Working together with my APC SmartUPS SC 620, this PSU was stable at loads up to 385 watts when powered by the mains but could only switch to the UPS’s batteries at a load of 280 watts.
The +12V voltage is very stable. It mostly keeps within 1% of its nominal value and never exceeds the latter by more than 2%.
The +3.3V voltage is but slightly worse. It deflects by 3% from the required level at very high or very low loads on all of the power rails but is going to be within 2% under typical loads.
The +5V voltage can deviate to the permissible maximum of 5% but only when the overall load is greatly misbalanced towards the +5V rail. At typical loads of modern computers this voltage, just like the others, is not going to deviate more than 2%.
Thus, the BPS-650C delivers stable voltages, yet doesn’t feel quite confident at near-zero loads.
Output Voltage Ripple
The high-frequency voltage ripple of this PSU is within the norm by some margin.
The voltage ripple is even weaker at the double frequency of the power mains.
Temperature and Noise
The Chieftec BPS-650C is cooled by a 7-blade Yate Loon fan (D14BH-12, 2800 RPM, 140 mm). About one third of the impeller is covered with a piece of translucent plastic to optimize air flows.
The fan starts out at a rather high 1070 RPM, which is just comfortable enough, but keeps this speed until a load of 400 watts. Then the speed is increased linearly until full load. The top speed of the fan is about 1600 RPM.
The BPS-650C is somewhat below average in terms of noisiness, yet most people are going to be satisfied with it in this respect. The rather high start speed of the fan may disappoint users who value silence.
Efficiency and Power Factor
The power factor is high, just as you can expect from a power supply with active power factor correction. The efficiency is not record-breaking but meets the 80+Bronze requirements: 84.1% at 20% load, 86.9% at 50% load, and 84.8% at 100% load. The peak efficiency is 87.6% in the load range of 256 to 278 watts.
The standby source meets the requirements of the industry standard.
The Chieftec BPS-650C is a reasonably priced PSU with no obvious flaws. We could only note such downsides as the reduced number of graphics card cables included in the box and the somewhat short length of the CPU power cable. The rather high start speed of the fan (almost 1100 RPM) may also be a downside for some users. If you are not among them, and if you do not plan to build a SLI or CrossFireX configuration out of two graphics cards with two power connectors each, and if the 59cm CPU power cable is long enough for you, the BPS-650C is going to be a perfect buy.