Delta Pro vs DIY in a minimalist backup battery application?

[sethcentral]

This question is about whether there is DIY solution that is cheaper than the Delta Pro for one relatively specific application.

The application is: temporary backup of a few circuits in my home panel in an outage. Specifically, I want at least 30 amps at 120v. I have a 30 amp 120v/240v inlet connected to my home panel via an interlock. In a power outage, the typical thing, of course, would be to hook up a gas generator. What I would like to know is what the cheapest battery-based alternative to this would look like. I specifically want a battery that can take full advantage of the 30 amp generator inlet already connected to my panel. A further constraint is that I would only want to charge the battery via 120v AC. Not solar/DC. So this question is about how this could be best achieved.

As far as I know (feel free to correct me), the cheapest "off the shelf" solutions here are the Delta Pro and the Bluetti AC300, both priced today at around $3.6K. However, the Bluetti can technically only achieve 25 amps at 120v, so for the application I am interested in, the Delta Pro wins. One Delta Pro can apparently push 30 amps at 120v. You would need two ($7.2K) to achieve 30 amps at 240v. 240v would be epic, but let's suppose 120v is fine for now.

OK, question: is there some DIY, or DIY-ish, solution that could compete with the Delta Pro in this exact application, i.e., achieving 30 amps at 120v, and charging via ordinary AC? I'm pretty ignorant about batteries and inverters so I hope you pros can help me. Evidently cheap LiFePo4 is plentiful. Suppose I get one of those EG4 racks, just for instance. That would give me more storage than a Delta Pro. What inverter/charger would be the easiest to pair with one of those EG4s in order to ultimately get one 30 amp plug I can connect to my home panel? Curious how the price would compare to the Delta Pro. Any advice welcome, thanks in advance.

 

[BentleyJ]

Published pricing for an MPP Solar 6548 and 1 EG4 or SOK 48V rack battery plus misc. wiring, lugs Etc. would be about the samve price. $3,500 and the system would have more battery storage and more than the 30Amp @120V output required. If you are comfortable with doing the wiring yourself and have the time, the DIY system is clearly the better choice.
Also, if you wanted to upgrade to 240V its easy enough to add another 6548 and another battery.

 

[sethcentral]

Published pricing for an MPP Solar 6548 and 1 EG4 or SOK 48V rack battery plus misc. wiring, lugs Etc. would be about the samve price. $3,500 and the system would have more battery storage and more than the 30Amp @120V output required. If you are comfortable with doing the wiring yourself and have the time, the DIY system is clearly the better choice.
Also, if you wanted to upgrade to 240V its easy enough to add another 6548 and another battery.

Amazing, thanks very much for this!! I would never have thought to consider the MPP Solar 6548. This indeed would be a more powerful system in both storage and amps. I've been trying to figure this out for a while, so many thanks!

On the spectrum from complete beginner to expert, how difficult would you say the assembly would be? I probably wouldn't attempt this with some expert supervision in any case, but I'm curious how hard this is overall. Most of the how-to videos I've watched on this kind of thing mix in issues about solar panels that aren't relevant to my application, so I've had some trouble gauging how complex this job is. In any case thanks so much again.

Incidentally it seems surprising to me that there are no inverters with a built-in 30 amp outlet (whereas inverters with built-in 15-20 amp outlets are ubiquitous). I think a lot of people would find a 30amp plug-and-play inverter pretty convenient.

 

[BentleyJ]

but I'm curious how hard this is overall.

Incidentally it seems surprising to me that there are no inverters with a built-in 30 amp outlet (whereas inverters with built-in 15-20 amp outlets are ubiquitous). I think a lot of people would find a 30amp plug-and-play inverter pretty convenient.

In your case with no solar panels to deal with, having that 30A receptacle & manual transfer switch installed already, all you really need to do is connect the AC input & output and battery wiring to the Inverter. Probably the hardest part is the compression lugs if you don't have a hydraulic crimper. This subject has been covered in detail on this forum so in the interest of not being redundant, please feel free to send me a private message and I would be happy to go over the details and answer any questions.

I share your surprise that there are no non gasoline plug-and-play back-up generator products out there.

 

[sethcentral]

In your case with no solar panels to deal with, having that 30A receptacle & manual transfer switch installed already, all you really need to do is connect the AC input & output and battery wiring to the Inverter. Probably the hardest part is the compression lugs if you don't have a hydraulic crimper. This subject has been covered in detail on this forum so in the interest of not being redundant, please feel free to send me a private message and I would be happy to go over the details and answer any questions.

