Hi all, I am new to solar power but not to electricity or electronics. I watched some of Will's youtube videos about the MPP Solar All-in-One inverters and decided to pull the trigger and get my feet wet with the MPP PIP-1012LV-MS. At first glance it is a very convenient and simple way to get started, but after further investigation, I have noticed what I perceived as a glaring mismatch between the inverter capacity (1000W) and the output rating of the MPPT (40A = 500W). With a 1kW inverter running anywhere near or over 50% (500W), it would exceed the capability of the MPPT to run the inverter AND keep the batteries charged. For the life of me I can't understand why anyone would market such a combination as it would be impossible to maintain the batteries even on a daily basis. Said differently it would take 2-3 days of full sun to run the inverter for only a few hours and then wait another 2-3 days for the batteries to recover to a usable SOC. I was very disappointed that Will didn't even glance over this fact in the videos I viewed. If I am missing something, please someone let me know. I have seen that MPP Solar now offers a PIP-1012LV-MK, which has an 80A (1kW) MPPT which makes more sense, but still only matches the inverter and after allowing for efficiencies, is still a bit short of ideal. I would prefer an MPPT 1.25 to 1.5 times that of the load (1kW inverter) to be comfortable.
MPP PIP-1012LV-MS MPPT output too small?
- Thread starter ken_am
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sunshine_eggo
Happy Breffast!
Your reasoning is flawed because you likely don't understand component sizing.
First, even 1.5X doesn't make any sense. If you're planning to run 1kW continuously, you're going to need a MASSIVE array - about 6000W, so the idea that 500W of solar vs. 1000W of power is a mismatch is flawed.
Here's how you size your components:
You size your solar based on your daily energy consumption and available solar (worth noting that a 1000W array will almost never put out 1000W).
You size your battery based on how long you want to operate between charging.
You size your inverter for the magnitude of your loads.
Most all-in-one (AiO) systems offer a PV power lower than the inverter power.
Most non-AiO systems have less PV power than inverter power.
Example: My friend has 24kWh battery, 4kW inverter and only 2kW solar for his 3200 sqft off-grid house. Anything he can run off propane he does, so his electricity needs are low. He tends to use < 7kWh/day. Since he might want to run his microwave, dishwasher, fridge and coffee pot at the same time (about 3400W total), he needs a 4kW inverter, but he certainly doesn't use 4kW regularly. He can harvest about 1.5X what he needs daily with his 2kW array even in the winter (2X in summer). If he only had a 2kW inverter to "match" his array, he couldn't run his coffee pot and microwave at the same time.
Tying it back to the sizing:
Solar: 1.5 days of energy harvest per day.
Battery: About 2 days of storage (lead-acid, so 50% discharge limit).
Inverter: 4kW, so he can power multiple high power loads simultaneously without worry even though his average power draw is far lower (<300W).
First, even 1.5X doesn't make any sense. If you're planning to run 1kW continuously, you're going to need a MASSIVE array - about 6000W, so the idea that 500W of solar vs. 1000W of power is a mismatch is flawed.
Here's how you size your components:
You size your solar based on your daily energy consumption and available solar (worth noting that a 1000W array will almost never put out 1000W).
You size your battery based on how long you want to operate between charging.
You size your inverter for the magnitude of your loads.
Most all-in-one (AiO) systems offer a PV power lower than the inverter power.
Most non-AiO systems have less PV power than inverter power.
Example: My friend has 24kWh battery, 4kW inverter and only 2kW solar for his 3200 sqft off-grid house. Anything he can run off propane he does, so his electricity needs are low. He tends to use < 7kWh/day. Since he might want to run his microwave, dishwasher, fridge and coffee pot at the same time (about 3400W total), he needs a 4kW inverter, but he certainly doesn't use 4kW regularly. He can harvest about 1.5X what he needs daily with his 2kW array even in the winter (2X in summer). If he only had a 2kW inverter to "match" his array, he couldn't run his coffee pot and microwave at the same time.
