Enphase M250 Specs for off-grid, tips and tricks and results

[ButchDeal]

Too many posts about the sun not coming out again like it has for billions of years. Ok in a northern climate you may have to double or even triple your solar array estimate, unless you live in the waaaaay north where darkness lasts for longer... I would say that geothermal or wind would be the best bet in those places for renewable energy sources. Gas is a short term not all year long option that is "easy" compared to solar, now as for the single inverter approach, I can see lots of issues with that, mainly a single point of failure that turns the lights out even if the sun does comes out tomorrow.

Either way the sun'll come out tomorrow, I'd bet my bottom dollar on that.

So that when it does my batteries would charge like they always seem to when the sunlight hits my solar panels.

ok this is getting silly. you are arguing with people who ACTUALLY live off grid and currently have solar systems. You can check their locations and they do not live north of the arctic circle. I live near DC and there are many weeks with no sun. That doesn't mean that the earth hasn't turned such that the sun is facing my little home but rather that the sun is behinds clouds all day. Thus not nearly enough power to run a home much less recharge batteries. Just take a little glance around PVOutput and you can see many homes with long stretches of not enough sunlight to do anything.

[solarddy]

The sun'll come out tomorrow.

IIRC they are both talking about AC coupled systems
Very bad idea and would require a generator and charger if the batteries ran too low. or lights out till the grid came back up

Too many posts about the sun not coming out again like it has for billions of years. Ok in a northern climate you may have to double or even triple your solar array estimate, unless you live in the waaaaay north where darkness lasts for longer... I would say that geothermal or wind would be the best bet in those places for renewable energy sources. Gas is a short term not all year long option that is "easy" compared to solar, now as for the single inverter approach, I can see lots of issues with that, mainly a single point of failure that turns the lights out even if the sun does comes out tomorrow.

Either way the sun'll come out tomorrow, I'd bet my bottom dollar on that.

So that when it does my batteries would charge like they always seem to when the sunlight hits my solar panels.

[solarddy]

No you are correct. The OP started out suggesting a minimum of 300-350Ah battery system and then stated (at least how I read the post) that batteries (or generator) were not really needed. That was confusing.

What I stated was that I agreed with solarddy when he stated a micro inverter mini grid would be a better choice to generate power for a home, with the condition that as long as you had a way to get power at night or when the sun didn't shine. How that power is generated is a choice. Or don't generate and you can read by candlelight and cook food over a wood fire. The choice is open.

No battery Enphase System Diagram M190.jpg

No batteries M190 diagram, sleep at night, use less batteries, for the "connected" internet family 300-350Ah battery bank is required for nighttime power needs, I call that phase 4 of a deployment of residential micro-inverters. After the system produces enough peak power as measured to allow for battery storage. Most people with grid power do not need to go Off-grid capable immediately, it's better to get your feet wet and pay off phases 1-3.

[Naptown]

IIRC they are both talking about AC coupled systems
Very bad idea and would require a generator and charger if the batteries ran too low. or lights out till the grid came back up

[lkruper]

Not sure what sort of gas you are sniffing, but last year, I had to run my generator quite a lot in winter, because we had many contiguous weeks of cloudy/rainy weather. If I did not run it, thousands of dollars of batteries would have been destroyed, and power would shut off.

I am going to keep on pressing them till I see an answer

I had said:
"I think you are missing the point. Yes, a generator could run out of fuel, however if that happened your underlying infrastructure was poorly designed. I can easily see a number of likely scenarios how a set of backup batteries which are intended to mimic a grid could be depleted by a single accident and then you will need another outside source of power to "reboot" the service. That is because the batteries are a single point of failure. But for a generator to run out of gas, it would take a series of failures AND the inability to get more gas, such as driving to the gas station or siphoning it from a vehicle gas tank."

And then Solardreamer said:
"Not really. You seem to be implying that you can go get gas for the generator but you can't go get batteries? If you can get gas for a car then you have a backup charger for batteries. (e.a.)

