Review Index:

Cooler Master V Series 850W Power Supply Review

Manufacturer: Cooler Master

Efficiency, Differential Temperature and Noise


The overall efficiency of a power supply is very important.  The less waste heat generated the better!  Efficiency is defined by the power output divided by the power input and is usually expressed as a percentage.  If a PSU were a 100% efficient (which none are) 850 watts of AC power going in would result in 850 watts of DC power coming out (with no waste heat to dissipate).  In the real world there are always inefficiencies and power is lost in the form of heat during the conversion process. Newer revisions to the ATX12V Power Supply Design Guide V 2.2 have continued to increase the efficiency recommendations for PC switching mode power supplies and now lists both required and recommended minimum efficiencies.

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We measured the AC power input to the Cooler Master V Series 850W PSU with an Extech power analyzer while the total DC load was found by adding all the individual +3.3V, +5V, +12V, -12V and +5VSB loads together.  

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During our tests the PSU easily met the 80Plus Gold requirements while operating on both 115 VAC and 240 VAC. The unit came very close to meeting 80Plus Platinum specs, even while operating at elevated, real-world operating temperatures – very good!  Cooler Master is to be commended for taking a conservative approach as this unit could easily have been marketed as an 80Plus Platinum unit.

80Plus Program

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    Note 1: Power Factor ≥0.90 (50% to 100% Load)
    Note 2: Tests conducted at room temperature (25°C)

Differential Temperature and Noise Levels

To simulate real world operation, some of the warm exhaust air from the PSU under test is recirculated back to the intake through a passive air duct, which allows the PSU air inlet temperature to increase with load, just like it would in a real PC.  

The differential temperature across the power supply was calculated by subtracting the internal case air temperature (T in) from the temperature of the warm exhaust air flowing out the back of the power supply (T out).  

Thermocouples were placed at the air inlet and exhaust outlet. The ambient room air temperature was 23ºC (74ºF) +/- 0.5ºC during testing.

T out = temperature of air exhausting from power supply
T in = temperature of air entering power supply
Delta T = T out - T in

Sound pressure level readings were taken 3’ away from the rear of the case in an otherwise quiet room.  The ambient noise level was ~28 dBA.  I was not able to take SPL readings at the higher loads due to the background noise generated by all the DC Load cooling fans cycling on and off.

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Below ~600W output and 30°C inlet air temperature, the Cooler Master V Series 850W PSU is very quiet.  As the load continues to increase, the cooling fan speeds up to where it becomes noticeable but never really loud. These are very good results, especially for a high-capacity 850W power supply.

March 22, 2014 | 01:40 PM - Posted by Anonymous (not verified)

The Main caps are not 230uF, they are 320uF...

March 24, 2014 | 10:13 AM - Posted by phillychuck

Looks like 330uf to me from the images, ZOMG.

March 25, 2014 | 02:45 PM - Posted by Lee Garbutt aka...

Thanks for pointing that out - my bad. Yes, they are 330 uF. Fixed!

March 24, 2014 | 10:16 AM - Posted by phillychuck

They had to use brown marker on the top of those caps, looks like a blown cap to me from a distance!

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