DIY home battery backup no solar

[rpatel18]

Brief Context: We're expecting our first child in December and one of things I've started to get worried about is the power outages in our area, Menlo Park, CA. This past winter, we had some pretty bad rain and wind storms where we lost power 3 times and it took about 30hrs for the power to come back on each time. I've been bouncing back and forth over a gas generator or a battery backup and I think I'm leaning towards a battery system now. One of the main reasons is the power outages are usually happening during a really bad rain storm with high winds and I don't feel comfortable running a generator overnight even though It'd be in a generator tent. I'm thinking if I got a battery system and rack mounted it, I could keep it in the garage.

I've had a Emporia Vue installed since December to monitor our energy use... with the data collected, I've seen that the house will pull a max ~3000watts/~25amps w/ the heat running (heat pump), lights on, fridge running, and tv running (this included home theater system). On average, it's pulling about ~1500watts/~15amps. Obviously we'd wouldn't be watching TV and using minimal light as the key is the keep the heat on and the fridge running. Since the heat is on 240v, I'll need some sort of split phase system I think?

I was looking at possibly getting one of those all in one systems like 2 Ecoflow Delta Pros and connecting them to a generator interlock so I can manually switch it to a battery system, but all of the systems I've seen (Bluetti, Ecoflow) can only provide 30amps of power at 240v and fairly lower wattage output too.

I recently started to look into a DIY setup and was wondering if I could accomplish the same as one of these prebuilt systems provide but for cheaper and provide 50amps of output and higher wattage? 2 inverters and some batteries to create a battery backup system that could wire into a 50amp interlock breaker into my main panel. What I don't know or I have question are a few things:

• Is this a realistic setup (generically) for what I'm looking to achieve?
• If I have a 120v 1800w gas generator, could I charge a system like this while its powering the house? This is something that I do like in the Ecoflow Delta Pro product
• If I could reasonably do this via a DIY setup, what would be my best options in terms of product lines... EG4, Victron, etc...

thanks in advance to tips and thoughts!

 

[DIYrich]

What is your budget? I have a Sol-ark 15k with 45kWh of batteries, and no solar (doing a remodel before putting panels on the roof). It will do what you are asking.

30 hours at 1.5kW is 45kWh. Any 5kW inverter (leave some margin) would work. I personally like the chargeverter with a cheap generator to recharge the batteries.

For a worst case scenario, you probably want 24hr worth of batteries so you can run the generator once a day. If you have 35kWh of batteries and a 5kW generator, it will take 7 hours to recharge the batteries from empty to full.

Once you have the inverter and batteries, it is not that much more to add solar.

 

[rpatel18]

I'd like to keep it under $6k if I can. You're spot on about the charging part too, hoping to charge during the day and use battery only at night. Just looked at my Vue charts again and it looks like on a winter day where we ran the heat a lot, we were consuming ~30kWh/day. We could use the heat less at night and maybe just keep a space heater in the babies room.

 

[GSXR1000]

you say 25amps at 220v is 5500 watts... and will need lots of battery for 30 hours...

 

[DIYrich]

$6,000: might be able to diy 30kWh with grade b batteries for around $4,000. That leaves $2,000 for an inverter, which is doable. Installation and generator are on top of that.

UL 9540 is a problem. DIY is not UL9540 certified. I think under $2k per 5kWh rack battery ul 9540 certified is about the cheapest I have seen.

 

[rpatel18]

you say 25amps at 220v is 5500 watts... and will need lots of battery for 30 hours...

yes... but that is the peak it'll pull which doesn't last too long... here is the a data export view on my hourly and daily stats. Our usgae would be much lower in the event of an outage as we wouldn't be doing things like running the laundry or running the dishwasher.

https://public.tableau.com/app/profile/ronak.patel4393/viz/hourlydailyusage/Dashboard1#1

 

[rpatel18]

$6,000: might be able to diy 30kWh with grade b batteries for around $4,000. That leaves $2,000 for an inverter, which is doable. Installation and generator are on top of that.