I fully understand the need to design safe and reliable battery based backup for solar systems but I don't see how generator is the really the answer. "

After that the other member of the tag team Solarddy came to Solardreamer's defense. So it looks like it to me that the both of them would rather you replace your batteries than buy gas to run your generator. But if they have a different explanation, I would really like to hear it.

[Mike90250]

BTW- this is "solar panel talk", not bash solar threads with gas generator comparisons, so let's do one.
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As we go into the winter months, having extra solar power production is key when considering cloud coverage, and shorter days, but solar power works every day all day without having to fill up a gas tank.

Not sure what sort of gas you are sniffing, but last year, I had to run my generator quite a lot in winter, because we had many contiguous weeks of cloudy/rainy weather. If I did not run it, thousands of dollars of batteries would have been destroyed, and power would shut off.

[SunEagle]

I have a fireplace for heat and cooking, plenty of batteries, candles, food stores, etc. But if I had expensive batteries I still would not want to let them sit in a discharged state for a few weeks because they would sulphate.

I agree. I have a situation where my battery system is not being used and is just sitting there waiting on the need to be used as a quiet emergency power source. But it takes work to keep them happy even though I know they are slowly losing life.

[lkruper]

No you are correct. The OP started out suggesting a minimum of 300-350Ah battery system and then stated (at least how I read the post) that batteries (or generator) were not really needed. That was confusing.

What I stated was that I agreed with solarddy when he stated a micro inverter mini grid would be a better choice to generate power for a home, with the condition that as long as you had a way to get power at night or when the sun didn't shine. How that power is generated is a choice. Or don't generate and you can read by candlelight and cook food over a wood fire. The choice is open.

I have a fireplace for heat and cooking, plenty of batteries, candles, food stores, etc. But if I had expensive batteries I still would not want to let them sit in a discharged state for a few weeks because they would sulphate.

[SunEagle]

Perhaps I am lost in this discussion, but I don't think so. This is what I understand, so please correct me if I am wrong.

The OP was proposing that grid-tie solar is fed into a battery system that mimics the grid exactly. Naptown asked what happens if the loads cause the pseudo-grid (battery system) to be depleted. That is a valid concern that I have not seen addressed by the proponents of this proposal.

I suggested that using a generator for the case where something happens to the battery bank makes a lot of sense. Others including the OP seem to have great objections to using a generator and made the comment that one could run out of gas and then what? My response is that the generator is a way to save the system as a last resort, because the battery backup is a single point of failure.

And when I one can get in the car to buy gas if it suns out then they say they can get more batteries! So I ask if they are going to buy more batteries every day if they get two weeks of cloudy weather. Of course that is ridiculous, and I said it to make a point, that they have no way to fix this situation if it happens.


So, am I not understanding what they are proposing? But now the OP says no batteries are involved. I don't understand that at all. So then what does the grid-tie inverter feed when the actual grid goes down?

No you are correct. The OP started out suggesting a minimum of 300-350Ah battery system and then stated (at least how I read the post) that batteries (or generator) were not really needed. That was confusing.

What I stated was that I agreed with solarddy when he stated a micro inverter mini grid would be a better choice to generate power for a home, with the condition that as long as you had a way to get power at night or when the sun didn't shine. How that power is generated is a choice. Or don't generate and you can read by candlelight and cook food over a wood fire. The choice is open.

[SunEagle]

You are way off base. I am not part of any tag team. Your comments about generators show you are mainly interested in being argumentative and not worthy of response. I am looking for constructive comments to address the shortcomings in OP's original proposal to make a more robust solar energy backup solution. So, my position remains the same that gas (or other non-renewable) generator is not the answer for a solar (or other renewable) energy backup solution.

As I stated earlier a gas gen set may not be the best (or most economical) energy backup system for everyone. But as of today in the US it is cheaper to run a gen set(s) using multiple fuel types (gas, propane, natural gas) then a comparable sized battery system.

If you need to run electrical loads all day long it doesn't matter how much a pv system can generate because there is ALWAYS a limited number of useable sunlight hours. So for other parts of the day you need to either generate the power from something beside pv or "store" the excess energy your pv system has generated during the day that you did not use.

