Growatt 12k setting 13 (Utility to Battery Transfer Voltage)

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I was testing our emergency backup setup today and when the battery reached 90% the inverter temporarily shut down and restarted. I had setting 1 set to UTL and setting 13 (Utility to Battery Transfer Voltage) set to 90%.

Based on how I'm using this inverter, I think I need to change setting 1 to SBU and set setting 13 to 100% so that the inverter never tries to switch over to another mode. I don't have solar, so this setting will ensure battery is the primary. When the inverter is powering the house, it is on batteries only...acting like a standard backup generator. I never want it to switch modes until it is disconnected from the load panel and replaced by my gas generator to be used to recharge the batteries. Only then should the inverter be looking to go into battery charging mode from utility/generator.

For those of you who have a Growatt...am I interpreting setting 13 properly? Below is what the manual says:


Thanks for any insight...

Here is my setup:

 

[Mattb4]

Inverter should not shut down unless a fault occurs. Such as high DC bus voltage. Or perhaps a trip of your BMS. The battery to utility setting only causes a transfer to inverter when the utility power (in your case a generator) does not meet parameters or is not there. Think of it as a UPS that you choose preference on with modes of operation like Uti, SBU, SOL and such. It transfers on loss of power or by a setting (voltage or SOC) such as Battery to utility or Utility to battery when operating in Non utility preferred modes.

Your setup does require special care to not feed the AIO Inverter's AC in from the Inverter's AC out.

 

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When the inverter shut down momentarily, it did display an error code 20. I was messing around with the BMS-test software and the laptop froze up, so maybe the shut down wasn't related to the battery voltage?

On the AC In/out issue...yes when using my Honda generator, the inverter will be manually disconnected since they share the interlock breaker. When running the house on the Growatt, the Honda will be physically disconnected as well as the AC input to the inverter. I have everything marked and labeled to ensure no mishaps.

 

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BMS Info:

 

[Mattb4]

Error 20