Simple modular UPS

[hicke]

Hi guys!

I need some advice.

I want to build a relatively small UPS for my office equipment. I have a fullsize computer and 30" monitor, NAS and a macbook air M2. It's not a lot in terms of wattage, maybe 200W or so. Maybe a little higher when booting the computer.

My thinking is to have AC going into a charger/inverter which passes through AC to a few outlets. It also charges my battery. When power (AC) fails, it should switch over to DC and keep the equipment alive for a few hours, maybe 3-4. I would also like to be able to attach solarpanels to charge the battery.

IT should be stand alone, not connected to my grid, just the one AC outlet for charging my island system.

- Inverter with failover and charging capability
- MPPT (option)

Batteries I can build myself in any voltage using raw cells.

I live in Scandinavia, we have 230VAC here and power NEVER goes out. But IF it did, I would like to be prepared.

Do you guys have any ideas? Has somebody done this?

 

[Supervstech]

Any inverter charger will do his…
But, you assay in one place you want ac to switch to dc, but then go on to say no grid connection… please explain.

 

[hicke]

I am sorry if o am unclear.

If powergrid goes out, I want all equipment that is connected to my UPS system to keep running for a few hours. If power returns, I want the AC to take over and begin recharging the batteries also.

Is this clear?

 

[HammaMan]

How often does this occur? You can use a standard UPS for this with a much larger battery. The only downfall is the long recharge time. A common thing I'd do for over a decade is to get a large 12v or 24v UPS and then use a car battery on it. You'd have to look at float voltages to see if you can use a LFP instead. Some have 13.8v or so floats which is plenty for a 4s LFP. Expect a day charge per hour of runtime. UPS units with larger batteries typically charge faster. They also cost more.

 

[hicke]

I have used regular UPSes for decades bit want to build out something new. Also to get into electrics and learn.

I guess I need some advice on actual components to buy. Brands etc.

I am looking into Victron and so on but have no clear picture of i can combine them to do what I want.

Thanks!

 

[OffGridForGood]

Budget?

 

[hicke]

Budget?

I don't know really. Maybe around 1000 USD without the battery. Cheaper if possible of course.

 

[OffGridForGood]

I live in Scandinavia, we have 230VAC here and power NEVER goes out. But IF it did, I would like to be prepared

More of a project than a required item then, to learn from.

If powergrid goes out, I want all equipment that is connected to my UPS system to keep running for a few hours. If power returns, I want the AC to take over and begin recharging the batteries also.

So charge from the grid, while it is available. When (if) the grid goes down, then the battery will supply an inverter that runs the equipment. No PV needed, or would be a separate project one day in the future perhaps, for fun.

I have used regular UPSes for decades bit want to build out something new. Also to get into electrics and learn.

I guess I need some advice on actual components to buy. Brands etc.

Since effectively the system will be a UPS: Grid - charge controller - battery - inverter - small loads.

maybe 200W or so. Maybe a little higher when booting the computer.

You could buy a small 12vDC charger - 230vAC 50Hz and connect to a 100Ah AGM battery,
Then connect a small 12vDC to 230vAC pure sine wave inverter to the battery, and plug in your equipment.
If the utility fails, your equipment continues to run from the battery.
When the utility returns, the charger re-charges the battery.
no transfer switch required.
Low loads and low charging rates AGM will not offgas, will be fine sitting at high SOC for long periods.
100Ah at 12vDC battery = 1200Wh - will run your 200W load for 4-5 hours (including losses for the inverter).
Battery $400-500
Charger $200
Pure Sine Wave inverter 230vAC 50Hz (FCHAO 2500 shown on Amazon for 272.USD, has EU style plugs)
About $1,000 USD all in.

 

[hicke]

More of a project than a required item then, to learn from.

Well, since utility never goes out, I guess. Solar would, however, offset the bill a bit later on. For now, it's more of a learning project, correct.

So charge from the grid, while it is available. When (if) the grid goes down, then the battery will supply an inverter that runs the equipment. No PV needed, or would be a separate project one day in the future perhaps, for fun.


Since effectively the system will be a UPS: Grid - charge controller - battery - inverter - small loads.

You could buy a small 12vDC charger - 230vAC 50Hz and connect to a 100Ah AGM battery,
Then connect a small 12vDC to 230vAC pure sine wave inverter to the battery, and plug in your equipment.

