Inverter Generator

[Ozark Tinkering]

I'm getting ready to purchase a new inverter generator to replace the old Troybilt 5550 gasoline jobber that I converted to propane many years ago. That generator while it served its purpose provided very dirty power. It needs to go. A year ago I installed a grid-tied 5kw Enphase rooftop system and am really appreciating having it.
Recently I found this site and have done some extensive reading here and find the knowledge base to be broad and the members to be generous in sharing.
So the generator I am looking at is a DuroMax 9,000-Watt/7,600-Watt Dual Fuel Remote Start Inverter Generator with Portable Digital Parallel that claims to produce power with <3% harmonic distortion at half load. My Enphase micro inverters can handle up to 5%.
So far it's the largest portable inverter I have found and I'm wondering if anyone here has one or experience with one.
My longer term plan is to get 2 of these units and parallel them so I can run everything in my home without rationing and eventually adding enough storage so I can energize my Enphase system during the day and use it as normal plus have a place to store the excess it will produce, all during an outage from the grid.

I'm trying to do this in some sort of logical order from where I already am, so that's where I'm starting from and here's where I think I need to go. I'm looking for suggestions and critique and wear flame retardant shirts. I'm looking for performance, compatibility and value for the $ spent. I'm not afraid to mix and match to get the best bang for my buck, but I won't leap into something without understanding the task in front of me first. I have a strong electrical construction and industrial troubleshooting background, but this is my first system where dc power will be the heart of the system, so I'll have a buttload of apprentice level questions.

I think this is the order I need to buy the pieces in to be able to build the system in it's entirety-over time (like 2+ years) so that when I'm done I have a legit self sustaining island grid and have reliable backup power from the start, that exceeds what my old generator has been providing only with clean power but allows me too also run my existing rooftop Enphase system to operate while I am disconnected from the utility grid.

Order of purchase and installation of the major components;
1. DuroMax 9,000-Watt/7,600-Watt Dual Fuel Remote Start Inverter Generator with Portable Digital Parallel
2. 5kw* of LiFePO4 cells and bms, connection hardware and 2-Mpp LV6548 All-in one (if harmonic distortion is <5%) (leaning toward prismatic cells, could DIY)
3. 48vdc battery charger
4. 10kw used solar panels 250watt or higher
5. 15kw of LiFePO4 cells, hardware and bms
6. 15kw of LiFePO4 cells, hardware and bms

So first off, does anyone have any experience with the DuroMax 9,000-Watt/7,600-Watt Dual Fuel Remote Start Inverter Generator with Portable Digital Parallel? I chose it because I can run it on propane and it is the largest unit I could find that I can run on a 100lb. propane bottle and still have clean inverted power to establish my island grid with. Plus I could buy a second one and parallel them to double my capacity should I ever need that option.
Thanks!

*I edited to change #2 from 15kw to 5kw to spend less and still be able test functionality.

​

 

[wattmatters]

Not going to be able to provide any input to your questions about the specific generator, but just making a general observation. It may or may not have relevance in your case.

The specifications of a generator suitable for powering a home directly vs one suitable for recharging a battery storage system may possibly be quite different.

Obviously a generator which can do the first can also do the second (output waveform being suitable and all that) but it perhaps does not need to be such a large generator if all it needs to do is keep batteries topped up when required.

A generator powering a home directly is quite possibly going to be ramping power up and down a lot and perhaps spending a lot of its time supplying just a small fraction of its capacity, and being quite inefficient. You specify the generator capacity based on the peak loads it needs to cover.

A generator which is recharging batteries can operate at a much higher and relatively constant load and be far more efficient in its operation. You most likely do not need to specify the generator to cover high peak loads in this case (and you can adjust the battery charge rate accordingly). All you need is for the power output to be sufficient to charge the battery storage quickly enough.

As an example, when we need to operate off-grid (grid outage backup), then I can use my 3kW (inverter) generator to power the home directly or I can use it to make sure batteries are recharged if the solar PV isn't able to (crappy solar day for instance).

2 hours of charging by my generator = 8 hours of backup supply in the battery. I'd rather run the generator for 2 hours than 8.

