# Enthusiast Power Protection: Four-Way 900 W UPS Roundup

## Why So Pricey?

Most of our enthusiast-class builds have an approximate value of \$2000. Because a \$200 UPS represents only 10% of the system’s price, we thought a roundup of those would bolster our “cheap protection” argument. That’s when the realities of modern hardware slapped us in the face.

Problem 1: Real vs. Apparent Power

Have you ever wondered why a UPS of enormous VA rating might be required to support a far more moderate wattage load? Aren’t watts calculated by multiplying volts by amps, the V and A in VA ratings? Getting to the bottom of this required us to think about a few of the things we learned in high-school science classes and apply those lessons to a Web search.

The AC (alternating current) power that comes from our wall jacks is graphically represented as a sine wave, where the center line is equal to ground. Voltage is rated using RMS values, so a 120 V line is 170 V peak (RMS * √2). In a perfect world, current (amperage) would track force (voltage) perfectly, resulting in a peak wattage (at the crest of the wave) that’s far higher than the average wattage for a single cycle. That is to say, even in a perfect world, the circuit must be designed to handle more than its rated power.

Unfortunately, amperage load doesn’t always track voltage perfectly, and this is where VA and watts part ways. When voltage and amperage are slightly out of phase, a portion of the energy from the load (such as a computer’s power supply) returns to the source (such as a UPS battery). Though the cancelled-out power reduces the energy required from the source, all the parts between the source and the load must be beefed-up to carry it.

VA ratings are a way for power supply companies to advertise the current-carrying capacity of those middle parts without discussing the continuous load the battery is able to supply to the PC.

Problem 2: Active PFC and Step Waves

While traditional PC power supplies focus on reducing electrical noise on the output rails, Power Factor Correction-equipped power supplies also attempt to reduce the noise the unit places on its power source. Filters align amperage and voltage cycles, reducing the portion of energy that is returned from the load to the source. That is to say, a power supply with perfect PFC (1.0) would never require the middle parts to carry more VA than the PC consumes in watts. With enthusiast PC power supplies now advertising 0.95-0.99 PFC, it’s time most of us learned to ignore VA ratings and focus on the wattage capacity of our UPS devices.

Yet active PFC power supplies can also be more sensitive to wave form than traditional PC power supplies have been. Dan Farnsworth of APC explains:

“For some basic info, Europe has required that all electronics devices now be made with PFC power supplies for a while now. And they are becoming more common here in the US as time passes. These power supplies are more efficient...but also more expensive. Accordingly, in order to minimize cost increases associated with active PFC power supplies, some manufacturers are cutting corners in their power supply designs, which can impact the compatibility of traditional desktop (modified square wave output) UPSs with computer systems that use these new power supplies. For example, in some cases, the PFCs' "hold up" time is shorter, meaning UPSs, which normally would work fine with a computer, now do not transfer to battery power fast enough to keep the computer running during an outage. Active PFC power supplies can also draw excessively large inrush currents upon initial operation or during switches to battery power, overloading a UPS that would otherwise have been properly sized. Some active PFC power supplies work better when they receive pure sine wave power (Smart-UPS units), rather than the "modified sine wave" output of a Back-UPS unit, although, our testing shows that some active PFC power supplies don't care which type of output they receive.”

The problem is graphically represented at the CyberPower Systems Web site as a zero-output state occurring as a step-wave crosses from positive to negative voltage. While that zero-output state persists only for milliseconds, that’s still far longer than the instant that it occurs on a true sine wave. For most UPS manufacturers, the option is to upsell their customers a true-sine-wave model that costs far more to produce.

CyberPower’s solution appears to clip the peaks on a triangular wave, eliminating the zero-output state at lower cost than pure sine wave equipment. CyberPower calls this its “adaptive sine wave” technology, and one of our goals is to test its capabilities using a mid-priced, “enthusiast market,” active PFC power supply.