Would the equipment run off of the inverter at all times, meaning alway be powered by the battery?
There is no way to provide 230VAC to the loads without using the battery in this setup?
Is there a way to do this with some sort of combined charger/inverter? Or are there products available that allow for an inverter to utilize the incoming AC power from the charger directly like a power supply to the inverter and switch between charger and PS?

If the utility fails, your equipment continues to run from the battery.
When the utility returns, the charger re-charges the battery.
no transfer switch required.
Low loads and low charging rates AGM will not offgas, will be fine sitting at high SOC for long periods.
100Ah at 12vDC battery = 1200Wh - will run your 200W load for 4-5 hours (including losses for the inverter).
Battery $400-500
Charger $200
Pure Sine Wave inverter 230vAC 50Hz (FCHAO 2500 shown on Amazon for 272.USD, has EU style plugs)
About $1,000 USD all in.

Thanks so much!

I'll consider all this! I am thinking about a combined AC inverter charger for this also. Is that a bad idea?

Henric

 

[Madcodger]

Several years ago, I yanked the internal batteries out of an 2000 watt APC brand UPS (48V) that was designed to run a computer server and connected it to 4 12V 100 AH marine (deep cycle) batteries wired in series (to get 48V). The UPS was plugged into household AC, which kept the batteries charged. I rewired a single 15amp (120v as I'm in US) circuit from our house so that I could plug it into this UPS, and put a refrigerator, DC motor pellet stove (very low current draw), security system, 42" LCD TV, and internet modem and router/wifi onto this circuit (all that rewiring was the hard part). When the power would go out, which happened 2-4 times per year at that house, for up to 5 days at a time), I could run that circuit for about 12 hours with all of that plugged into it. This allowed me to turn off the generator at night from about 7PM-7AM and still have all those devices running. The batteries recharged during the day when the generator was running. HOWEVER, I did have to use external automotive style battery chargers (one on each battery) to do this, as the internal charger on the UPS couldn't recharge that many batteries, fast enough. I didn't have to disconnect them, and just left them connected to the batteries but unplugged until I needed to recharge. Turning those chargers on was the only "manual" part of the system.

I think this is similar to what you are trying to do, and that was my experience. I'm fairly certain it violated the electric code, so I undid all of that when we sold that house and can't recommend that you do what I did. But it sure worked great for what I needed. If I were to do it over again, the only change I would likely make is to use a single, 48V LiFePO4 battery, as they are now cheap enough to justify that.

 

[OffGridForGood]

Well, since utility never goes out, I guess. Solar would, however, offset the bill a bit later on. For now, it's more of a learning project, correct.


Would the equipment run off of the inverter at all times, meaning alway be powered by the battery?
There is no way to provide 230VAC to the loads without using the battery in this setup?
Is there a way to do this with some sort of combined charger/inverter? Or are there products available that allow for an inverter to utilize the incoming AC power from the charger directly like a power supply to the inverter and switch between charger and PS?

Thanks so much!

I'll consider all this! I am thinking about a combined AC inverter charger for this also. Is that a bad idea?

Henric

Honestly, if you just want back-up, keep the AGM on a dedicated AGM battery maintainer style power source,
keep the small inverter in a box near-by ready to go with some simple battery terminals.
If the power fails one day, open the box and set up the inverter connection to the battery, and plug in your equipment.
When the utility power returns, put your equipment back on utility plugs, remove the inverter back to it's box, and let the battery recharge.

However, if you really want to play with the system, maybe add some PV for fun, and such, I think you will find this an educational and fun project.

My tablet I am using right now, to type this message, is powered by an MPP2724 connected to one DIY 304Ah 8S LiFePO4 battery, and one 440W PV panel which at the moment is bringing in x10 the power I am using, but it is fun and entertaining to write/learn about solar energy, while using solar energy.
Enjoy!

 

[krby]

This is totally possible. I built this a few months ago. If you don't care about weight, and you expect the batteries to be full most of the time (not cycled like a typical solar install) SLA is a much cheaper option.

I bought a $150 RV converter / charger. It charges the batteries.
I had an AIMS 600W pure sine wave inverter. I connected both of these two a couple of 12V deep cycle AGM batteries. The converter/charger will charge the batteries, then provide up to 55A at 12VDC to run the inverter. The inverter runs 24/7. My load is about 110-120W AC from the inverter, maybe 250W max. My hope is the inverter will be ok running long term with this low of a load.