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Must Inverter 5KW, 48V - Grid/battery/hybrid setup


bartalz

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Hi Team,

I was reading quite a bit around setup of the MUST inverters. I would like to ask some questions, maybe you can give me more light in to the darkness...

1. I want to have a SbU (1) - Solar/Battery/Utility setup

2. I like to use Solar power first on loads and after charging - LBU (5)

3. I want to charge the batteries only with solar power - OSO (10)

4. And if on top of the load and the battery charging I will have some energy left I want to send back to the grid - GRE (9)

For battery I have information from manufacturer LiON (14cellls - 3.3V cutoff and 4.1V max, 46.2V cutoff and 57.4V max)

My setup is: 17-57.3V, 18-57V, 19-46V, 20-47.5V, 21-54V

My issue is, when I set up GRE (9) -> it will check with LBU setup parameter 20 and if it is higher than 47.5V start to feed solar and battery power back to the grid. Which is not my intention to do.

Do you have any recommendation? Or any idea what could I set up differently(LBU/BLU)? Or maybe I'm completely wrong? Thank you!

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According to your settings, its working correctly, as described in the manual.

I guess you could try setting #20 to a higher value, since in SBU/LBU configuration it seems to be relevant only when grid is available:

SmartSelect_20230403-203238_SamsungNotes.thumb.jpg.ae3179fd8642b24b46cd33895594551b.jpg

If grid is not available, the low voltage cutoff setting #19 will be relevant.

I do wish there was another option to never discharge to grid from the battery, but there isn't.

It does make some sense though: if solar is enough to power loads and battery is "full enough" then you benefit from putting some of that extra power into the grid. I guess you just need to have a high enough setting for #20 (like 80-90% SOC). It makes sense for OSO, where battery is charged only from solar, so basically you are maximizing your solar power (minus losses from DC to AC conversion).

Not ideal, but that's what it is...

Edited by meetyg
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9 hours ago, bartalz said:

Hi Team,

I was reading quite a bit around setup of the MUST inverters. I would like to ask some questions, maybe you can give me more light in to the darkness...

1. I want to have a SbU (1) - Solar/Battery/Utility setup

2. I like to use Solar power first on loads and after charging - LBU (5)

3. I want to charge the batteries only with solar power - OSO (10)

4. And if on top of the load and the battery charging I will have some energy left I want to send back to the grid - GRE (9)

For battery I have information from manufacturer LiON (14cellls - 3.3V cutoff and 4.1V max, 46.2V cutoff and 57.4V max)

My setup is: 17-57.3V, 18-57V, 19-46V, 20-47.5V, 21-54V

My issue is, when I set up GRE (9) -> it will check with LBU setup parameter 20 and if it is higher than 47.5V start to feed solar and battery power back to the grid. Which is not my intention to do.

Do you have any recommendation? Or any idea what could I set up differently(LBU/BLU)? Or maybe I'm completely wrong? Thank you!

As @meetyg

suggested just set #20 as high as you want to keep the battery. As per #9 you enable exporting battery and PV to grid. It should keep the battery SOC high but export PV to the grid. 

As exporting to the grid is only allowed when you have grid it seems as #20 should work as you want it. 

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Hi,

my issue with that is, than I can't use my battery energy at night, what was the intention. I want to have not a backup, however more island solution. If I will setup 80-90% SOC it would mean that I'm not using my battery power at al, while he will feed back in to the grid 10-20% and after in the night he will stop discharging while I have grid power. Or maybe I'm wrong?

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4 hours ago, bartalz said:

Hi,

my issue with that is, than I can't use my battery energy at night, what was the intention. I want to have not a backup, however more island solution. If I will setup 80-90% SOC it would mean that I'm not using my battery power at al, while he will feed back in to the grid 10-20% and after in the night he will stop discharging while I have grid power. Or maybe I'm wrong?

But you decide if you want it 98% SOC then you only "loose" 100Wh. If you have a single cloud during the day you might "loose" 500Wh or more per cloud of PV-or on a bad day 10 times more. 

Sometimes equipment is designed in a way that does not suit all of us. 

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Hi, thank you maybe in this case I need to try it, however if I have the setup what is above and I set up 20 for 90% SOC. For me it would mean:

1. Feed back 10% battery power to grid, at day time after you charged the battery (sunny day)

2. Do not use anything from 90% battery at night time, when I want to use battery power, while I have grid power and don't want to drain below 90%.

Is this assumption wrong? Inverter will use the 90% SOC at night with this setup? Thank  you for your feedback

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1 hour ago, bartalz said:

Hi, thank you maybe in this case I need to try it, however if I have the setup what is above and I set up 20 for 90% SOC. For me it would mean:

1. Feed back 10% battery power to grid, at day time after you charged the battery (sunny day)

2. Do not use anything from 90% battery at night time, when I want to use battery power, while I have grid power and don't want to drain below 90%.

Is this assumption wrong? Inverter will use the 90% SOC at night with this setup? Thank  you for your feedback

When at 90% at sunset you can set priority to SBU so that you can use the battery power during the night. Next day PV will charge battery back if set to charge only from solar. All extra solar when battery is at 90% or whatever you set it to will be exported and battery kept at 90%. 

Here you have to decide to export solar or use some yourself for standing loads during the day. 

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1 hour ago, Scorp007 said:

When at 90% at sunset you can set priority to SBU so that you can use the battery power during the night. Next day PV will charge battery back if set to charge only from solar. All extra solar when battery is at 90% or whatever you set it to will be exported and battery kept at 90%. 

Here you have to decide to export solar or use some yourself for standing loads during the day. 

Thank you I will check that!

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To summarize for the the people who want to have similar setup (basically it works based on documentation):

1. With SBU/LBU/OSO setup it is not possible to feed just solar energy back to the grid. It will take/drain also the batteries.

2. In SUB/LBU/OSO it is possible to feed back just the solar power, however in this setup the battery is just active when utility power is not available

3. in SOL mode you can't use setup 9 feed back to grid, more island solution, with bypass possibility.

I tested out all of this options. Thank you for your comments.

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