I'm still trying to get my system to prioritise DC coupled solar when it is available to keep my batteries at 100%.
My system comprises: Multiplus 12/3000, Rpi running venus v2.66, BMV600s, DVCC on, 1400W of solar (overspec'd for winter), mppt100/50, 1480Ah UPS battery. (hence the desire to keep it charged). AC load of 1.2Kwh/day.
This is primarily a UPS system to cover power cuts and it works great for that. but I have DC solar so would like to prioritise it.
The way I understand it, the Mppt controller is a battery charger so it needs to see a load on the battery which drops it's voltage enough for the Mppt to pass current.
In order to load the battery, the multiplus ac input needs to be off (multi in inverter-only mode).
I can't feed back to the grid so can't use ESS.
I can manually switch the multi to inverter-only on sunny days via remote console and this works great but is a PITA and should ideally be automated.
Options I've tried:
lowering multi float and abs voltages by 0.1V below MPPT voltages. this works to an extent but only when the battery is under load or is partially depleted. (which makes sense)
lowering multi charge current, this still prioritises ac input for load use but does prioritise solar for charging a partially depleted battery. (which makes sense)
I've also fiddled around with venus coding to switch to inverter only when PV OC volts are high enough but I'm struggling to get it to work. I don't fully understand the venus coding.
Ideally I would do this in venus but-
Alternatively I could schedule when the multi switches between "inverter only" and "on" based on time of day or possibly using an irradiance sensor.
As a very basic way to get it working I'm going to try a time switch on the ac input to schedule the switching but this seems like a poor way to to do it when venus could schedule it.
I can't use the generator relay to do the scheduling as I use it for a generator.
I can't use the virtual switch as I use assistants for input current limit control.
I could use ignore ac input assitant based on SOC of battery but with such a big battery compared to the load it takes a while for it's SOC to drop low enough for the AC input to come on.
Has anyone else played around with this? would be good to bounce ideas off someone else.