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Message |
David J. Silva (Cypress) (65.179.97.171)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, January 09, 2003 - 3:31 pm: | |
Following the dot-com implosion there are a lot of UPS' on ebay for not much money.
Is the inverter from one of these as good or better?
There are a bunch of 2000 and 3000 watt units for a lot less than comparable inverters. Shipping can get a little crazy but in addition to the inverter you get the zero delay switch and those pricey deep cycle batteries.
I know they were only designed to run for 45 minutes or so but I can't see why a solid state inverter would not work indefinately.
dave |
Peter (Sdibaja) (209.242.148.130)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, January 09, 2003 - 4:03 pm: | |
The UPS rigs have batterys that _are_ designed to run for 45 minutes or so, but only with the load of a computer... that would only keep your microwave and VCR from blinking at you, perhaps a night light for 10 minutes or so... |
David J. Silva (Cypress) (65.179.80.204)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, January 09, 2003 - 4:40 pm: | |
I politely disagree,
the time factor is a function of battery power. The more you have the longer it lasts. The UPS under your desk may have something less than a single deep cycle 12V.
The output or load is a function of wattage. So, a 3000 watt UPS which is currently on ebay for a lot less than a 3000 watt inverter should power the same appliances as the inverter.
The question is, will it work as well and as long as the inverter?
The UPS also comes with a nice auromatic battery charger and a load switch. |
Jojo Colina (Du1jec) (209.75.20.72)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, January 09, 2003 - 4:46 pm: | |
The UPS's have a small charger designed to bring the batteries up over a longer charging period than you would want for RV usage.
The Inverter sections themselves are okay in the high end UPS units. You would have to derate them considerably to run them for longer periods. I would not run a 3kva ups with loads over 1200 watts for extended periods. On the positive side most high end UPS units have a sine wave output.
If you use an external charging source be sure to disconnect the UPS from your battery bank prior to charging. Chargers are not clean DC sources and the UPS DC inputs are sensitive to this.
I have used a Best Power 3kva unit continously for about 16 hours with an external battery bank at my home to test its performance and it had no problems.
Be careful as high wattage units may require 48v or as in some of my UPS units here at work 144v.
As for those pricey deep cycle batteries, we use 100AH 12v AGM batteries for our UPS strings. They are very reliable considering that they are most often in a charging state and only switch to load twice a year when we load test them.
Out of a pool of about 200 batteries I have only lost 3 in the last two years. We use Powersonic brand baterries. We cycle them out based on age whether good or not.
I use 24 of the same batteries to power the Trace DR3624 in my bus and they perform much better with no maintenance than the Trojan's that I used to have.
Jojo |
Peter Broadribb (Madbrit) (65.37.90.130)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, January 09, 2003 - 4:48 pm: | |
......and can you stop it Beeping the "NO shore power" warning because it thinks that there is a power outage all the time you will be running off your house batteries.
Peter. |
Jojo Colina (Du1jec) (209.75.20.72)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, January 09, 2003 - 5:52 pm: | |
All the beeping is made by a small piezo buzzer that you can unsolder or otherwise disable. Some UPS units allow you to turn it off.
Jojo |
Gary Stadler (Boogiethecat) (68.7.217.217)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, January 09, 2003 - 6:03 pm: | |
One thing you're all forgetting. It's not so much about the batteries as it is the heat generated by the UPS's guts. JOJO is lucky....
UPS units are made for intermittent duty only, to operate long enough to shut your computer down safely, and then go away. MOST UPS units have heatsinking and transformer wire size that is totally inadaquate for continuous duty, are purposely engineered for a particular battery capacity, and will fry themselves in short time if given larger sized batteries and actually asked to use them up in one run.
That said, some of the really big units "MAY" have hefty enough internals to take continuous duty, but I have seen very few that will do this.
I've fried a few myself testing this out. And I'm an electronic designer/engineer by trade so though I may not be the total authority on this, I do sometimes have a bit of a clue in what I blab about....
Cheers
Gary Stadler |
Jojo Colina (Du1jec) (209.75.20.72)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, January 09, 2003 - 9:02 pm: | |
Gary is very correct about the heat issue. Most low or mid range UPS units will NOT have the heat dissipation required to cool adequately for continous operation.
Notice my recommendation to use a high quality UPS as well as derate to about 50% of rated UPS capacity. The load of a TV for a few hours and the occasional toaster or microwave will probably be adequately handled by a quality 3kva UPS with a properly sized battery bank. You definitely would want to turn it off when you do not need AC power as these inverters have a significant idle power consumption.