Tying it back to the sizing:
Solar: 1.5 days of energy harvest per day.
Battery: About 2 days of storage (lead-acid, so 50% discharge limit).
Inverter: 4kW, so he can power multiple high power loads simultaneously without worry even though his average power draw is far lower (<300W).
Let me start my reply with thanks for your input and give you a little more insight into what I am trying to accomplish. I am looking to run a single dedicated load during the daylight hours to help reduce my electric bill. Your statement that "you're going to need a MASSIVE array - about 6000W" seems extreme. Clearly the solar needs to surpass the load or the system will shut down when the batteries drop below their usable SOC. Obviously, my statement of 1.5 times solar meant usable PV output, not advertised output, but 6kW, phew! I'm assuming that's advertised output. As I said when I started this thread, I purchased a PIP-1012LV-MS to run this load, but I doubt if 500 watts of PV power will be sufficient. By my measurements, 700 watts should get the job done. I get that the Inverter power has to meet the max expected load, which in your example, is transient and not continuous as in my case, but the PV output needs to exceed the 700 watt inverter load.
sunshine_eggo
Happy Breffast!
The unit you purchased is suitable for someone that needs 2000-2500Wh/day of energy production and for loads of up to 1000W. This is clearly not appropriate for your stated goal. You're criticizing the unit for your lack of planning.
You should have sized your system based on energy use, not power.
"Daylight hours" - lets assume an average of 12 hours/day. 700W * 12h = 8400Wh.
You'll need about that much in batteries and solar of about 2000W.
Again,
You size your solar based on your daily energy consumption and available solar (worth noting that a 1000W array will almost never put out 1000W).
You size your battery based on how long you want to operate between charging.
You size your inverter for the magnitude of your loads.
The only thing you considered was your load. You omitted the other three.
Wrapping back around to 1000W of panels rarely producing 1000W, here's an example of a 3kW array:
Red line is 3kW. Note how it's only over 2500W for a few hours in the middle of the day, and it never reaches 3kW at all. This was a partly cloudy day, so that's why there's dips. I sketched in the full power profile.
That day, we harvested 16kWh - enough to power a 16000Wh/24h = 667W load for 24 hours.
You should have sized your system based on energy use, not power.
"Daylight hours" - lets assume an average of 12 hours/day. 700W * 12h = 8400Wh.
You'll need about that much in batteries and solar of about 2000W.
Again,
You size your solar based on your daily energy consumption and available solar (worth noting that a 1000W array will almost never put out 1000W).
You size your battery based on how long you want to operate between charging.
You size your inverter for the magnitude of your loads.
The only thing you considered was your load. You omitted the other three.
Wrapping back around to 1000W of panels rarely producing 1000W, here's an example of a 3kW array:
Red line is 3kW. Note how it's only over 2500W for a few hours in the middle of the day, and it never reaches 3kW at all. This was a partly cloudy day, so that's why there's dips. I sketched in the full power profile.
That day, we harvested 16kWh - enough to power a 16000Wh/24h = 667W load for 24 hours.
I didn't omit them. I assumed things about the AiO (capable of continuous operation at or near full load) that in hindsight are clearly not the way the manufacturer intends it to operate. As I said in the beginning, "NEW TO SOLAR". This is a learning experience. Isn't 12 hours of daylight EXTREMELY optimistic? I would think 8-10 to be more realistic. By your own chart it looks more like 9ish hours.
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sunshine_eggo
Happy Breffast!
You've provided no evidence that you've considered the four aspects.
Don't blame the product for your assumptions.
Agreed. Unfortunately, your initial post is more of a rant about how things aren't how you perceive they should be. I'm trying to help you learn.
