Stand alone off grid solar charging, given CA &PG&E

[swngdncr]

That's what I don't get, the inverter and batteries seems excessive. But I don't understand this well enough. I have another solar company that is supposed to give me a quote, I was waiting to see what they come up with..

Why the 30kW of hybrid inverters and $20k in batteries?

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[Oneand0]

There are some other advantages of the off grid/ground mount idea. The panels are easier to clean, we can at the very least do the panel purchase and installation ourselves, for a lot less money. We can place them for maximum efficiency. No permitting from the County or PG&E, which when we expanded our rooftop solar was a major hassle. And no worry about PG&E rate increases. Do let me know what you find out on the buffer Mario... -cj-

So I asked the question on a DIY Solar forum, about the buffer for a battery connected to an inverter. Here is the link to my question, where an admin is answering my question. My monthly usage for my home is low, so I can get away with a 4K system for a back up off grid. I’ll let you know what they say. I can build my system for about $6500 without electrician fees to hook everything up properly. Buying used solar panels, $1500 inverter and about 1500 for a ground mount ballast using cement blocks and a $1500 5k old server battery.

https://diysolarforum.com/threads/newbie-setting-up-in-tahoe.42350/

 

[Avocadodude]

I can’t believe I haven’t participated in this thread. First off Will and DIY solar is a great internet resource.

I really don’t have a choice when it comes to charging my Lightning at my farm. I’m looking at ~70k to get electricity and grid connection so my situation is a little different. I have been running a small system to keep our trailer running. That system is getting a lot bigger (and will probably get repurposed). I am switching from 24vdc based 3000w 120vac system to a 48vdc dual inverter 240vac system. Panels were free on Craigslist. Not the strongest, but will do for now. 20kw of battery for the “mini grid”. Installing everything on/in 20’ shipping container. ~10k for everything, so for my situation it’s a huge savings (and as a bonus I’ll have enough juice to run the AC in the trailer).
I’ll definitely detail everything in the system and how the pro charger works. Trying to get through this heatwave so I don’t lose crop, so I’m a little slow right now.

 

[swngdncr]

Please do let us know when your system gets designed. I'm still trying figure out the battery side of things. I talked to a vendor who recommended 36KW hr of battery! Thats over $8K. That starts pushing the price of doing a solar charge station into the not cost effective range. He said that we'd need it to make sure that the batteries don't get run all the way down if cloudy etc. I explained that most of the time we can drive the car for several days before we'd deplete the battery and we'd have a backup charge in the garage for the occasions when we need more than the solar can provide. It seems to me that with proper settings on the charge controller, we can prevent the batteries from being overly depleted, isn't that what charge controllers are for?

I can’t believe I haven’t participated in this thread. First off Will and DIY solar is a great internet resource.

I really don’t have a choice when it comes to charging my Lightning at my farm. I’m looking at ~70k to get electricity and grid connection so my situation is a little different. I have been running a small system to keep our trailer running. That system is getting a lot bigger (and will probably get repurposed). I am switching from 24vdc based 3000w 120vac system to a 48vdc dual inverter 240vac system. Panels were free on Craigslist. Not the strongest, but will do for now. 20kw of battery for the “mini grid”. Installing everything on/in 20’ shipping container. ~10k for everything, so for my situation it’s a huge savings (and as a bonus I’ll have enough juice to run the AC in the trailer).
I’ll definitely detail everything in the system and how the pro charger works. Trying to get through this heatwave so I don’t lose crop, so I’m a little slow right now.

 

[Yellow Buddy]

For what you’re trying to do, the battery is irrelevant. I’ve got 2 solar banks. One is a standard grid tied system. The second is a hybrid system that can work grid tied or off grid.

Im using SMA Sunny Island inverters, they’re pricey new but you can find them used or from bankrupt solar companies at fractions of the cost. I purchased 5 inverters and used 4 of them to create a 20kW micro grid for $1500 total a couple years ago and I have them tied to two SMA solar inverters that connect to the solar panels. The Sunny Islands are also connected to a very small and cheap battery bank (4 AGM 100Ah batteries) as they do require a 48V bank to operate.

In off grid mode, the inverters will pull power from the batteries if there is not enough solar. I can program in my own shut off point so it won’t drain them. When the sun comes back up, it will automatically communicate with the solar inverters and start powering the panel, power is adjusted based on the needs and usage of that panel.

So as long as the charger for the truck is connected to that dedicated panel, this is a way to be able to make it work.As the panel powers up, the truck would start charging, so will the small battery bank. I can even connect additional loads and use load shedding to manage if/when and which car charges, I do this today with my Teslas.

