Help with home battery backup system

[bcfromfl]

Hi everyone --

I've been watching Will's videos for quite some time, and have been researching a specific application of home backup systems for emergencies for three years, ever since we were devastated by Hurricane Michael in 2018. I live in the southeast, and you'd think this would be prime territory for plenty of competition, knowledgeable contractors, and great service. Well, my experience has been the complete opposite. There are surprisingly few solar contractors, and the ones I contacted either wouldn't install simply a battery backup because they wouldn't make enough money doing it, or they tried to "up-sell" me into solar panels on my roof with a 30-year loan "...paid for with the savings off my electric bill." One contractor was especially proud of the fact that he had been selling $50-80,000 systems in our area. He padded his estimate with about $8,000 for "engineering, permits, and labor" just for a PWRCell subpanel! Scam city.

I tried contacting Generac about their PWRCell, also telling them about the miserable experience I received trying to work with two of their "dealers," but got no response. One of my criteria is an automatic transfer switch, and I thought I might have to go a more "noob-friendly" DIY approach. Seeing that EcoFlow will be offering an automatic transfer switch for their Delta Pro, I sent their customer service a question about amperage limits, and got an answer this morning that was embarrassingly brief and, frankly, stupid. They will offer a 30-amp circuit.

What I'd like is a ~12kW system that will switch automatically, and charge automatically again from the grid. That said, I'd like the option of adding solar later via a simple connection so that I could charge the batteries in a potential multi-day outage, placing the panels on the ground and tracking the sun manually. Being miserly with usage, and setting up the backup subpanel for only critical circuits (eliminating a/c, dryer, hot water, etc.), that would get us about two days.

This is the problem: We are the second owners of this home, which has a deep well (220 feet) using a pump with unknown power requirements. It's wired through the house subpanel 110v, using two 20-amp circuits tied together. If it's a 3hp pump, it could be drawing 36 starting amps. I've contacted a local well-drilling service (the original driller has gone out of business) to see if they can help shed some light. If it is, in fact, a 3hp pump, I exceed the capability of all the mid-level, "portable" home solar generators out there I know of. (Bluetti is out anyway, because their transfer switch is manual.) They cap their systems at 30 amps. A potential workaround: would it be harmful to a submersible pump to install a soft-start module ahead of it, to limit the starting amps, and, therefore, open up options like the EcoFlow unit?

I just learned today about a new company offering a home battery backup system, Franklin. However, there is very little information available on them, and, since they are a Chinese company, service would be limited. I don't want to be one of the first guinea pigs to test something out.

Given what I've described above, what other options might be available to me? Many of the larger units by more established companies, i.e., Generac, Enphase, Tesla, are all ridiculously overpriced, although, certainly they would do the job and I would have a higher confidence level in service. But, at this point, I've really moved on from them, and am ready to consider something perhaps a bit more reasonable and appropriate, but still proven and reliable. I like the sophistication of the performance-tracking apps I've seen, so that would be a real plus. This has to be simple to operate/maintain, and I want something my wife can benefit from when I'm no longer here. (In that regard, if necessary during a multi-day event, the option for her to be able to call someone to bring a gas generator to charge the batteries would be great.)

Also, since I'd be hiring a local contractor to do the subpanel, I'd need parts that have very explicit instructions. We're a bit backwoods around here!

Thanks so much for any help!

 

[Mattb4]

A lot of what you are asking is do-able but unless you are comfortable in going the DIY route (and your locality allows you to) you must needs deal with those than can. This does put you at risk for the fly by night companies.

Well pumps are difficult to power as they are always under load and have high starting amps. I do not think you have a 3hp one based on your 20amp breaker supplying it. There are work arounds and even special built pumps that may do the trick. Grundfos markets such submersible pumps.

None of those portable battery packs (solar generators) will do what you need.

 

[svetz]

Welcome to the Forums!

...vendors...Scam city....

Yes, there are a lot of folks only too ready and willing to cheat you blind. Even in the DIY route you can hire folks to do simple things you might not be physically able to (e.g., get panels onto the roof) or uncomfortable with (connect the wires to grid).

I have solar and a battery and it's great. But a generator is more cost-effective than a battery if you have natural gas piped in and it doesn't get turned off during a crisis. But if you have to truck in fuel or it's unavailable in a crisis nothing better than solar (or wind or hydro if you've got it).

