Posted December 14, 20222 yr Hi everyone, Total noob here, and I'm hoping the question isn't completely daft. On Friday, I installed a Sunsynk 5K-SG01LP1, connected to a Greenrich U-P5000 battery. No solar, because my money is not infinite. Solar is definitely the next goal, but I digress. On Sunday, our load shedding ended at 20:30, but the power never came on. So, newly kitted out with protection against load shedding, I went back to the stone age along with the rest of Kempton Park. Here's my question: The battery depleted, and I expected the BMS to cut off the battery supply at around 10%, to protect the battery. The inverter also has a 10% battery cut-out configured, but neither did their job. So, my shiny new battery depleted all the way to 2%. Does that mean the BMS is either faulty or misconfigured? And, if misconfigured, how do I fix that? Second, while the inverter stopped supplying the home at 10%, the inverter still continued drawing about 70W from the battery, depleting it until nearly empty. This setting is then NOT a backup for the BMS.
December 15, 20222 yr The BMS only protects against out-of range values. So it will allow the cells to discharge to the absolute minimum safe voltage. (If the BMS cut out before you had used the entire advertised capacity, then the battery manufacturer would face all sorts of lawsuits about false advertising.) The inverter should cut out at the configured 10% though, but IIRC there are two cut-outs for the Sunsynk - a soft cut-out that kicks in when grid is available, and a hard cut-out which kicks in only based on battery SOC. You may need to double check that configuration (and read the manual carefully).
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