UL 9540 is a problem. DIY is not UL9540 certified. I think under $2k per 5kWh rack battery ul 9540 certified is about the cheapest I have seen.

I maybe misunderstanding the DIY concept here... I was thinking DIY is buying rack batteries, inverter, etc.. and wiring it up yourself vs buying in Ecoflow or similar product.

 

[DIYrich]

I maybe misunderstanding the DIY concept here... I was thinking DIY is buying rack batteries, inverter, etc.. and wiring it up yourself vs buying in Ecoflow or similar product.

Kind of like cooking from scratch. Some consider starting with a box of dry pasta and a can of chicken stock as cooking from scratch. Others make their own pasta and chicken stock.

Diy grade b battery cell is about $100 per 300ah cell. You need 16 cells, a bms, and some other stuff, or about $2,000 minimum for about 15kWh.

 

[rpatel18]

ah I see…yeah, I’m more of the pre made pasta and store bought chicken stock. I wonder if a setup with a split phase inverter and 3 5.12kwh rack mount batteries. I also have a 1800w generator that I can use to charge the batteries during the day. I think that could get me through ~30hrs without power or close to it.

 

[50ShadesOfDirt]

You have a grid connection, so I'd go the DIY route of building your own "solar generator" ... an AIO, some LiFePO4 batteries, and a chargeverter battery charger, all in a 48v design, all designed to meet your specific constraints. It's a full solar energy system, just without the mppt & panels (which you could add later).

You'll run it "parallel" to the grid when the grid is down, and the only thing it reaches into the grid for is the power to run the chargeverter, when the grid is back up. Up to you and your electrician to decide how manual or automatic the switchover is, during an outage. Because it is parallel, there is little to no grid-connected or code issues.

Your current generator, depending on its capabilities, might also stand in for the grid, if the outage lasts longer than some given time frame. It just needs to be able to drive the chargeverter.

Can easily size it to meet current budget, and expand it later as more money becomes available (get a stacking/parallel-able inverter; battery-banks are also easily expandable).

Hope this helps ...

 

[rpatel18]

when you say "building your own "solar generator" ... an AIO"... is that the same as getting an inverter? or is this something different?

 

[ghostwriter66]

I have NO association at all with this company BUT you might want to look at the EEL product line ... the POC there is
howard@eelbattery.com ... instead of building your own batteries these guys build it for a little more than we can for work ...

also these have turned out to also be some really good already made batteries (pasta in a box) https://www.amazon.com/gp/product/B0B56DS84F/ref=ox_sc_saved_image_8?smid=AXKE0HN8EKC3C&th=1

just my 02 ... EEL will take about 40 days to get to you .. the DEESPAEK about 4 ... both are solid ... if yo have time to wait then EEL is the way to go ...

After building probably our 100th battery we just realized that prices and hardware have came down so much its just easier to buy ready made then put it together yourself ... unless you just really like doing that ...

 

[DIYrich]

I have NO association at all with this company BUT you might want to look at the EEL product line ... the POC there is
howard@eelbattery.com ... instead of building your own batteries these guys build it for a little more than we can for work ...

also these have turned out to also be some really good already made batteries (pasta in a box) https://www.amazon.com/gp/product/B0B56DS84F/ref=ox_sc_saved_image_8?smid=AXKE0HN8EKC3C&th=1

just my 02 ... EEL will take about 40 days to get to you .. the DEESPAEK about 4 ... both are solid ... if yo have time to wait then EEL is the way to go ...

After building probably our 100th battery we just realized that prices and hardware have came down so much its just easier to buy ready made then put it together yourself ... unless you just really like doing that ...

UL 9540?

 

[DIYrich]

You'll run it "parallel" to the grid when the grid is down, and the only thing it reaches into the grid for is the power to run the chargeverter, when the grid is back up. Up to you and your electrician to decide how manual or automatic the switchover is, during an outage. Because it is parallel, there is little to no grid-connected or code issues.

Not exporting to the grid solves the "interconnection", "permission to operate", but code is code. If it touches the wiring in the house (other than taking power from a socket), it has to meet code. Pushing power into the Main Panel that is connected to the Grid is definitely a code issue.

