead acid but a clue would be good
How are they charged and with what and to what voltage ?
No. SOC from voltage is a generally poor indication due to various factors including battery temperature and time since charge
SOC during a known rate discharge is a better bet
Big falls in SOC or voltage during steady discharge at a rate that should last 5 hours or so generally indicate a cell fault or worn out battery (which also confuse chargers )
Are these 5 12V batteries or a single 50 V.
The voltages you quote suggest lead acid but a clue would be good
How are they charged and with what and to what voltage ?
No. SOC from voltage is a generally poor indication due to various factors including battery temperature and time since charge
SOC during a known rate discharge is a better bet
Big falls in SOC or voltage during steady discharge at a rate that should last 5 hours or so generally indicate a cell fault or worn out battery (which also confuse chargers )
As stated it is 52 v empty 60 V full. It comprises of tens of Li cells don't know how many but 30 + I am told. The BMS between the inverter and battery control the charging. When volts low it is trickle charging, above 20% SOC or thereabouts starts increasing charge rate to 3.6Kw until 70 to 80 % is reached then slows down again and battery is charged more slowly and as gets closer to 100% and if volts at 61V say, will discharge and will do this discharging and charging continuously as each cell is equalised. The charging voltage I do not know the display shows what the battery is at so maybe it varies. Each cell is monitored and each cell will be adjusted so as they are all the same. This is the reason why Li batteries have a longer life than LA as less chance of getting a dead cell affecting the whole battery. It is difficult to get the lowdown on what really is happening there are very technical explanations on you tube explaining the technical make up of operation of EV batteries and I expect a solar battery is similarly constructed. I am only saying what I know and it is what I have gleamed from those that purport to know, they are rather coy at revealing the detail to protect algorithms involved in the charging and makeup but would have thought a competitor could soon unravel the codes if that really was the reason. So my question really was to find out what others know that would give me more information so can understand the technology better. I think there is a relationship between V and SOC and it is different when charging and discharging and maybe exhibiting a hysteresis but cannot fathom it out.
that's how they are suppossed to work to extend the life of the lithium cells and get the 6000 charge cycles they are rated for. Exactly what goes on within the BMS is a mystery to me, and no-one is likely to tell you as that would be set within the engineering R&D dept, so no one else is likely to know the full workings of that. I'm guessing the voltage set by BMS affects charge rates?
