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use for ups's
By Budgreen, Section Homebrewed Electricity Posted on Fri Sep 26, 2003 at 09:03:57 AM MST
what can be done here....

Before to long I will be getting some old ups's (660va and 720va) and either the charging section or scr controller in these units is bad and basically unrepairble but the actual inverter section is good, what good use could I put these units to work doing? I do have a large battery bank but that is reserved for future use at the moment. within the next month I will have up a small windmill to provide power for them, just loking for an interesting use.

use for ups's | 4 comments (4 topical)

I use[d] one as an inverter for a long time.. (none / 0) (#1)
by TomW on Fri Sep 26, 2003 at 10:57:44 PM MST

Budgreen;

I used an APC brand 650 UPS very successfully for several hours a day for about a year as an inverter. It worked beautifully but finally died a couple weeks ago.

One note that i will make is that it got awfully hot when drawing 20 to 25 amps continuously which more than likely contributed to its failure and also is wasted power.

They are not designed for anything but intermittent short term use. You will want heavier cable from the batteries to the internal cable than they use from the factory to connect to the batteries also.

Add a cooling fan if at all possible such as a computer fan.

I had to trick out the buzzer and you need to press the "test" button to get it to fire up without grid. Considering it was a dumpster find I felt it did well as an inverter. I have used them for years when camping in the RV where there was no juice bush, too.

Cheers.

TomW

The Truth is the Truth, even if no one believes it; and a lie is a lie even if everyone believes it

Dead UPS and a post mortem... (none / 0) (#3)
by TomW on Tue Sep 30, 2003 at 08:55:59 AM MST

Folks;

That comment reminded me to dig that UPS out and look into the problem.

What I found is a first for me that I can remember in 30+ years of electronic work.

2 of the power resistors had gotten so hot [no cooling fan] that they became unsoldered and were lying in the bottom of the case. Pretty darned weird. If i can get to it I will be soldering them back in and adding a cooling fan to get rid of that heat. The PC board in there is at the top of the case with all the components hanging down and the traces up with about 3/8th inch clearance to the cover.

Considering they are only designed for intermittent short term use it is amazing it lasted this long running about 5 hours regularly at pretty much full load plus.

Again it was a dumpster find so no loss if I can't get it working again plus its a goldmine of parts too.

Just passing on the experience. If you intend to use one as an inverter I highly recommend a fan that kicks on when its running. You could modify the battery door to hold a fan easily without even pulling the cover. I will modify the top of the case for a fan because its off already.

Cheers.

TomW

The Truth is the Truth, even if no one believes it; and a lie is a lie even if everyone believes it

[ Parent ]

Re: use for ups's (none / 0) (#2)
by dconn on Tue Sep 30, 2003 at 05:11:59 AM MST

Hi Budgreen,

I have two APC upses here and I did a bit of playing around to see what I could do with them. They are rated at 650VA and 800VA. I was hoping to dedicate one to running a fridge.

I had no problem at all connecting directly to the UPS battery wires from a big battery bank and then switching on. They made a little beep every now and then but I didn't mind that (it was in the battery shed). It was also great that I was able to connect a serial cable to the UPSes and read battery voltage (and lots of other not-so-useful stuff) - (I used apcupsd to read the UPS details).

I gave up though because when I switched on the fridge the ups would switch with over-current protection. Ok - I know that an induction motor draws a lot of current starting up but I think the computer UPS units are, perhaps, over-protected. Another thing to note is that VA does NOT equal watts in APC UPS land (maybe the VA is battery draw/charging and watts is AC output? I dont know) so a 800VA UPS only gives around 600 watts.

As usual I've found that the answer is to somehow get the cash and buy a new Inverter.

All the best,

Derek

Re: use for ups's (3.00 / 0) (#4)
by srnoth on Sat Oct 02, 2004 at 12:55:04 PM MST

Hey guys,

Just to share my UPS as an inverter experience.

I had an old 300 watt APC UPS, and I was getting tired of no lights when the power went, so I decided to hook it up to the car battery, and use it to run a couple lights when power went (usually power only goes for an hour or two).

I had the car engine running, and I was able to power about 4 100W light bulbs with this thing. It worked great for about an hour and a half, but then the lights flickered and went out, and when I looked outside, there was smoke pouring from the UPS! Not only that, but when I went outside to disconnect it from the car (as fast as possible!), in the darkness, I accidently shorted out my cars electrical system, and basically melted the wire between the alternater and the battery! Not good.

I managed to fix the car the next day, but the UPS was a gonner. The insides were fried from the heat. This shows that while UPSs will work, they are designed to only function as an inverter for short periods, and therefore most have no form of cooling. If you do decide to use one as an inverter, cut a hole in the side of the caseing, and put one of those cheap 4" 12 volt computer cooling fans on the outside. I did this for my other UPS, and I was able to run the sound system at my school for over an hour with no troubles and no overheating.

Cheers,
Stephen.

[ Parent ]

use for ups's | 4 comments (4 topical)

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