Thanks -- that is super generous of you. I really appreciate it. I will definitely take you up on that if I move forward with this sort of project. You've already answered questions that have saved me many hours of research, so thanks again for that.

Regarding the inverter you suggested, just curious -- is this a popular choice that most enthusiasts around these parts would know about, or did you choose it as just one out of a number of equally good options? I am guessing the former but I just thought I'd check. (Or maybe you chose it particularly for the expandability to split phase?)

On the one hand, this would clearly take many more hours more work (for me) than just buying a Delta Pro, and the system itself would take up more space than the Delta. But it would clearly be a considerably more powerful system than the Delta Pro, for around the same cost. So I have to figure out if the added power is worth the time cost, which is partly a matter of figuring out how steep the learning curve is for me here! I'll try to watch a few more videos to get a sense what I'd be in for. Anyway thanks again for the generous assistance.

 

[BentleyJ]

Will Prowse has reviewed several MPP Solar Brand Inverters on YT and has had good results. Overall the product seems to be one of the best value propositions available. Value being defined as Reliability and Features for the price. There are other brands that fall into the same price vs. function category but overall MPP Solar would be my choice for your situation based on what I've seen and read.

 

[Supervstech]

I think the 6548 is a great inverter.
But it is pricy BECAUSE it is so versatile.
It has TWO MPPT solar charge controllers.
So, since you aren’t planning to use solar it may be more than you want.
It ALSO has a 120V charger, so it may work out, with options for solar in the future.

Sigineer and a few others sell 6000W inverter/chargers. No solar input. However, they are HEAVY because they are low frequency high long lasting surge wattage.

 

[SparkyJJO]

If you're not looking for any solar input etc you can get inverter chargers withoutbthat extra for "cheap ish" - AIMES, SunGoldpower, Sigineer (all basically the same) have some inverter chargers that are simple but likely do what you want. $935 for a 4kw 120v output.

 

[sethcentral]

Thanks SparkyJJO for pointing this out! Yep, that's the sort of thing I was mostly looking at. At first, I thought maybe the MPP Solar 6548 is overkill for my needs. However, for that additional $550, it is interesting to see how much more you get: 50% more wattage, the option to scale up to 240V, and of course the option to add solar. It's true that these benefits aren't relevant to my target application (except for the 240V part!). But it does make the Sungoldpower 4kw 120v output inverter look almost pricey at $935, and makes me reconsider whether I should just go bigger.

 

[Dank Farrik]

I actually scoped out an entire build with MPP Solar AIO and SOK server rack batteries, when I decided that I'm too busy/exhausted and just went the Delta Pro route. It's definitely cheaper to go DIY, but it won't be as tidy/compact, and won't be as integrated. Do note that periodically the Delta Pro goes on sale at Costco for $2850 (at least that was the price for the last 2 times). So if you can pick it up during a sale, the prices are a lot better than the retail price.

 

[LazyDragon]

As Dank Farrik alluded to, you're missing a huge component in your price calculations: Your time!
If you want this to be a big learning exercise in solar power, then go the DIY route and you will learn a lot. You might even get the solar bug and start putting panels on your roof Your time will be invested in education.
If you just want to solve the problem of powering your load during an emergency, buy a decent dual fuel inverter generator for $1k, put it in the corner of the garage, and move on. Spend your time on your next project.

 

[12VoltInstalls]

further constraint is that I would only want to charge the battery via 120v AC. Not solar/DC. So this question is about how this could be best achieved.

Not to diverge off your stated goals but I am curious where you wound up. I was reading and just thinking what I might do.

As a temporary power solution the 6548 makes sense, but adding at least some solar would get it to paying some of its own room’n’board by shaving some of your electrical bill. I believe you can set it to use solar while not leaning on the battery.
It could make cents for you as a lot of daily electricity costs midday are also lower demand times for many people because they’re at work and not home.

 

[sethcentral]

Not to diverge off your stated goals but I am curious where you wound up. I was reading and just thinking what I might do.

As a temporary power solution the 6548 makes sense, but adding at least some solar would get it to paying some of its own room’n’board by shaving some of your electrical bill. I believe you can set it to use solar while not leaning on the battery.
It could make cents for you as a lot of daily electricity costs midday are also lower demand times for many people because they’re at work and not home.

Thanks, I haven't made a decision yet. Here's a recent video of Will's that is exactly the kind of system we have been discussing here:

As Dank Farrik and LazyDragon note, this is not braindead simple like a Delta Pro would be. However, the storage gap between the two solutions is large. Ideal for me would be able to to supply 240 loads. With the Deltas that's around $7.5K (unless you catch a sale at Costco -- thanks for the tip Farrik!), and you get 7.2kWh. With a system like BentleyJ/Will's, you get 15kWh for around the same price, and further expansion is much cheaper. Is the extra power worth the time it takes to setup? That's subjective, but for me, probably I'd say "yes". (Will says it took him an hour. So figure it takes me a day? And/or I hire some wiz on the forum here to walk me through every step/doublecheck my work.)

