diy solar

diy solar

Having trouble deciding between inverters...

Lt.Dan

Solar Wizard
Joined
Dec 25, 2020
Messages
3,567
Location
Tulare, Ca
Hey guys, I know I've gone back and forth SO many times between my choice on inverter/charger/scc. I need some help!

Its going in my RV, I live full time, and want to use less power and reduce my bill from the grid (Which is on average 1200kWh every month). I know I want the inverter to support split phase input and output w/ 48v DC input. I have my 272ah cells coming from Michael already and I'm getting closer and closer to pulling the trigger on my inverter, but I dont want to regret it! lol

I originally wanted 2x LV3048 MPP Solar inverters, which really gives me everything I need, including 2x PV inputs (I will have a PV Array on top of the trailer, and on top of a metal building I park next to), but its lacking in the surge power capability, high idle consumption and mounting 2 units and wiring 2 units is a little bit of a bummer.

Then I really turned my attention to the Growatt SPF 6000T that watts247 sells. Its a transformer unit with great surge capacity, a better UI, better warranty, and is a stand alone unit. Downside being a stand alone unit, and it only accepts 1x PV input with a max 150v. Also, with it having a transformer, its HEAVY!! The new Growatt 12000T has 2x 250v PV inputs which is really appealing, but its even heavier, and is twice the cost.

Now I'm looking at Victron units, plain and simple because of their reliability and well know company for putting out great products... at a price. So far the MPP and Growatts are both under $1500, which I really like, but both have their own downsides. Victron I understand will require 2x units like the MPP LV3048 units, which raises costs alone much higher than the others, but again, superior quality. Then I would have to get a separate SCC, which again adds more cost and more wiring, more space required, etc.

Does the Victron unit even give the options to prioritize power like the MPP or Growatts? Like I want it to mainly use PV to power stuff (when available), then use inverter the rest of the time until the battery gets low, then switches to Grid? If the Victron doesn't offer this, its more than likely out for me.

Any other manufactures or models you guys recommend? I'm not afraid of spending more if the cost is worth it! ROI is important, but not a deal breaker.
 
Also consider the Schneider CSW 4048.


I bought mine from them online without consultation but they get good reviews from folks who call and ask for free advice. Take advantage of that service.

You will need to add a ComBox or Gateway to get full communication and adjust settings.

One nice feature is that the 4048 has a built in auto transformer so you can feed it with 240v mains power or 120v generator power and it will put out 240v.

Since you’re using 48v Victron makes a relatively cheap 48v SCC:


You might need one for each of your arrays but make sure 100v is high enough for your use in cold weather.
 
Last edited:
Seems like both of you have recommended to seperate inverter/charger from the SCC, any reasoning behind that?

The Victron 100/50 is not really good enough for me, as I'd like to have 38VOC panels in 2x 3s5p which is 114v~. Ideally I'd like to have a 250v MPPT so I can run them in 2x 5s3p instead. And that is just the array that will be on the metal building I park next to, not including the panels on the roof of the trailer.

After reading that victron page about prioritizing solar, it still doesn't give me the warm fuzzy feeling that I wanted about prioritizing power.

I really like the Victron Inverter RS Smart Solar, but its 230v output w/ 50hz. So I would need an auto transformer on both the input and output... arg! Why is it all the good equipment has the wrong voltage! Lol
 
Seems like both of you have recommended to seperate inverter/charger from the SCC, any reasoning behind that?

For me I just don't like having all my eggs in one basket.

I also don't see that many of the higher quality equipment manufacturers doing the all in one thing.

Also, I have changed my SCC needs before and never know if I will again.

It's much easier to adjust your well laid plans that life laughs at when you have the ability to change one part.
 
I'm looking into the Growatt 6000T and 12000T further, and notice they only accept 240v single phase input, which is fine for grid because after speaking with Ian, I can common the neutral with the neutral output. But, my generator has L1 and L2 that are in phase with each other, so they will not create 240v. I've emailed Ian back, so we'll see.

I jumped on MPP Solars website and found this though; LVX6048, and I gotta say, I'm pretty much sold. 450V PV input, built in wireless, split phase capable in/out, 6kw inverter. I'm going to hit up Ian and see if he can get one because I see their relatively new. If he can't I'll probably be ordering one direct.
 
