StarTech.com WattSmart 650 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. All the tests described below were taken with a room temperature between 44° C and 48° C. During our tests the power supply temperature was between 49° C and 53° C.
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 how the reviewed unit behaved under each load. In the table below we list the load patterns we used and the results for each load.
+12V2 is the second +12V input of our load tester and on this test it was connected to the power supply EPS12V connector.
If you add all the power listed for each test, you may find a different value than what is posted under “Total” below. Since each output can vary slightly (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. On the “Total” row we are using the real amount of power being delivered, as measured by our load tester.
| Input | Test 1 | Test 2 | Test 3 | Test 4 | Test 5 |
| +12V1 | 5 A (60 W) | 10 A (120 W) | 14.5 A (174 W) | 20 A (240 W) | 28 A (336 W) |
| +12V2 | 4.5 A (54 W) | 9.5 A (114 W) | 14 A (168 W) | 18.5 A (222 W) | 20 A (240 W) |
| +5V | 1 A (5 W) | 2 A (10 W) | 4 A (20 W) | 5 A (25 W) | 6 A (30 W) |
| +3.3 V | 1 A (3.3 W) | 2 A (6.6 W) | 4 A (13.2 W) | 5 A (16.5 W) | 6 A (19.8 W) |
| +5VSB | 1 A (5 W) | 1.5 A (7.5 W) | 2 A (10 W) | 2.5 A (12.5) | 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 | 135.3 W | 266.3 W | 394 W | 522.9 W | 644.9 W |
| % Max Load | 20.8% | 41.0% | 60.6% | 80.4% | 99.2% |
| Result | Pass | Pass | Pass | Pass | Pass |
| Voltage Regulation | Pass | Pass | Pass | Pass | Pass |
| Ripple and Noise | Pass | Pass | Pass | Pass | Pass |
| AC Power | 162 W | 309 W | 459 W | 621 W | 785 W |
| Efficiency | 83.5% | 86.2% | 85.8% | 84.2% | 82.2% |
StarTech.com could deliver its rated power, which is great. Voltage regulation and efficiency were the best features of this unit. All voltages were really stable, being inside a 3% limit from the nominal voltage in all our tests – which is really great, as the limit is 5% –, except the +3.3 V output during test number one, which was at +3.41 V – yet inside the 5% limit.
We were really impressed by this power supply efficiency, always above 82% peaking 86.2% at test number two.
However the main problem with WattSmart 650 W is the level of electrical noise it generates. Even though it was inside ATX specs (i.e., below 120 mV for +12 V outputs and below 50 mV for +5 V and +3.3 V outputs) it was almost reproved on test number five, where noise level on +12V2 peaked 115.4 mV. On all tests noise level on +12 V inputs from our load tester was very high, as you can see in the table below. Noise level on +5 V and +3.3 V inputs was fine.
| Input | Test 1 | Test 2 | Test 3 | Test 4 | Test 5 |
| +12V1 | 53.2 mV | 68.8 mV | 80.4 mV | 90.2 mV | 109 mV |
| +12V2 | 55.4 mV | 72 mV | 83.8 mV | 96 mV | 115.4 mV |
| +5V | 15 mV | 19 mV | 20.2 mV | 22.8 mV | 24 mV |
| +3.3 V | 11.8 mV | 17.2 mV | 14.2 mV | 14.2 mV | 17 mV |
Below you can see screenshots from our oscilloscope for test number five.
Figure 16: Noise level at +12V1 input of the load tester.
Figure 17: Noise level at +12V2 input of the load tester.
Figure 18: Noise level at +5V input of the load tester.
Figure 19: Noise level at +3.3V input of the load tester.
