Hello
I have three multiplus II in use.
I would like to program them (node red and/or MQTT) so that if the battery is below 30% for more than 2 days, the batteries are recharged up to a certain point.
However, I can only use 1 phase, i.e. only one Multiplus II, as I am only allowed to draw a minimum current.
I have the problem that I don't know how to forbid 2 Multiplus to charge the batteries and allow one. In the Cerbo gx I can only activate or deactivate all at once.
Hi @EDSTOBI
Not sure if there's a better supported method in the victron for this. This is just my guess attempt at a solution:
Put a relay on each of the Multiplus II's that you don't want to draw from the grid.
When your node red code for charging the battery is active
if( currentTime - lastTimeAbove_30% > 3day){
//code to send off command to multiplus ii's you dont want to draw from grid
/* maybe code to check that the off command work maybe check voltage on ACIN L2 and L3 to make sure relay is off
*/
//set min SoC to x%
}
//Some other logic to change min SoC back down to a lower number after you inflated it to x%
You'd need a fairly large relay for this but activating the relays wont use much power so you could do that either via the GX relay controlled via node red. Or buy a cheap smart switch just for the activation (ie a shelly smart switch)
If it's critical that the 2 multplus dont draw from the grid it may be worth looking into building a check into node red before increasing grid setpoint just to make sure the relays have turned off the grid on those multiplus. Some sort of check of voltage maybe of ACIN on L2 and L3 or whatever lines those multiplus ii's you want off are connected to.
Hello matt1309
Thank you for your solution.
Unfortunately, this is not feasible, as I would then have to operate the other two Multiplus II via the batteries during the charging time. This means that I would now reduce the total load of the previous 3 phases to one phase. Then I would get exactly into the dilemma I have: I can only draw a limited amount of current from the phase with the lowest load for extra current for charging.
I had hoped that you could programme in the Multiplus II in the basic configuration (VE Configur) under Charger or under Assistants to program an assistant that only one Multiplus woud charge from Grid
So just to clarify the desired outcome.
You want to charge batteries if below 30% for more than a day using a single phase.
but you cant use the method of disconencting L2 and L3 grid supply from multiplus as you'll have additional loads running on L2 and L3 at the same time and disabling L2 and L3 will mean that all the power for those phases is coming from batteries/L1 grid. And L1 has insufficient power for this? So you want L2 and L3 to be covered by power from grid L2 and L3 and the power from L1 is charging the battery?
And disabling grid on L2 and L3 with a relay doesn't work because L1 wont have enough power to charge batteries with enough excess to charge the battery plus cover the loads that L2 and L3 would be drawing from the battery? Have i understood?
I'm not sure of a solution for that, if I've understood correctly. Maybe you could move loads on L2 and L3 to ACIN side of inverter and use an energy meter with multiphase regulation set to individual phase but then turn L2 and L3 multiplus to inverter only mode forcing the grid to cover those loads/stopping the multi's from charging the battery. I'm not sure if that works in three phase configurations though or if it just give an error as the inverters are in different modes.
Could you use my relay method but charge the battery slightly ahead of time from L2 and L3 grid. Just to cover the loads on those phases during the time period where you're charging from L1. ie draw a little extra from L2 and L3 for the time period leading up to the threshold of 1 day of time less than 30%. Just to cover those phases from the battery when L2 and L3 grid are disconnected?
A solution I've seen else where on the forum: much simpler but unfortunately more expensive. To buy an AC battery charger (could be another multiplus or something else).
Leave the current three phase system as it is and have an addition AC battery charger that uses L1 to charge the battery rather than doing it via the multiplus. Then use a smart shunt to monitor the power being added to the battery from this external AC charger. This could be turned on and off using Node red/relay.
Hello
This is how I will do it.
I will get a charger, which I will then switch on via node red on when the values allow it and take off the grid when I reach the load max point.
I have the basic problem that my grid supply comes as an undersupply from the main house.... Old small line which is weak. That's why I bought the PV
