Corsair CS850M Power Supply Review

1. Introduction2. Corsair CS850M (Bundle & Cables)3. Corsair CS850M (External)4. Corsair CS850M (Internal)5. Corsair CS850M (High Res Gallery)6. Testing Methodology & Results7. Closing Thoughts8. View All Pages

Today we look at one of the latest power supplies from Corsair, the CS850M – a semi modular unit which ships with 80 Plus Gold certification. Corsair have a wide range of power supplies available as it stands so how does this unit slot into their current portfolio?

Regular readers of KitGuru may remember our review of the CS650M way back in November of 2013. At that time there was no 850watt unit available – you could buy the CS ‘M' range in 450W, 550W and 750W capacities.

The CS Series power supplies are ideal for basic desktop systems where low energy use, low noise, and simple installation are essential – this is a direct quote from the product page on the Corsair website.

Features:

• The latest ATX12V v2.4 and EPS 2.92 standards and it is backward compatible with ATX12V 2.2, 2.31 and ATX12V 2.01 systems.
• 4th generation Intel® Core™ processor Ready (Intel Haswell and Z87 motherboards)
• 80PLUS Gold certified, delivering over 90% energy efficiency at real world load conditions
• Modular cables allow you to remove unneeded cables.
• The low-profile, flat modular cable design reduces air friction and helps maximize airflow through your computer’s chassis.
• A three year warranty and lifetime access to Corsair’s legendary technical support and customer service.
• Active Power Factor Correction (PFC) with PF value of 0.99.
• Universal AC input from 100~240V
• Multi-GPU Ready
• Over-voltage protection, under-voltage protection, and short circuit protection, over power protection, over temperature protection provide maximum safety to your critical system components
• Safety and Agency Approvals: FCC, ICES, UL, CUL, TUV, CCC, CE, RCM, CB, EAC, KC, BSMI, ROHS, WEEE.

This box artwork hasn't changed since 2013. The ‘CS' series range is highlighted top right on the box, with an artistic image of the fan taking up most of the front panel.

The modular cables are stored in one side of the box, with the power supply itself protected between two thick pieces of foam. Cable ties, mounting screws and a user manual rest on top.

The user manual, cable ties, mounting screws and regional specific power connector.

Not all of the cables are modular. The main ATX cable is hardwired into the chassis, along with a 4+4 pin EPS/ATX12V cable. The main ATX cable is the only cable which is sleeved, not flat. All of the cables are high quality.

The diagram shows the breakdown of cabling with the unit. The CS850M supports two high end graphics cards if you want to run in Crossfire or SLI. It is good to see a reasonably long 650mm 4+4EPS/ATX12V cable supplied. A total of 8 SATA connectors are available, across two cables.


The Corsair CS850M is finished to a standard we would expect from Corsair. The lettering is white and green, on a black background.

The large fan is visible behind the black grill. We will have a closer look at the specifics of the fan when we open the unit.

The unit passed our ‘screwdriver’ stress test, which involves running a Philip’s head driver down the side of the chassis with weak to modest pressure. How often have you accidentally hit a power supply with some tools during a system build phase?

One side of the power supply is vented to aid with airflow. At the side is a power connector and switch.

The CS850M isn't a pure modular design, the main ATX and EPS cables are hardwired into the chassis. The modular panel only takes up about half the space of the panel at this side and is labeled as well for ease of install. The Peripheral and SATA cables are all 3+3 pin connectors and the PCI-E and 4+4 CPU connectors are 4+4 pin.

Corsair CS850M Power Supply
DC Output	+5V	+3.3V	+12V	-12V	+5Vsb
Max Output	25A	25A	70.8A	0.8A	3A
Max Combined Wattage	130W		849.6W	9.6W	15W
	850W

The power supply can deliver almost 850W to the +12V rail. Both +5V and +3.3V rails can deliver 25A each.

The Corsair CS850M power supply is cooled by the Ong Hua HA1425L12F-Z fan.

Interesting to see Corsair are using a larger 140mm fan in this newer 850 watt unit – rated to spin at a maximum of 1,800rpm. The older CS650M which we reviewed incorporated the 120mm HA1225L12S-Z. There is a partial clear cover across the fan to direct the air specifically across the heatsinks.

It would appear that Great Wall are the OEM partner for this unit. The build quality is quite good, although we have seen better. There are only a few heatsinks inside, but if the 80 Plus Gold Efficiency is accurate they should be fine, especially with a large 140mm fan overhead.