This next part is theoretical…

The Sunny Island can also manage different inputs. Currently I have a generator connected to it. So if it’s not sunny, I can still power the panel from the generator.

The plan with the lightning if I don’t get the home backup inverter is to then install a generator input panel that I can plus the pro power into. That input would feed into the generator side of the Sunny Island, which has a transfer switch, disconnect, and software to switch over.

I don’t have the truck so idk if it’s always on but theoretically, it would be able to read my battery bank, see it has dropped to 60% capacity, shed the circuit that charges the lightning, trigger the call for a generator (pro power) to power other loads. When the sun comes up, the solar kicks on, disconnects the pro power, and reactivates the shed circuit and start charging the lightning again.

Not sure it will work, but it’s what I’ll be exploring before I go and pay sunrun..

 

[watchdoc]

SolarEdge also makes a Hybird inverter with EV charger built in. It appears to be expensive vaporware at this point since noone has them in stock (projecting 1st quarter 2023). Currentlly SolarEdge battery eco system kinda sucks though.

Level 1 charging would be like peeing in the ocean so Level 2 is the onlly thing worth while. I would try something like SOK or EG4 server batteries and a Growatt or MPP 240v inverter wired to a 14-50 outlet. PV alone wouldn't be able to keep up with the load. You're better off letting the inverter buffer with batteries. Panels are cheap, batteries are expensive.

$1500 EG4 battery (buy as many as your budget allows)
$900 Growatt 5000ES 240v inverter
$300 commerical 14-50 outlet and misc wiring and breakers
$3-$5k 6000 watts of PV panels to max out the Growatt solar input

The rest is just labor putting it all together.

 

[Avocadodude]

Please do let us know when your system gets designed. I'm still trying figure out the battery side of things. I talked to a vendor who recommended 36KW hr of battery! Thats over $8K. That starts pushing the price of doing a solar charge station into the not cost effective range. He said that we'd need it to make sure that the batteries don't get run all the way down if cloudy etc. I explained that most of the time we can drive the car for several days before we'd deplete the battery and we'd have a backup charge in the garage for the occasions when we need more than the solar can provide. It seems to me that with proper settings on the charge controller, we can prevent the batteries from being overly depleted, isn't that what charge controllers are for?

SolarEdge also makes a Hybird inverter with EV charger built in. It appears to be expensive vaporware at this point since noone has them in stock (projecting 1st quarter 2023). Currentlly SolarEdge battery eco system kinda sucks though.

Level 1 charging would be like peeing in the ocean so Level 2 is the onlly thing worth while. I would try something like SOK or EG4 server batteries and a Growatt or MPP 240v inverter wired to a 14-50 outlet. PV alone wouldn't be able to keep up with the load. You're better off letting the inverter buffer with batteries. Panels are cheap, batteries are expensive.

$1500 EG4 battery (buy as many as your budget allows)
$900 Growatt 5000ES 240v inverter
$300 commerical 14-50 outlet and misc wiring and breakers
$3-$5k 6000 watts of PV panels to max out the Growatt solar input

The rest is just labor putting it all together.

That one growatt will only give you 15amp capability from the charger (safely). They are stackable though, so might want to consider 3 to get to at least 40a capability. I've gone through a lot of back and forth on the inverter and decided on split phase capable 6548s (because I still need 120 and didn't want to add transformer). Still, that configuration will neuter (derate) the pro charger to ~40a, but in the future might and another pair of 6548s.

" Panels are cheap, batteries are expensive." Your not kidding, I found panels for free, haven't found a free battery yet , although real estate for panels is not free. So if I need to increase solar I will need to buy more efficient panels. I used the panel savings to buy 20kWh of batteries.

Hoping to use the three day weekend to set this up and do some current measurements with the travel charger while I wait for the Pro charger. That's with that I get my truck tomorrow.

 

[watchdoc]

That one growatt will only give you 15amp capability from the charger (safely). They are stackable though, so might want to consider 3 to get to at least 40a capability. I've gone through a lot of back and forth on the inverter and decided on split phase capable 6548s (because I still need 120 and didn't want to add transformer). Still, that configuration will neuter (derate) the pro charger to ~40a, but in the future might and another pair of 6548s.

" Panels are cheap, batteries are expensive." Your not kidding, I found panels for free, haven't found a free battery yet , although real estate for panels is not free. So if I need to increase solar I will need to buy more efficient panels. I used the panel savings to buy 20kWh of batteries.

