UPS Upgrade

APC calls that a "Double Conversion On-Line UPS": APC has some of those but I don't recall the model numbers. A variation on the same theme is their "Delta Conversion On-Line UPS". I locked horns with an early version in the APC SmartUPS 1400RH. I don't recall which of these two systems was used in the 1400 RH but I think it was the "Delta Conversion On-Line UPS": Here's another 8 waiting for me to throw them off the deck and haul off to the recyclist: It's claim to fame was the ability to destroy four 12v 7A-hr series-parallel batteries in an amazingly short amount of time, with the added bonus of having the sides of the batteries bulge to the point where they cannot be removed from the housing. As a side benefit, operating like this usually caused some circuitry to blow up resulting in low output and the fan permanently running. My rants on the topic from 2003: Short summary: This particular model doth suck.

However, that's not why I mentioned it. The way it works is to run the switcher continuously and in phase with the AC input power. The voltage from the AC line is always slightly higher than that from the battery powered switcher section. This way, the AC line is providing almost all the power to the load, with the battery powered section just idling along. When the AC disappears, the battery powered section is already switched on, is running in phase, and is active with zero transfer time. When it worked, it was fairly good, if you didn't mind the steel case buzzing at 60 Hz or the heating and loss of efficiency running the UPS full time.

So what I am getting out of this is

Mod a UPS that uses only one battery i.e. 12V Get a higher capacity SLA.

These UPSs I already have so I would not need to buy a larger USP.

May need several UPS to get the VA I need.

This is for an unattended security system.

I really need to do a cost benefit analysis on this.

(snip)

From the personal safety viewpoint, DO check that the battery system is at or close to earth - ground to you furriners - and/or UPS output neutral potential. What you *may* discover is that a lot of UPS inverters have the batteries at half-AC-output voltage. Whether you are at ease with that is something you should consider.

When I wired up the APC 1000 my plan was to put it on the line only for part of the time (manually or using a clock) just to keep the big batteries topped up, and to connect it only in the case of a prolonged power outage. Over here, energy is expensive and the line is very reliable, it actually is hard to maintain a UPS with an MTBF higher than that of the line so systems behind a UPS often experience more power failures due to UPS defects or maintenance than due to a power break.

However, once it fails it can remain off for hours, and I thought it might be a good idea to have some backup power on standby.

Unfortunately, it turned out that the APC SmartUPS 1000 (and some other APC models as well) CANNOT be switched ON when the mains has failed!! It has to be running all the time and then it will take over when the mains fails, you cannot use it as a portable power source that can be switched on when it is already charged... bummer.

Wouldn't help for that anyway--even unloaded, it'll only run half an hour or so.

Cheers

Phil Hobbs

With the big batteries it (initially) worked much longer than on the standard batteries, as is to be expected. But indeed its usefulness is quite limited. I was thinking along the lines of keeping the gas central heating or the fridge working, but each of those requires intermittent power at 100..200 watts, and of course 2 60Ah 12v batteries store only about 1400 watt-hours, with the losses included the whole thing will probably not work for 5 hours. When kept closed all the time, the fridge can overcome a 5 hours outage and being 5 hours without heating is also not really much of a problem here.

Looks like the APC SmartUPS 1000 is one of those that is synchronized to the line frequency and running full time on battery. Unfortunately, there are about four APC UPS's that are called 1000 so I can't make the determination:

What you're experiencing is what most grid tied solar power system owners run into. The inverter is synchronized to the power line. If the power line goes away, there's nothing to synchronize with, so there's no output. That makes grid tied solar not very useful for emergency backup power. There are some workarounds, such as running a gasoline generator in place of the utility power to provide the necessary 60 Hz, which won't work for you because you don't have an array of solar panels. Might as well run everything off the generator.

Perhaps it might be useful if I estimate how long a 700 watt load will run from your proposed two marine deep cycle batteries. These batteries are not really made for this type of operation, but I'll assume that you'll eventually buy some decent batteries. Size 27A is quite common. CCA=Cold Cranking Amps, MCA=Marine Cranking Amps, and RC=Reserve Capacity, which are 3 different ways to badly specify a battery. Compared to a starting current, your 350 watts per battery load is quite mild. I'll pull a number from my hat and call it about 100 Amp-hrs.

So, you have two 12v 100A-hr batteries with a total capacity of: 24v * 100A-hr = 2400 Watt-hrs Unfortunately, you can't just drain the battery to zero and expect it to survive for long. At best, you can get about 60% of that out of the battery. I'll call it 50% or 1200 Watt-hrs.

