Trying to choose best system for our situation

[Debiann]

We have a small on-grid ranch house, and want to create a 120v backup system connected via interlock to one side of our 200a panel. We don't currently have a good situation for solar, as the only place with full sun is our small nursery (we grow native plants to sell). Our shed could fit 2kw of solar panels, but our neighbor is growing large trees nearby, which will block all morning sun within a few years. So I'm not sure investing in solar panels is worth it with only partial sun.

We're only looking to backup our fridge, freezer, lights, fans, microwave, cell phones, and some computer work. I'm in the process of using a watt meter to get a better idea of our power needs, but for now I'm roughly estimating 2500 watt hours a day. What I'm considering is installing a 30a input plug, connected to a 120v 30a breaker via an interlock in our panel. Have a battery system, sized for 1-2 days of power needed. Use an inverter generator to recharge the batteries as needed during a prolonged outage, or to occasionally run larger items for short periods (such as a dehumidifier in our conditioned crawl space or small window AC during extreme heat).

I have very limited knowledge about electricity. It all sounds like latin to me, and I find it very confusing. I don't really want to learn a lot about it, just the basics needed for a simple system. However, I'm able to follow clear instructions. Well enough for me to successfully wire our entire new house, including the main panel (an electrician friend helped with connecting it to the meter base).

I'm looking for a fairly simple, user-friendly system. One that is pretty reliable, and with decent customer service for dealing with any problems. I definitely want a battery system with some type of 30a connection to run power to the panel. And the house will need power at the same time that the battery system is being re-charged by the generator. Either a system with full pass through capability, or have the generator power the house while the battery is being charged on a house circuit (then switch the interlock power source back to the battery). Whatever I install will need to pass inspection by the town.

I've been reviewing information about the Titan, Delta Pro, and EG4 systems. Though I can handle basic wiring, I'm a bit scared about creating any DIY 48v systems. I don't want to risk creating a fire or getting badly shocked. I don't think I have enough knowledge to be really safe with that much voltage. Any suggestions for what might work well in my situation? I'm kinda leaning towards the Delta Pro. Thanks.

 

[Browse]

Any of the portable battery backup systems will work. Ecoflow Delta Pro and Bluetti AC500 both provide a decent amount of power and can be expanded with extra batteries. Based on reviews and videos of these companies, both may have some small percentage of quality problems and issues with customer service. Both solutions are expensive.

I needed a larger system with 240V split phase output, so I ended up with a Growatt 12k inverter and 4 rack mount batteries (20kWh total). I also have a backup 240V inverter generator adapted for tri-fuel use that can be used to recharge the batteries.

 

[Cmiller17363]

I was thinking either the Bluetti AC300 or Bluetti AC500.

I think both would work well for your application. The AC300 is rated for 3000w and the AC500 is rated for 5000w.

The AC500/B300S battery I received had issues but bluetti replaced it and the replacement works great.

 

[MichaelK]

We're only looking to backup our fridge, freezer, lights, fans, microwave, cell phones, and some computer work. I'm in the process of using a watt meter to get a better idea of our power needs, but for now I'm roughly estimating 2500 watt hours a day.

I think that number is a bit too optimistic. With my own cabin, running what you just described, I am at 3.5-4.0kWh per day. So, I would ratchet up your needs to at least that level.

I'm a bit scared about creating any DIY 48v systems. I don't want to risk creating a fire or getting badly shocked. I don't think I have enough knowledge to be really safe with that much voltage. Any suggestions for what might work well in my situation? I'm kinda leaning towards the Delta Pro. Thanks.

There is nothing to be afraid of with 48V. My worst battery accident happened at 6V, so voltage is not going to play as big a role in being safe as you think it is.

I've been reviewing information about the Titan, Delta Pro, and EG4 systems. Though I can handle basic wiring, I'm a bit scared about creating any DIY 48v systems. I don't want to risk creating a fire or getting badly shocked. I don't think I have enough knowledge to be really safe with that much voltage.