... got an answer this morning that was embarrassingly brief and, frankly, stupid...

That's not all that uncommon either. Even with good companies, a lot of times the salesperson assumes you're the village idiot and answers what they think you should be asking rather than what you are asking. All companies have bad salespeople, I find it's better to call so that when they realize they're over their head they can transfer the call to someone more knowledgeable.

What I'd like is a ~12kW system that will switch automatically, and charge automatically again from the grid. That said, I'd like the option of adding solar later

12 kW is pretty big for an inverter... Sol-Ark, SMA, Tesla, & Enphase are the ones that come to mind for that. Enphase is probably the easiest and allows the most flexibility for adding as you go (that is you might start with 3 kWh of battery and grow over time, or decide to add more solar panels). But, it's probably the most expensive way to go too.

If you mean energy (kWh) rather than power (kW) and need a lot less KW then there are a lot more options.

...a deep well (220 feet) using a pump with unknown power requirements... it could be drawing 36 starting amps

You can measure the "starting amps" with a clamp meter (just linked the first one I saw, hunt around for one with good feedback) that can measure in-rush current. If you can find the LRA (locked rotor amps) on the motor that'll give you an idea (a lot of times you can look it uyp on the web if you have the model number, add 10% for age).

...would it be harmful to a submersible pump to install a soft-start module ahead of it...

I have one on my air conditioner and the inrush dropped current went from 86 to 28A. Not sure how well they work on pumps. Supposedly a soft-starter is beneficial for an AC compressor.

I like the sophistication of the performance-tracking apps I've seen, so that would be a real plus.

Solar array tracking generally isn't worth it. Between the initial cost and maintenance for the system, it's usually cheaper to just add a couple of extra panels. In my case (hurricane force winds) I had to keep the panels parallel to the roof to minimize wind forces. SAM is a program that can let play what-if games easily switching between fixed, 1 dimensional, and 2 dimensional PV tracking. It's a beast though, so look at the training videos.

Hope that's of some help! Below the "signature" block has a number of helpful hyperlinks you might find useful. Best of luck!

 

[Mattb4]

Dont know if it would tell you anything that you already don't know but ZDnet does have a list of home battery setups and costs: https://www.zdnet.com/home-and-office/energy/best-home-battery/

 

[bcfromfl]

Thank you very much Mattb4 and svetz. I really appreciate it!

What I meant by the performance tracking apps are the ones that you use on your phone, or a standalone module. I can track panels by myself if necessary, without voiding the warranty on my roof.

I might have to pay for a service call from the well-drilling service, to see if they can estimate the pump's power perhaps using the method you described.

This area was in a bad way after Hurricane Michael, which was a Cat 5. No fuel in the area for days. No nat gas in this part of the country, either. You could do propane, but then you have an above-ground tank. As a matter of fact, the very first Generac contractor I called for an estimate came to my home, didn't know what a PWRCell was, then a few days later e-mailed me an estimate for a $22,000 nat gas generator. This is what I have to deal with around here...

What I meant by sizing the potential system for our home was ~12kWh.

Thanks!

 

[bcfromfl]

Thanks again for the link, Mattb4. All of those systems would be in the $28 - 35,000 range installed here. We have a bit of money to invest, here, but I'd like to keep it under $15k.

 

[Bluedog225]

Welcome!

Plan B. Off-grid 48 volt rack batteries. No tie in to the house or grid. Plug in your needed loads to the inverter/charger. Keep the batteries charged with a small array. Forget about the pump and store 300 gallons of water in a tank.

I wonder how this would have worked out last hurricane. Save a bundle and meet many of your needs.

I had no luck getting help from companies for a diy install. Just 3 years of telemarketing.

 

[svetz]

What I meant by sizing the potential system for our home was ~12kWh.

For an inverter selection you'll want to know both the power you need and the energy (which is probably what you mean by 12 kWh).
An Energy Audit spreadsheet can help you with that.

Power
Power is the sum of all the things that might be on at once. For example, a 60 watt TV and a 10 watt LED bulb running at the same time is 70 watts.