So pick your poison. When it is dark and you need power, you can produce it from a gen set, battery, wind power, and a few other places that are probably not practical. Or you get the power from the grid.

If you don't want to use non-renewable power source then as of this time expect to pay more for the power being generated then what you can purchase from your POCO.

What is confusing is that the OP started this thread suggesting batteries and now is stating you really don't need batteries until you expand your pv system.

So unless you do not run any electrical devices at night (or on rainy days like today for me in Florida) you need need to use the grid or generate the power by some other means.

I am not being argumentative. I am simply stating the physical and scientific facts concerning solar technology. It only works when the sun is shining on the solar cells.

[lkruper]

Except for a the presumption of why Enphase is building their micro inverters with anti-islanding software, I agree with what Solarddy stated concerning a micro inverter grid being better.

IMO the biggest issue is the chance of a long string of days without sunshine which would put you in the dark without any device working. So there needs to be a balance of what the micro grid can generate when the sun is out and some other power source to cover the periods of time when the sun is not out. At this time batteries are not economical but running a gen set every day will also be very costly.

So the grid is still the best power source to use when the sun is not out with the availability of having a short term form of emergency power generation (gen set, battery, squirrel cage, etc.). What that source is will depend on what is best for the user which will not be the same for everyone.

Perhaps I am lost in this discussion, but I don't think so. This is what I understand, so please correct me if I am wrong.

The OP was proposing that grid-tie solar is fed into a battery system that mimics the grid exactly. Naptown asked what happens if the loads cause the pseudo-grid (battery system) to be depleted. That is a valid concern that I have not seen addressed by the proponents of this proposal.

I suggested that using a generator for the case where something happens to the battery bank makes a lot of sense. Others including the OP seem to have great objections to using a generator and made the comment that one could run out of gas and then what? My response is that the generator is a way to save the system as a last resort, because the battery backup is a single point of failure.

And when I one can get in the car to buy gas if it suns out then they say they can get more batteries! So I ask if they are going to buy more batteries every day if they get two weeks of cloudy weather. Of course that is ridiculous, and I said it to make a point, that they have no way to fix this situation if it happens.


So, am I not understanding what they are proposing? But now the OP says no batteries are involved. I don't understand that at all. So then what does the grid-tie inverter feed when the actual grid goes down?

[solardreamer]

Solardreamer and Solarddy are a tag team. When one makes a comment that is refuted, the other comes and moves away from that line of thought. Now they have abandoned the premise of the OP. I think they are trolls.

This last post is rhetorical nonsense.

You are way off base. I am not part of any tag team. Your comments about generators show you are mainly interested in being argumentative and not worthy of response. I am looking for constructive comments to address the shortcomings in OP's original proposal to make a more robust solar energy backup solution. So, my position remains the same that gas (or other non-renewable) generator is not the answer for a solar (or other renewable) energy backup solution.

[SunEagle]

Solardreamer and Solarddy are a tag team. When one makes a comment that is refuted, the other comes and moves away from that line of thought. Now they have abandoned the premise of the OP. I think they are trolls.

This last post is rhetorical nonsense.

Except for a the presumption of why Enphase is building their micro inverters with anti-islanding software, I agree with what Solarddy stated concerning a micro inverter grid being better.

IMO the biggest issue is the chance of a long string of days without sunshine which would put you in the dark without any device working. So there needs to be a balance of what the micro grid can generate when the sun is out and some other power source to cover the periods of time when the sun is not out. At this time batteries are not economical but running a gen set every day will also be very costly.

So the grid is still the best power source to use when the sun is not out with the availability of having a short term form of emergency power generation (gen set, battery, squirrel cage, etc.). What that source is will depend on what is best for the user which will not be the same for everyone.

[solarddy]

Enphase M250 works for battery-less daytime micro-grids (mostly) But could be better.

