Do you know whether you had extra PV capacity at that time? It is difficult to know whether the inverter derated or the PV wasn’t available.
My 5kVA MPII ran at roughly 4.5kW form the DC side for an hour (3kW geyser + 0.75kW pool pump plus house idle between 0.15kW to 0.35kW). You can see the grid is zeroing around 20W (grid setpoint). For one 1min snapshot it went up to 200W, but it also corresponds to a small dip in the PV yield, so I think it was just the MPPTs looking for the optimal point again.
The above happens every day between 12:00 and 13:00 and I’ve not noticed it drawing from the grid. However, I’m also asking the inverter to do its full capacity (it is really easy to keep my house’s constant loads below 5kW), so perhaps that is why it can operate at 4.5kW for at least an hour.
if there was not enough pv, then the rest would come from the battery, not from the grid, and, yes, there was enough pv, i switched of the geyser for 15 minutes, upon switching it on again, the pv was back to 2700 watts, and not drawing from the grid and within half an hour it was derating again.
this was yesterday, bright, cloudless day in Cape Town
The battery voltage is at 52.4V and he’s got Pylontechs, so we know the MPPT is limiting on voltage (there is probably more PV available).
He’s got 2250W of load and he gets around 300W from the grid, which puts him just under 2kW actual production on the AC side. I would expect it closer to 2400W… so it does appear to be derating at this point.
Also note that the MPPT has to make around 200W more than is actually produced on the AC side to cover the balance. So he’s got about a 90% conversion efficiency there…
@Plonkster , is that normal for a standard Multiplus II or does it have anything to do with the Easysolar II GX having the mppt in the same housing and affecting cooling
I’ve heard at least one other person saying that the cooling is a little lacking with the MPPT in the same case. I can attest that I’ve never had issues with the older aluminium cased units. I ran a 1600VA unit at max power in a hot garage through 42°C summers with no derating, so maybe there is something to it.
The easy way to test it is put some extra airflow through it (just as a test), or open the case so it can breathe… or the lazy method would be to wait until autumn and see if it still does the same…
This is what I used to use: Root the GX device: https://www.victronenergy.com/live/ccgx:root_access Log in using SSH (Windows people use PuTTY) Run: dbus-spy (that’s a bit like regedit on a windows machine… don’t touch things you don’t know) Go to: com.victronenergy.vebus.whatever and scroll down to:
/Hub4/L1/AcPowerSetpoint - you can see the power level that is commanded by the GX device (how much it should feed into the INPUT)
/Ac/ActiveIn/L1/P - you can see the actual power being fed in.
Compare the two.
Divide /Ac/ActiveIn/L1/P with inverter VA to get % derating.
But surely the actual derating would happen on component temperature? If ambient is 25, but there’s a nice wind blowing, there should be much less derating as if ambient is 25 but there’s no wind blowing (ignoring the effect of the fan).
Correct - actual derating is based on component temperature.
Datasheet derating numbers are given based on ambient temperature, with no external cooling (eg wind) added.
This way, installers can know that if they install the inverter in a room, where the temperature does not exceed 25°C, then they can be sure the inverter will produce 100% power continuously, without derating.
The installer has no control over component temperatures - only the installation environment.
NOTE: Victron does not specify altitude derating factors. If the datasheet numbers are sea-level, then you can probably subtract 5-10°C from those on the derating table for the highveld.
I doubt that, Hot air rises, with the help of the fan the hot air is also forced out of the enclosure, if you look at the layout of the enclosure, the MPPT is already right on top with a plate between it and the inverter side. The chances of the heat transferring imo is very slim unless the fans blow down and not up…
As I understand it it is simply not available on VE.Bus. Adding it would require a modification to the entire pipeline (Multi firmware, VE.bus driver, log it to vrm, make it available via modbus-tcp, show it on the gui, etc). Also, it’s not a neutral element. Adding it will surely cause more questions for the support staff…
I agree with this, but heat is transferred by means of convection, radiation and conduction. I’m not sure how the Multi looks inside, but radiation heat goes in all directions and conduction would move inside materials.
Guess it could still be possible that the radiation could heat it up. Like standing in front of a braai. Typically you feel radiated heat, not the warm air.
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