Hoping to use the three day weekend to set this up and do some current measurements with the travel charger while I wait for the Pro charger. That's with that I get my truck tomorrow.

So a single LV6548 will run 240v@40 amps???? I thought you had to stack them for 240v output.

The LV6048 does 240v natively and will output 25amp I believe.

 

[Avocadodude]

So a single LV6548 will run 240v@40 amps???? I thought you had to stack them for 240v output.

You are correct, 2 are required. I am using 2 to start and see how well it performs charging, before considering a second set. I.e is 40a enough to support my daily mileage needs.

 

[watchdoc]

seems like anytime you have to step up to two unit and their associated wiring, you might be better off with a single 12kw inverter. Something like the Growatt 12kw??

 

[rlbussard]

Has anyone considered/looked into doing a dedicated off grid charging station for their EV? We have solar already, but we are not net 0. So, we'd have to add on, but the cost of upgrading our current system, running out of roof space, it would be expensive. Add to it PG&E's continuing effort to increase cost of solar and I"m thinking off grid might be the best option. We are on 2.5 acres and have plenty of room for a dedicated system with ground mount solar, with short run to a parking area on the driveway. I'm retired and can charge during the day. Saw a video about such a system that referenced this inverter: https://watts247.com/product/lvx-6048-hybrid-solar-inverter-split-phase-120v-240v/?wpam_id=3. Thoughts, complications? Thanks. -cj-

You should without a doubt do an off roof installation if you have the space. You will generate a lot more energy that with a roof mounted system. I have 24 solar panels that are ground mounted and am getting about 60-65KW generated a day even with these 100+ degree Texas days on non cloudy days. During the spring hours I can get more than 70KW in a day. My neighbor has a roof mounted system and gets much less than that. My solar people tried to talk me into doing a roof, but I already did my homework to know that ground mounts will get sun on the all day long unlike roof mounted panels.

 

[Avocadodude]

seems like anytime you have to step up to two unit and their associated wiring, you might be better off with a single 12kw inverter. Something like the Growatt 12kw??

I looked at that unit, but it is not expandable and I suck at predicting the future (or my original system would have included charging a Lightning). My charging calculation on that unit dropped to 32a. The wiring cost of adding additional inverters is pretty painless at this point.

It does simplify the installation and I like that it is split phase included (no transform needed). It could be the perfect choice for someone if the numbers work for them.

This will be the third evolution of my system so I'm really trying to build in expandability versus rip and replace (since I have 12v and 24v systems I'm now finding way to repurpose).

 

[watchdoc]

I looked at that unit, but it is not expandable and I suck at predicting the future (or my original system would have included charging a Lightning). My charging calculation on that unit dropped to 32a. The wiring cost of adding additional inverters is pretty painless at this point.

It does simplify the installation and I like that it is split phase included (no transform needed). It could be the perfect choice for someone if the numbers work for them.

This will be the third evolution of my system so I'm really trying to build in expandability versus rip and replace (since I have 12v and 24v systems I'm now finding way to repurpose).

what do you mean by charging calculation? The Growatt looks like it could push 40 amps with room to spare. I haven’t built a system like you have and I would be interested in seeing your calculations. Also, are you looking at a standard range truck with 9.6?

 

[Avocadodude]

what do you mean by charging calculation? The Growatt looks like it could pus 40 amps with room to spare. I haven’t built a system like you have and I would be interested in seeing your calculations. Also, are you looking at a standard range truck with 9.6?

At perfect efficiency the Growatt would deliver 50A total. 80% of that would be 40A (what you should draw across a breaker). The problem is I haven't seen an inverter with 100% efficiency (Growatt is listed as 88% peak efficiency), so 88% would put it at 44A and 80% of that is 35A. Again that's stating that the only thing you are running is the charger at the time. I'm sure you can push these limits and may never experience a failure. Also these limits are based on continuous operation numbers provided by the manufacturer, not the peak numbers (which are usually rated as sustainable for a couple seconds i.e Growatt is 36kW surge, 12kW continuous).

 

[Tenetke]

Ground mounting adds significant cost to a solar install. You might just add a second system (using the HIS) on the same meter (second subpanel?) and lease it from SunRun. They might eat any panel/service work needed. You could add all critical loads to the new HIS based system as well at the same time.

My ground mount wasn’t much more because it’s of the proximity to my meter. With my batteries online for the past two months my bill is around -$650. I wanted a solar and battery system that would power my entire home and two EV’s. So far it’s been doing that and I haven’t lost any power like my neighbors have in the past 3 months. Worth it to me.

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