squowse
Solar Enthusiast
- Joined
- Jan 4, 2021
- Messages
- 582
Hi. I am hoping someone is an expert and can tell me about how it calculates the state of charge.
It seems to be that it has two methods
1) estimate from cell voltages using the values set in the configuration
2) "coulomb counting" where it measures the current in and out of the battery
So method 1) is obviously going to be very rough and I would only expect it to be used when it has no other information eg when it's first used.
I noticed the first time I used it - it measured and adjusted the battery capacity based on the first discharge 100% to 0%. This changed from the 272Ah I set it to and changed it to 290Ah.
At some point since then it has changed it to 230Ah.
So I would like to understand when and how it changes this value.
But more importantly - it seems to use method 2) a lot.
For example - when I attach a mains charger, as soon as the "cell voltages" (actually the charger voltage) gets to 13.2V (cell voltage 3300mV) the state of charge jumps to 100%. Even though the battery is only about 25-50% at this point.
This is puzzling and annoying. So I wait for the charge amps to fall near zero before disconnecting the charger. But if I disconnected it before then it would still think it's on 100%, or try to estimate from the settled battery voltage.
So - why does it abandon the coulomb counting?
Thanks
Roger
It seems to be that it has two methods
1) estimate from cell voltages using the values set in the configuration
2) "coulomb counting" where it measures the current in and out of the battery
So method 1) is obviously going to be very rough and I would only expect it to be used when it has no other information eg when it's first used.
I noticed the first time I used it - it measured and adjusted the battery capacity based on the first discharge 100% to 0%. This changed from the 272Ah I set it to and changed it to 290Ah.
At some point since then it has changed it to 230Ah.
So I would like to understand when and how it changes this value.
But more importantly - it seems to use method 2) a lot.
For example - when I attach a mains charger, as soon as the "cell voltages" (actually the charger voltage) gets to 13.2V (cell voltage 3300mV) the state of charge jumps to 100%. Even though the battery is only about 25-50% at this point.
This is puzzling and annoying. So I wait for the charge amps to fall near zero before disconnecting the charger. But if I disconnected it before then it would still think it's on 100%, or try to estimate from the settled battery voltage.
So - why does it abandon the coulomb counting?
Thanks
Roger