I’m looking to add extra charge power to DESS and switch it automatically.
Setup:
- 40A single phase 230Vac
- Multiplus II 5000 GX running DESS in Trade mode, no solar
- One 43kWh Li-Ion batterybank, allowing 0,25C upto 0,50C charging (10-20kW)
- Smartshunt on battery
- Multiple 3kW high efficiency chargers, can-bus protocol known, pull-to ground enable available
- All AC loads on output feeding small home, 200 to 400 kWh monthly, weather and heating to most varying conditions and loads.
With grid supply available upto 9400W, I’d like to boost charging upto 9000W by enabling three(3) 3kW high efficiency chargers, that are connected to AC OUT2 of the MP. This will allow for the MP II to automatically reduce it’s own charge current not to exceed the 40A AC IN1 limit.
My question concerns the use of (relais) assistents to switch on (one or more) boost chargers when prices are low. I found some settings in VE.Config that would use the VE.Bus signals to determine when to switch on or off some relay but to my best knowledge that won’t work because the VE.Bus is practically always in BULK mode, with DESS charge or discharge operation being controlled by the positive/negative difference between the measurred SoC (smartshunt) and the SoC target provided and regularly updated by the DESS assistent on the GX
Could anybody point me to a usable scheme to get this implemented in such a way that the boost chargers will only be enabled when DESS is requesting more charge power then (a certain percentage of) the maximum charge current (70A) of the MP II? And visa versa stops when requesting less.
Have you found a solution yet? I’m looking for a similar (preferrably easy) solution to use electrical heating when price is low as opposed to burning expensive oil. VEconfigure assistants didn’t have any option to use price as a control function for aux contact or acout2. I think this needs to be done with Venus OS large + node red but haven’t had the time to educate myself how I would do this. Would be a very nice upgrade to assistants imho (wink wink 
Edit: I looked around for a bit and found this, but I’m a bit unsure how to implement it. It would be helpful if original poster could provide us with the code so we could modify it for our needs?
Also found this guide which might be dumb enough for me once I find some time to actually read it through with thought:
Hi @sarka9000 , welcome to the forum.
And thanks for reminding me I need to look into this again. Short answer to your question is no, I didn’t figure it out yet how to automate this, didn’t find the time to dig into node red DESS. What I do, as dissatisfactory as that is, is checking what DESS trade plans for the next day and manually set a relay timer on the chargerbank to play along with that, dayly. I know that is a copout from an engineerings point of view but that’s the best I could muster, for the time being.
Had some spare time and came up with this monstrosity. Someone more capable with scripting might get something more elegant, but at least now in summer time this seems to work.
I used norpool-api+ and a switch to read price for the correct hour, then a function to get €/kWh with tax etc. and then another switch to send commands to Easysolar 2 MPPT relay. The nordpool api gives correct price for current day hours 01-24 but for hour 00-01 I get tomorrows price for some reason, so I have a “extra” node getting that price info from “yesterday”…
If someone needs, I can send the flow.
Also found out that the ACout relay and alarm contacts on MP2 can only be used via assistants, not node red. I was saved by the MPPT in my Easysolar.
