I’ve completely wired up my system and now want to power it up. What I’m unsure about is the sequence of the individual steps.
The system is configured as follows:
Off-grid system
3-phase
3 MultiPlus II 10000
3 SmartSolar MPPT RS 450/200
14,400 kWp in 12 arrays
6 Pylontech US 5000
Busbar: Lynx Distributors
Cerbo GX control
Based on everything I’ve been able to find out, the procedure should now be as follows:
Commission the batteries (switch on all the switches on the Pylontech units, briefly press the red SW button on the master module once, and wait until all the LEDs are lit — the batteries will now supply power to the system)
Switch on the circuit breakers in the generator connection box (the PV arrays will now supply power to the system)
Switch on the MPPTs
Connect the MK3-USB to the last MultiPlus (they are already connected via an RJ45 bus) and connect it to the PC
Switch on the Multis
Configure the MultiPlus 3-phase system in VictronConnect using the MK3 and the PC
The system should now basically be operational
Configure the ESS via VEConfigure (there are several relevant YouTube tutorials on this; if anyone can point out anything in particular that I should pay attention to, please do!)
Remove the MK3-USB and connect the Cerbo GX to the last MultiPlus instead.
Is this the correct procedure, or does anyone with experience know of a better or different way to do it? In other words, what should I pay particular attention to so that I don’t damage anything in the system?
How can I phrase this appreciatively? It is quite an extensive installation, after all, so I’m a little surprised by your (simple) questions.
You’re probably familiar with this document; it’s useful to follow along during commissioning:
@HolgerBle has already mentioned it: batteries are a little on the tight side, but with the small PV system you’ll only reach 300 A of charging current.
How many battery cables have you installed?
During commissioning, I always let the batteries charge fully and balance themselves for an extended period first, without any load.
What does the string configuration look like for the MPPT RS units?
If I simply divide the 14.4 kWp down, I get three panels per string, so the 120 V start-up voltage could already be a bit marginal.
You have a diesel generator for an off-grid system as well, I assume?
Because it’s the diesel generator that gives the off-grid system the power to make it through the dark winter
Thanks for your replies! That reassures me
To clarify the setup:
Designed as an off-grid system, because it is switched manually using a “Grid - 0 - Off-grid” switch, so there is never a direct connection to the grid. So I already have grid power available if I want it.
Sizing: This system is just the starting point for now. I want to at least double the number of PV panels over the coming years (there is still plenty of space on the roof), and then expand the battery storage as well. I chose the 10,000 model because of its throughput; I don’t want to keep the system’s “bottleneck” too small, so that the lights don’t go out when the heat pump or oven draws a lot of power. According to my calculations, this setup should get me through roughly mid-April to mid-October, and after the “full build-out”, I should be fully covered from February to November. From December to January, I’ll probably never be able to manage entirely without grid power or a generator.
Battery cables: Two Pylontech units are always connected together, with a cable connection to the busbar at both the “front and back”; in other words, each battery has a connection (with a switch/fuse).
Each MPPT has 10–11 panels with an open-circuit voltage of 35.21 V connected to it. According to the datasheet, the MPPTs can handle 450 V, so that should be fine. I distributed the panels among the individual trackers based on shading, so that I can get as much out of them as possible.
One more question about the ESS: If I use the system as described, do I need an ESS or not? As I understand it, I generally need the ESS to tell the system how to use the energy—for consumption, charging the battery storage, how far the batteries should be discharged (reserve), and so on? Or does that not matter when there is no grid connection, because the current flow regulates this automatically via the busbar anyway (apart from the shut-off setting once the battery reserve is reached)—in other words, power flows and is consumed, and if it isn’t consumed, it simply flows into the battery anyway?
The Pylontech cables are rated at 125 A, but only for up to 100 A.
All three MP10ks add up to 500 A net, probably around 575 A in reality.
That is very close to the batteries’ limit (600 A), and the cables (3 × 100 A) will certainly be overloaded.
The same applies to the three MPPTs 48/200.
I consider designing the system as a pseudo-off-grid system to be disadvantageous, since the inverter has to supply all the loads. With an ESS system, you can simply purchase the peak demand from the grid and keep the system considerably smaller (among other things because of the standby consumption of 33–38 W per MP).
Generally, an MP2 3000 or 5000 is entirely sufficient for a three-phase ESS in many cases.
At least for the time being, you can still sell the surplus electricity as well…
You can also take a look at the Conditional AC Input Control. Whenever the grid is available, I would always favour an ESS system.
From operating a genuine off-grid system with 25 kWp, one MP 8000 and 38 kWh of storage, I can only say this: far too much electricity in summer, far too little electricity in winter—in other words, the diesel generator chugs away beside the babbling brook.
If you can switch your house between the grid and the MP2’s AC_out, and AC_in cannot be connected to the grid, then you could use a power supply to recharge the batteries in winter. Have a look on eBay for Huawei or Eltek FlatPack 2 units.
Then your system would essentially be off-grid.
However, the definition of “island” is interpreted differently by each grid operator. We probably shouldn’t go into that again.
Thanks! @Dirk: I have 6 cables connected to the batteries, rated at 600 A, so it should be sufficient. I’ll see how I get on with the system, especially over the winter. In summer, I’d like to “refuel” the hybrid car with the surplus electricity (in winter, I’ll mostly drive it on diesel). Whatever I don’t have enough of in winter, I’ll draw from the grid, and then see how things develop after expanding the system further. It’ll need to evolve and be optimised over time…
Thanks for now and best regards, Franz
After switching on the batteries, check that the GX is receiving power and boots up; that gets the system’s brain running. Then bring the MPTTs online, and connect the grid last. I always wait/update after sunset, as this protects the switch contacts in the GAK.
The latest firmware, country code and configuration of the Multis can all be set up in advance without any stress. To do this, connect a power supply or battery to DC, then connect the MK3 adapter and laptop.
Maybe…
However you look at it, the more I think about the subject, the more I come to the conclusion that
there will never be a perfect general solution that meets everyone’s (needs),
there will always be too little or too much power somewhere or at some point,
opinions and views differ widely on this.
I’ve learnt from experience several times in life that going too small, too cheap or with too little headroom comes back to bite you later. (“Buy cheap, buy twice”). A friend is currently replacing his Multis with ones two levels higher, for precisely this reason. I calculated my maximum household load, added some headroom and made a decision. (As a “tinkerer”, I could live with having to think about when to switch which appliance on, but that’s less practical with a family — the power needs to flow just as it does from the mains. And if there isn’t enough, I’ll simply switch over). Apart from that, I’ll be expanding the system later, so I want the system’s “backbone” to work and still have some capacity in reserve.
But it’s all a matter of philosophy…
Many thanks again to you all for the tips!
Best regards, Franz
