backup inverter for longer grid outages

[JimP]

Let's say I have a grid tied sol-ark 15K with 30kwh of 48v batteries.

If there is a long term grid outage, what is the best way to economically have a backup solar charger/inverter on hand? Another 15K would be great, and maybe that will happen along with 2 or 3 more strings of panels in the future, but in the mean time, is there any way to realistically swap in a lesser solar charger/inverter (doesn't need to be 15K - ~5K would be a LOT better than nothing to keep some lights, fridge/freezer, starlink going). I know I'd have to jury rig some of the connections in that situation. Turn off the exterior AC disconnect, hook up the backup to the bus bars on the batteries, and move a string or two of panels to the backup, and backfeed a breaker on my critical load panel from the backup inverter load output.

I would want to hook it all up once to test it and make sure I have everything needed to hook it all up, and then hopefully never have to use it again. Having to spend a few hours to switch over would be fine.

Any thoughts?

 

[eod1991]

Why do you need an extra inverter. The solark can run off grid by itself. That way you can use your same inverter but in off grid mode.

 

[Crowz]

Well one tp6048 will do 6kw worth of load. So you could have one of those cheaply to run at least 6k of your needs.

But considering how much the solark cost you could have 2 tp6048's in a parallel setup and that would run your entire load in the event of a problem. Just have a transfer switch on the solarks ac input to switch to the tp6048's inputs and you can do the same on the pv and battery too.

Now all of that I just typed is in case the solark fails which you elude to in your post but you also state grid outage so why not just run on the solark in the outage?

 

[hwy17]

This is a backup like for in case the Sol Ark dies?

 

[Tulex]

OP is saying that if there is a long term outage, they want a backup inverter incase the Sol-Ark fails. Yes, the Sol-Ark has a 10 year warranty, but that doesn't help when getting it repaired/replaced during grid down.

I actually plan to add AC coupling to my 15K (DC will be full) with a yet to be determined inverter. A major consideration for the inverter will be, can I temporarily swap out a few wires and bypass the Sol-Ark if it fails.

 

[JimP]

Why do you need an extra inverter. The solark can run off grid by itself. That way you can use your same inverter but in off grid mode.

As a backup for the sol-ark failing of course. Two is one and one is none.

 

[JimP]

This is a backup like for in case the Sol Ark dies?

Exactly

 

[mkimid]

Exactly

Maybe a portable generator should be better, and 33kWh is too small I guess

 

[JimP]

Maybe a portable generator should be better, and 33kWh is too small I guess

30 kwh will last me several days, maybe a week, without water heater or hvac.

"long term grid outage" means "run out of fuel for generators" (I have two, one gas and one propane). Think weeks or months. Basically indefinitely.

 

[mkimid]

30 kwh will last me several days, maybe a week, without water heater or hvac.

"long term grid outage" means "run out of fuel for generators" (I have two, one gas and one propane). Think weeks or months. Basically indefinitely

i am using XW pro with 30kWh for temporary backup, and using a fuel generator for long term back-up. I have 8kW, and average power usage is 16kWh/day, worst solar energy (cloudy & rainy days) is 6 days in my place, and storage demand is 106kWh (it means, I need 106kWh*110% to be independent from grid). While continuing sunny day, need to fully charge the battery, and keep loosing power while continuing cloudy day.if you are using a generator to add a power on battery while cloudy day, that is a good idea also, I should try also.
in NJ. maximum back-up time is around 6 days under 20% solar generation, and 3-4 times in a year, if have 6 gallons gas, I can make-up +50% of battery capacity, so, if I keep, 20-30 gallon gas, I can standing a year without grid power.

 

[OffGridForGood]

More like the question is: "What is a reliable, low cost inverter, I can store just in case my 18kpv were to fail during a long term grid outage".

you could have a spare 18kpv but these are pricy.
you could have a 6k in storage, and hook it up if/when needed for about half the cost. but maybe never use it.

Another way: have a smaller more portable complete system that you actually use (and then you know it works) put it to work around the yard - far from regular outlets, put it to work during camping/fishing trips. If you pick a smaller inverter that can still use 48 volt, then all the batteries you have can still be used.