I am not a fan of AiO systems. I am very much a components guy. I power a lot of starting surge loads, like my well-pump, and all these AiO systems are noted for their mediore starting surge capability.

We don't currently have a good situation for solar, as the only place with full sun is our small nursery (we grow native plants to sell). Our shed could fit 2kw of solar panels, but our neighbor is growing large trees nearby, which will block all morning sun within a few years. So I'm not sure investing in solar panels is worth it with only partial sun.

Let's crunch through the numbers to come up with what will work for you. Let's go with 4kWh to be a bit more conservative. One of the things though that you have not yet mentioned is how many day's of autonomy you need? That is, how many days you need to get through if there is no solar, such as a big snow-storm? People fail to plan for that and find their systems failing the day after a storm rolls in. Let's plan on at least two days. If you don't feel that number is right, fill in whatever you think is right.

First, what location? The shed is going to get progressively more shaded over time? One of the nice options you have with high-voltage solar is you can position arrays hundreds of feet away with very little voltage drop. At my own cabin, I am wiring four grid-tie panels in series for 120VDC. I transmit the power ~130' from the array to the controller with standard 10 gauge solar cable without measurable voltage drop. You can have multiple arrays wired in parallel, positioned in different locations. Maybe 1000-2000W on your shed roof, and many 1000-2000W of ground mounts located in other spots. It's up to you to come up with those spots.

Let's say you purchase 12 250 residential grid-tie panels. They are ~80$ each right now on Craigslist. You get far better deals with local cash and carry solar than ordering through the mail. If you wire them up 4S3P, you'll be making ~21-24A ~120VDC total.

How cold are your winter lows? Solar voltage goes up as the temperature goes down. At -20, you need to multiply your voltage by ~1.18X for temperature compensation. So, if each of the panels is putting out 37.5Voc at room temp, a four-panel string might reach 37.5Voc X 4 panels X 1.18X = 177V. So, that means you'll need at least a 200V charge controller. The amperage going into the battery with 3000W of panels is going to be 3000W/50Vcharging = 60A. Under real-world conditions I'd de-rate that to 85%, or 51A, but I'd say look at getting a 80A controller, which would allow for future expansion. Take a look at Epever's Tracer 8420AN, which is running ~270$ on Ebay today.

As for an inverter, I would look at UL listed brands like Outback, Schneider, and Victron. I have Schneider's Conext 4024. Their 4048 is about the same price.

Last, the battery. Let's say you want to support 4000Wh each and every day, and you don't want to deplete more than 25% (4X) of your battery capacity per day, and you want two days of autonomy. So, the math works out to be 4000Wh X 4 X 2days = 16000Wh. With a 48V battery that's 16,000Wh/48V = 333Ah battery.

That's just a bit less than the Trojan L-16 RE-B batteries I used to have, which are great performers. They are ~350$ each, and you need eight of them, so that's 2800$.

Then there are the little do-dads that come along with every system. Budget another 500$ or so for a power center, breakers, heavy copper wire, ect.

Summed up....
8-12 panels: 640-960$
80A charge controller: 270$
4000W sine-wave inverter: 1800$
8 Trojan batteries: 2800$
stuff: 500$

 

[Bluedog225]

Sorta surprised you would recommend a flooded battery to someone who doesn’t want to learn about the system.

Some expensive lessons are possible.

LiFePO4 seems more friendly in this situation even if initially more expensive.

 

[MichaelK]

Sorta surprised you would recommend a flooded battery to someone who doesn’t want to learn about the system.

I seem to have done OK. I recommend to others what I myself use.

 

[Bluedog225]

But you’re a photon sorcerer! ?

 

[MichaelK]

But you’re a photon sorcerer! ?

Actually, what is that supposed to mean?

The first set of Trojan T-105s I installed in 2014 are still in use. I don't think I was a sorcerer back then? The key to good performance with lead-acid is ample charging.

 

[Bluedog225]

I don’t know about the tag lines. Only that I am unworthy.

I love my old trojan but she drinks a lot. And it gets to be a pain. As does properly venting the off gassing. I’m done with lead acid except for a dry charged battery for emergency backup.