 

[offgriddave]

There's no real good high capacity battery charger but if you get one (maybe inverter-charger combo) make sure it matches 95% of the capacity of the generator for fuel efficiency. if you have a 9000w generator and only use 800w of charging, you're going to waste a lot of fuel. better to get a 3000w charger and a 3500w generator.

 

[Ozark Tinkering]

There's no real good high capacity battery charger but if you get one (maybe inverter-charger combo) make sure it matches 95% of the capacity of the generator for fuel efficiency. if you have a 9000w generator and only use 800w of charging, you're going to waste a lot of fuel. better to get a 3000w charger and a 3500w generator.

Thanks for that response! So the reason I have a 48vdc charger on my list really isn't to charge my batteries, but to provide a constant load on the ac side of my "island grid" once it's been established, so that my Enphase system will have a place to feed the excess power it produces during daylight hours. I've been watching that system pretty close for the past year and very seldom have I put more than 1kwh at a time. I figure one of those 1000watt charger would be plenty for that? Am I making any sense or am I headed down a rabbit hole? I think all that would cost me power-wise would be whatever loss occurs at that charger?

Not going to be able to provide any input to your questions about the specific generator, but just making a general observation. It may or may not have relevance in your case.

The specifications of a generator suitable for powering a home directly vs one suitable for recharging a battery storage system may possibly be quite different.

Obviously a generator which can do the first can also do the second (output waveform being suitable and all that) but it perhaps does not need to be such a large generator if all it needs to do is keep batteries topped up when required.

A generator powering a home directly is quite possibly going to be ramping power up and down a lot and perhaps spending a lot of its time supplying just a small fraction of its capacity, and being quite inefficient. You specify the generator capacity based on the peak loads it needs to cover.

A generator which is recharging batteries can operate at a much higher and relatively constant load and be far more efficient in its operation. You most likely do not need to specify the generator to cover high peak loads in this case (and you can adjust the battery charge rate accordingly). All you need is for the power output to be sufficient to charge the battery storage quickly enough.

As an example, when we need to operate off-grid (grid outage backup), then I can use my 3kW (inverter) generator to power the home directly or I can use it to make sure batteries are recharged if the solar PV isn't able to (crappy solar day for instance).

2 hours of charging by my generator = 8 hours of backup supply in the battery. I'd rather run the generator for 2 hours than 8.

Thank you for your response too! So one reason I am looking at a larger inverter is because I definitely need 240vac for my whole home system and I have some fairly heavy loads. I have a deep well pump, central a/c, 4500watt water heater, Electric range, 3 freezers and a frig...you know all the appliances a 90s version home has that never thought about going off-grid, That 5550watt Troybilt has a 30amp breaker but by the time it's pulling 30 amps, the voltage is down to 185volts so it behooves one to really ration the number of things run at one time and it barely gets us by.
The DuroMax I've spec'd out also only has a 30amp 240 volt plug but I believe I'll have clean 7000 watts at full voltage available and won't have to juggle things so much. It also has remote electric start.
If you know of a 240volt dual fuel electric start inverter that is smaller the it I'm interested in looking at it.

 

[wattmatters]

If you know of a 240volt dual fuel electric start inverter that is smaller the it I'm interested in looking at it.

I'm in Australia. It's all electrically different here. If I wanted an inverter generator to run the whole joint, then I'm looking at a large diesel unit and that's going to cost A$15-20k.

you know all the appliances a 90s version home has that never thought about going off-grid

Mine was built in the 1970s along with a builder's workshop. We have grid 3-phase power. Off-grid just isn't feasible/sensible. Off-grid backup is, but for essential power needs only, many of the high powered items are non-operational during backup periods.

 

[wattmatters]

4500watt water heater,

Mine is 3.6kW but I am installing a smart power diverter for the hot water system.

It will monitor excess solar PV being exported to the grid, and divert that same amount of power to the water heater. If there is only 1kW of excess, then that's all the power it will send to the resistive heating element. If the available excess energy increases (more sun on the panels, or less load) then it will heat the water more quickly. Only if insufficient heating has occurred through the day will the diverter then choose to use off peak grid power to complete the job.

I doubt that will happen often as we only require an average of 5kWh/day for the water heater.