Huh? Your first post in this thread clearly talks about using batteries to create your micro-grid. Now battery free? It isn't just the islanding feature that prevents the micro-grid from working. As you sort of pointed out, if load isn't exactly matched to what is being generated, you've got nothing. Without some kind of storage to buffer the fluctuations, too much or too little load will knock the whole micro-grid voltage out of range and shut the whole thing down.

Actually I said there were fluctuations in voltage. My off-grid testing showed that there is a small voltage surge 1-2 volts and a frequency increase but my system didn't shut down until it was massively overproducing and then it did shut down my primary grid sine producer. However Micro-inverters operate without batteries in a normal grid-tied situation. It really wouldn't be much of a thing to make them work without batteries in an islanding situation.

The problem is typical design guidelines show a BIG battery bank where all solar goes through it first. I think that piggy-backing the micro-inverters on the output of the primary sine wave inverter is the best way, load balancing is the issue, but like I said, it took massive overproduction to shut down my off-grid array, if balanced, there is no shut down. Do you "need" batteries? No. The solar panel provides a D.C. source and the sun shines every day.

Let's look at the problem another way: If load demand increased, and there was an intelligent microprocessor program monitoring the line voltage, when the line voltage dropped below a certain level, another micro-inverter(s) which was already powered up and waiting to sync would sync to the 0 crossing and shore up the power on the next cycle. Intelligent load balancing would take a snapshot of the demands and look for patterns and map the drops and peaks to anticipate the loads such as Air conditioning or other motors which have a distinct signature when coming on over discrete periods of time, such as per sec, 5 seconds, 10 seconds, 30 seconds, and 5 minutes.
An entire array of micro-inverters would only be utilized if/when the load demanded them to be used. This would significantly increase the lifespan of the micro-inverters, because peak demand differs from continuous load.
In the case of a load so great it looks like a dead short, as long as the protection devices installed are correct, the micro-inverters should push till those weak points blow which they would in the case of a dead short. Separation of each string of M250's is limited to the wire rating on the Enphase cable.

In a grid-interactive manner intelligent load balancing would limit your credits in "islanding" mode but would maintain power during the day if it was available. Surge output can be many times the rated output of the normal inverter, so the surge of 300 watts could likely be accomplished by a M250 if the load was limited to a few seconds and the M250 was connected to a 300 Watt solar panel. A new micro-inverter array would be developed that would not produce more than the local customer demanded when switched to Islanding mode.

And in the case of too-much power being generated in islanding mode the micro-inverters could sense this and turn their outputs off in one cycle or less utilizing a line sniffer program.

I think the next generation of micro-inverters could accomplish the goal of battery-less micro-grids during the day which eliminate their power bills during daytime hours. Oh wait they already do. Enphase M250. Just not in off-grid mode for several of the above listed reasons.

Using batteries to power the base sine wave inverter for a 90%+ floating M250 micro-grid tied is something like I mentioned earlier, if you Y the output from the solar panels, one to a PWM or MPPT controller and the other to the micro-inverter, the batteries for the base sine wave grid generator get charged till they are full and then the power goes to the micro-inverters, no generator needed. If we only had load balancing micro-inverters there would be no question as to which was superior.

Why are Micro-inverters better: lower Cost, massive scalability, less downtime on individual failure, TCOO is going to be cheaper if you keep them cooler. You lose a string inverter and you lose 1/3 or more of a small array production, you lose 250 watts, you can shrug it off and it takes minutes to install a new one.

[lkruper]

Huh? Your first post in this thread clearly talks about using batteries to create your micro-grid. Now battery free? It isn't just the islanding feature that prevents the micro-grid from working. As you sort of pointed out, if load isn't exactly matched to what is being generated, you've got nothing. Without some kind of storage to buffer the fluctuations, too much or too little load will knock the whole micro-grid voltage out of range and shut the whole thing down.

Solardreamer and Solarddy are a tag team. When one makes a comment that is refuted, the other comes and moves away from that line of thought. Now they have abandoned the premise of the OP. I think they are trolls.

This last post is rhetorical nonsense.