LazyDragon, way ahead of you there -- I have a 7.6kW system on the roof and a gas backup generator in the garage I opted not to get a battery backup during install of the panels because the price didn't make sense. (With prices coming down the way they have since, I am so glad I didn't do it.) I do at least have an SMA inverter with an SPS power supply that can deliver 2kW to one dedicated outlet in the garage the event the grid is down. Not much, but not nothing... and could be used to extend the life of a lithium backup battery in the event of an outage.

I do agree that a simple gas generator is the cheapest and easiest solution to the problem (that's why I have one!). But you know, gas sucks. Generators need to be maintained, have to be outside, are noisy, need.... gas, and you're just not really going to wheel it out for those random two hour outages, etc. A battery system would be so much nicer.

But yeah to come back to 2VoltInstalls, the question does arise how to get the most benefit from this system given the expense. It's a bit silly to have a beautiful 15kW $8K battery system like this sitting there doing pretty much nothing waiting for an outage. So that's probably why I haven't moved on this. My solar system is oversized, so with net metering here in California I already pay nothing, so I woudn't really get added value running the house on batteries at night.

One benefit that could tip the balance in favor of the batteries is to use them so as to increase the overall power available to the house at any given time. Our home panel is rated to 200 amps but our service from the street is 125 amps. This has never been a problem but I can see issues down the road with an EV, since our dryer and stove are both electric, we use central AC in the summer, etc. So if I go for this kind of system that might be the decisive reason. (Then again, if somebody can make an EV with built-in bidirectional charging that can service a generator panel at 240 volts...)

 

[binkdog]

Thanks, I haven't made a decision yet. Here's a recent video of Will's that is exactly the kind of system we have been discussing here:

As Dank Farrik and LazyDragon note, this is not braindead simple like a Delta Pro would be. However, the storage gap between the two solutions is large. Ideal for me would be able to to supply 240 loads. With the Deltas that's around $7.5K (unless you catch a sale at Costco -- thanks for the tip Farrik!), and you get 7.2kWh. With a system like BentleyJ/Will's, you get 15kWh for around the same price, and further expansion is much cheaper. Is the extra power worth the time it takes to setup? That's subjective, but for me, probably I'd say "yes". (Will says it took him an hour. So figure it takes me a day? And/or I hire some wiz on the forum here to walk me through every step/doublecheck my work.)

LazyDragon, way ahead of you there -- I have a 7.6kW system on the roof and a gas backup generator in the garage I opted not to get a battery backup during install of the panels because the price didn't make sense. (With prices coming down the way they have since, I am so glad I didn't do it.) I do at least have an SMA inverter with an SPS power supply that can deliver 2kW to one dedicated outlet in the garage the event the grid is down. Not much, but not nothing... and could be used to extend the life of a lithium backup battery in the event of an outage.

I do agree that a simple gas generator is the cheapest and easiest solution to the problem (that's why I have one!). But you know, gas sucks. Generators need to be maintained, have to be outside, are noisy, need.... gas, and you're just not really going to wheel it out for those random two hour outages, etc. A battery system would be so much nicer.

But yeah to come back to 2VoltInstalls, the question does arise how to get the most benefit from this system given the expense. It's a bit silly to have a beautiful 15kW $8K battery system like this sitting there doing pretty much nothing waiting for an outage. So that's probably why I haven't moved on this. My solar system is oversized, so with net metering here in California I already pay nothing, so I woudn't really get added value running the house on batteries at night.

One benefit that could tip the balance in favor of the batteries is to use them so as to increase the overall power available to the house at any given time. Our home panel is rated to 200 amps but our service from the street is 125 amps. This has never been a problem but I can see issues down the road with an EV, since our dryer and stove are both electric, we use central AC in the summer, etc. So if I go for this kind of system that might be the decisive reason. (Then again, if somebody can make an EV with built-in bidirectional charging that can service a generator panel at 240 volts...)

Thanks for this thread - I'm definitely not in the same boat, but am looking for a grid down solution and the delta pro (dual for 240) is calling my name .

I'm curious - you said your 7.6kw system is totally covering your needs now and you're paying nothing on the electric bill with a grid tie in? I'm wondering how that is if I understood correctly.

