Battery back up without solar

[brownerd]

OK, I know this is going to sound weird, but stick with me
I would like to build a 48 volt 280 AH battery using the 3.2 volt cells. I would like to charge the battery during off peak hours from the grid, then during peak hours I'd like to run my home. In the event of a grid outtage, I'd like to power my home from battery. I do not have solar (yet), so that wouldn'y be an option at this time. Are there any products out there that would allow me to schedule when I run from battery and when I run from the power company? I'd like to automate it instead of manually flipping transfer switches. Am I whacked, wanting to build something like this?

 

[chrisski]

That is an option among many inverters. You can set times usually referred to as SBU (Solar, Backup, and Utility) are primary throughout the day At different times.

I’d look at the rates in your area. A system like this may run $12k for a 10 kWh battery pack installed and at a savings of $.10 to $20 per kWh, payback time would be immense if you used 7 to 8 kWh battery backup per day.

EDIT: If you plan on expanding to solar later, make sure you talk through with the installer the placement of these future products. 3’ Spacing for batteries surprised me. This means they can only be placed 1 high on a typical wall.

 

[brownerd]

That is an option among many inverters. You can set times usually referred to as SBU (Solar, Backup, and Utility) are primary throughout the day At different times.

I’d look at the rates in your area. A system like this may run $12k for a 10 kWh battery pack installed and at a savings of $.10 to $20 per kWh, payback time would be immense if you used 7 to 8 kWh battery backup per day.

EDIT: If you plan on expanding to solar later, make sure you talk through with the installer the placement of these future products. 3’ Spacing for batteries surprised me. This means they can only be placed 1 high on a typical wall.

Thank you - you make a great point on ROI - I was kinda just wanting a project to work on, but was hoping it would be cheaper . I was looking at these batteries https://www.18650batterystore.com/products/eve-lf304-grade-a-cells-3-2v-lifepo4-304ah-battery to get 16 of them would give 300 AH at 48 volts ($2,160) then all the other stuff BMS, inverter... was hoping to spend $6,000 +/-
I hadn't thought about the spacing of components - thank you for that tip!

 

[Kenny_]

Well, not the same but I just put together a system using a Sungold 10K (about $1500) + sungold 48v batteries at about $1400/100AH.
a starter system with a single battery would be about $3k and would provide the functionality you want. Other batteries could be substituted or expanded etc... (I do have solar as well), but the Sungold 10k can be used without panels (or batteries for that matter). Check out the manual. It also allows scheduled charging times etc. but I have not used it that way or even tested the functionality.

But also like @chrisski says the savings are not necessarily that great. Payback time would be enormous...but if it's just something for you to experiment with then go for it!

 

[chrisski]

Thank you - you make a great point on ROI - I was kinda just wanting a project to work on, but was hoping it would be cheaper . I was looking at these batteries https://www.18650batterystore.com/products/eve-lf304-grade-a-cells-3-2v-lifepo4-304ah-battery to get 16 of them would give 300 AH at 48 volts ($2,160) then all the other stuff BMS, inverter... was hoping to spend $6,000 +/-
I hadn't thought about the spacing of components - thank you for that tip!

You could spend about that, but it would need to be DIY. I can’t handle the permitting side of DIY grid tied.

Those EVE cells are not UL approved and I doubt they’d pass an inspection.

 

[42OhmsPA]

Thank you - you make a great point on ROI - I was kinda just wanting a project to work on, but was hoping it would be cheaper . I was looking at these batteries https://www.18650batterystore.com/products/eve-lf304-grade-a-cells-3-2v-lifepo4-304ah-battery to get 16 of them would give 300 AH at 48 volts ($2,160) then all the other stuff BMS, inverter... was hoping to spend $6,000 +/-
I hadn't thought about the spacing of components - thank you for that tip!

Welcome to the forum.

What you are trying to accomplish is definitely attainable at a low cost.

The biggest question is are you worried about inspections and are you capable of installing it yourself?

Your ROI won't be great if your only concerned with charging during off peak rates. It will be completely worth it the first time the grid goes down in your area...

If you plan to do this yourself on a budget I'd recommend the Envision 305ah cells from 18650 (they are restocking next month) and a budget AIO inverter so you can add solar later.
I'm running the same inverter that @Kenny_ mentioned, I got mine from the OEM SRNE. I have over 1Mwh of solar and AC through it with no issues.
You could easily do this for under $4000 including the cost of, BMS, tools, wire, fusing, enclosure, etc.
If you're looking for full compliance and inspections that cost could easily double.

 

[brownerd]

Thank you for all the replies! You have given me a lot to think about. Now my head hurts

 

[hwy17]

If you're on PG&E you can consider just installing one single cheap DIY heat pump or HPWH in order to get onto the E-ELEC rate.

If you're on SMUD you really probably can't save any money at all. They're already cheap.

 

[brownerd]

If you're on PG&E you can consider just installing one single cheap DIY heat pump or HPWH in order to get onto the E-ELEC rate.

If you're on SMUD you really probably can't save any money at all. They're already cheap.

I'm on SMUD - it's funny - I went to their web site and looked at the solar options... It shows how long until there is a return on the investment, but for me it said N/A. My wife works a goofy schedule, so she is sleeping at 5:00PM, in the summer i crank down the AC, so she can sleep, but my electric bill gets pretty high for doing that. I was thinking if I could run from battery during the peak I could save some $$$. Our AC is newer (21 seer), but living in a 2 story (and not having a split/zoned HVAC) makes it difficult.

 

[tmprof]

Originally, I was thinking about doing the same thing, but after I got my solar and battery backup, I realized there is loss when you convert from AC/DC, and in this case, you convert AC to DC to put it in the batteries, and then convert DC back to AC to use in your house so just know it's not 100% efficient.

 

[Vigo]

My Growatt inverters have a setting for that. You can also put the ac input to an inverter/charger on a simple timer switch as long as it can handle the current. So that part is cheap and easy.

But you really need to figure out how many Kwh you're trying to cover with batteries. That's going to determine how expensive this is going to get.