"Daylight hours" is your term. It's vague. That chart is for 11/25/2021 and had "daylight hours" for just shy of 10 hours on the chart. In July, I get over 14 "daylight hours." On that basis, I don't think my "average of 12 hours/day" is "optimistic." It's simply an attempt to quantify a numerical value to a vague term.
Let's use your 8 hour number:
8 * 700W/.85 = 6588Wh (.85 is an efficiency factor).
You will need a solar array capable of harvesting 5600Wh. Assuming 4 solar hours (you can refine this for your location with https://pvwatts.nrel.gov/), you'll need 1650W PV. 1650W of PV will require 1650W/12V = 137A of charging at 12V.
You will need a battery bank capable of providing 5600Wh of capacity (467Ah @ 12V)
You will need an inverter capable of handling a 700W load. More if there is surge current.
You will see seasonal variations. You may find that in winter, even with "8 daylight hours," your array will produce substantially less power than it will in summer. PVWatts linked above can give you daily solar hours by month and simulate an actual array that also considers weather for your location. If you're a numbers guy, you can download HOURLY solar performance data
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Thanks sunshine_eggo. I appreciate your input. Since the load is seasonal and only during the summer months, I am not considering the loss of output during fall/winter/spring. Still, I will have to check my location to see what realistic expectation of power I can get. I apologize if my initial post sounded like a rant, it's just not what I expected. I wasn't blaming them as much as not understanding why the MPPT was so much smaller than the inverter. Again, not what I was expecting. Realizing that it's intended use is primarily intermittent and not continuous explains a lot. I don't need it to run for 12 hours, 6-8 would do fine. I haven't mentioned the batteries because they are only required by the AiO. I would run strictly off PV if I could and as the MPPT can't handle the load of the inverter by itself, I was wondering if it was even possible. the link you sent says I might expect ~6kWh/m^2/day at my location. If I understand this (and that's a BIG IF), I might expect to enough PV for about 3 hours of operation/day depending on the size of my array. I'm assuming a bell shaped power curve similar to the one you showed before with enough power available only during the middle 1/3. Does that make sense?
Hi smoothJoey, The whole intent is to move the load off mains and it is not so critical as to require generator backup, so it could revert back to mains on cloudy days.
Hi smoothJoey, The whole intent is to move the load off mains and it is not so critical as to require generator backup, so it could revert back to mains on cloudy days.
sunshine_eggo
Happy Breffast!
It is possible, but it means you'll need enough solar to provide at least 700W of power + inefficiency + inverter consumption. If you have a moment where a cloud shades part of the array, are you okay with the inverter shutting down and powering off the load, turning on and off multiple times in partly cloudy situations? Or are you okay with the unit switching to grid when solar is insufficient?
If you go battery-less, you'll need a unit that's capable of that kind of operation. Not all are.
PVWatts gives good average. There will be some days you blow that out of the water and other days that solar just stinks. Here's what a 1.5kW array would do at my location, 35° tilt and 180° facing:
I'm in AZ, so my numbers are pretty solarly sexy.
If you're just looking at seasonal usage, it would be ideal to tilt your panels to the optimal angle for that season.
Conceptually, yes. There are other ways to spread out the solar. If you had a 1000W array facing SSE and another 1000W array facing SSW, you could widen the peak output period of the day and lower the highest peak. Sketched very crudely here:
This unit:
Can accept up to 4kW PV and can run without a battery (though it's VERY hard to get 4kW PV on this inverter with the 250Voc and 18A PV input limits.
You could plug this into a wall output to provide AC input (fabricate your own power cord, or cut an extension cord).
Set priority to SUB (solar, utility, battery)
"Solar energy provides power to the loads as first priority. If solar energy is not sufficient to power all connected loads, solar and utility will power loads at the same time. Battery provides power to the loads only when solar energy is not sufficient and there is no utilityI
Attach up to 4kW (3.6kW more reasonably) PV
Attach your load with a timer to the AC output of this unit. You would want a timer that retains its time even when power is off.