Assuming no losses and 100% inverter efficiency (fair enough considering all the other bad guesses I've made here), your inverter will run for: 1200Watt-hrs / 700 watts = 1.7 hrs Of course, some of your loads are intermittent loads. The 1.7 hrs would be how long your system would run if everything were turned on full time, which is worst case. So, you get to make a list of all your loads multiplied by their expected duty cycle. Add those up, and you get a more realistic load estimate. Divide that figure into

For what it's worth, I had a system similar to yours for about 15 years. I live in the deep dark forest, where solar power isn't possible. So, I would charge a random 12v battery from an AC powered float charger, and use it to power my emergency toys (scanner, 2way radio, ham radio, AM/FM radio, some lighting, cell phone charger, DSL modem, router, etc) directly from the 12v. I also had a small automotive AC inverter for the few loads that required AC (laptop). It mostly worked, but required that I carefully manage my loads.

The fridge is where things get interesting. Before I pontificate on the subject, I suggest that you insert a thermocouple probe into the fridge, close the door, start some kind of data logger, kill the power to the fridge, and record the temperature as it climbs. Also try this with different types of refrigerators, presumably owned by friends and neighbors. I think you'll find that insulation and thermal mass varies radically between brands and age. Once you determine how long your fridge needs to be running before the contents are no longer safe to eat, you can then calculate how big a battery will be needed to run it.

Suggested skimming:

Good luck.

Ok I was not the original poster, just someone who has tried the same thing in the past. But I see you have calculated the case of the original poster an I'm sure he will read that.

Sure there is lots of variation with fridge isolation and power consumption. It can often be wise to replace it while it still works, because the cost will be recovered through less use of energy (especially here).

Unfortunately, the expected lifespan of household equipment decreases so quickly over the years that it often happens that 20 year old stuff is still working today, while new equipment bought 5-10 years ago is already defective beyond repair. That means once you enter that cycle you have to replace again and again...

Sorry, but your comments on the APC 1000 sounded very much like the OP. I have to deal with considerable "nym shifting" in other newsgroups. The result is that I try to use context instead of the name in the header as an identification. Usually, that works for me, but not always, as in this example.

I did some testing of temperature drop and have some old data somewhere. Also, a crude test of fridge insulation by measuring the difference between inside and outside case temperature. I found considerable variations including one fridge where I think the manufacturer forgot to install styrofoam insulation in the walls. These measurements are impossible to make in the appliance dealers showroom and are not on Consumer Report's test list. There are also installation problems, such as the common "alcove" install, that blocks air flow past the top and rear of the fridge, which reduces efficiency. This is probably sufficiently off topic to stop here.

Yep. That's the theory. However, I'm not so sure. Electricity is still quite cheap. Paying more for a genuinely energy efficient fridge will be balanced by the savings in electricity if fridge remains efficient (no compressor leaks or friction) and lasts for a long time. Again, this is sufficiently off topic that I don't want to grind the numbers.

Yep. It is now possible to computer design a product for a specific lifetime. Simple component cost reduction does the most to reduce product life. Lack of repair parts and facilities does the rest. The idea is to design a product where everything fails simultaneously somewhat after the warranty period. If some component just happens to NOT fail at the prescribed time, a dash of cost reduction should bring it in line with the other simultaneous failing parts. Should it fail prematurely, it is often cheaper to replace a defective product than to repair it. Of course, some enterprising manufactory could produce a truly reliable fridge, designed to last, lifetime warranty, and easy to service. For example: Just one problem... they're really expensive.

Here we pay the equivalent of about $0.25 per kWh...

Also the life is sometimes shortened by the mandatory use of environmentally friendly procedures and parts, and coolant in the case of fridges. That also reduces the functionality, e.g. it reduces the allowed range of environment temperature.

Make sure the UPS has proper fan cooling for extended run.

I tried just this years ago and the UPS overheated and then exploded (all the power transistors blew up). It was never designed for extended use off larger external batteries. Whoops.

Some units require that you PRESS AND HOLD the on off button for a few seconds to start without AC power.

Mark

I can personally attest that APC UPS' suck so bad they suck at sucking.. They overcharge and end life early for the batteries installed into them.

They also fritz out and act like there isn't even a battery installed and recover after a power line cycling, which is beyond lame if one's intent is to keep what is plugged into it up and running.

I got a used APC 330 XT Plus; ran without any problems for 5-6 years, handling brownouts and blackouts like a champ. Then had to change the battery as it was finally dying. The new battery is still going like a champ after about 5 years. Equipment must fall apart around you, because (other than you) i have heard only good stories about the APC brand (if not abused).

True: But a lot of APC brand units take the attitude that if there's no utility power, there's no point *letting* you power the load.

All that will happen is it will lose power again when the batteries expire. So no. You can't :)

This is a problem if you plan to use it as a short-term portable power source.