 

[wattmatters]

I have a deep well pump, central a/c, 4500watt water heater, Electric range, 3 freezers and a frig

The pump is a challenge. You may need to consider adding a soft starter device to the pump reduce the surge demand on your inverter.

We are all electric, with 1 x ducted reverse cycle aircon (for heating and cooling) plus 4 x other split system aircon units (again for heating and cooling) across three buildings. We have an induction cooktop with 4 hobs and electric oven of course. Plus the cooktop and oven in the second dwelling. Water heater I've mentioned.

Frankly if I were to attempt going off grid then I would be up for some serious coin.

 

[Ozark Tinkering]

I'm in Australia. It's all electrically different here. If I wanted an inverter generator to run the whole joint, then I'm looking at a large diesel unit and that's going to cost A$15-20k.


Mine was built in the 1970s along with a builder's workshop. We have grid 3-phase power. Off-grid just isn't feasible/sensible. Off-grid backup is, but for essential power needs only, many of the high powered items are non-operational during backup periods.

It's not going to be cheap here either. The Enphase system by itself was just under $13k and as you can see it only covers about 1/3 of my annual use. The inverter/gen I'm looking at will be running on propane. I have a 1000gal tank that gets filled once a year when prices are their lowest. Then I fill my own 20lb. and 100lb. bottles for use on different appliances using a withdrawal hose I had installed on the tank. That saves a buttload verses having a 20lb. bottle filled at the feed store. The price on that inverter/gen is $2600 and change.
Do you know what the exchange rate is between our 2 currencies? If you say something costs $15k, is there much difference between US and Australia $?
I use about 20mwh per year and average about 43kwh per day after my 5kw rooftop Enphase system has done it's thing each day. It produced 6.5mwh last year and the grid provided the other 1.4mwh.
Based on that I'm thinking the inverter I'm looking at will be able to cover my needs when or if I finish the battery storage installation. Until I reach that point in my project that inverter/gen will for sure get me by much better than that old generator that my GFCIs in the kitchen don't like it when the coffee maker is on and the well pump starts and dirty power abounds. Pretty sure nothing else likes it either.

Mine is 3.6kW but I am installing a smart power diverter for the hot water system.

It will monitor excess solar PV being exported to the grid, and divert that same amount of power to the water heater. If there is only 1kW of excess, then that's all the power it will send to the resistive heating element. If the available excess energy increases (more sun on the panels, or less load) then it will heat the water more quickly. Only if insufficient heating has occurred through the day will the diverter then choose to use off peak grid power to complete the job.

I doubt that will happen often as we only require an average of 5kWh/day for the water heater.

I'm very interested in that smart power inverter...have link?!

The pump is a challenge. You may need to consider adding a soft starter device to the pump reduce the surge demand on your inverter.

I'm also interested in a link to follow up on that as well!

Mine was built in the 1970s along with a builder's workshop. We have grid 3-phase power. Off-grid just isn't feasible/sensible. Off-grid backup is, but for essential power needs only, many of the high powered items are non-operational during backup periods.

I built my detached shop in '95 and it's equipped for wood and metal work and I haven't even begun to calculate what I'll need to make it stand alone but as a one man shop I can also run whatever single piece of equipment I need at a time with my current dirty crappy generator. The biggest problem I have in my shop is my heavy lighting loads. Back in '99 I scrapped several dozen 4' and 8" t12 fluorescent fixtures from an elementary school in Kansas City we did a remodel on and lit my shop up like the sun. Well not really lit like the sun but the wattage was stupid high. I didn't care at the time, I had Light! Then about 10 years ago I came across a pile of t8 ballasts and swapped out all my t12s for t8s and it got brighter but still has a stupid high current draw. Over time I will be removing all my fluorescent or incandescent lighting in my shop as I have done in my house and replace it with LED lighting. The 8' fixtures I have each use 6-34watt t8 4' tubes, so each fixture requires over 200 watts and without going out and counting them I think there's a total of 2.4kw of fluorescent lighting out there if I flipped all the switches at once. I can probably get the same thing done with 200 watts of LED lighting and most anytime I'm out there won't use more than 20-30 watts of LED lighting.
I spent my working life building electrical infrastructure for others. Now I'm mostly motivated at this point to build something for my grandsons that is sustainable and self sufficient. By the time this late bloomer completes this project I'll be knocking on the door. I made my living as an electricain and both my sons are doing likewise. There's a good chance 1 of my grandsons will follow suit. I've got my eye on him to pick this never ending project up in 10 years, when it will probably once again be falling behind the times.
During blackout periods (very rarely in the summer) my shop is where I run my generator from. It's far enough away I barely hear it running and it stays out of the ice and snow that way.

