Using a UPS with generator?

[garandman]

In a Hurricane Sandy lessons learned thread on NASIOC [Subaru forum] one of the guys had purchased used a large Uninterruptible Power Supply unit. He replaced the batteries for a couple of hundred dollars, so for around $500 he had enough backup power to run his house for hours, until the power came on or he hooked up a generator. They are also gaining popularity for use with for pellet stoves, which typically seem to draw less than 500 peak watts and only about 100 while running steady state. Sump pump backup has been mentioned but that's typically a lot higher current requirement.

We power a large UPS with a Honda EU2000i at work during power outages. This got me to thinking that even at a quarter throttle, an inverter generator might be generating excess power for a period of time, and that a good-sized UPS might lower fuel consumption.

Anyone ever try this, or know of anyplace to research it? I'm going to get a small UPS for our PC and internet hardware, but if it made sense I could buy a bigger one. I've seen quite a bit about people buying batteries and inverters but the UPS seems to have a lot of advantages.

In checking into this I learned that Fairbanks, Alaska actually has a UPS big enough to power the entire city [population 32,000, metro area 100,000] for up to 15 minutes, giving them enough time to switch to backup generation.

 

[eisenhow]

Using a UPS would be a great way to provide continuous power to low draw devices and allow you to cycle your generator. With a honda inverter you'll probably be fine but many UPS's, at least consumer variety, won't charge the batteries from "dirty" generator power. My conventional generac won't charge my UPS's. You'll need to get a higher end UPS that will tolerate the dirty power, or use an inverter generator.

 

[JayMan]

Do you have a link to the Subaru forum thread? Do you know if he's done any testing? I'm currently working out a system at my house, but my UPS testing has been dismal. We run UPS units the size of refrigerators at work, but scaling down hasn't worked out so far. My current setup is using marine batteries, and the next one will be using some sort of industrial storage batteries.

 

[BenDover]

At 300 watts the EU2000i uses .1 gallon per hour with Eco throttle on FYI. It produces true sine wave output and will have no trouble powering loads thru a UPS.

If you could extrapolate the fuel consumption curve below 300 watts you probably see it bottom out because it requires fuel to keep the parts rotating etc.

At .35-.40 cents per hour for gas you are not going to save any money adding a UPS. You also need to factor in the charge/discharge efficiency of the UPS. Gel batteries have a 80 percent charge efficiency and depending on the load and batteries could be 50 percent efficient during discharge.

Let's say you spent 1 gallon of fuel charging your UPS and then shut down the generator. You have .8 gallons worth of fuel "stored" in the UPS batteries. Lets say you powered a light for many hours and used up the UPS. The inverter in your UPS is typically 90 percent efficient at converting your DC battery voltage to AC (we will assume 100% discharge efficiency on the batteries). Bottom line: you spent 1 gallon of fuel to get .72 gallons worth of electricity.

You are not going to save very much if any fuel using a UPS.

 

[fshalor]

Using a UPS would be a great way to provide continuous power to low draw devices and allow you to cycle your generator. With a honda inverter you'll probably be fine but many UPS's, at least consumer variety, won't charge the batteries from "dirty" generator power. My conventional generac won't charge my UPS's. You'll need to get a higher end UPS that will tolerate the dirty power, or use an inverter generator.

Our Ham Radio el-cheapo emergency stations for hurricanes included a line conditioner. Usually a ~$100 line conditioner and a $200 cheapo B&S 3.5 HP based auto-throttling genset working together kept our UPS's charged.

We mostly used either 900va Conext's, or older smartUPS 1500's. Some UPS's will die a horrible death if you plug them in to a genset without the conditioning.

Honda's were by far the cleanest power for the money we found. (But most of us couldn't afford them.)

 

[Jaymass2175]

I have a Honda 2000 eu. I know they say pellet stoves are very finicky and you can fry the electrics very easy. I believe the Honda makes clean power, but the stove was very pricey so I have been rather hesitant from using yet. Any thoughts!

