LFP "UPS" and Load Shifting

[Shimmy]

My house has ~7kWh/day of IT loads, most of it centralized in a single cabinet and more that could be placed in it. Is there any product out there that can act as a true UPS and also a load-shifting device to push grid consumption to PV hours? I picture it charging ~4 hours per day, operating grid-tied an additional ~4 hours, and running from battery the remaining 16h or so. A 5kWh battery would still give me 6h of runtime beyond full discharge.

I don't want to modify an existing UPS; their charging systems are generally not rated for a 4-hour recharge; and most traditional grid-tie/hybrid inverters don't seem to have sub-cycle transfer times between operating modes.

 

[meetyg]

Do you already have a UPS ?
If you do, all you need is a grid tied inverter. It will feed the grid with PV power.

 

[John Frum]

I made my own.
My IT load is also ~7kWh/day.
It floats/boosts from 7:00pm to 7:00am then runs off battery from 7:00am to 7:00PM.
It has reserve capacity for ~12 more hours.

 

[Shimmy]

Do you already have a UPS ?
If you do, all you need is a grid tied inverter. It will feed the grid with PV power.

It is a bit clumsy to do it that way; I still need to maintain the UPS batteries, and it has a lot of known interruptions that will happen each day. They aren't really that reliable.

I made my own.

Please elaborate!!

 

[John Frum]

It is a bit clumsy to do it that way; I still need to maintain the UPS batteries, and it has a lot of known interruptions that will happen each day. They aren't really that reliable.

Please elaborate!!

The main components of my system are...
8s 280ah battery with overkill bms.
samlex pst inverter 1500 watts
iota 25 amp converter
An ac rated relay to control power to the converter
An SSR to switch the converter between float/boost.
A raspi to monitor the BMS and control the relays.

If I didn't need the double conversion I would just use one of these

Samlex EVO-1224F-HW 1200W, 24V Pure Sine Inverter/Charger | DonRowe.com

The Samlex America EVO-1224F-HW, 1200 Watt, 24 Volt Pure Sine Wave Inverter/Charger is a rugged inverter/charger designed for mobile and off-grid applications

www.donrowe.com

or

Samlex EVO-1224F 1200W, 24V Pure Sine Inverter/Charger | DonRowe.com

The Samlex America EVO-1224F, 1200 Watt, 24 Volt Pure Sine Wave Inverter/Charger is a rugged inverter/charger designed for mobile and off-grid applications

www.donrowe.com

with one of these
An ac rated relay to control power to the converter
controlled by a raspi
and a battery.

Some coding is required.
@melkier 's jbdtool does almost all of the heavy lifting.

 

[John Frum]

This relay makes things easy.

IoT Relay

Create the Internet of Things with safe, reliable power control. Universal control voltage 3-60VDC or 12-120VAC connects to Arduino, Raspberry Pi, PIC or other micro. Or connect directly to a 12V to 48VDC or even 120VAC circuits. High voltage wiring and safety hazards are eliminated. A single...

dlidirect.com

 

[Shimmy]

I am back revisiting this issue now; I'll need two identical units to cover my office and my network cabinet. Typical load 220W max, 5kWh/day. I am currently hoping to charge 5 hours a day, so 70-100A at 12V or 20-25A at 48V. I have 5 UPSs that have all had their batteries die so I need to do something.

The two things that kept me from action before were the losses on the inverters and the cost/challenge of charging at ~1kW. I can't easily modify some of the equipment for DC power, which would really be my preferred solution to address the first problem.

Ultimately I plan on these systems eventually supplementing a whole-house hybrid solar/inverter/battery system, as I really do need to make sure this equipment has backup power, although it is possible I could limit the load-shifting energy at that point.

Is there anything out there now that would make this an easier project?

 

[Brucey]

I am back revisiting this issue now; I'll need two identical units to cover my office and my network cabinet. Typical load 220W max, 5kWh/day. I am currently hoping to charge 5 hours a day, so 70-100A at 12V or 20-25A at 48V. I have 5 UPSs that have all had their batteries die so I need to do something.