There are UPS units which are fan cooled which will help as well. If one was on a tight budget and found a 3kva Best Power FE for next to nothing there would be some possibilities.
If you have ever opened up a Best FE you would know that it is capable. The 3kva without batteries is about 150lbs. You purchase batteries based on your intended backup time. Although at a certain point a generator is cheaper than batteries.
The big issue as I have said is that the internal charger is not what you would want for an RV as typically a UPS has a lot of time to recharge between uses hence the low capacity of the charger. Another issue is most high capacity UPS units require 48volts and up. This further complicates the charging requirements for your battery bank. There may be some 24 volt 3kva UPS's out there but they are few. Our 36kva units take 144volt DC input.
All this being said I have a Trace DR3624 in my bus. The mods necessary to a UPS was too much hassle since I wanted to use an inverter for significant loads and significant periods of time. Usually at least a few days at a time.
Jojo |
Scott Whitney (66.82.9.24)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, January 10, 2003 - 12:54 pm: | |
Seems like even if you used a UPS, you'd still want a hi amp dedicated 3stage charger so you can minimize genset runtime to recharge batteries. All the cost savings of the UPS would go out the window in fuel cost if you have to run the genny for hours and hours on end recharging at a float rate.
Having to buy a good charger, unless found used or surplus also, may outweigh the savings of using a UPS when compared to getting an RV inverter with built-in charger. (also doubles the bulk)
Scott |
Keith-Flx-FL (Keith) (65.33.37.243)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, January 10, 2003 - 2:52 pm: | |
Buy the time you buy a high end UPS of the size necesary to run much of anything on your bus, the savings are not that great. You can buy recertified inverters at much more reasonable rates than brand new which would work better over all... After all, your talking the same battery bank anyways! As a computer tech, I would recommend a small UPS like the Belkin 350va or 500va be hooked to the computer. It uses a little more juice, but provides alot of protection from both under and over voltage situations and will prolong the life of your computer. As for powering the coach..... I'm not an expert, but IMHO the headaches and performance issues aren't worth the minimal savings. |
Richard Bowyer (Drivingmisslazy) (66.190.119.82)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, January 10, 2003 - 5:31 pm: | |
A word of caution. Many UPS's do not have the inrush capability required for starting motor loads such as A/C's.
Richard |
Chuck Harris - PD4104 (207.172.11.147)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, January 11, 2003 - 8:07 am: | |
There are two kinds of "UPS"s:
One is the true UPS, or Uninterruptable Power Source. The true UPS has a built in inverter, usually sinewave, that supplies ALL the power that comes out of the sockets, all the time. Whether running on batteries, or on the power line. These are expensive. Usually more so than a good inverter.
The other kind of "UPS" is a Standby Power Source. This kind of "UPS" only provides power when the power line goes away. Power switch over takes a cycle or two, and hopefully the computer will still be running after that. All other times, the power is provided directly by the power line. These are the cheapy units made by APC, and others.
Inrush current at load start up is a problem for both kinds of UPSs. The manufacturer, can either provide a monster battery, and an inverter to suit, or they can pass the inrush load to the power line. The latter is more common.
If you want an inverter, you would be better off buying a real inverter.
-Chuck |
Skorpio (24.92.193.195)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, January 14, 2003 - 6:51 pm: | |
The biggest problem I see is that UPSs don't run off of any kind of DC voltage that is present in a coach and most of the larger, better quality UPSs on ebay are 3 phase. I've been a data center fiesability engineer for 20 years and have worked in lots of places that are all DC power (Phone company central offices run off of 48V DC power for AC stuff they run inverters). Your better bet would be to figure out how to get a 48V charging circuit in your bus (actually -48V) and pick up Data Center inverters. they are obscure enough to be cheap on ebay. Bankrupt data centers have lots of those too, if they are not on ebay they are at an auction somewhere, and they will be a lot more forgiving since they are made to run off of a similar kind of set up, and with similar batteries. I've seen rows of Die Hards and Delco Freedom deep cells in data centers all the time.
AT&T used both as standard issue for many years. |
FAST FRED (209.26.115.105)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, January 20, 2003 - 5:43 am: | |
--> UNINTERRUPTIBLE POWER SUPPLY UNITS RECALLED
American Power Conversion is recalling 2.1 million uninterruptible
power supply units. The units can overheat and catch fire. In several
cases, the units' outer casing melted, resulting in minor property
damage. The recall covers Back-UPS CS 350 and CS 500 units. APC will
replace the units. Details are available at:
http://www.apc.com/rely/index.cfm
FAST FRED |