Parallel Sungold 6548 inverters

[BillSF]

If I connect 2 (or 4) Sungold 6548 inverters in parallel, can I put AC grid power into the inverter as a low priority backup for keeping the batteries charged? Trying to understand the complications of ground / neutral when paralleling these units, especially with grid power as a backup.

This is for taking my house (mostly) off-grid...as such I don't want the system back feeding into the grid.

The goal would be to reroute / replace my house panel with system output only. The grid would then only be keeping the batteries topped off after days / weeks of cloudy days.

Since I have an EV (Leaf, 6.2 kW charge), electric: water heater (5 kW), stove (varies), and oven (and I'll probably add a mini split), I will probably be going with 4x 6.5 kW 6548 inverters so that I have plenty of room especially if I upgrade to an EV with 9kW to 11 kW L2 charging at some point. This will be with 4x 48V 5 kWh LiFePo batteries to start. I'm going with the Trophy batteries since they have built in heaters and my area gets a little below freezing (25⁰ to 30⁰ F) for a few to several weeks of the winter. Do I need a T-class fuse for a 20 kWh battery bank or is this still small enough to avoid that?

I have 5.6 kW in face value of used panels (mostly Santa Solar 250W panels), but I will probably buy 3kW to 4kW of new panels to mount on my roof and then ground mount the used panels with some kind of diy ground mount. New panels are partly to make sure the system is "new" in terms of getting the solar tax credit.

Note I get 6 or 7 hours of solar irradiance during the summer, probably 3 to 4 during the winter.

 

[Clifton]

If I connect 2 (or 4) Sungold 6548 inverters in parallel, can I put AC grid power into the inverter as a low priority backup for keeping the batteries charged? Trying to understand the complications of ground / neutral when paralleling these units, especially with grid power as a backup.

This is for taking my house (mostly) off-grid...as such I don't want the system back feeding into the grid.

The goal would be to reroute / replace my house panel with system output only. The grid would then only be keeping the batteries topped off after days / weeks of cloudy days.

Since I have an EV (Leaf, 6.2 kW charge), electric: water heater (5 kW), stove (varies), and oven (and I'll probably add a mini split), I will probably be going with 4x 6.5 kW 6548 inverters so that I have plenty of room especially if I upgrade to an EV with 9kW to 11 kW L2 charging at some point. This will be with 4x 48V 5 kWh LiFePo batteries to start. I'm going with the Trophy batteries since they have built in heaters and my area gets a little below freezing (25⁰ to 30⁰ F) for a few to several weeks of the winter. Do I need a T-class fuse for a 20 kWh battery bank or is this still small enough to avoid that?

I have 5.6 kW in face value of used panels (mostly Santa Solar 250W panels), but I will probably buy 3kW to 4kW of new panels to mount on my roof and then ground mount the used panels with some kind of diy ground mount. New panels are partly to make sure the system is "new" in terms of getting the solar tax credit.

Note I get 6 or 7 hours of solar irradiance during the summer, probably 3 to 4 during the winter.

I know, older post but I used a 200A DC breaker from Ebay, https://www.ebay.com/itm/222304797420. 15kw batteries. You can wire a 240v water heater as 120v and use 1/4 the watts. It will take longer to heat but reduce your inverter load. I did this and it works fine. I run timers on that and other large draw items ( pool, under sink water heater Main h20 heater, cooler for garage), slow start on a 3.5 ton a/c and a 240v dryer. on 2 6548's inverters. I rarley am above 54 ish % load.

I use grid to charge at night but only 2A but it can be more if you want. For battery charge you have solar only, solar + utility or solar then utility if no solar. The 3rd will charge at night to what you want.

 

[BillSF]

I know, older post but I used a 200A DC breaker from Ebay, https://www.ebay.com/itm/222304797420. 15kw batteries. You can wire a 240v water heater as 120v and use 1/4 the watts. It will take longer to heat but reduce your inverter load. I did this and it works fine. I run timers on that and other large draw items ( pool, under sink water heater Main h20 heater, cooler for garage), slow start on a 3.5 ton a/c and a 240v dryer. on 2 6548's inverters. I rarley am above 54 ish % load.

I use grid to charge at night but only 2A but it can be more if you want. For battery charge you have solar only, solar + utility or solar then utility if no solar. The 3rd will charge at night to what you want.

Hmm, interesting. It didn't occur to me that I could wire the water heater to 120V. I still need 240V for a well pump, but that makes reducing the load of the water heater even more beneficial.... Someone taking a shower is going to trigger both the water heater and well pump to turn on.

This house only has a 30 gallon water heater, but it is a weekend/vacation house for now. 30 gallons is essentially storing 9 to 10 kWh of heat based on how long it takes to fully heat from being off. Once I have solar installed, if I big a bigger cabinet and throw in an 80 gallon tank, that would be around 26 kWh of energy stored as heat and it reduces the visibility of slowly heating at only 120V

 

[BillSF]

Hmm, interesting. It didn't occur to me that I could wire the water heater to 120V. I still need 240V for a well pump, but that makes reducing the load of the water heater even more beneficial.... Someone taking a shower is going to trigger both the water heater and well pump to turn on.

This house only has a 30 gallon water heater, but it is a weekend/vacation house for now. 30 gallons is essentially storing 9 to 10 kWh of heat based on how long it takes to fully heat from being off. Once I have solar installed, if I big a bigger cabinet and throw in an 80 gallon tank, that would be around 26 kWh of energy stored as heat and it reduces the visibility of slowly heating at only 120V

I probably have 60 to 80 ft of rise on my property from the house to the top of the hill. At some point I'm going to try to setup at least a 275 gallon tank up the hill so I can store more energy that way (not necessarily power storage, but to still have water pressure even if there's no solar and my batteries are drained)

 

[Clifton]

Hmm, interesting. It didn't occur to me that I could wire the water heater to 120V. I still need 240V for a well pump, but that makes reducing the load of the water heater even more beneficial.... Someone taking a shower is going to trigger both the water heater and well pump to turn on.

This house only has a 30 gallon water heater, but it is a weekend/vacation house for now. 30 gallons is essentially storing 9 to 10 kWh of heat based on how long it takes to fully heat from being off. Once I have solar installed, if I big a bigger cabinet and throw in an 80 gallon tank, that would be around 26 kWh of energy stored as heat and it reduces the visibility of slowly heating at only 120V

We a 40 gallon heater. It's on a timer for 1 hour a day at 10 am. It's enough for two people to shower in the summer at 5 pm or in the morning. In the winter I turn the tank temp up and the timer but it holds the temp long enough. We use a 2.5 gallon 120v tank under the kitchen sink. On a timer too, on at 8 am, off at 4pm. I did the hot water heater to 120v and a 120v pool pump before going solar to see how load I could reduce even if needed to runthem longer.