Some back and forth with Ian we confirmed the generator will not work with the Growatt units. So they are out. He said neither the MPP or Growatt can accept a different voltage input from the output.

He's now recommending i get the new LV6548 and just run 120v, and tape up one of the phases coming in from the grid. This allows charging from either the generator or the grid, but does not allow the full 100 amps from the grid if I need it.

Any ideas? A transformer on the output of the generator to convert to Split phase? A bypass switch (transfer switch?) to bypass the inverter and allow the full 100 amps straight to the breaker panel when I need it?
 
Also consider the Schneider CSW 4048.


I bought mine from them online without consultation but they get good reviews from folks who call and ask for free advice. Take advantage of that service.

You will need to add a ComBox or Gateway to get full communication and adjust settings.

One nice feature is that the 4048 has a built in auto transformer so you can feed it with 240v mains power or 120v generator power and it will put out 240v.

Since you’re using 48v Victron makes a relatively cheap 48v SCC:


You might need one for each of your arrays but make sure 100v is high enough for your use in cold weather.
Looking more at the Schneider, it fits the bill nicely especially being able to charge from 240v Grid and 120v Genny power. Only downside is its a little underpowered for me with only 1 unit, and I should get 2, but maybe I'll get 1 at first and upgrade later.

The SCC options are limited. I'm going to want somewhere between 24-30 PV panels, w/ 38VOC and 250Watts, so a 100VOC SCC like the Victron you posted is severely under powered. Victron makes a 250v 100amp for $932!!!! Cheese and rice thats expensive! In all reality, I can use 3x 150V 35A SCC, but even they are $325/ea. (Somehow, 150v X 35a = 5250watts, but they limit at 2000w for 48v battery? Wow.)
 
Looking more at the Schneider, it fits the bill nicely especially being able to charge from 240v Grid and 120v Genny power. Only downside is its a little underpowered for me with only 1 unit, and I should get 2, but maybe I'll get 1 at first and upgrade later.

The SCC options are limited. I'm going to want somewhere between 24-30 PV panels, w/ 38VOC and 250Watts, so a 100VOC SCC like the Victron you posted is severely under powered. Victron makes a 250v 100amp for $932!!!! Cheese and rice thats expensive! In all reality, I can use 3x 150V 35A SCC, but even they are $325/ea. (Somehow, 150v X 35a = 5250watts, but they limit at 2000w for 48v battery? Wow.)

Your 150V * 35A is not valid.

35A is the battery charging current. 48V * 35A = 1680W (but its higher because the peak battery voltage is higher).
150V is the absolute maximum PV INPUT limit (Voc), and panels can't operate at that voltage. They operate at lower voltage (Vmp vs. Voc).

A 250/100 will handle 5900W, and it can be overpaneled substantially. I love mine. In the end, I will have just under 6kW attached to it (18 330W panels).

You can likely get away with a $150 cheaper 150/100 unit if you go 3S8P.

The Schneider unit linked can't handle as much as the 150/100 or 250/100 power-wise. It's only an 80A charger (probably around 4800W). The difference is it can handle up to 550Voc input, and it costs WAY more. If you need to have a ridiculously long wire run from your array to your SCC, they are a good choice.

This stuff is expensive. If you're really lucky, you might break even in 3-5 years vs. grid. You use more than the average U.S. house, so it ain't going to be cheap, and 40kWh/day is going to need more than 6kW of panels.

Have you actually run the numbers?

Have you bought at least 48 272Ah cells?
 
Your 150V * 35A is not valid.

35A is the battery charging current. 48V * 35A = 1680W (but its higher because the peak battery voltage is higher).
150V is the absolute maximum PV INPUT limit (Voc), and panels can't operate at that voltage. They operate at lower voltage (Vmp vs. Voc).

A 250/100 will handle 5900W, and it can be overpaneled substantially. I love mine. In the end, I will have just under 6kW attached to it (18 330W panels).

You can likely get away with a $150 cheaper 150/100 unit if you go 3S8P.

The Schneider unit linked can't handle as much as the 150/100 or 250/100 power-wise. It's only an 80A charger (probably around 4800W). The difference is it can handle up to 550Voc input, and it costs WAY more. If you need to have a ridiculously long wire run from your array to your SCC, they are a good choice.

