Cold Test Results

For the testing of PSUs, we are using high precision electronic loads with a maximum power draw of 2700 Watts, a Rigol DS5042M  40 MHz oscilloscope, an Extech 380803 power analyzer, two high precision UNI-T UT-325 digital thermometers, an Extech HD600 SPL meter, a self-designed hotbox and various other bits and parts. For a thorough explanation of our testing methodology and more details on our equipment, please refer to our How We Test PSUs - 2014 Pipeline post.

Meanwhile, by request, we're also including 115 VAC results with this PSU review, for our readers in North America and other 115 VAC regions. Modern power supplies work on both systems, however the nature of switching means that they are slightly more efficient with higher voltage inputs. So this lets us show where their efficiency stands on a 115 VAC system.

The BitFenix Formula Gold 650W meets the 80Plus Gold certification standards when powered from either a 230 VAC or 115 VAC source. With an input voltage of 230 VAC, the peak efficiency is 92.2% at 50% load, while the average nominal load (20%-100%) average efficiency is 90.9%. The conversion efficiency drops when the unit is powered by an 115V/60Hz source, peaking at 90.4% at 50% load and delivering an average efficiency of 89% across the nominal load range. However, the efficiency drop is not uniform. At low loads the difference is insignificant but it widens as we load increases, up to a maximum of 2.6% at maximum load.

BitFenix kept things simple and did not implement a semi-fanless thermal control scheme but the thermal control parameters are very well programmed. The fan is staying indiscernibly quiet with a load up to about 400 Watts, providing adequate cooling with very low noise levels. As the load increases beyond 400 Watts, the fan's speed slope increases, decreasing the rate at which the internal temperature rises. The maximum noise level coming from the Formula Gold 650W unit at room temperature is 40.6 dB(A) at maximum load, meaning that is clearly audible but most users would not find that uncomfortable in an office/gaming environment.

The BitFenix Formula Gold 650W PSU Hot Test Results (~45°C Ambient Temperature)
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  • DanNeely - Wednesday, June 13, 2018 - link

    "Modern power supplies work on both systems, however the nature of switching means that they are slightly more efficient with higher voltage inputs. "

    Is there something specific to switch mode design that makes lower voltage hurt? I'd always assumed it the difference was due to the 4x higher I^2*R resistive losses on the input end.
    Reply
  • E.Fyll - Thursday, June 14, 2018 - link

    That is generally correct. Actually, a lower input voltage will decrease the switching-related frequency losses as well (the switching cycle is longer to maintain the same energy output). That's why this PSU displayed almost identical efficiency at lower loads regardless of the input voltage -the resistive losses are higher with a 115V input but the switching losses at low loads are lower, so they virtually negate each other. At higher loads however, the switching losses are minimized regardless of the input voltage, whereas the resistive losses are (theoretically) always four times higher. They actually tend to be even higher than that, because higher component temperatures increase the resistive losses, and the higher resistive losses increase the component temperatures even further. It's a vicious circle. Reply
  • benedict - Wednesday, June 13, 2018 - link

    Sell it for 60-65$ and it will be a hit. At 80$ it's just one of many. Reply
  • Orange14 - Wednesday, June 13, 2018 - link

    For $10 more I could purchase an equivalent wattage Seasonic that is fully modular and has a 10 year warranty, At this price point, there is no compelling reason for this PSU to exist. Reply
  • AdrianB1 - Wednesday, June 13, 2018 - link

    You are totally right. For this price it should be at least semi-modular and have better features, like passive mode and/or higher efficiency. Reply
  • qlum - Thursday, June 14, 2018 - link

    I personally prefer non modular over modular as I prefer not ot use a shroud and non modular just looks better on the front of the case. Tje few extra cables I can easily hide on the back anyway. Reply
  • AdrianB1 - Thursday, June 14, 2018 - link

    Semi-modular is the best of the 2 worlds, you have the ATX 24 pin cable built in like in a non-modular PSU and the other cables are connected only if you need them, so you don't have to hide anything on the back, leave it in a drawer. Reply
  • Death666Angel - Friday, June 15, 2018 - link

    I don't follow. How do you see your PSU from the front of your case? What kind of shroud do you use with your PSU and why are more cables better in that case? Do you use some very specific cases?
    My last non (semi) modular PSU was a Silverstone one I used in a Lian Li mATX box (V351b) with a few short cables that fit my need. At that point, modular was still a good bit more expensive. After that though, I had at least semi-modular or fully modular PSU and like the ease of use of installing them, as well as the less clutter. But I also use mATX or smaller cases.
    Reply
  • boozed - Wednesday, June 13, 2018 - link

    Not to be confused with Bitfinex.

    I did once see the Bitfenix logo used by accident at a fraudcoin conference.
    Reply
  • crashtech - Saturday, June 16, 2018 - link

    At this very moment, the SeaSonic SSR-650RM is a few dollars less, so there's no reason to buy this PSU, which ought to be in the $65to be at all interesting. Reply

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