Run your load from 9a - 3p
You could have the unit enter idle mode, or even better, turn it off. Even better, have the AC input on a timer as well - turn it off when you have no more PV. THis part is important, because if you leave it on for 24 hours, it will consume 1.2kWh of energy (50W 24/7). You'd want to turn it on when the array can produce 100W and turn it off at the end of the day when it's producing 100W.
Other considerations:
In most locations, even if no permit is required, rooftop mounted solar must comply with NEC2017. This has additional implications that may increase cost by $60-75/panel. Ground mount avoids this.
I could use battery power to bridge the cloud gaps but this unit doesn't have enough PV input to even run the load alone so running off mains would be the only viable option. If I read the spec sheet correctly on the link you provided, that GroWatt seems to have more PV input than inverter output. Perhaps that is because of it's batteryless operation capability? Hmm... something to look into. On a different point, if the Voc of my array doesn't exceed the max input voltage of the MPPT, wouldn't I be able to theoretically add an infinite number of parallel PV strings to the MPPT input? As you stated,
This was a question I had wondered about. Could I add (not practical) say 10kW PV to the MPPT input, all angled to take advantage of the sun at different times of the day & different locations that get shaded and unshaded, as long as I don't exceed the 105V max DC input of the MPPT. Is there anything that could be a problem for the MPPT other than the obvious physical design, distances and size of the array? Also, with multiple strings in parallel, are blocking diodes necessary for each string so a shaded string doesn't load down the entire array and do they affect the MPPT's ability to track the MPP?
Here are my numbers for CT. with a 1.5kW array at 18° tilt and 180° facing:
This was a question I had wondered about. Could I add (not practical) say 10kW PV to the MPPT input, all angled to take advantage of the sun at different times of the day & different locations that get shaded and unshaded, as long as I don't exceed the 105V max DC input of the MPPT. Is there anything that could be a problem for the MPPT other than the obvious physical design, distances and size of the array? Also, with multiple strings in parallel, are blocking diodes necessary for each string so a shaded string doesn't load down the entire array and do they affect the MPPT's ability to track the MPP?
Here are my numbers for CT. with a 1.5kW array at 18° tilt and 180° facing:
sunshine_eggo
Happy Breffast!
I'm not sure if the unit you have will work without batteries.
You could add a separate MPPT to the system as well. Nothing prevents this.
No. Because it's the 48V version of a 24V model. 80A MPPT charger means you have 2X the power at 48V vs. 24V. In most cases, 48V systems will require more than 3000W of power.
Sorta.
With Voc limits, you need to allow for cold temp effects as cold causes PV voltage to increase. In CT, you'll likely want to limit your panel series Voc to about 60-80V.
But you definitely could have multiple arrays sprinkled to have peaks at different parts of the day for more even delivery over longer period of time, but there's a practical limit. A SE array working with SW array are probably going to get you 90% of the benefit compared to several arrays at different facings. More arrays could help with shading.
Running a cheap MPPT at it's maximum current for the entire day is not necessarily a good idea and may reduce their life.
Blocking diodes are generally never needed provided the shaded parallel panels aren't completely covered with a physical barrier. Even the ambient light from shading will permit a panel to produce Voc higher than the operating panels' Vmp thus preventing backfeed through the shaded panel.
Looks pretty good Mar-Sep.
Is the 18° roof mounted? That will add cost and complexity you likely want to avoid.
sunshine_eggo
Happy Breffast!
Depends on PV module. A common number seems to be -0.33%/°C
As for the 18° tilt, no that's not roof mounted, just my estimated optimum angle for the summer months at 41° North latitude. I was wondering why yours was 20°. I guess because you want 4 season performance where as I am only concerned with summer. If I wanted 4 season performance, I would need to increase my tilt angel.
I agree running anything at maximum will definitely shorten it's life expectancy. That is not my intention, just theoretical spit balling at this point.
