Hi

I have an issue that I hope someone can shed some light on. 

The system in question is the following:

1x 8kw Sun Synk inverter + 1x 10.62kwh Sun Synk battery

The inverter is set to shut down at 20% which is the recommened shut off SOC. The client has her geyser on the system with a timer to control on her phone. The run down was given to her on how and when to switch her geyser on to avoid crazy drops in SOC. However, this client forgot amd had her geyser on during loadshedding which caused the SOC to drop fast. 

Thats fine because shut off SOC should come in to effect as it is set to 20%. The problem is that i noticed it went right past the 20% without shutting off. It went down to zero (which i REALLY don't want) still supplying the geyser load. I would expect it to get to 20% and flatline with a very low consumption from the inverter itself. 

Any advice or reasons would be greatly appreciated. Thank you 

 

 

 

 

 

 

 

 

Edited July 29, 20233 yr by WIRED

On 2023/07/29 at 9:21 AM, WIRED said:

Hi

I have an issue that I hope someone can shed some light on. 

The system in question is the following:

1x 8kw Sun Synk inverter + 1x 10.62kwh Sun Synk battery

The inverter is set to shut down at 20% which is the recommened shut off SOC. The client has her geyser on the system with a timer to control on her phone. The run down was given to her on how and when to switch her geyser on to avoid crazy drops in SOC. However, this client forgot amd had her geyser on during loadshedding which caused the SOC to drop fast. 

Thats fine because shut off SOC should come in to effect as it is set to 20%. The problem is that i noticed it went right past the 20% without shutting off. It went down to zero (which i REALLY don't want) still supplying the geyser load. I would expect it to get to 20% and flatline with a very low consumption from the inverter itself. 

Any advice or reasons would be greatly appreciated. Thank you 

This is quite a common occurrence. The SOC is not accurate. It is an estimate and basically an algorithm. Many factors influence it, including temperature, cell chemistry, cell age, etc. It is very common for batteries to overestimate the SOC (or underestimate but not in this case), so what happens is that even if the battery reports a SOC of 23% for example, it might be close to zero actually, the BMS of the battery then all of a sudden see the voltage dip heavily (thanks to the geyser running), then it simply sets the SOC to 0 directly from 23% or whatever percentage it was. Maybe put the geyser on a relay so it is not switched on during load shedding.