Thanks again for your insight and thoughtful input!

 

[Ozark Tinkering]

As an example, when we need to operate off-grid (grid outage backup), then I can use my 3kW (inverter) generator to power the home directly or I can use it to make sure batteries are recharged if the solar PV isn't able to (crappy solar day for instance).

2 hours of charging by my generator = 8 hours of backup supply in the battery. I'd rather run the generator for 2 hours than 8.

Circling back...I'm thinking that later down the road (probably at least 3 years) I will pick up a small inverter/gen jsut for the purpose of topping off my batteries and push that big inverter out of the way, but only after I have enough storage and solar to become full time off-grid. Otherwise the propane I waste idling the big inverter/gen during low power use outages, over a 2-3 day period I can handle. We were down and dirty about 3 weeks ago for just over 48 hours and I burned through about $30 worth of propane and let the house go dark overnight. If I was having to do that long term it would be a real burden, but as a short term cure in an outage it seems well worth the $15 a day. The large inverter/gen will NEVER run unless there is an outage, even after I have installed the lv6548s (or equivalent). I believe by the time I get the batteries and additional solar installed, I will likely have a very gently used 9000watt dual fuel inverter/generator for sale, that if I choose the right time of the year to sell, it will very li8kely sell for close to what I paid for it. Around here when an ice storm hits everyone goes looking to buy a generator as soon as the ice melts. They don't want to be stuck that way a second time. You would think that after a few years we would run out of people panic buying generators, but noobies keep on showing up and the hardware store shelves are bare empty in the generator aisle. There's a seasonal market here on generators just like with propane. If you wait until the dead of winter you will pay 50% more to have propane delivered here. If you buy it in the summer it's pretty reasonable. I use just under 400 gallons of propane per year and my 1000 gallon tank holds a 2 year supply at 80% full.

 

[labeeman]

I live here on the Gulf coast and I can tell you why there is a run on generators every time there is a storm. People do not store them right they leave some gas in the tank and it will go bad and gum up the carb and will not start the next storm. My two neighbors did that the last two years and have bought new generators two years in a row with propane that will never happen. My generator is over 30 years old it is only 5kw with a 4 cylinder motor water-cooled.

 

[Ozark Tinkering]

I live here on the Gulf coast and I can tell you why there is a run on generators every time there is a storm. People do not store them right they leave some gas in the tank and it will go bad and gum up the carb and will not start the next storm. My two neighbors did that the last two years and have bought new generators two years in a row with propane that will never happen. My generator is over 30 years old it is only 5kw with a 4 cylinder motor water-cooled.

Boy Howdy!! I haven't run more than a gallon of gasoline through my generator since converting it after the very first storm it went through 13 years ago. I do nothing but change the oil annually. Maybe I should send it down their way? It has a very clean carb? I've got partners in Lake Charles that I would think would have solved that decades back but they don't...and won't.

 

[wattmatters]

The Enphase system by itself was just under $13k

Yeah, Enphase isn't cheap, but then solar PV in the US is expensive relative to here (about double what it costs here). A 5kW enphase system here would be ~A$7-8k (~US$5-6k) fully installed by accredited Enphase installers. A good quality grid tied 5kW string inverter system with 6.6kW of panels would average about US$3.5k - 4k to be fully supplied and installed here.

The inverter/gen I'm looking at will be running on propane.

That's a good choice IMO, for various reasons.

The price on that inverter/gen is $2600 and change.