The two things that kept me from action before were the losses on the inverters and the cost/challenge of charging at ~1kW. I can't easily modify some of the equipment for DC power, which would really be my preferred solution to address the first problem.

Ultimately I plan on these systems eventually supplementing a whole-house hybrid solar/inverter/battery system, as I really do need to make sure this equipment has backup power, although it is possible I could limit the load-shifting energy at that point.

Is there anything out there now that would make this an easier project?

Yes something that is just now trickling into the US are the 120V sub 2k multiplus inverter/chargers.

Currently there's just the 12/500 available but apparently full range will be available sometime this year.

Victron PMP121500100 MultiPlus 12/500/20-16 120V VE.Bus

Combine this with an ecoworthy 12V 280Ah (3.5kWh) for $519 from Amazon and you should be pretty solid. Downside is only a 20A charger.

The 12/1200 model has a 50A charger:

Victron PMP121500100 MultiPlus 12/500/20-16 120V VE.Bus

 

[Brucey]

You can run them in parallel or three phase as well like the bigger units (12/500s below)

 

[Shimmy]

Yes something that is just now trickling into the US are the 120V sub 2k multiplus inverter/chargers.

It is an interesting option; do you know if it supports load shifting? Spending the money on something like this really makes that a necessity to me.

I need to try harder on the DC power for the equipment, but it is tricky to deal with the time needed for the modifications.

 

[Hedges]

"If you're happy with your UPS, you can keep your UPS" (and other big lies)

You could accomplish load shifting separately with an AC coupled battery.

For instance, I picked up Sunny Boy Storage and LG RESU-10H (just a statement, not an endorsement.)
It is capable of shaving exports by charging battery, then shaving imports by discharging battery. With time windows for each.

I think many AC coupled batteries (PowerWall) and hybrids can do the same.

 

[Brucey]

It is an interesting option; do you know if it supports load shifting? Spending the money on something like this really makes that a necessity to me.

I need to try harder on the DC power for the equipment, but it is tricky to deal with the time needed for the modifications.

I believe it supports ESS under the "Other" grid code. Or program some assistants to switch from grid to battery and back at certain times (if possible) otherwise I think Node Red allows control of the relays assuming you have a Cerbo or pi running venus os

 

[ksmithaz1]

I've supported a 48VDC data center. Not real fun.

I keep knocking down my home footprint. I broke down and got a 1/4 rack at a small DC here in town, I'm rolling a single 20A, about $250/mo. Best money I've ever spent, they deal with power problems, air problems, etc. I had to drive over last week to replace a 1U server fan that died. Had not been there in over 6 months. Home cruft is mostly a single 240 L6-20 to a Small 240v UPS and I re-pigtailed to a Nema 5-20 strip (heheheheh, don't tell Tim and I be careful what you plug in there friend, though I did cook an non-autoranging power supply. Most all this stuff is 110-240 these days, the magic smoke was unexpected but predictable. I would have done it the same with a C13.

The point? Home went down to 200W, with another 100W in the closet which took load shifting out of the equation for me, then I went full solar, so it just adds on to my zero line. 2.1KWH (7 * 300) was like $0.60/day on peak. With the right gear, I could probably get another 50-100W off that, the switching is ancient, my total POE load is like 50W, and my 8 bay syno needs to be replaced, I've got it soldered to work around the Atom chipset issue, I'm lazy. I have MY DC power footprint down to 120v/3.5A, as well, it's all low power gear. 240v seemed to drop my usage around 30-35%, I do have 2 small wall warts on a house outlet still, but the 120V UPS showed just under 300W (280-295) and this 240v one shows right at 200 (190-210). YMMV.

To make a long story even longer. . . That being said, you could keep the UPS's you have as is and just put a small ATS in front of the feed breaker for the equipment. Pull it from the panel to ATS common, fresh wire panel to ats secondary, AIO to the ATS primary. Program AIO to turn on at peak, off at the end, and charge off-peak. Nothing fancy, 3 components, ATS, AIO, battery, and some wire, 12/3 or 10/3. Existing UPS's should handle any switch lag from the ATS. Throw a few panels at it later just for fun.

