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Can the BMS activate a relay based on current?

I don't see a trigger option for current, is this something that you are planning to add? The intended use for me would be to trigger the water heater if the batteries are almost full, and the solar panels are still charging significantly.


I like your practical thinking and many people would have the same requirement.  The code for "current based triggers" already exists in the firmware, but not yet activated as I have no practical use cases.  The challenge with your request is that the water heater needs to be controlled by 2 triggers (SOC and current) - the and function would require changing a lot in the code / applications. Lets think through the scenario where I want to turn the water heater ON at 80% SOC, while there is charging taking place:

  • SOC reaches 80% AND there is a charge current of 40A -> turn ON the water heater (draws 100A)
  • net battery current is now -60A (no longer charging) -> do we turn water heater OFF?

I imagine that in many situations the power of the water heater is greater than what the solar can supply (clouds, end of day...) - so current will be negative and SOC will start going down as soon as the water heater is ON.  It seems to me that what we want is to turn water heater ON at a set high SOC, and be sure that we do not take the SOC down too much (my water heater uses about 10% of battery capacity before it regulates).  To accomplish that just use a "high SOC" trigger with a "OFF value" set at "ON value" minus xx% (for example turn water heater ON when SOC reaches 80% and turn it OFF when SOC goes down to 70%).  Would that work for you?


Michel Leblais has reacted to this post.
Michel Leblais

Yes it will work, I was mainly interested if it was possible, the benefits are not that big to be honest. And everything is better than the current setup with a cable out from the engine compartment and a timer on the phone 😉