The Diode bridge handles AC/DC rectification of the incoming AC voltage. Soldering quality on the main PCB is acceptable although there are some rough traces visible.



The Corsair CS850M uses two high grade Japanese grade Rubycon primary capacitors both of which are rated 400V, 390uF. They are not the higher grade 105c rated capacitors from the company, but are still better than Chinese counterparts. Secondary capacitors are primarily TEAPO branded, clearly to save some costs.

All cables are protected against the metal chassis by a rubber grommet and then tied into place. On this page we present some high resolution images of the product. These will take much longer to open due to the dimensions, especially on slower connections. If you use these pictures on another site or publication, please credit Kitguru.net as the owner/source.







Additional technical assistance: Peter McFarland and Jeremy Price.

Correctly testing power supplies is a complex procedure and KitGuru have configured a test bench which can deliver up to a 2,000 watt DC load. Due to public requests we have changed our temperature settings recently – previously we rated with ambient temperatures at 25C, we have increased ambient temperatures by 10c (to 35c) in our environment to greater reflect warmer internal chassis conditions.

We use combinations of the following hardware:
• SunMoon SM-268
• CSI3710A Programmable DC load (+3.3V and +5V outputs)
• CSI3711A Programmable DC load (+12V1, +12V2, +12V3, and +12V4)
• Extech Power Analyzer
• Extech MultiMaster MM570 digital multimeter
• Extech digital sound level meter
• Digital oscilloscope (20M S/s with 12 Bit ADC)
• Variable Autotransformer, 1.4 KVA

DC Output Load Regulation
Combined DC Load	+3.3V		+5V		+12V		+5VSB		-12V
	A	V	A	V	A	V	A	V	A	V
100W	1.57	3.34	1.76	5.04	6.66	12.12	0.50	5.03	0.20	-12.06
225W	3.75	3.33	3.86	5.04	15.59	12.07	1.00	5.03	0.20	-12.05
450W	7.54	3.33	8.35	5.02	30.78	12.04	1.50	5.02	0.30	-12.05
675W	11.33	3.31	12.35	5.00	47.46	11.98	2.00	5.02	0.50	-12.06
850W	1.52	3.33	1.17	5.02	63.53	11.95	0.50	5.02	0.20	-12.06

Load regulation is quite good, although there is some noticeable shift on the +12V rail.

Corsair CS850M	Maximum Load
	899W

We managed to get the PSU to achieve 899W before it would shut down, delivering around 50W more than rated specifications.

Next we want to try Cross Loading. This basically means loads which are not balanced. If a PC for instance needs 500W on the +12V outputs but something like 30W via the combined 3.3V and +5V outputs then the voltage regulation can fluctuate badly.

Cross Load Testing	+3.3V		+5V		+12V		-12V		+5VSB
	A	V	A	V	A	V	A	V	A	V
760W	1.0	3.34	1.0	5.04	60.0	11.94	0.2	-12.05	0.50	5.02
165W	15.0	3.32	18.0	4.94	2.0	12.10	0.2	-12.04	0.50	5.02

The power supply deal with the intensive Cross Loading test without a problem. It was tasked with 60A on the +12V rail and it held at 11.94V. The other rails delivered good results also.

We then used an oscilloscope to measure AC ripple and noise present on the DC outputs. We set the oscilloscope time base to check for AC ripple at both high and low ends of the spectrum.

ATX12V V2.2 specification for DC output ripple and noise is defined in the ATX 12V power supply design guide.

ATX12V Ver 2.2 Noise/Ripple Tolerance
Output	Ripple (mV p-p)
+3.3V	50
+5V	50
+12V1	120
+12V2	120
-12V	120
+5VSB	50

Obviously when measuring AC noise and ripple on the DC outputs the cleaner (less recorded) means we have a better end result. We measured this AC signal amplitude to see how closely the unit complied with the ATX standard.

AC Ripple (mV p-p)
DC Load	+3.3V	+5V	+12V	5VSB
100W	10	10	15	10
225W	15	15	20	15
450W	15	15	25	15
675W	15	15	35	20
850W	20	20	45	20

Noise suppression results are decent, with all rails falling within the rated tolerance guidelines. The +3.3V and +5V peak at 20mV at full load. The +12V rail hits a maximum of 45mV at 850 watts load.