 

[rhino]

How much are you willing to spend? Are you looking for an all in one that has both solar charge controller and inverter? If that's the case would consider a EG4 6000XP which is around $1400. If you want to install something so that it can actually be used fairly easily you could install a manual transfer switch so you can have both system connected and just manually switch between them.

 

[JimP]

How much are you willing to spend? Are you looking for an all in one that has both solar charge controller and inverter? If that's the case would consider a EG4 6000XP which is around $1400. If you want to install something so that it can actually be used fairly easily you could install a manual transfer switch so you can have both system connected and just manually switch between them.

Under $2000 if possible. I don't want a $7000 Sol-Ark 15K sitting on the shelf for sure. Although that would be good EMP protection

Both charger and inverter.

I don't mind rewiring if/when it becomes necessary. The PV wires aren't difficult to move (and extend if needed). With a ~6K inverter I'd probably only connect 2 strings 4.4KW strings in the winter, and one in the summer. If the outage looked to be indefinite I'd probably shorten the strings to maximize PV wattage. Need to remember to have extra PV wire and some connectors, just in case. The main panel after the sol-ark will have a 30A/240V gen input, so hooking up the spare inverter can be done using that path.

 

[Shimmy]

One approach is to use a second system as a critical loads inverter with interlocks to be able to energize everything with either system for such a scenario... with proper load management.

 

[JJJJ]

A consideration is critical systems versus whole house. Some have built portable units that could be moved to a fridge or freezer as needed. This might be too small for your needs.

 

[Jbird905]

OP is saying that if there is a long term outage, they want a backup inverter incase the Sol-Ark fails. Yes, the Sol-Ark has a 10 year warranty, but that doesn't help when getting it repaired/replaced during grid down.

I actually plan to add AC coupling to my 15K (DC will be full) with a yet to be determined inverter. A major consideration for the inverter will be, can I temporarily swap out a few wires and bypass the Sol-Ark if it fails.

I have a similar situation. My 15k DC side is maxed out, and I have roughly 8kW of panels ready to AC couple. At first, I was going to use micro inverters, but for 20 400+ watt panels, it's $2000, IF I can get them for 100/each. We're pretty well eating into the cost of another inverter here.

So, if I get another inverter to AC couple into the 15k, I have a "backup," that wouldn't just sit on a shelf. And I can use the extra DC parts I already have. And I'm not dealing with Enphase. I wish it could be another Sol Ark, but not at 15k prices.

Tulex, have you found inverters you're thinking of using for your setup?

 

[DIYrich]

I would parallel two 15k's. If one goes down, take it offline and reprogram the working one to be solo.

 

[Tulex]

I have a similar situation. My 15k DC side is maxed out, and I have roughly 8kW of panels ready to AC couple. At first, I was going to use micro inverters, but for 20 400+ watt panels, it's $2000, IF I can get them for 100/each. We're pretty well eating into the cost of another inverter here.

So, if I get another inverter to AC couple into the 15k, I have a "backup," that wouldn't just sit on a shelf. And I can use the extra DC parts I already have. And I'm not dealing with Enphase. I wish it could be another Sol Ark, but not at 15k prices.

Tulex, have you found inverters you're thinking of using for your setup?

I'm not that far along, that's likely an end of next year project.

 

[n2aws]

Under $2000 if possible. I don't want a $7000 Sol-Ark 15K sitting on the shelf for sure. Although that would be good EMP protection

Both charger and inverter.

This seems like a perfect use-case for the EG4 6000xp. 6kw of output, offgrid and 2 MPPTs. $1300. solid hardware. At this price, it seems like a solid "put in metal trashcan for the WhatIf kinda days". 2 of them, and you could likely run the majority of your house indefinitely should things really go sideways.

 

[JimP]

This seems like a perfect use-case for the EG4 6000xp. 6kw of output, offgrid and 2 MPPTs. $1300. solid hardware. At this price, it seems like a solid "put in metal trashcan for the WhatIf kinda days". 2 of them, and you could likely run the majority of your house indefinitely should things really go sideways.

Looks like it would fit as a partial, off-grid, 15K replacement pretty easily. 2 480V PV instead of 3 500V MPPTs would be fine.