Bobster. Posted August 17, 2020 Posted August 17, 2020 Just happened here? My system has occasionally shown this sort of behaviour before, but not as egregiously as this. 76% to 100% in 5 minutes. Which figure do I believe? The 76% of the five minutes later 100%? Goodwe ES inverter. Revov batteries with a BYB BMU and the Goodwe configured to "see" a BYD B-BOX. Quote
___ Posted August 17, 2020 Posted August 17, 2020 5 minutes ago, Bobster said: Goodwe configured to "see" a BYD B-BOX Sounds as if the inverter gets its SOC from the battery. BYD batteries can drift quite a bit, because their current sensors can't sense well below 2A (per module, multiply by number of modules). So if your batteries have been subject to a low charge or discharge currents (in this case I suspect slow charging to be the culprit), the battery SOC might well have been higher than the BMS estimated... until the cell voltage suddenly went up and the BMS realised it had to reset. Youda 1 Quote
Bobster. Posted August 17, 2020 Author Posted August 17, 2020 19 minutes ago, plonkster said: Sounds as if the inverter gets its SOC from the battery. BYD batteries can drift quite a bit, because their current sensors can't sense well below 2A (per module, multiply by number of modules). So if your batteries have been subject to a low charge or discharge currents (in this case I suspect slow charging to be the culprit), the battery SOC might well have been higher than the BMS estimated... until the cell voltage suddenly went up and the BMS realised it had to reset. Thanks. So I believe the 100% then? Don't know about the slow charging. We had good sunshine, but the pool pump was running and then appliance was piled upon appliance and certainly it would have got to 100% SOC later than usual. Quote
___ Posted August 17, 2020 Posted August 17, 2020 9 minutes ago, Bobster said: Thanks. So I believe the 100% then? There is always some sort of algorithm in the BMS that it uses to decide when to go to 100%. Usually it is something like 1) all cells above 3.45V and 2) at least one cell just spiked above 3.5V. One reason why seeing per-cell voltages, or at least the lowest and highest voltages, is a very good diagnostic tool. Quote
Ironman Posted August 30, 2020 Posted August 30, 2020 On 2020/08/17 at 2:47 PM, plonkster said: One reason why seeing per-cell voltages, or at least the lowest and highest voltages, is a very good diagnostic tool. Is it possible to see this in a blue system? MPII, Venus, 4 * pylontech us3000... Quote
___ Posted August 30, 2020 Posted August 30, 2020 54 minutes ago, Ironman said: Is it possible to see this in a blue system? MPII, Venus, 4 * pylontech us3000... Ask Pylontech if the firmware that implements this is available yet... I know they were working on it. Quote
Youda Posted August 30, 2020 Posted August 30, 2020 On 2020/08/17 at 2:02 PM, Bobster said: Just happened here? My system has occasionally shown this sort of behaviour before, but not as egregiously as this. 76% to 100% in 5 minutes. Which figure do I believe? The 76% of the five minutes later 100%? Goodwe ES inverter. Revov batteries with a BYB BMU and the Goodwe configured to "see" a BYD B-BOX. This is pretty normal, like @plonkster explained. If happens once a while then it's okay. But, if that happens everyday, then it means that the real capacity of the cells is much lower than what's hardcoded in the BMS FW. Everyday jump from 90% to 100% is okay. Everyday jump from 76% to 100% is not. ___ 1 Quote
Bobster. Posted September 8, 2020 Author Posted September 8, 2020 On 2020/08/30 at 11:11 PM, Youda said: This is pretty normal, like @plonkster explained. If happens once a while then it's okay. But, if that happens everyday, then it means that the real capacity of the cells is much lower than what's hardcoded in the BMS FW. Everyday jump from 90% to 100% is okay. Everyday jump from 76% to 100% is not. It is occasional. Thanks all for the input and information. Quote
Bobster. Posted July 21, 2021 Author Posted July 21, 2021 Necro post. This is still happening and the trigger for the big jump in SOC (usually from mid 70s to 100) is when SOC drops to the 40% that I have reserved for load shedding. But now this morning I see this for the first time - a sudden DROP. In this case from 48 to 40. There is a spike in the load there, but not unusually high for this time of day in my house (kettle being turned on whilst the heat pump is still running) and the spike was 3.2 kw. Note that later on I get the sudden big increase in reported SOC. I don't know whether to worry or not. Quote
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