Inverters are sized by power, typically two ratings. One for how much it can output continuously, and a second for how much it can "burst" to for handling inrush currents. Inverters also have a conversion efficiency and a self-consumption rating.

Energy
Energy is how long you need power for. So, if each day you run the light for 4 hours and the TV for 2 hours, you need 4x10 + 2x60 = 160 watt-hours per day. If you want 3 days of energy it would be 3 x 160 = 480 watt-hours

How big of a battery would you need for that 480 watt-hours? Well, if the inverter was 90% efficient and had a self-consumption of 20 watts/h, you'd need 480 / .90 + 3 days reserve x 20 watts/h x 24 hours/d = 533 wh + 1440 wh = 2 kWh.

 

[bcfromfl]

Hopefully we'll never have another hurricane, but if you'd seen this area afterwards, you'd rethink the water tank idea.

I need to come up with a system that's hand's off for my wife. I lol'ed at your telemarketing! Thanks!

 

[bcfromfl]

Thank you, svetz. I've already done all those energy calculations...that's why I know that 12kWh will hold us for about two days, in "survival mode."

 

[svetz]

Thank you, svetz. I've already done all those energy calculations...that's why I know that 12kWh will hold us for about two days, in "survival mode."

That's good, most people confuse power and energy and forget how big the self-consumption and inefficiencies are for an inverter and end up undersized. Don't forget the battery-round trip losses when you (someday) add solar.

Still can't recommend an inverter as we don't know your peak power requirements are (6 kWh sounds like your daily energy needs).

... I'd like to keep it under $15k....

If you can do as Bluedog225 suggests above you won't need 6 kWh/d, but let's say it's fall when the biggest hurricanes hit and for your location, the insolation is 4.2. Then 6 kWh/day recovery/4.2 = 1.5 kW array (e.g., five 300W panels).

New panels can be had for $1/W, so that's about $1500. Batteries are expensive, but you only need the battery for when the sun is down. So you need night-time energy use. From Will's page, DIY LFP is around $180/kWh for raw cells.

So, if the consumption was 3 kWh overnight, that would bring the total to 3x $180 + $1500 = $2000. If the Inverter was $2500, that would bring it up to $4500. Add is +30% for the balance of systems (e.g., wire, BMS, racking), and you're probably under $7k DIY. As it's for emergencies and you could probably not rack them, just keep them in the garage until needed and be off-grid while the power is out, that would reduce the BoS and inverter costs.

Impossible? ; -)

Check out @upnorthandpersonal's thread: off-grid 10kW solar system with 28kWh LiFePO4 battery, inverter, BMS and charge controllers for under €10K

 

[Bluedog225]

Hopefully we'll never have another hurricane, but if you'd seen this area afterwards, you'd rethink the water tank idea.

I need to come up with a system that's hand's off for my wife. I lol'ed at your telemarketing! Thanks!

I was in corpus for celia. So I’ve got some idea. Depending on your needed level of surviveability, heavy plastic 55 gallon drums would work. If they get destroyed, you may have transcended the need for power.

Hurricane Celia - Wikipedia

en.m.wikipedia.org

 

[bcfromfl]

Thanks, svetz. Yes, I actually figured in quite a bit of "slop," to account for efficiency losses, and, for things like, if we're out of power during the winter and freezing, we could run a space heater for a couple of hours. Our must-haves are thus: side-by-side refrig/freezer, chest freezer, a few lights sparingly, maybe a fan, a small lift-station pump for our septic, and the well pump. Enough to keep us in the house and protect our food. Probably on the order of 3-4kWh per day, 1.5kW per hour if we add a heater.

Panels on the roof are a no-go. We paid extra for a 50-year transferable warranty for the roof replacement, which would be voided by panels. If I decide to add panels in the future, they would be stored in the garage until needed. My wife wouldn't be strong enough to horse them around, though...

 

[stienman]

If you want to go the inexpensive DIY route, and you're really only running lights, fridge/freezer, and the well pump, then your best option is probably a 6kW, low frequency, split phase, off grid, 48V inverter. The low frequency means it's heavy, but it'll start the well pump and fridge compressors without a problem. Split phase is necessary since you'll be running both 120v and 240v loads. Off grid because a grid-tie only works when the utility has power, and 48V because you'll be running heavy loads occasionally (well pump triggers while the fridge is already running, and maybe someone is using the microwave...).