My petrol powered inverter generator is a Yamaha EF3000iSE and I picked it up second hand for A$2k, new they are A$4k. It had ~10 hours use. Very reliable despite not being propane and not being used all that often. I had considered at one time buying a propane conversion kit from the US but really I've no need for that. I just go out and fire it up every so often and also put a battery charger on it at times. Starts first go every time. I usually have plenty of fuel here as the mower needs a good supply and it's cycled regularly. No snowed in Winters here (Winter daily max temp averages 20°C). More likely Summer storm damage (usual cause of grid outages) or flooding events which might cut road access in the region.

Do you know what the exchange rate is between our 2 currencies? If you say something costs $15k, is there much difference between US and Australia $?

It fluctuates but is roughly US$0.70 = $A1.00

So take about 70% of any one of my A$ numbers and that's about the US$ equivalent.

I use about 2mwh per year and average about 43kwh per day after my 5kw rooftop Enphase system has done it's thing each day. It produced 6.5mwh last year and the grid provided the other 1.4mwh.

Not sure a completely follow your numbers. 43kWh/day = 15.7MWh/year. Not that it matters, you know how much you need.

Keep working on the demand side of the equation though, as it makes a big difference to the scope of the supply side of your project. Here's our annual average daily consumption (updated quarterly) for our home since we moved here:

That's a reduction of 20kWh/day since the first full year.

Our grid imports still average 21.5kWh/day, even with our solar PV. Consumption is highly seasonal, with Summer cooling and Winter heating being the biggest single component of energy consumption (47% of our home's total consumption).

I'm very interested in that smart power inverter...have link?!

Mine is this unit:

Green CATCH | CATCH Power

CATCH Power is the Australian Made device that allows you to heat your water for free from the sun. High efficiency taking care of upto 95% of your hot water costs.

www.catchpower.com.au

Haven't installed it yet but sometime in the next month I expect.

But there are various options for this. Some use PWM, others burst fire for adjusting the power delivered to the resistive heating element. There is the Fronius Ohm Pilot, AWS Sunmate, and a raft of others. These are all of course designed for our supply, not sure what sort of systems you have available in the US but googling Solar PV Hot Water power diverter will probably come up with some info.

I'm also interested in a link to follow up on that as well!

I'm no expert in this area but plenty of people do discuss installing soft starters for pumps. Some pumps have this tech built in (like my pool pump, has a very gentle start cycle), or use other means to reduce the surge demand. This item hopefully gives you some ideas to consider:

Choosing Between Soft Starters & Adjustable Frequency Drives

Motors often require large amounts of energy when quickly accelerating to full speed. Using soft starters and adjustable frequency drives reduce in-rush currents and limit torque—protecting valuable equipment and extending the motor's life by reducing motor heating caused by frequent starts and...

www.pumpsandsystems.com

I built my detached shop in '95 and it's equipped for wood and metal work

Yeah, mine was a dilapidated old builder's workshop/shed which I resurrected.

Over time I will be removing all my fluorescent or incandescent lighting in my shop as I have done in my house and replace it with LED lighting.

Good move. Lighting nowadays should consume a trivial amount of energy.

There are LED replacements for T8 fluoro tubes which can go right into existing fittings. Here's an example but you'll need to find something suitable for your local voltages:

LED Tubes

Our LED fluro tubes are a suitable replacement for any existing T8 fluorescent tube light. LED tubes are energy-efficient, long-lasting and mercury free. Simply replace your existing fluro lights with the LED fluro tube and LED starter, and you're done. We stock all common sizes of LED...

reductionrevolution.com.au

I spent my working life building electrical infrastructure for others.

You are far better placed to get this right than most. Four years ago I had zero training, experience or knowledge of this stuff. Since then I've learned a whole heap and built my first off-grid system.

There's a seasonal market here on generators just like with propane.

Happens here in the Summer typically when storms cause outages. Funny though, this Summer (so far) we've not had one outage and I've noticed quite a few generators for sale on local marketplaces, more than normal. I waited nearly a year before buying mine. I knew exactly what I wanted and just waited for the right opportunity. Way better than trying to buy something quickly right when everyone else wants one.