This stuff is expensive. If you're really lucky, you might break even in 3-5 years vs. grid. You use more than the average U.S. house, so it ain't going to be cheap, and 40kWh/day is going to need more than 6kW of panels.

Have you actually run the numbers?

Have you bought at least 48 272Ah cells?
That makes more sense for the battery voltage, I was pretty burnt out when looking at them lol.

I did run the numbers, at 42kWh/day, but about 40% of that is during Sun Hours (I have 2 toddlers and a wife that are always home, so they use up a ton of power during sun light) and about the 37% of the remaining power used is from space heaters at night, which winter time is coming short soon, and I can also start using the propane furnace instead.

So that leaves roughly 10kWh with needing battery power per day, but to be super conservative id say 20kWh. I have 16x 272ah cells on the way, and I do plan on 16x more in the next few months.

Also, im not dead set on being 100% independent. If I have to supplement with the grid, then that's fine. I'll still be cutting my bill by a considerable amount.

There is 1 reason why ROI isn't as important is because we take the trailer out to the desert/sand dunes, etc, where there is no grid, and having solar/inverter while being out there just makes it a little easier, especially with less generator usage, so its a win/win for us.
 
I have a hard time believing those numbers unless you've seen the hourly use. Electric space heaters are horrifyingly costly to an off-grid system.

IMHO, trying to base your battery size off your anticipated nightly use is sketchy at best. Most recommend you size your battery for 24 hours of daily use. Electric heat and A/C power requirements are devastating.

Probably worth running a sanity check on your usage via an energy audit if you haven't done so.

I'm not trying to be obstinate or argumentative - I'm just encouraging you to be certain of your numbers.
 
I agree electric heat is horrifically expensive, but here in Central California, nights are already barely getting down to 45*, and Southern California Edison (our energy provider) does give us hourly breakdowns online. I can check every day for the last year (I think). Also, im starting to shut off the electric heaters and run the propane furnace instead. Im even running our fridge and water heater on propane instead also (which im sure is another big hit of energy usage)

I do agree I should shoot for more battery storage, as I would like to have 48 hours, or a minimum of 24 hours of backup power.

I dont think you're being argumentative at all, and I hope I don't come off that way either. I enjoy others reminding me to think! Lol

Just to check my math, I run a 1500 watt heater in the kids room (kill a watt confirmed runs at 1300watts) and a 500 watt heater in our room (kill a watt confirmed at 450watts for a total of 1750 watts) from roughly 9pm to 6am every night. I think that adds up to around 16kWh right? About 38% of my daily usage.
 
Sounds good. A typical RV fridge on electric can use 5kWh/day. I've watched it happen on VRM. 1.5 hours on, 45 minutes of... 16 hours @ 300W.

You didn't come off as argumentative. I can come off as a dick sometimes, and I don't always recognize it. :)

Math: 1750 * 9 = 15.75kWh

Does your RV A/C run as a heat pump too? Good chance that would use less power than those space heaters. One unit runs 1500W, and it shouldn't run all night (as your heaters likely don't either).

Our oldest is living in our Class A saving some dough, and he's keeping it warm with only 1 of the 2 heat pumps running.
 
Sounds good. A typical RV fridge on electric can use 5kWh/day. I've watched it happen on VRM. 1.5 hours on, 45 minutes of... 16 hours @ 300W.

You didn't come off as argumentative. I can come off as a dick sometimes, and I don't always recognize it. :)

Math: 1750 * 9 = 15.75kWh

Does your RV A/C run as a heat pump too? Good chance that would use less power than those space heaters. One unit runs 1500W, and it shouldn't run all night (as your heaters likely don't either).

Our oldest is living in our Class A saving some dough, and he's keeping it warm with only 1 of the 2 heat pumps running.
You are 100% right on the fridge! Its amazing how much it uses, and ill be looking into doing the compressor conversion in the future after I get the inverter/solar situated. Im already emailing JC Refrigeration back and forth about it.

Yes the heat pumps are more efficient, but only when above about 42*~ ive found. Now this is for ours, as I know a lot of people claim theres is good in 35* weather, but when it gets down to 42* ish, it's not pumping very hot or even very warm air for that matter, so I only use it when 42*+. We also only have 1 heat pump in the main zone and we have 3 zones total so its a little underpowered imo.
 