I've had good success with the Growatt SPF6000T DVM. It runs my well pump (just shy of 200 feet, but I'm pretty sure it's on a 240V breaker larger than 20A so more power than yours), and everything else with two exceptions just fine. The 4 ton AC unit, which is over 20 years old, causes a shutdown (which could probably be relieved with a soft start, or a newer inverter AC system), and I eventually took the oven off it because it could eat 4kW, and with our regular load it was probably ok, but then someone would use the microwave, or a toaster, or a space heater, etc, etc, etc and overload the inverter, causing a shutdown. This is compounded by an imbalance in the 120V circuits - the reality is that most of these split phase inverters are really two 1/2 size inverters stacked to make 240V, so if one phase goes over 3kW, then the inverter shuts down even if the other phase is only lightly loaded. I added an autotransformer to assist with this, but it's something you need to keep in mind.

Most of these off grid inverters have a transfer switch built in, and an AC charger. So you hook the utility to the inverter, and the output feeds your AC panel. If the utility shuts off - even briefly - the inverter takes over and at most you might notice the lights flicker. The AC charger is set up to keep the batteries at, say, 80% charge, and if a storm is brewing you tell it to go to 100%. They usually have solar MPPT charge controllers and setting up solar panels is pretty straightforward in an emergency, particularly if you install quick connect fittings on the inverter.

Solark, SMA, outback, and schneider all have inverters that will do this, and 5kW and up should suit your needs. You can probably go with a high frequency inverter as well, but you may have to up-size it a little to handle the startup load for your pump.

Assuming you're not really interested in DIY, you should contact several electricians in your area and see which would be willing to do the work. Indicate that you'll work with a company that will provide the package and manuals, as well as and installation help-line, indicate that everything will be provided and they just need to do permitting and installation - not design - and schedule time with one of them.

Then work with an online supplier to design and sell the kit and provide the installation support. "Solar kit diy" on google will yield a plethora of companies - get each one to provide a suggested system and a quote for your needs and you'll be given so many opinions it'll be easy to see where people differ, and where the designs are similar. Focus on the differences to learn which direction you want to go, consult with your electrician regarding the designs and make sure any questions they ask up front you ask the supplier prior to choosing a system and supplier. Pre-sales support is usually better than post sales support, but you'll get a good idea of which companies are worth working with, and which aren't really going to provide the support you and your electrician need.

If I wanted to do it quick and easy, I'd buy one Growatt SPF 6k ($1,500), three 5kW 48v batteries ($1,500 each - $4,500 total), and the cables, electrical boxes, etc to support them, and have the electrician add a sub-panel, moving critical loads to the subpanel. Then put the growatt between the main panel and the sub panel, connect the batteries, and you're done for under $10k, including labor and all the additional electrical parts the electrician and your local jurisdiction requires. Given your budget, you should consider going with a Solark system - I expect you'll be happier with the online dashboard and control than you would be with the growatt "shine solar" app, and you should receive better support directly from the company (though having never dealt with them I don't have first hand knowledge)

Be prepared to have this process take several months, to schedule, permit, install, and go back and forth with the inspector a few times. Be willing to switch electricians in the middle if the guy you chose ends up being flaky.

Worry about solar panels later, but don't worry too much - they are plug and play with all-in-one units like this.

And be aware that growatt, while reliable, is cheap and there are some tradeoffs you make for that savings, mostly in terms of support, configurability, and solar input capacity.

But configured to supply a backup panel, you'll find the system is automatic and you'll never have to touch it unless you want to charge it using solar during an outage.

 

[Mattb4]

If you can get an autotransfer switch wired at you place it does open up several options to you. Platt electric has some you can look at. https://www.platt.com/platt-electri...+30a+240v&SectionID=7&GroupID=5919&CatID=5921

Whole house ones are pricey and you would need to limit what you powered when in backup mode. Likely better to serve a critical panel. Any electrician could do a critical loads to sub panel setup transfer switch. After that you decide what your backup power is. Generator or battery pack hooked to a inverter.

 

[bcfromfl]

Wow -- Celia was no joke! We had probably 140-150 sustained here at the house for a couple of hours, with gusts I'm guessing to 160. Much more at the coast. Tornadoes reported close by -- might account for some additional damage. NEVER want to go through that again!

