UPS as an Inverter

[captain ron]

I have an UPS that has bad batteries 12volt set up, I got it to use just for my printer and will hook it to it's own battery bank. My question is why wouldn't you use these as your primary inverter? There are several sizes in wattage, they would be auto  switching, you could use several to power different zones, they can be bought used with no batteries on Ebay pretty cheap, they are true sine and filter your power source some are 24 volt, And I would assume they have a built in charger.

[gene lewis]

How about enlightening us more on the UPS thingie.

[Len Silva]

Charley

My only concern is that the UPS is not intended to operate for more than a few minutes at a time, just long enough to save data and shut down, unless you are talking about large commercial units.

Try it.  Hook one up and run it at near full load for a couple of hours.  You might have to add a small fan to it.

Len

[Slow Rider]

A UPS (uninterrupted power supply) takes A.C. (alternating current) from the wall and charges an internal sealed battery.  It then converts the D.C. (direct current) back to AC.  It has from two to four outlets on it for whatever you want to plug into it.

The theory behind it is that when the ac from the wall stops, the battery is fully charged and can continue to provide uninterrupted ac to your devices.

The capacity of your internal battery determines how many amp hours of power your ups can supply.  It was designed to give you time to safely power down your computer or bridge the gap on short power outages.

If your house battery bank replaced the sealed battery, it should basically work the same.  The thing I would make sure of is the current limitation.  I don't know how things you could power at once.

You also might run into some problems with the charging of the house bank.  The charging circuit will more than likely be limited.

But I am sure the smart guys will correct my errors and give you the real poop. 

Charlie,


Make sure your printer will work with the UPS.  Laser printers especially don't like them.  They will destroy the power supply in laser printer.  The owners manual for the printer should have a warning if it is a problem. 

Frank

[belfert]

A UPS (uninterrupted power supply) takes A.C. (alternating current) from the wall and charges an internal sealed battery.  It then converts the D.C. (direct current) back to AC.  It has from two to four outlets on it for whatever you want to plug into it.

Most (all?) of the smaller UPSes do not generate AC from DC when the UPS has power from the wall.  The UPS turns on the inverter only when input power is lost.  You need to get into some of the larger commercial type units.  APC calls this double online conversion, but it is commonly known as an online UPS.

You can certainly get this type of UPS on Ebay probably cheap, but your garden variety UPS from a retail store is not going to have this.

[captain ron]

Reading some of the data I believe most of them filter the ac power coming through it. A couple of them on Ebay right now are larger more expensive units that have bad or no batteries that are selling cheap. Shipping more than unit cost but if your near them or have a friend near them you can eliminate shipping costs. Some of them are of the smart variety and have usb and multi pin connectors so you can hook up your computer and monitor battery condition, power condition and other cool things. Of course my reading electrical data and understanding it is about the same as me reading the koran and translating it.

If you were to plug them into an outlet that is between your power supply and your electrical panel they would be auto switching . Some creative thinking outside of the box and you've got a cheap true sine inverter system.

[belfert]

I'm pretty sure all UPSes do power filtering based on my reading.  They are not all doing it by running all power through the batteries.  I called APC for the heck of it earlier and you have to buy an office/commercial UPS that retails for over $1000 to get filtering through the batteries.  The less expensive models only use battery when there is no AC coming in.

There is certainly nothing at all wrong with using a UPS for an inverter.  I'm just making it clear that not all of them run the power through the batteries all the time.

[captain ron]

I'm pretty sure all UPSes do power filtering based on my reading.  They are not all doing it by running all power through the batteries.  I called APC for the heck of it earlier and you have to buy an office/commercial UPS that retails for over $1000 to get filtering through the batteries.  The less expensive models only use battery when there is no AC coming in.

There is certainly nothing at all wrong with using a UPS for an inverter.  I'm just making it clear that not all of them run the power through the batteries all the time.

I wouldn't want them running power through the batteries all the time. I would think that would put extra wear on the batteries. The filtering would be great when running on a cheap generator. I should get Federal funding and use my bus as a Guinea pig for trying weird things out that others think won't work.

[Len Silva]

There are many, many people on this board that have successfully done weird things that everybody said wouldn't work.

Len

[DrivingMissLazy]

Off line UPS's do some filtering of the AC input power and then connect it directly to the load. The built in inverter only operates when there is a utility power failure and the switch time from AC power to inverter power is less than one AC cycle. Typically about 13 milliseconds. These inverters are not designed for full time operation as an inverter. Typically limited to two hours or less.

On line UPS's have the inverter operating full time to supply power to the load. The charging circuit keeps the batteries at float voltage and this does no harm to the batteries. The inverter is designed for full time 24/7 operation.

Batteries fro larger UPS's come in typically three designs. five year, ten year and twenty year life. We typically changed them out at about 80% of their expected life cycle.

And you can forget the bull about not replacing a failed battery in an older set set of batteries with a new one. I can assure you that if there were 300 batteries in a set and one failed, we only replaced the one failed battery, not the whole 300.

Richard