 

[Shimmy]

I keep knocking down my home footprint.

I am down to one Synology, one solid-state QNAP, two NUCs, and a Universal Devices Polisy for "servers," but I have a lot of POE cameras and an NVR that represent the bulk of my load.

My NVR and main switch are Ubiquiti with the RPS ports, so I might be able to run them off 52+12VDC; my router (Ubiquiti ER4) is a little more opaque, but should be similar.

To make a long story even longer. . . That being said, you could keep the UPS's you have as is and just put a small ATS in front of the feed breaker for the equipment. Pull it from the panel to ATS common, fresh wire panel to ats secondary, AIO to the ATS primary. Program AIO to turn on at peak, off at the end, and charge off-peak. Nothing fancy, 3 components, ATS, AIO, battery, and some wire, 12/3 or 10/3. Existing UPS's should handle any switch lag from the ATS. Throw a few panels at it later just for fun.

The problem is the UPSs need new batteries and significantly longer run-time. An AIO might make sense, but I don't think I want to connect solar to it, so the losses are significant.

 

[John Frum]

An AIO might make sense, but I don't think I want to connect solar to it, so the losses are significant.

Converting AC to DC is $x efficient and converting DC to AC is $y efficient.
The values for $x and $y depend on the hardware used.
A good quality inverter charger in bypass mode is nearly 100% efficient.
Are the losses significant because you will be paying for the AC power from the mains?

 

[Shimmy]

Converting AC to DC is $x efficient and converting DC to AC is $y efficient.
The values for $x and $y depend on the hardware used.
A good quality inverter charger in bypass mode is nearly 100% efficient.
Are the losses significant because you will be paying for the AC power from the mains?

Maybe not $ significant, but energy significant. Trying to improve efficiency where I can. The UPS power conversion isn't the only loss though, you have battery float losses and equipment power supply losses as well.

Really the right solution is to go ahead and add solar, but permitting and everything else is a pain here. I am hoping for something I can deal with easily.

 

[John Frum]

Maybe not $ significant, but energy significant. Trying to improve efficiency where I can. The UPS power conversion isn't the only loss though, you have battery float losses and equipment power supply losses as well.

Really the right solution is to go ahead and add solar, but permitting and everything else is a pain here. I am hoping for something I can deal with easily.

Float losses are roughly the same as charge losses.
LFP round trip efficiency is ~99%.

 

[Hedges]

Maybe not $ significant, but energy significant. Trying to improve efficiency where I can. The UPS power conversion isn't the only loss though, you have battery float losses and equipment power supply losses as well.

Really the right solution is to go ahead and add solar, but permitting and everything else is a pain here. I am hoping for something I can deal with easily.

When the source is grid, don't worry about saving energy. Convert everything into units of dollars and optimize that (unless greenwashing is necessary for marketing purposes.)

When source is PV panels or batteries, then efficiency may matter. PV panels so much these days, but batteries are the bottleneck.

 

[Shimmy]

When the source is grid, don't worry about saving energy. Convert everything into units of dollars and optimize that (unless greenwashing is necessary for marketing purposes.)

When source is PV panels or batteries, then efficiency may matter. PV panels so much these days, but batteries are the bottleneck.

Part of my issue today is the utility transformer is grossly overloaded in export-- 25kVA for 25 homes... and I have 8.3kW of solar. Half of my neighbors have at least 4kW as well. The utility is a run-to-fail operation and when it does fail it creates a significant fire hazard. Reducing my daytime export by 2kW is kind of significant there.

...but I know you are right. The most realistic solution is to just stick with lead acid for backup only and pick my battles with efficiency.

 

[Hedges]

Your neighborhood may be able to burn up the neutral, according to my analysis that says unbalanced 120V loads can draw 2x the neutral current it was designed for.

You'd think the utility would only approve interconnection up to what they could handle.
25 homes x 4kW / 2 = 50kW. Their 25kVA transformers maybe can handle 50 kVA for quite a while.
If the homes are running A/C at same time, less going through transformer.

But sounds like it is at its limits.