In the interim I had a crappy little 2-stroke generator we were gifted but it did the job before I got the Yamaha. Since then I've put together our grid outage solution, a 2.2kW PV, 4kW AIO inverter and 18kWh of SLA battery storage, as described here:

Backup down under

Greetings from down under. I live in a home near the small town of Bellingen, in northern NSW, Australia. Glorious country: That's our home at left centre, and obscured by the tree and slightly off the left of the image is a secondary dwelling where my Mum lives. 12 acres, behind our home (to...

diysolarforum.com

 

[Ozark Tinkering]

Not sure a completely follow your numbers. 43kWh/day = 15.7MWh/year. Not that it matters, you know how much you need.

Oops good catch. I dropped the zero. It should have read 20mwh and the about is a low about. I went back and changed it.
So my wife was sitting here when I clicked on your thread. She's out in the driveway loading the truck and headed for the boat. I think I could handle it there too. Eucalyptus was the only hardwood that would grow where I came from.

 

[Ozark Tinkering]

July and August are the 2 months out of the year we run air conditioning and is the next project to reduce demand. My central a/c is probably 50 years old (yes older than the house and perfectly good when I saved it from the scrap yard and stuck it up there in "93?) and is pretty inefficient. Who would guess that? Not too unlike that adapted troybilt dinosaur I need to trash, so I'm going to replace it with 3 mini split units and just cool zones we're using. If I can get demand down for those 2 months it will help a whole bunch.

 

[rmaddy]

It should have read 20mwh

Do you mean 20MWh? 20mWh is 0.02Wh. 20MWh is 20000000Wh. Important difference. m means milli (1/1000th). M means mega (1,000,000).

I know a lot of people don't pay much attention to typing in units correctly, and in most cases the intent is understood. But in some cases the correct case is critical. I'm not picking on you. This is just a good example of where it can have a big difference in meaning.

 

[labeeman]

Do you mean 20MWh? 20mWh is 0.02Wh. 20MWh is 20000Wh. Important difference. m means milli (1/1000th). M means mega (1000).

I know a lot of people don't pay much attention to typing in units correctly, and in most cases the intent is understood. But in some cases the correct case is critical. I'm not picking on you. This is just a good example of where it can have a big difference in meaning.

Do you mean 20000000Wh or 20000KWh.?

 

[Ozark Tinkering]

Do you mean 20MWh? 20mWh is 0.02Wh. 20MWh is 20000Wh. Important difference. m means milli (1/1000th). M means mega (1000).

I know a lot of people don't pay much attention to typing in units correctly, and in most cases the intent is understood. But in some cases the correct case is critical. I'm not picking on you. This is just a good example of where it can have a big difference in meaning.

Yes I mean 20 megawatt hours, expressed 20MWh. That is my annual usage including the 6.5 megawatts my 5kw system produces. Design on that system is to produce around 20kWh daily on the AVERAGE. That would be 20,000 watt hours X 365 days. That totals up to 7300kWhs also expressed as 7.3megawatt hours. You can see I did not produce 7.3MWh but only made 6.5MWh. I took down several trees well into April that were knocking out the last hour of good sun I think will get me closer to design. I stated that my usage from the utility was around 43 kWh per day. 43,000watts X 365days = 15,695,000watts. 15.6 megawatts... 15.6mwh. I apologize for the generally approximate numbers of my usage but I don't have my actual records at my disposal. Not sure that ought to be a thang really. Most of the powerhouses I helped build had outputs of 600megawatts or higher. The powerhouse I finished my apprenticeship on totaled 2900megawatt with 3 units. Do 1 megawatt for an hour and you have 1MWh. 1,000,000watts =1mw, 1hr at1megawatt =1MWh.
Did I get all my caps in the right order? LOL!

Do you mean 20000000Wh or 20000KWh.?

20,000,000watts = 20MWh that's what I mean, even if it's not the exact amount I used. It is probably closer to 22,000,000 watts I burned through last year.

 

[Ozark Tinkering]

Hopefully I got all my caps right so nobody thinks I'm putting out milliwatts. Carry on.

 

[rmaddy]

Do you mean 20000000Wh or 20000KWh.?

Oops. I fixed my embarrassing mistake.

BTW - that would be 20000kWh (little k for kilo)

 

[Ozark Tinkering]

Oops. I fixed my embarrassing mistake.

That's okay without the rest marks I got lost counting up the zeros anyway...