Seasonic X-Series 850 W Power Supply Review
Load Tests
Contents
We conducted several tests with this power supply, as described in the article Hardware Secrets Power Supply Test Methodology.
First we tested this power supply with five different load patterns, trying to pull around 20%, 40%, 60%, 80%, and 100% of its labeled maximum capacity (actual percentage used listed under “% Max Load”), watching the behavior of the reviewed unit under each load. In the table below, we list the load patterns we used and the results for each load.
If you add all the powers listed for each test, you may find a different value than what is posted under “Total” below. Since each output can have a slight variation (e.g., the +5 V output working at +5.10 V), the actual total amount of power being delivered is slightly different than the calculated value. In the “Total” row, we are using the real amount of power being delivered, as measured by our load tester.
The +12VA and +12VB inputs listed below are the two +12 V independent inputs from our load tester. During our tests, both were connected to the power supply single +12 V rail (the EPS12V connector was installed on the +12VB input of our load tester).
| Input | Test 1 | Test 2 | Test 3 | Test 4 | Test 5 |
| +12VA | 6 A (72 W) | 13 A (156 W) | 18.5 A (222 W) | 25 A (300 W) | 31 A (372 W) |
| +12VB | 6 A (72 W) | 12 A (144 W) | 18.5 A (222 W) | 25 A (300 W) | 31 A (372 W) |
| +5V | 2 A (10 W) | 4 A (20 W) | 6 A (30 W) | 8 A (40 W) | 10 A (50 W) |
| +3.3 V | 2 A (6.6 W) | 4 A (13.2 W) | 6 A (19.8 W) | 8 A (26.4 W) | 10 A (33 W) |
| +5VSB | 1 A (5 W) | 1.5 A (7.5 W) | 2 A (10 W) | 2.5 A (12.5 W) | 3 A (15 W) |
| -12 V | 0.5 A (6 W) | 0.5 A (6 W) | 0.5 A (6 W) | 0.5 A (6 W) | 0.5 A (6 W) |
| Total | 173.7 W | 350.2 W | 512.3 W | 685.4 W | 848.7 W |
| % Max Load | 20.4% | 41.2% | 60.3% | 80.6% | 99.8% |
| Room Temp. | 45.2° C | 44.3° C | 45.5° C | 48.9° C | 45.2° C |
| PSU Temp. | 48.6° C | 48.7° C | 49.7° C | 52.2° C | 52.7° C |
| Voltage Regulation | Pass | Pass | Pass | Pass | Pass |
| Ripple and Noise | Pass | Pass | Pass | Pass | Pass |
| AC Power | 196.7 W | 386.3 W | 572.3 W | 779.0 W | 981.0 W |
| Efficiency | 88.3% | 90.7% | 89.5% | 88.0% | 86.5% |
| AC Voltage | 114.4 V | 112.2 V | 109.2 V | 107.1 V | 104.5 V |
| Power Factor | 0.988 | 0.994 | 0.993 | 0.995 | 0.996 |
| Final Result | Pass | Pass | Pass | Pass | Pass |
The Seasonic X-Series 850 W can really deliver its labeled wattage at high temperatures.
Efficiency was very high, between 86.5% and 90.7%. Unfortunately this unit can’t hold 87% efficiency during full load (850 W) at high temperatures, even though the 80 Plus Gold certification promises 87% minimum at full load. This happened because Ecos Consulting (the company behind the 80 Plus certification) tests power supplies at only 23° C, and we test power supplies between 45° C and 50° C, and efficiency drops with temperature. But 86.5% is far from being a “bad” result.
Voltage regulation was another highlight of this product, with all voltages within 3% of their nominal values – including the -12 V output. The ATX12V specification allows voltages to be up to 5% from their nominal values (10% for the -12 V output). Therefore this power supply presents voltages closer to their nominal values than necessary.
Noise and ripple levels were always extremely low. Below you can see the results for the power supply outputs during test number five. The maximum allowed is 120 mV for the +12 V and -12 V outputs, and 50 mV for the +5 V, +3.3 V, and +5VSB outputs. All values are peak-to-peak figures.
Figure 21: +12VA input from load tester during test five at 848.7 W (17.2 mV)
Figure 22: +12VB input from load tester during test five at 848.7 W (20.2 mV)
Figure 23: +5V rail during test five at 848.7 W (13.6 mV)
Figure 24: +3.3 V rail during test five at 848.7 W (12.6 mV)
Let’s see if we can pull even more from the Seasonic X-Series 850 W.