Avoid sell back when prices are negative

Q&A and troubleshooting DESS
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Hi,
My setup is a Multiplus-II 48/5000/70-48 & Cerbo GX with a BYD battery and a separate SMA Sunnyboy 5 PV inverter. I have a dynamic contract (In Belgium, Frank Energy) and setup ESS.

When prices are negative I want:

  1. avoid to sell to grid - assume battery is already 100% (since that would cost me money)
  2. buy from Grid - even while it is forecasted that my PV will generate enough to fill my battery (since I want to take advantage to do laundry, use the dryer, charge my EV battery etc)

Any suggestions how to accomplish this? I have Venus OS large installed and know how to work with node-red but don’t know what’s available in Venus OS large to accomplish this. (not sure if this is the route to take either…)
For the SMA Sunnyboy I know how to work with ModbusTCP.
Any suggestions are welcome.

2

Hi, Belgian ESS installer here aswell. I do a lot with Node-Red and see no issue why not to automate this in de Node-Red platform. I would keep the ESS at +10W and write a slave PID controller for the SMA Sunnyboy using the EMxx/ETxx GRID meter (if you have one) as actual value,. -10W as a desired value and the Mod-bus protocol towards your solar inverter as output for that PID controller. The difference of 20W should keep the slave PID saturated to charge your batteries.