 

[bcfromfl]

Thank you very much, Stienman! I'm going to have to study your post carefully. Good tips...

 

[bcfromfl]

Thanks for the link, Mattb4. I think what you're describing is more what I feel comfortable with -- having an electrician install the subpanel and/or ATS, then all I'd have to do is plug in the remainder.

 

[bcfromfl]

Wow...I'm reading the specs on the Sol-Ark all-in-one. No subpanel! That would make things SO much easier!!

Just checked their map on their website to see their nearest dealer/installer, but they're 100 miles away. Just called the company, and left a message to see if there might be a recent addition closer.

 

[wattmatters]

A bunch of thoughts to be considered/tossed out as you see fit....

Does the switching to backup really need to be an ATS? I assuming this isn't a regular thing. Any reason why it couldn't be a simple but very effective manual transfer switch?

You could as stienman suggests go with an all-in-one inverter with specification sufficient to manage your power loads (well pump being the clear issue) and wired in line to pass through grid power supply, cutting over to battery if grid power is cut. The only issue with this approach is the system is operating the whole time and so it will add a little to your daily grid energy consumption.

I'm going to do both. At present my off-grid all-in-one inverter provides power to designated home circuits via a manual transfer switch. This means when we want backup power I need to manually switch over. However I have the option of simply leaving the transfer switch "permanently" switched on the backup side. My AIO inverter is supplied with power via grid powered circuit and it can pass power though and operate as an automated backup as described by stienman (it also has a small off-grid PV array and of course the battery).

The advantage I see with this approach (using the AIO inverter feeding via a transfer switch) is the dedicated essential circuits can be switched back to grid-only supply and bypass the backup system entirely. I do not want my essential circuits to be reliant on an off-grid inverter for power. If the off-grid inverter fails and I can't bypass it, then I'm SOL.

The downside to the above is they are all but permanent installations, versus a portable power station which could be connected to an essential circuits panel with a power inlet and transfer switch in much the same manner as a regular generator. This still provides a power inlet into which you can also connect other sources of power, such as a regular generator. To me it just seems a good idea to have options / flexibility when dealing with emergency scenarios.

I think I'd also still keep a smaller propane fuelled generator and a spare propane tank on hand as well. Unlike gasoline, propane does not go off and can be safety stored for many years. Much better than gasoline for infrequent emergency use. It can be used to recharge the battery if needed, or feed the home directly if you allow for that option. Just check the portable power station's charger power supply. Many are pretty low power chargers and so most smaller generators are going to have ample power capacity to manage several hours of recharging, while a single 45kg propane tank has a lot of energy, could last 1-2 weeks with regular use (obviously depends on the generator and how much power you use).

A propane tank is also a source of gas for heating water and cooking, both very power intensive activities which can mean a battery backup system lasts a lot longer if they don't need to supply that energy. Portable camp stoves are cheap and work great and can be tucked away for when needed.

Or even consider one of those $10-15 single burner camp stoves which runs on those aerosol can sized butane cylinders. We have one in the cupboard and a six pack of the butane cylinders. They actually last quite a decent amount of time and being dirt cheap are a really handy backup option for boiling water/cooking. Better than using our 2.2 kW electric kettle on (wife likes a cup of tea).

Having some solar panels to deploy is great but assumes the weather clears up enough such that they will generate useful power. If the weather remains pretty lousy then they are not going to be all that helpful. In cloudy conditions you need a LOT of panels.

If above ground water tanks are not an option (understandable) I think I'd still be keeping a large drum of water on hand or at least have some secured stores you can use for drinking water as that's what's most critical. Sterilising water via boiling is energy intensive and so it's better if that's not required because backup energy reserves are precious, or as described above have a portable gas option on hand for that job, take the pressure off an electrical backup system so it can do the things for which you don't have reasonable alternatives.

Sewerage systems are another to think though. For many it's not an issue (e.g. we have gravity fed septic system so it just needs water for flushing) but if they rely on pumping it needs consideration. We have one smaller sized above ground tank (~4000 litres) which is pretty much always full and can serve as an emergency supply. So if main water supply was not available then we can always dump a bucket of water into the cistern.