Sounds like you're on top of things.

I don't think I'll ever do the JC Refrigeration route, but there are 24" residential fridges that almost drop in with a little tweakery, seal and trim work. The last one I looked at actually had 10 cu-ft in the same space as my 7.6 cu-ft unit due to the volume the absorption cooling unit occupies (whole back of fridge), and was rated for 327kWh/year. With the JC option, you don't get to use the extra space.
 
Sounds like you're on top of things.

I don't think I'll ever do the JC Refrigeration route, but there are 24" residential fridges that almost drop in with a little tweakery, seal and trim work. The last one I looked at actually had 10 cu-ft in the same space as my 7.6 cu-ft unit due to the volume the absorption cooling unit occupies (whole back of fridge), and was rated for 327kWh/year. With the JC option, you don't get to use the extra space.
The JC Refrigeration thing is sort of a double edged sword. I have a Norcold 2118 18cu-ft fridge in our trailer now, decent size, but not very deep at all. The plus side to converting it to compressor style is no extra work, (I am NOT a wood working guy!) no trim work, no modifying brackets to put it in. On top of that, I have a kitchen island, and when the fridge slide is all the way in, theres only about 1/8" between the fridge and one of the island drawer handles! So I have to be really careful on which fridge I can put in there, especially if there is handles that stick out or anything.

But the flip side of that, is the compressor conversion is ~$1000!! Thats the cost of a decent residential fridge! It also involves removing the fridge from the slide to work on it, which again, involves a lot of work.

Any idea the power consumption of a residential fridge vs 12v compressor vs absorption?
 
OMG. That Norcold has a 600W pull on AC. OUCH! it could easily use 9+kWh/day.

For comparable volume fridges, absorption type use about 5X more AC energy than modern efficient compressor-based residential fridges. DC versions are likely a little more efficient due to the potential for variable speed operations.

In your case, DC is provided by Solar to batteries to inverter to converter for 12V... In that configuration, anything 12VDC is only about 75% efficient back to the inverter battery capacity. You can gain 12V efficiency with a suitable DC-DC converter to convert high voltage DC to 12VDC. rather than go through multiple conversions.
 
IMHO, trying to base your battery size off your anticipated nightly use is sketchy at best. Most recommend you size your battery for 24 hours of daily use. Electric heat and A/C power requirements are devastating.

I am a proponent of sizing battery for one night's use, but then I'm not the one who is going to be shivering in the dark.
I run electric heat (net metering) but have gas so can switch to battery powering just the fan.

Batteries are certainly getting cheaper, but last I heard they still cost a couple or a few times as much as PV panels (per kWh of lifetime use.)
So I favor overpaneling beyond requirements by a factor of 2x to 5x, operating loads while the sun shines, curtailing loads to match available power, and running a generator when the sun doesn't cooperate (puts out < 20% of minimal requirements.)

Within some range, sure, just buy enough battery to make life comfortable. But when battery bank costs as much as inverters and PV panels combined, I look for ways to reduce that. My battery cost about 25% of what PV panels, battery inverters, and GT inverters cost.
 
OMG. That Norcold has a 600W pull on AC. OUCH! it could easily use 9+kWh/day.

For comparable volume fridges, absorption type use about 5X more AC energy than modern efficient compressor-based residential fridges. DC versions are likely a little more efficient due to the potential for variable speed operations.

In your case, DC is provided by Solar to batteries to inverter to converter for 12V... In that configuration, anything 12VDC is only about 75% efficient back to the inverter battery capacity. You can gain 12V efficiency with a suitable DC-DC converter to convert high voltage DC to 12VDC. rather than go through multiple conversions.
It uses on average 7.9kWh per day. I was able to measure with my kill a watt meter. And yes, its stupid lol

I'm still trying to figure out the 48v to 12v thing, just because I'm hesitant to spend $300 on a buck converter that would support the DC loads i need, such as starting the Genny, putting in and out the slides (80a), the auto leveling system, lights, fridge, stereo, etc.

I've been trying to find efficiency numbers on my Progressive Dynamics converter, but nothing!
 
Back
Top