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I need to realise an off grid system and I'm considering the Victron ecosystem.
I'll have roughly 12kW of panels in two strings going to an MPTT and probably a Multiplus II 5000/48.
I often need to run loads in the order of 6kW and maybe even 7kW for a few minutes. Is it possible for the Multiplus to draw some of the power from the grid? For example 5kW from the battery/solar and 1-2kW from the grid?
Yes it can borrow from the Grid with power assist, manual says peak is 9000watts on that unit but does not say how long for and what temperature that it can achieve that in. If you look through the spec the hotter it gets the more it restricts. I would give yourself some breathing room and go one above hell if you can just go for the 48/10000 gives a lot more flexibility I wish I followed my mind and got it instead of settling for the 48/5000 which is a good unit but the 48/10000 would have given much better options and flexibility load wise of what I run and when it’s run. But price does play a part but if you can get the big one after all it is the heart of the system!
Power assist is batteries supplementing insufficient grid, not grid supplementing batteries.
The use of a CT clamp suggests it would be working in a grid tie mode, which I would like to avoid as it's theoretically illegal.
@jacoscar you mentioned it drawing from the grid so assumed that’s what you wanted! Ive no idea when it comes to the legality as I’m in the UK and we can as long as we get approval from our DNO.
If just for off grid then I would not get the 48/5000 IMHO and look at only the 10000 or the 15000, is the solar AC or DC? How many batteries are you using as these systems need at least a minimum amount.
The Multi will use grid power if available over battery power, even if you set it to prioritize solar/wind for battery charging. You can set the AC input current limit to its minimum value but it will still draw that much from the grid even if battery power is available.
You can use the ignore AC assistant and base that on the AC output power but remember that the grid takes a few seconds to kick in after ignore AC input goes false.
@Daza what I mean with ‘off-grid’ is having the grid connected to ‘AC in’ and the house to ‘AC out’; so you can draw from the grid but it’s impossible to export to it
On-grid inverters have a single grid connection and need to rely on a ct clamp to measure the energy exported
Oh you just change the feed in limit to Zero, but what is your solar AC or DC? But I would still look at the bigger unit as you don’t want to continually overload the unit more so when temps are high
@daza if you change the feed in limit to 0, there are still short times when there is export (switching off high loads for example); not sure what you mean by solar being AC or DC, as far as I know there are no AC solar panels, mine would connect directly to the inverter
Ok so DC for solar, so all of your generation is done through DC in which case I would get a bigger unit to supply the load, yes you can limit feed into the Grid, not too sure how it deals with high loads other than to loss as heat, i imagine it’s the same way in a grid down situation if you have an AC inverter on AC1 out of the victron the same thing will happen with over production and no grid connection granted it won’t happen for too long if frequency shift is used but I’m pretty sure that’s why they have a ratio on AC solar on the AC outside. Does that make sense? A distributor would give a better explanation if now one else can expand or give a better explanation than what I have said.
I think Jacopo asked a simple question and I would also be interested in an answer but it seems that people overcomplicate the scenario. The question is if you have a 5k multiplus 2 with grid connected to ac in and load connected to ac out what happens if you have 8kw load? will it get 3 kw from the grid and supply 5kw from the inverter? Will it go in overload?
Assume a 120 volt system with current limit set to 10 amps. That's 1,200 watts from the AC input.
If loads are under 1,200 watts then ALL power comes from the grid and any remaining power charges the battery.
If power exceeds 1,200 watts, lets day 2,000 watts then 1,200 watts is drawn from the grid and 800 watts comes from the battery via the inverter.
This assumes power assist is enabled.
It's a logic whose intent I don't understand; it would make more sense to start drawing from the grid only what's necessary, rather than drawing a fixed amount from the grid and supplementing with inverter power, but maybe there is a technologic limitation I'm not aware of.
ESS is probably your best choice if it can be used in your system. ESS does not require feeding to the grid.
Thanks.