I agree running anything at maximum will definitely shorten it's life expectancy. That is not my intention, just theoretical spit balling at this point.
So, adios to the blocking diodes but do they affect the MPPT's ability to track the maximum power point?
sunshine_eggo
Happy Breffast!
That's about right for the summer solstice, but you might want slightly steeper to get a better average for the whole season.
Default on that site is 20°.
I'm actually at 29.5° due to my latitude and:
No.
After running multiple tilt angles on the web page you recommended I have a few questions. The tilt angle at peak output seems to be optimum at about 12.5° in July but I calculated more like 18° and expected it to occur in June. Could you shed some light on why the results from the web page differ from my expected results?
My calculations were based on 23.5° northern inclination of the sun at solstice, June 20th or there about, and my 41.25° north latitude, yielding a difference (tilt angle) of 17.75°.
My calculations were based on 23.5° northern inclination of the sun at solstice, June 20th or there about, and my 41.25° north latitude, yielding a difference (tilt angle) of 17.75°.
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sunshine_eggo
Happy Breffast!
PVWatts doesn't always show an improvement. One would have to run the two scenarios, download the hourly data and then dig in to find two a day where there was clearly no weather effects and then compare the two. I've never gone to that level with that in mind.
The method on solarpaneltilt considers other factors relating to the actual path of the sun. When the sun is at high noon, it's to the South at any latitude above 23.5°, but at sunrise and sunset, it's pretty much due East and West, respectively. The shallower tilt angle means the array can capture more of the morning and evening sun that is less South than compared to mid-day. Apparently the hit during peak solar is minimal, but the extra you get morning and evening is a net gain.
It's likely a tiny refinement (he indicates 4% on the site), but I'm happy with my results. Even at the Winter Solstice, my array can pull in 70-80% rated (sometimes 20% more than rated with cloud edging effects and cold panels) at a year-round tilt of about 29° for my ~35° latitude.
The method on solarpaneltilt considers other factors relating to the actual path of the sun. When the sun is at high noon, it's to the South at any latitude above 23.5°, but at sunrise and sunset, it's pretty much due East and West, respectively. The shallower tilt angle means the array can capture more of the morning and evening sun that is less South than compared to mid-day. Apparently the hit during peak solar is minimal, but the extra you get morning and evening is a net gain.
It's likely a tiny refinement (he indicates 4% on the site), but I'm happy with my results. Even at the Winter Solstice, my array can pull in 70-80% rated (sometimes 20% more than rated with cloud edging effects and cold panels) at a year-round tilt of about 29° for my ~35° latitude.
Rednecktek
Solar Wizard
Man, even your CT numbers are sexy compared to my 2 and change average. 
But as to the OP, yeah, the system was designed for small constant loads and the occasional surge of 1kw. Your math is correct, the unit just isn't designed to do what you want. Still, it's a good learning experience!
Also, if you decide to replace it and get rid of it cheap PM me, I'm looking for a cheap AIO for a class I'm throwing next summer.
But as to the OP, yeah, the system was designed for small constant loads and the occasional surge of 1kw. Your math is correct, the unit just isn't designed to do what you want. Still, it's a good learning experience!
Also, if you decide to replace it and get rid of it cheap PM me, I'm looking for a cheap AIO for a class I'm throwing next summer.
Thanks sunshine, I didn't realize they were averaging the output over the whole solar day, Duh! That explains a lot. I was thinking instantaneously at peak output (high noon). Given that, (only considering absolute peak output) are my numbers correct or am I off somewhere else?
Hi Rednecktek, I don't expect to be getting rid of it for what you might consider "cheap" as it is still a perfectly good unit, just not up to my needs by itself, but if I change my mind, I will let you know.
Hi Rednecktek, I don't expect to be getting rid of it for what you might consider "cheap" as it is still a perfectly good unit, just not up to my needs by itself, but if I change my mind, I will let you know.
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