Summary
Comment from the forums
• aldaia
This is a quite inefficient & expensive approach to the problem. We take AC and use a transformer to convert to DC and store in a battery, meanwhile another transformer is also taking AC and converting to DC to feed our components. When there is a blackout, we take DC from the battery, convert to AC and feed the computer PS where we convert back to DC to feed our components. Wouldn't be more cost effective and energy efficient to use the same unit to both feed our components with DC and the battery? Most of the time a PS has a surplus of power that can be used to charge the battery. When there is a blackout we could just take DC from battery and feed our components without the inefficient double DC->AC->DC conversion. I think an integrated UPS/PS would be cheaper (most components are replicated). That would be enough for most enthusiasts, that only need a relatively short battery life to be able to save work. A different matter is in professional environments where a UPS feeds dozens of computers that cannot be stopped. ¿Anyone knows if such a think exists?
• sudeshc
Have been using APC for last 2 years now without any issues what so ever.
Would recommend it although they might be a bit costly but they perform really well.
• hmp_goose
Soooo you have nothing to say about the TripLite atoll? Dead last? Distant second? Muddled mess? Nice part for not-our-application?
• dEAne
I have several units of APC and a hundred after-sales issues which remains unanswered, I opted to installed the generator set and a AVR than a UPS.
• Emperus
Most folks would just be happy to ignore on the need for a backup power source.. Hope this article enlightens them on getting one to protect their precious components and/or be ready if and when the situation arises.. Would be great if Tom's could put up a tier based classification on suitable UPS choices for various PC's (gaming, server, home theatre etc.)..
• super_tycoon
What about AVR? (Automatic Voltage Regulation) I have a CP1500AVRLCD and I've seen (at least I'm pretty sure) I've seen the AVR feature kick in when one of the local power lines got knocked out and the voltage drooped to ~100. (killed some of my non-dimmable cfl's) I went to CP's website and it claimed the pfc units still have AVR functionality. So here comes the confusion, what's the point of the voltage tolerances? If it has an AVR, why would it matter what voltage it's fed as long as there steps on the transformer? I thought the unit was supposed to take 90-140 without having to engage the battery while still passing ~120v?

You've also made me want to test my non-pfc ups with my 850hx, but my gaming rig and my workstation are an hour apart....
• aldaia
This is a quite inefficient & expensive approach to the problem. We take AC and use a transformer to convert to DC and store in a battery, meanwhile another transformer is also taking AC and converting to DC to feed our components. When there is a blackout, we take DC from the battery, convert to AC and feed the computer PS where we convert back to DC to feed our components. Wouldn't be more cost effective and energy efficient to use the same unit to both feed our components with DC and the battery? Most of the time a PS has a surplus of power that can be used to charge the battery. When there is a blackout we could just take DC from battery and feed our components without the inefficient double DC->AC->DC conversion. I think an integrated UPS/PS would be cheaper (most components are replicated). That would be enough for most enthusiasts, that only need a relatively short battery life to be able to save work. A different matter is in professional environments where a UPS feeds dozens of computers that cannot be stopped. ¿Anyone knows if such a think exists?
• wrxchris
I've been using a CyberPower 1350AVR for the past couple years and it has been great. Gives me approx. 17 mins of runtime at idle / basic tasks (approx. 250 watts between my rig and main LCD). It's good for 810W, and I believe I picked it up on sale for \$120.
• Anonymous
while i personally use APC XL series, what about eaton powerware??
• g00ey
I've always been wondering about the possibilities to replace the small batteries in those UPSes with standard car batteries or deep cycle (marine) batteries. Since the batteries in the UPSes are standard 12V lead cells it shouldn't be a problem and this would be a cheap way to keep the computer alive for days without external power.
• nebun
g00eyI've always been wondering about the possibilities to replace the small batteries in those UPSes with standard car batteries or deep cycle (marine) batteries. Since the batteries in the UPSes are standard 12V lead cells it shouldn't be a problem and this would be a cheap way to keep the computer alive for days without external power.

wrong
• bull2760
I have a Tripp Lite power inverter hooked up to 3 90ahr batteries and I have 3 Servers connected into it, a cisco router, and a firewall. Works perfectlty.
• g00ey
nebunwrong

No it's not wrong, a small UPS equipped with a bunch of low-cost standard deep cycle SMF/gel-cell batteries is a lot cheaper than a big UPS that comes factory equipped with that capacity. APC's Smart-UPS units come with ~2700 VAh and their price tags start at about \$8000. Sure they are also able to provide up to 40 kW power from the batteries but this is far more than needed for home use.

The problems that may arise is that the inverter circuit may be too weak to operate for longer durations which is a problem among low-budget UPSes. It may not be able to run equipment for hours since its intended use to deliver power from batteries lies within a time-span of maximum half an hour. A sign to look for is if the UPS has cooling fans. Those that don't have that are probably not constructed for longer durations.

