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Аn idea to reduce self-consumption by a hybrid inverter.

Anatol

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Sep 3, 2022
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Hi,
There is an idea to reduce self-consumption by a hybrid inverter, but I don’t know how to put it into practice.
I am planning a solar system, for 2 hybrid inverters of 5 kW each. Basically, they will perform the function of a UPS, since power failures are rare, and the function of selling excess energy to the network.
The unpleasant moment is that the idle consumption will be almost 2.5 kW per day (for both inverters).
A good solution, I think, would be to turn on the bypass mode at night, when the solar panels are still not working early. The power circuits would be in an economical sleep mode, the MPPT controller would not work at all, and the battery would be connected only in the event of a critical voltage drop. But, unfortunately, for some reason, the bypass mode in the inverter is activated only in case of overload, it cannot be forced to turn it on.
The question is: is there any circuitry for manual, or even better, automatic transfer of the inverter to bypass mode at night, without primitive two-way mechanical switches?
I would be grateful for feedback, or for some similar implemented ideas.
 
How can a pair of 5kW inverters have an idle consumption of 2.5kW? That would mean that each has an idle consumption of a quarter of their full rated output. ?‍♂️
 
How can a pair of 5kW inverters have an idle consumption of 2.5kW? That would mean that each has an idle consumption of a quarter of their full rated output. ?‍♂️
I am sure he means kWh.

The SCC use very little self consumption . The inverter draws a fair amount. Most power is lost keeping the system ready to perform its functions. Everyone and their brother is trying on ideas to reduce idle self consumption.
 
What inverters?
I have two models available:
1. MUST POWER PV1800 PRO 5.2 кВт
https://www.mustpower.com/pv1800-pro-series-high-frequency-off-grid-solar-inverter-3-5-2kw/?utm_term=&utm_campaign=DSA广告-10.16&utm_source=adwords&utm_medium=ppc&hsa_acc=9913708007&hsa_cam=6782256161&hsa_grp=80698932638&hsa_ad=432461606353&hsa_src=g&hsa_tgt=dsa-19959388920&hsa_kw=&hsa_mt=&hsa_net=adwords&hsa_ver=3&gclid=Cj0KCQjwuuKXBhCRARIsAC-gM0gV_Tr-u3zrT6QPM6neGf4jspNC1pJqymGJsUQcfbn_87jo0DpicU0aAjx2EALw_wcB
2. MPP Solar V2-5048
https://www.mppsolar.com/v3/catalogs/HYBRID V_V2.pdf

Sympathy is a little more on the MUST side, since the manual indicates a slight resistance to inrush currents. Of course, this is not much, especially compared to inverters with toroidal transformer, but MPP Solar generally lacks such data.
Here are the figures for self-consumption per day:
1 A (idle consumption) * 48V * 24 hours * 2 inverters = 2.3 kW
Quite a bit of.
 
Like you, idle consumption is just ridiculous, it reminds me of fantom load. I have a MPP hybrid sitting on my bench, doing some testing. It seems the only way to eliminate the idle load is to turn that switch off. Since my configuration is strictly UPS like, I am thinking of using a simple AC relay to control the MPP switch: ON upon grid-outage, OFF with grid-on.

In fact I was thinking of also switching the PV-DC between the GT and the MPP, but am concerned with DC arching. Now I am wondering whether the PV-DC switching may not be necessary with the MPP main switch already controlled by the AC-relay. Can the PV-DC stay connected to both the GT and the MPP at the same time ? my GT is a Fronius ig3000. The GT promptly shut-down upon grid-outage, and slowly (rebooting/self-test) upon grid-on. Have to do this test on the bench. Thanks for triggering this aha moment.
 
If idle current is a concern it is better to look for an inverter that doesn't have such a high idle current. One of the costs of going with a "cheap" inverter. As example, my old Outback VFX3648 had an 18W no load consumption and they could be paralleled. Separate charge controllers like a Victron has no load current in the low mA range.
 
Over the past year or so I’ve been really interested in a 24v 3k growatt for our off grid cabin, but the more and more I’m looking at a Victron Multiplus because of the idle current. I already have a small Victron SCC 150/15 that is used to trickle charge the lifepo, so the AIO features of one box isn’t that big a deal for me.

This is a weekend cabin that may get used for a week or so at a time, so having 2 300w panels dedicated to idle consumption doesn’t make sense.

Sure costs are another story but I’m in no rush to buy now.
 
Over the past year or so I’ve been really interested in a 24v 3k growatt for our off grid cabin, but the more and more I’m looking at a Victron Multiplus because of the idle current. I already have a small Victron SCC 150/15 that is used to trickle charge the lifepo, so the AIO features of one box isn’t that big a deal for me.

This is a weekend cabin that may get used for a week or so at a time, so having 2 300w panels dedicated to idle consumption doesn’t make sense.

Sure costs are another story but I’m in no rush to buy now.