I'm in TX and we are admittedly energy hogs (i've got family members who think electricity is free and they run lights and fans 24/7) - we're in a big house (3,000 sq ft) with two 3.5 ton AC/Heat (central air - all electric), a well system that includes a submersible pump and a booster pump, both 240v (booster runs pretty much non-stop pulling from a 1,500 gallon storage tank whenever a tap is open, submersible kicks on about every 20-30 mins and tries to push water to tank if float switch is low enough).

We have all electric - 240v water heater, oven, along with the big dual blower units in the attic. We also have an extra fridge and freezer in the garage. And the topper - a 30 ft above ground pool with a 1hp pump running constantly in the late spring and summer. Obviously we won't run all these things in grid down.

My main concern is the water and our food storage in the fridges/freezer. With those 2 pumps @ 240v and wired into a breaker box that's tied to the main breaker (they're about 50-100 ft away), my solution has to include 240 (thus the delta pro "dual" setup seems perfect (especially with the plug-compatible 240v box) for a non-electrician like myself ).

I recently had a solar installer give me a solution based on our usage from the utility company - we are basically taking 2-3x the national average - let's just say we are nowhere near the average daily usage. He wanted to install a 30kw solar solution "daytime" tie-in, but auto disconnect system which would cover most things except the water heater, 1 hvac unit and the pool. The system design is awesome, but it's very pricey - somewhere in the 80K range.

I already have the 30amp receptacle and interlock switch for the dual fuel generator we got after the big freeze. What I'm looking for is something I can use over and over (only have limited generator fuel), assuming I could charge up a solar-based system fast enough (obviously depends on time of year, weather, etc ...).

I like the flexibility and "portability" of the delta, just curious how you're powering an entire house on electric for under 10kwh daily? I guess with only a single HVAC unit, no extra fridges and no well, it's probably very doable Now I'm debating the need for the dual system with an extra battery on each delta pro to make sure I have enough surge watts and potentially get an electrician to hook me up the smart home panel ... and if I'm doing that, might as well get a less portable, more powerful DIY setup and pay somebody to do it - LOL.

 

[12VoltInstalls]

shortage of carriage returns

 

[binkdog]

shortage of carriage returns

lol - sorry about that - I don't usually drop a giant block of text like that . It's been fixed

 

[sethcentral]

Thanks for this thread - I'm definitely not in the same boat, but am looking for a grid down solution and the delta pro (dual for 240) is calling my name .

I'm curious - you said your 7.6kw system is totally covering your needs now and you're paying nothing on the electric bill with a grid tie in? I'm wondering how that is if I understood correctly.

I'm in TX and we are admittedly energy hogs (i've got family members who think electricity is free and they run lights and fans 24/7) - we're in a big house (3,000 sq ft) with two 3.5 ton AC/Heat (central air - all electric), a well system that includes a submersible pump and a booster pump, both 240v (booster runs pretty much non-stop pulling from a 1,500 gallon storage tank whenever a tap is open, submersible kicks on about every 20-30 mins and tries to push water to tank if float switch is low enough).

We have all electric - 240v water heater, oven, along with the big dual blower units in the attic. We also have an extra fridge and freezer in the garage. And the topper - a 30 ft above ground pool with a 1hp pump running constantly in the late spring and summer. Obviously we won't run all these things in grid down.

My main concern is the water and our food storage in the fridges/freezer. With those 2 pumps @ 240v and wired into a breaker box that's tied to the main breaker (they're about 50-100 ft away), my solution has to include 240 (thus the delta pro "dual" setup seems perfect (especially with the plug-compatible 240v box) for a non-electrician like myself ).

I recently had a solar installer give me a solution based on our usage from the utility company - we are basically taking 2-3x the national average - let's just say we are nowhere near the average daily usage. He wanted to install a 30kw solar solution "daytime" tie-in, but auto disconnect system which would cover most things except the water heater, 1 hvac unit and the pool. The system design is awesome, but it's very pricey - somewhere in the 80K range.

I already have the 30amp receptacle and interlock switch for the dual fuel generator we got after the big freeze. What I'm looking for is something I can use over and over (only have limited generator fuel), assuming I could charge up a solar-based system fast enough (obviously depends on time of year, weather, etc ...).

I like the flexibility and "portability" of the delta, just curious how you're powering an entire house on electric for under 10kwh daily? I guess with only a single HVAC unit, no extra fridges and no well, it's probably very doable Now I'm debating the need for the dual system with an extra battery on each delta pro to make sure I have enough surge watts and potentially get an electrician to hook me up the smart home panel ... and if I'm doing that, might as well get a less portable, more powerful DIY setup and pay somebody to do it - LOL.