Another problem is that many of these UPSes are equipped with circuitry that monitor the health of the batteries. If you swap the original batteries with batteries that have higher capacity they will need more time to recharge and the circuitry may misinterpret this as that the batteries are "dead" since they don't take the charge at the same rate as is expected from smaller batteries.

The recharge voltage of the recharger circuit may not match the recommended voltage of the standard batteries if you use cheaper open-cell batteries. I've been told that the electrolyte of open-cell batteries tend to evaporate over time if you feed them with a higher than recommended recharge voltage. The solution to this is to make sure that the ventilation is good and keep refilling the cells with distilled water. Sealed gel-cell batteries should have the same recommended recharge voltages as those lead batteries that are used in the UPSes.

The solution to the last two issues could be to put on an additional (smart) recharger on the batteries that is connected to them 24/7 and let the battery/recharger circuit sit behind a rectifier just to be on the safe-side. This may of course confuse the battery health monitor circuitry of the UPS making it think that something is wrong with the batteries. If I had the budget I would definitely try these things out.
• g00ey
bull2760I have a Tripp Lite power inverter hooked up to 3 90ahr batteries and I have 3 Servers connected into it, a cisco router, and a firewall. Works perfectlty.

I looked at them and if you want 120V power, they are good but if you want 230V then there is a problem. The models that provide 230V and are not crazily big (6 kW is far beyond household needs ...) use 12V as input. It's much better to use 48V or at least 24V as these setups with serially connected batteries can use thinner wiring. But this is an interesting option indeed since they come with an automatic utility power pass-through switch and a recharger.
• kureme
I'd like to see a similar article for a budget/office PC. Sure enthsiasts may have the money to blow for the top end gear, but what's the best bang for the buck on the budget end for an office/workstation PC or is a laptop the way to go?
• mresseguie
My Tripp Lite model G1000UB died recently after only 2 1/2 months of use. It was my first Tripp Lite and likely my last. I'll get something more reliable (like the APC that backs up my TV system) next time.
• cyclocommuter
I have an APC Smart-UPS 1500 and a Smart-UPS 700 and these have protected my computers for years. With the 1500, I did not even install the APC software, Windows 7 (and Vista) can interface with it directly via the OS' built in Power Management applet when the UPS is connected to the PC through the USB. They usually have these on sale at online stores for less than half the price from time to time. My smaller unit has been in service for more than 7 years and has undergone two battery changes. This is one advantage for APC Smart-UPS UPSes, replacement batteries are available in many places.
• bouncergriim
I have a 550W Cyberpower ups, it was very nice during our last black out during a storm. It shut down the computer (no one was using at the time) and then I was able to use it to power a CF light for hours as we waited for our power company to restore the power.
• joebob2000
g00eyNo it's not wrong, a small UPS equipped with a bunch of low-cost standard deep cycle SMF/gel-cell batteries is a lot cheaper than a big UPS that comes factory equipped with that capacity.

In a word, "wrong" was the right answer. Ignoring everything else, for the simple reason that charge management isn't where it needs to be; you will destroy the UPS trying to charge and float anything behind 2x or 3x the normal capacity. There are vendors (apc is one of them at the entry level position in the market) that offer expandable runtime UPS solutions; if you are going to be relying on your backup and not just using it as a hobby project (there is nothing wrong with that) you are going to need a properly engineered solution.
• bpislife
You can't test back up UPS just how long they last, but you need to see how well they protect it from lightening. I would like to see Tom's test for isolation when hitting the pin with high voltage. I would also like to see a test where they vary the voltage at the input to see what triggered them.
• hellwig
Sorry, I'm not buying the Sine Wave vs. Square Wave and zero-power state argument, pure PR BS (I've seen power strips promise this same Sine-Wave miracle technology, wonder what the excuse is there). I would love to see any UPS produce a true square-wave in the first place. Mathematically, it's impossible. In fact, BAD digital devices produce something closer to a sine-wave than a square-wave anyway.

I'd like to see Tom's test an old square-wave UPS, see if they can actually trigger an Active-PFC PSU shutdown on a swap to battery power. I'm guessing it won't have anything to do with the waveform coming out of the UPS.

And before you come back at me, I have a degree in Electrical Engineering, I actually have an educated basis for my beliefs.