The cost of those panels and the cost of the unusable battery capacity adds up pretty quick making the Growatts substantially less attractive. Tack that on to the price of the Growatt, and it's likely to be higher than the MP since you already have the MPPT.
 
My inverter uses 70w. I was thinking of switching it out of the supply at night. I have a heavy duty 100a generator/mains switch that I could switch it out of the loop and then turn of the inverter.
 
My inverter uses 70w. I was thinking of switching it out of the supply at night. I have a heavy duty 100a generator/mains switch that I could switch it out of the loop and then turn of the inverter.
it may depend on the inverter brand, you would need to determine how to turn off your particular inverter. My bench test of the MPP U5648GK tells me that the inverter is on with grid AC-IN and PV-IN, regardless of the ON/OFF switch. It's completely off without AC-IN, PV-IN and switch OFF; BATT-IN can still be connected.

I've functionally tested with an external ATS to disconnect AC-IN & PV-IN and use the ATS' dry relay NC to also keep the inverter switched OFF. Upon outage, the ATS dry relay looses AC power, thus de-energizes and turns on the inverter. After ~13-sec boot-up, the inverter generates backup 240vac which then triggers the ATS to swap to backup mode, connecting PV-IN and transfer AC-OUT to the critical load sub-panel.

Here's a similar ATS, mine is a 4-pole for an extra $6
 
Well there are many possibilities depending on the type of the inverter, but as a transfer switch i can recommend using a light sensor (one with a nc and no connections) installed on the roof that feeds an off delay timer one that counts to 30 minutes which will activate 1 contactor (2 nc + 2 no) and 1 relay to function as an automatic transfer switch, the contactor will take 2 inputs, inverter output and mains electricity and the contactor's outputs will connect to the house's main box.
the relay will cut the power on the inverter after the signal from the timer is active

workflow will be as such:
the sensor will start to turn on and off as the sun is setting , thus the importance of a timer.
after 30 minutes of the sunset the timer will output the signal activating the contactor and switching to mains power
and the relay will disconnect any power feeding the inverter thus enabling to go into power saving mode as there is no power input and no load consuming about 30 to 100w from the batteries.
 
My inverter uses 70w. I was thinking of switching it out of the supply at night. I have a heavy duty 100a generator/mains switch that I could switch it out of the loop and then turn of the inverter.
70w * 24hours * 365days * $.15/1kwh ) = $92 a year or $7.66 a month.....is it worth your time?
 
Can you have an auto transfer switch kick the inverter on, treating the inverter like a generator? Then the inverter could in turn kick on a generator is absolutely necessary.

Now if you can get by with smaller loads, Victron Phoenix inverters have some really impressively low idle current.
 
Well there are many possibilities depending on the type of the inverter, but as a transfer switch i can recommend using a light sensor (one with a nc and no connections) installed on the roof that feeds an off delay timer one that counts to 30 minutes which will activate 1 contactor (2 nc + 2 no) and 1 relay to function as an automatic transfer switch, the contactor will take 2 inputs, inverter output and mains electricity and the contactor's outputs will connect to the house's main box.
the relay will cut the power on the inverter after the signal from the timer is active
plz share source link to the light sensor and delay timer, thanks
 
I have two models available:
1. MUST POWER PV1800 PRO 5.2 кВт
https://www.mustpower.com/pv1800-pro-series-high-frequency-off-grid-solar-inverter-3-5-2kw/?utm_term=&utm_campaign=DSA广告-10.16&utm_source=adwords&utm_medium=ppc&hsa_acc=9913708007&hsa_cam=6782256161&hsa_grp=80698932638&hsa_ad=432461606353&hsa_src=g&hsa_tgt=dsa-19959388920&hsa_kw=&hsa_mt=&hsa_net=adwords&hsa_ver=3&gclid=Cj0KCQjwuuKXBhCRARIsAC-gM0gV_Tr-u3zrT6QPM6neGf4jspNC1pJqymGJsUQcfbn_87jo0DpicU0aAjx2EALw_wcB
2. MPP Solar V2-5048
https://www.mppsolar.com/v3/catalogs/HYBRID V_V2.pdf

Sympathy is a little more on the MUST side, since the manual indicates a slight resistance to inrush currents. Of course, this is not much, especially compared to inverters with toroidal transformer, but MPP Solar generally lacks such data.
Here are the figures for self-consumption per day:
1 A (idle consumption) * 48V * 24 hours * 2 inverters = 2.3 kW
Quite a bit of.
At my MUST PV1800 3kW 24V VPM I measured following self consumption:

From battery:
- Bypass mode: 17W
- Inverter mode: 28W
- Standby mode: 1W

From the grid at any mode: 2W

All measured without load.

Discussed this with MUST support and they confirmed me, that PRO version has same or near the same consumption.
Could you measure it at yours MUST PRO at differetnt modes as I did please? Thanks
 
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