AC Inverter / Prioritize Solar -> Battery -> Grid

[Mark1988]

Hi All,

I'm working on my first solar system and wanted to ask you to help me pick an inverter that would be able to automatically prioritize which data source gets used to power my house like this: solar panels -> battery pack -> the grid.
Please note that I am not interested in exporting any electricity back to the grid AND I want to only charge my battery pack using solar (and not the grid).

I've come up with 2 basic designs:
Option 1: Includes a separate Victron charge controller, and
Option 2: No separate charge controller

Which of these two make more sense and can you recommend any specific inverters that would allow me to prioritize which power source gets used first please?

Thank you,
Mark

 

[K8MEJ]

You didn't say where you live. That matters a lot in terms of voltage and frequency of your mains and expected amount of solar irradiance. Are you sure you never, ever would want to charge the batteries from the grid? Hopefully you live somewhere with consistent solar to keep your batteries charged and don't have to suffer through a day or two of cloudy weather. You also don't mention what you hope to power in your house. That said, let me 'splain what I have in my RV:

My travel trailer is a 28 foot bunkhouse. I replaced the roof top air conditioner with a 12k BTU mini-split to conserve power. It has a 30amp input with only one leg of 120v power. I use all Victron gear: MultiPlus 12v/3000/120-50, two solar MPPTs, Cerbo GX (main controller), 7ish KWh of battery, 1.6KW of roof-top solar, 300 watts of ground solar, etc. I have my system programmed to prioritize solar but allow grid power under a couple of conditions. One condition is based on state of charge (SOC) of the battery bank and the other is sustained high AC loads. I have also wired in a physical SPST switch to force the AC battery charger inside the Multi to charge the batteries. About the only time I would want to do that is when I want to ensure my batteries are fully charged before going on a trip or if I know I will have some cloudy weather and no connection to the grid (or a generator) at my destination.

Even if you're absolutely sure you'd never want to charge the batteries from the grid, you'll likely need a transfer switch. In the case of Victron, I would suggest you go for a Multi even though it has a charger for the integrated transfer switch. Both the Multi and Phoenix inverter are programmable as I mentioned above. If you pair it with a GX device (I like the Cerbo), then you have an easier means of programming the conditions I mentioned above, but you can still do it without a GX device.

Now, depending on your voltage needs, size of loads, solar irradiance, daily consumption, etc., you'll pick and choose capacities of the equipment you'd need. For example, if you live in North America where we have split-phase power 120/120/240 volt, and you want to power any 240v loads, you'll need at least two Multis (maybe more depending on how many VA you need).

Certainly there are other OEM options you can choose from, but I prefer Victron right now.

Also, I have another 7ish KWh of battery that should be here in a week or so (I've been saying that for 3 weeks!) because even in my camper, 7KWh of battery is not enough for me to be able to run air conditioning and survive one cloudy day here in hot, humid Ohio.

Have you performed a thorough power assessment for your needs?

For option 2, maybe look into some of the all-in-one units. Growatt, MPP, and SolArk seem to be popular on this forum but I don't have any real-world experience with them.

 

[Goldriver]

You didn't say where you live. That matters a lot in terms of voltage and frequency of your mains and expected amount of solar irradiance. Are you sure you never, ever would want to charge the batteries from the grid? Hopefully you live somewhere with consistent solar to keep your batteries charged and don't have to suffer through a day or two of cloudy weather. You also don't mention what you hope to power in your house. That said, let me 'splain what I have in my RV:

My travel trailer is a 28 foot bunkhouse. I replaced the roof top air conditioner with a 12k BTU mini-split to conserve power. It has a 30amp input with only one leg of 120v power. I use all Victron gear: MultiPlus 12v/3000/120-50, two solar MPPTs, Cerbo GX (main controller), 7ish KWh of battery, 1.6KW of roof-top solar, 300 watts of ground solar, etc. I have my system programmed to prioritize solar but allow grid power under a couple of conditions. One condition is based on state of charge (SOC) of the battery bank and the other is sustained high AC loads. I have also wired in a physical SPST switch to force the AC battery charger inside the Multi to charge the batteries. About the only time I would want to do that is when I want to ensure my batteries are fully charged before going on a trip or if I know I will have some cloudy weather and no connection to the grid (or a generator) at my destination.

Even if you're absolutely sure you'd never want to charge the batteries from the grid, you'll likely need a transfer switch. In the case of Victron, I would suggest you go for a Multi even though it has a charger for the integrated transfer switch. Both the Multi and Phoenix inverter are programmable as I mentioned above. If you pair it with a GX device (I like the Cerbo), then you have an easier means of programming the conditions I mentioned above, but you can still do it without a GX device.

Now, depending on your voltage needs, size of loads, solar irradiance, daily consumption, etc., you'll pick and choose capacities of the equipment you'd need. For example, if you live in North America where we have split-phase power 120/120/240 volt, and you want to power any 240v loads, you'll need at least two Multis (maybe more depending on how many VA you need).

Certainly there are other OEM options you can choose from, but I prefer Victron right now.

Also, I have another 7ish KWh of battery that should be here in a week or so (I've been saying that for 3 weeks!) because even in my camper, 7KWh of battery is not enough for me to be able to run air conditioning and survive one cloudy day here in hot, humid Ohio.

Have you performed a thorough power assessment for your needs?

For option 2, maybe look into some of the all-in-one units. Growatt, MPP, and SolArk seem to be popular on this forum but I don't have any real-world experience with them.

Hi
I have a quite similar system as yours ( multiplus II, 150/85 mppt’s, 1.5kw roof solar, 300 watt portable solar, Cerbo and 7kw batteries) I am a new year in this world and I am struggling to configure my system to prioritize solar over grid in my rv. I am in Canada by the way.
Would you be kind enough to share in details how you have programmed you system do do so ?
Remember, I am new to this but ready to work hard to learn, I would much appreciate the more detailed steps possible.
Thank you so much,