Your current generator, depending on its capabilities, might also stand in for the grid, if the outage lasts longer than some given time frame. It just needs to be able to drive the chargeverter.

His 1,800 watt generator is barely capable of handling his 1,500 watt average load. That assumes he is willing to run the generator 24/7 starting as soon as the batteries hit 50%.

Note: 1,500 watts is 83% of the generator's rating. You don't want to run the generator more than 80% for a prolonged period of time. Also assume a conversion loss (10%?) from AC to DC to charge the batteries.

1,500 watts is 36kWh per day. Let's say you want to run a generator 8 hours to recharge your batteries for another day's load. That means 4.5kW of power into the batteries (4.5kW x 8h = 36kWh). A 5.6kW generator running at 80% would produce 4.5kW. Assuming a 10% conversion loss, you would need a 6.25kW generator running at 80% to net 4.5kW to the batteries. 5 hours would be the recommended minimum charge time for LiFePO4 batteries. 4 hours (12.5kW generator) is probably ok a few times a year.

 

[ghostwriter66]

UL 9540?

Probably not ... I keep forgetting that some of you guys live in counties with CODE enforcement ...

 

[HarryN]

This is the big challenge with the concept of moving to an all electric future.

With a fuel based heating system, it only takes a small amount of back up power to run a furnace. With a heat pump, the load is nearly impossible to support with battery back up.

I know exactly what you mean about the outages- I live in the east bay and between the seasonal fires, storms and earthquakes - outages are a given.

My suggestion is to start by looking at a heating method that does not depend on more than a nominal amount of electricity.

The next priority honestly is to keep the refrigerator going.

Some lights and device charging are the easy part.

 

[DIYrich]

Probably not ... I keep forgetting that some of you guys live in counties with CODE enforcement ...

Most

 

[rpatel18]

here is what I'm thinking in terms of setup, would something like this work? I think this will meet my power needs and if I do run short, I can always expand the battery capacity I'm thinking...

the part I also couldn't quite figure out is where exactly do I mount the charging terminal of the battery charger? do I need to put those in a specific spot on the bus bar in the rack>

 

[David_532]

Your concern about power outages, especially with the expectation of a new child in the house, is completely understandable. Choosing a battery backup system over a gas generator seems a wise decision, given the weather conditions and your reluctance to operate a generator overnight. Below is a response to your queries:

Is this a realistic setup (generically) for what I'm looking to achieve?

Yes, your DIY battery backup system is a realistic and feasible project. You can configure a system with 2 inverters and sufficient batteries to cater to your needs. Make sure to involve a certified electrician to ensure everything is done according to code and safety standards.
If I have a 120v 1800w gas generator, could I charge a system like this while its powering the house?

Charging a battery bank while also powering your house is possible. However, you'll have to carefully calculate the load, and it might be best to use a separate charger that can be driven by the generator. You'll also want to make sure your generator has the capacity to handle both tasks.
If I could reasonably do this via a DIY setup, what would be my best options in terms of product lines... EG4, Victron, etc...?

Both EG4 and Victron are reputable brands for inverters and other power systems. Victron, in particular, has a wide range of products that cater to different needs, and their equipment is known for its reliability and efficiency. You may also consider talking to local suppliers to see what they recommend based on your specific requirements.
Regarding your home theater system, you mentioned it in your energy consumption calculations. Since entertainment systems are something you seem to value, you may also consider energy-efficient options for your home theater setup. For expertise on home theater systems, particularly in terms of audio quality, you can visit hifiaudios.com, a site specializing in high-fidelity audio solutions.

It's worth noting that building a DIY battery backup system that meets your requirements could be a complex project. Consulting with a professional electrician who has experience in renewable energy systems would be a good idea to make sure you get a system that meets your needs and complies with all local regulations.

 

[DIYrich]

the part I also couldn't quite figure out is where exactly do I mount the charging terminal of the battery charger? do I need to put those in a specific spot on the bus bar in the rack>

Connect charger either C-G-B or G-B-C.