So I was looking at some rack mount UPS's on ebay and it looks like you can get some decent deals... About $100 for a 1000 watt Pure Sine rack mount (professional) system with no batteries.What if you were to install such a system in your RV inline with the general use circuit (Not the Air Conditioner circuit)? It yould be in line passing the normal 15 amp load through as long as you were plugged in to shore power. Unplug and it clicks over to your house batteries and provides up to 1000 watts of pure sine electricity to the non air conditioner circuit in your RV. Flip the switch and turn it off when not needed or keep off until needed... Of course you would have to disable your converter at least while operating the inverter... Plug back intoshore power and it starts passing shore power through and trickle charges your batteries. It seems like someone with a bit of understanding could wire this up safely. I don't think these things are known for bursting into flames when they kick on...

Um, excuse me for raining on your parade, but do be aware that all the UPSs _I_ have ever heard about are Modified Sine Wave, not true sine wave. $100 is way, way, way cheap for a true sine wave inverter in the 1,000 watt range. In spite of the UPS peddler's best efforts to tout their systems as "safe for computers and other sensitive devices," the fact is that computers, being inherently VERY sensitive, have been designed with robust power supplies so that predictable crummy power, like from $100 UPSs, cause no problems.The power brick for my Macbook Pro says on it "100-240 volt, 50-60 Hz" input, which says to me that it is a switched and regulated power supply, not a transformer power supply, and that as such, it can handle some pretty crummy power.Now I'm sure that with enough money and an electrical engineer to design it, such a system could be put together. But not for $100.

Seems to me like a lot of extra hulabaloo for little advantage. UPS only runs for a little while until power runs out. Usually just used to allow orderly shutdown of equipment, not to run equipment normally.

I almost did this a few years agoUntil I noticed the track mounted ups system used A 48v battery system, external.. no batteries includedAnd rack are designed for controlled clean air & temp environments they may have fans, but some don't have cases, like floor mounted ones do

I hate to add to the bad news... but I considered this myself but based on my experiences with the hundreds of them that I maintain, there were a few things that concern me about this idea:1) batteries are not cheap and require replacing every 3 years (less than 1 year if you regularly drain them). UPS batteries are designed to maintain a charge (like a car battery), but not meant to be drained regularly (like a Deep Cycle battery). One full discharge can be enough to kill the batteries.2) batteries are very heavy: a 3000kva rack mount UPS with batteries will come in at about 50-75lbs, a 5000kva will be over 100lbs.3) most do have fans, but they do not come on until it flips to battery power, at which point they are quite noisy.4) most UPS's, even the cheap $40 ones are very noisy and irritating when on battery, they beep constantly to warn you they are on battery5) most UPS's even the cheap ones will beep for everything, brown out, black out, low battery, really low battery, replace battery etc....Regardless of the quality of power, the weight, type of batteries and noise was enough to turn me off. If you are really concerned, just do something like a cheap APC SmartUPS 350 and use it like a power bar, just for your critical/expensive equipment ie TV, Laptop etc. It will at least give you a really high joule protection rating, smooth out the bumps and give you a bit of time to finish what you are doing. But if you already have an RV Surge Protector on the rig, you already have most of the benefit anyway.If you are really set on this idea, I would consider something more like this:http://www.apc.com/products/family/?id=310I believe these UPS's designed for entertainment systems provide much more "pure" power (term used loosely as I do not think any are true sine).

Uninteruptible Power Supply as RV Inverter? | Good Sam Community

16 Replies

pianotuna
Nomad III
Aug 21, 2014
Hi,

I did get a 2000 watt UPS. However it was MSW and 24 volts DC input, so I never used it in the RV.
gatorcq
Explorer
Aug 21, 2014
Inverter Vs UPS are the same design.
MrWizard
Moderator
Aug 21, 2014
We just use an inverter attracted to the house batteries
CT_WANDERER
Explorer
Aug 20, 2014
I have used UPS units in my MH for a few years. The First one lasted about 5 years. I ran it on the house batteries. I did have to plug the beeper. It finally died. The next unit did not do as good as the first one. Seems like it did not like it when the batteries were on a high charge, it would set off an alarm every time the voltage went over 13.8. I liked them because it would switch back and forth between house power and normal AC without missing a beat. Worked great for the TV and Sat system in the MH. Now I am using a PSW inverter, when on the road and might be dry camping.
abideejay
Explorer
Aug 20, 2014
Yes, they can be 12v....for the smaller units. Anything over 500va is generally going to have two batteries in series to create 24v, four batteries to create 48v, etc.

Now, as for the time that they will run, many of the larger units have extended battery capabilities, allowing them to run for longer periods of time. I have several in the racks at work that are (intentionally) oversized for the load in the rack. They will run for 30-45 minutes or more easily without overheating. Granted, small load on a big unit. The only reason they stop running is because the battery runs out during a power outage.

Will you be able to do what you want for $100 though? Probably not.
rwbradley
Explorer
Aug 20, 2014
smkettner wrote:
How much are the batteries? Are you assuming they are 12 volt?

Otherwise where is the link to this item?

My experience is mostly with APC brand, but the UPS's are rated to last 5 years and the batteries 3 years. The replacement batteries typically cost about 50-75% of the original cost of the UPS.

They are typically 12v. All the APC ones I have seen are 12v.
RockyMt
Explorer II
Aug 20, 2014
You should listen to RWBradley.What he states is spot on,I am/was an engineer and worked on several UPS systems-not for RV use!
time2roll
Nomad
Aug 20, 2014
How much are the batteries? Are you assuming they are 12 volt?

Otherwise where is the link to this item?
Veebyes
Explorer II
Aug 20, 2014
$100 for a pure sine wave anything comes under the "If it seems too good to be true" heading.

Yup, paid far more for mine, but I am very confident with my 2kw pure sine wave inverter/charger.
wa8yxm
Explorer III
Aug 20, 2014
The difference between a UPS and say a Xantrex Prosine inverter/converter.

The UPS is designed to deliver 120 volts from batteries for perhaps five minutes max.. If you are running it at 50% or more it will quickly overheat. Also many UPS units are MSW though you specifically said the one you are looking at is TSW which is good.

The Prosine is designed to run anything up to its maximum rating all day, all night and as long as the 12 volt holds out.. It is also a true sine unit.

Battery re-charge is faster as well since the prosine is a 3-stage (Bulk Absorption and float) and the UPS is likely just the last two.
I strongly recommend True Sine