Efficiency (%)
100W	86.78
225W	89.89
450W	91.93
675W	91.21
850W	90.11

Efficiency is excellent, peaking at just below 92 percent at 50 percent load. This drops to just above 90 percent at full load.

We take the issue of noise very seriously at KitGuru and this is why we have built a special home brew system as a reference point when we test noise levels of various components. Why do this? Well this means we can eliminate secondary noise pollution in the test room and concentrate on components we are testing. It also brings us slightly closer to industry standards, such as DIN 45635.

Today to test the power supply we have taken it into our acoustics room environment and have set our Digital Sound Level Noise Decibel Meter Style 2 one meter away from the unit. We have no other fans running so we can effectively measure just the noise from the unit itself.

As this can be a little confusing for people, here are various dBa ratings in with real world situations to help describe the various levels.

KitGuru noise guide
10dBA – Normal Breathing/Rustling Leaves
20-25dBA – Whisper
30dBA – High Quality Computer fan
40dBA – A Bubbling Brook, or a Refrigerator
50dBA – Normal Conversation
60dBA – Laughter
70dBA – Vacuum Cleaner or Hairdryer
80dBA – City Traffic or a Garbage Disposal
90dBA – Motorcycle or Lawnmower
100dBA – MP3 Player at maximum output
110dBA – Orchestra
120dBA – Front row rock concert/Jet Engine
130dBA – Threshold of Pain
140dBA – Military Jet takeoff/Gunshot (close range)
160dBA – Instant Perforation of eardrum

Noise (dBA)
100W	<28.0
225W	<28.0
450W	31.4
675W	33.3
850W	35.7

The fan spins slowly until around 600 watts is demanded and it spins up quickly to compensate for rising temperatures. At full load the fan is clearly audible as it is spinning close to the rated limit.

Temperature (c)
	Intake	Exhaust
100W	37	41
225W	38	45
450W	42	49
675W	45	56
850W	47	60

The large fan helps to ensure that rising load demands are met with increased air flow.

Maximum load	Efficiency
899 watts	89.7

At 899 watts, the efficiency level measures 89.7%. Not a practical situation to be running 24/7 however.As we head into 2015 there are a staggering range of power supplies available in every price zone. The Corsair CS850M is a solid addition to the CS range – it doesn't excel in any area, but it also doesn't exhibit any particular weakness either.

There is no doubt the Corsair CS850M has been created to target the enthusiast audience building a new dual GPU SLi or Crossfire system – at a very specific price point.

CS850M ripple suppression is quite good, and load regulation results indicated solid performance across a wide range. Efficiency is strong, peaking around 92 percent between a 40 and 60 percent load.

Internally Corsair have cut a few corners to meet a price point. While they are using high grade Rubycon capacitors in the primary stage, they are the lower cost 85c variants. Secondary stage is primarily TEAPO – these cheaper Chinese caps help reduce production costs in the factory. I am not a big believer in these caps as we have seen several fail over the years in our labs.

One of the biggest issues that Corsair face however, is the bewildering options available in their own range of products.

Their flagship modular AX860i '80 Plus Platinum' unit is available for £169.99 at Overclockers UK. The AX860 (non ‘i' version) is priced at £149.99. The gold certified RM850 is priced at £124.99. These all ship with higher grade internal components, which is reflected in the extended 7 and 5 year warranty terms. Their platinum rated HX850i is fully modular and is priced at £124.99 at Overclockers UK. Finally, their budget bronze rated CX850W targets the lower end and is priced at £89.99.

Taking all this information into consideration, I was initially shocked to see the Corsair CS850M listed on the Corsair website with a recommended retail price of £139.99. At this price, the RM860W would make a much better buy – for £10 extra it seems like a no brainer. Additionally, the HX850i is only £125, Platinum certified and incorporates a fully modular design. With these two giving competition, the CS850M seems a less tempting offering at £139.99.

Overclockers however are selling the CS850M at £99.95 with a price reduction this week to £91.99. For a couple of quid extra, the CS850M is a much better proposition than the CX850W.

If the price holds at under £100 and your budget will stretch no further then the CS850M should be given some serious consideration.

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Pros:

• Solid all round performance.
• reasonably quiet below 600W load.
• good cabling.
• quality finish.

Cons:

• Not a fully modular design.
• 3 year warranty, not 5+
• Chinese capacitors in secondary stage.
• Corsair's range of power supplies and models is becoming very saturated.

Kitguru says: A solid unit which supplements Corsair's range of CS-M power supplies around the £100 mark.

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