 

[appraiser]

A eu2000 is going to give you the cleanest power you are going to find, probably cleaner than your utility company.

I run PC's, HDTV, modems, my Yamaha amplifier, and a bunch of other stuff off of mine and I have never had a problem after hundreds of hours of use.

UPS's are great to keep you up and running while you get the inverter up and running (in my case 5 minutes) but the EU2000 is not going to fry your equipment and in EcoThrottle mode it sips gasoline

BTW how does a UPS make 120v AC 60 Hz? The exact same way the EU2000 does, except the EU has to take the AC output from the generator, convert it into DC, then it process it into AC.

I challenge anyone to find a documented case of a Honda Inverter damaging something.

 

[jjm403]

Honda EU2000 is the way to roll!

 

[Kevin_NH]

I think the efficiency calculation works out better with other generators. With diesel, for example, you don't want to run the genset for hours at very low load. So you run the generator at +3KW for a couple of hours to chill a chest freezer, refill your pressure tank and charge the batteries, then coast along on battery power at a few hundred watts for the rest of the day.

We mostly used either 900va Conext's, or older smartUPS 1500's. Some UPS's will die a horrible death if you plug them in to a genset without the conditioning.

Even if it works, most UPS manufacturers will not warranty their "consumer" products if used with any generator.

 

[Jaymass2175]

Wow very good to know, thanks guys!

 

[Hiltonizer]

depending how large of a UPS you're talking about, you're probably better off with a charge control, inverter, and actual solar batteries.

I've given consideration to it for my well pump, its hard to justify the cost though unless its just a phase-in process to off-grid power.

 

[garandman]

Do you have a link to the Subaru forum thread? Do you know if he's done any testing? I'm currently working out a system at my house, but my UPS testing has been dismal. We run UPS units the size of refrigerators at work, but scaling down hasn't worked out so far. My current setup is using marine batteries, and the next one will be using some sort of industrial storage batteries.

Haven't been able to find it.

I'm just going to get a small UPS to keep our internet hardware up in case of a power outage. With a two EU2000i setup it doesn't appear there would much of any benefit. Getting a UPS big enough to be able to run the heat [circulation pump] overnight doesn't sound cost-effective - although it might help extend your gas supply if you did everything right.

 

[Kevin_NH]

I'm just going to get a small UPS to keep our internet hardware up in case of a power outage.

I've found that consumer UPS are seldom designed to provide long runtime at low load, and will self-shutdown after an hour or two to avoid deep cycling the battery. Some UPS manufacturers make "XL" models rated for extended run times.

Before you invest in UPS, take a close look at your internet hardware (cablemodem, firewall, wifi, etc). If everything already runs on 10-14 volts of DC, you may be able to save money and get MUCH longer runtimes by powering the internet hardware through a simple voltage regulator (or better yet, a charge controller) and oversized 12V deep cycle battery. Basically you skip the 2 extra conversions when running from battery power.

 

[noxin]

I've found that consumer UPS are seldom designed to provide long runtime at low load, and will self-shutdown after an hour or two to avoid deep cycling the battery. Some UPS manufacturers make "XL" models rated for extended run times.

Before you invest in UPS, take a close look at your internet hardware (cablemodem, firewall, wifi, etc). If everything already runs on 10-14 volts of DC, you may be able to save money and get MUCH longer runtimes by powering the internet hardware through a simple voltage regulator (or better yet, a charge controller) and oversized 12V deep cycle battery. Basically you skip the 2 extra conversions when running from battery power.

Additionally consider that most network nodes (fios Comcast etc) may not have backup power. Even if your stuff is up, the upstream hardware may not be

 

[Chet0729]

Generac Xp series generators will power ups's and provides cleaner power than the utility companies. They also have models large enough to run your whole house including 220 appliances. Last time we lost power, I was back up in less than 10 minutes. Whole house no issues.
I have a UPS that takes 2 car batteries and it works fine on generator power