To clarify, my solar panel system is 7.6kW, but this doesn't mean that it's max daily generation is under 10kWh... rather, the system can (theoretically) generate up to 7.6kW per hour (if conditions were ideal). So, today, for instance, it produced a total of 48kWh.

Our house is 1500 sq ft, no pool, no well, one fridge, central AC, electric dryer and range, gas furnace and hot water. Looking at my Sense monitor, we used 571kWh last month, so call it about 20 kWh/day. (Goes up in the winter.) On the other hand our solar generation last month was 1064kWh, so almost double what we used. The way it works here in CA (for now...) is that you get credited for your excess kWh, and you spend those credits at night, in the winter, on days with low sun, etc. So at the end of the day, no bill.

You definitely use way, way, way more power... still, a 30kW solar panel system seems way too big to me. (Note again that we could have used *twice* the amount of power we actually did last month and my 7.6kW system still would have basically covered it!) Average residential solar installs in the US are like 5-6 kW. So even you are 3x the natural average (which is sounds like you are) that would suggest 15-18kW, not 30. Are you in some sort of super low-light situation, with a lot of shade obstructing where the panels would be? Otherwise 30kW sounds way bigger than you need.

 

[Dank Farrik]

To clarify, my solar panel system is 7.6kW, but this doesn't mean that it's max daily generation is under 10kWh... rather, the system can (theoretically) generate up to 7.6kW per hour (if conditions were ideal). So, today, for instance, it produced a total of 48kWh.

Our house is 1500 sq ft, no pool, no well, one fridge, central AC, electric dryer and range, gas furnace and hot water. Looking at my Sense monitor, we used 571kWh last month, so call it about 20 kWh/day. (Goes up in the winter.) On the other hand our solar generation last month was 1064kWh, so almost double what we used. The way it works here in CA (for now...) is that you get credited for your excess kWh, and you spend those credits at night, in the winter, on days with low sun, etc. So at the end of the day, no bill.

You definitely use way, way, way more power... still, a 30kW solar panel system seems way too big to me. (Note again that we could have used *twice* the amount of power we actually did last month and my 7.6kW system still would have basically covered it!) Average residential solar installs in the US are like 5-6 kW. So even you are 3x the natural average (which is sounds like you are) that would suggest 15-18kW, not 30. Are you in some sort of super low-light situation, with a lot of shade obstructing where the panels would be? Otherwise 30kW sounds way bigger than you need.

It really depends on the direction and angle of your roof. My 12kw system is unfortunately mostly east-west facing, and a nice sunny day right now only produces around 60 kWh per day.

 

[binkdog]

To clarify, my solar panel system is 7.6kW, but this doesn't mean that it's max daily generation is under 10kWh... rather, the system can (theoretically) generate up to 7.6kW per hour (if conditions were ideal). So, today, for instance, it produced a total of 48kWh.

Our house is 1500 sq ft, no pool, no well, one fridge, central AC, electric dryer and range, gas furnace and hot water. Looking at my Sense monitor, we used 571kWh last month, so call it about 20 kWh/day. (Goes up in the winter.) On the other hand our solar generation last month was 1064kWh, so almost double what we used. The way it works here in CA (for now...) is that you get credited for your excess kWh, and you spend those credits at night, in the winter, on days with low sun, etc. So at the end of the day, no bill.

You definitely use way, way, way more power... still, a 30kW solar panel system seems way too big to me. (Note again that we could have used *twice* the amount of power we actually did last month and my 7.6kW system still would have basically covered it!) Average residential solar installs in the US are like 5-6 kW. So even you are 3x the natural average (which is sounds like you are) that would suggest 15-18kW, not 30. Are you in some sort of super low-light situation, with a lot of shade obstructing where the panels would be? Otherwise 30kW sounds way bigger than you need.

Thanks for the info - that makes sense ! We’re actually in an ideal spot for solar - fairly unobstructed, back of the house faces due south, a nice shiny metal roof, and I’m in south texas - I need to get some panels on the roof

 

[binkdog]

It really depends on the direction and angle of your roof. My 12kw system is unfortunately mostly east-west facing, and a nice sunny day right now only produces around 60 kWh per day.

wow such differences!. Based on our roof angle, facing due south and our zip code, looks like my peak sun hours are over 5 , but we'll round down to 5. I'm assuming that means in theory my system should produce around that (system size * peak) per day, considering it will produce some in non-peak hours of daylight? Assuming that, I can see where seth said a 15kw system would probably cover our 3x the national average usage. In theory, a 10kw system with 5 hours of peak sun would generate around 50kwh/day if I'm understanding all this Thank y'all for the guidance. Need to watch that will video next