Overload Tests

Before overloading power supplies we always test first if the over current protection (OCP) circuit is active and at what level it is configured.

Here we were limited by our load tester, which can pull “only” up to 33 A from each one of its +12 V inputs, giving us a total of 66 A, while Corsair HX850W officially has a 70 A limit. However, when we configured both inputs at 33 A the power supply wouldn’t turn on, indicating that one of its protections was active.

The idea behind of overload tests is to see if the power supply will burn/explode and see if the protections from the power supply are working correctly. This power supply didn’t burn or explode and it shut down when we tried to overload it.

Below you can see the maximum we could pull from this power supply with it still working within specs. Even under this overloading efficiency was above 80%.

Input Maximum
+12V1 32.5 A (390 W)
+12V2 32.5 A (390 W)
+5V 27 A (135 W)
+3.3 V 20 A (66 W)
+5VSB 3 A (15 W)
-12 V 0.5 A (6 W)
Total 1,000 W
% Max Load 117.6%
Room Temp. 54.9° C
PSU Temp. 57.0° C
AC Power (1) 1,204 W
Efficiency (1) 83.1%
AC Power (2) 1,334 W
Efficiency (2) 75.0%
AC Power (3) 1,231 W
Efficiency (3) 81.2 %
AC Voltage 100.4 V
Power Factor 0.998

We could easily pull up to 1,000 W from Corsair HX850W. Under this extreme condition, efficiency was still above 80% (the results marked with "(3)" were measured with our precision equipment and thus are the correct ones). See how the AC voltage drops a lot as we pull more watts! Power factor was excellent, showing that the active PFC circuit from this unit is excellent.

Gabriel Torres is a Brazilian best-selling ICT expert, with 24 books published. He started his online career in 1996, when he launched Clube do Hardware, which is one of the oldest and largest websites about technology in Brazil. He created Hardware Secrets in 1999 to expand his knowledge outside his home country.