Thermaltake Smart BM3 850W Semi-Modular Power Supply Review

We love ultra-high-end hardware here at eTeknix, but at the same time, I'm fully aware that that isn't what everyone really needs, nor does everyone want to pay the price for it either. While the Smart BM3 isn't the most exciting power supply in the world, albeit even the best power supplies aren't that exciting either, it looks like it ticks all the right boxes for a pretty high-end gaming PC build without costing the Earth. With a choice of 550, 650, 750 and 850W units, there's one to suit most requirements and the top model is more than enough for a powerful CPU combined with a fairly high-end graphics card such as the RX 7800 or RTX 4070 Ti SUPER. Thermaltake Smart BM3 850W The Smart BM3 is also 80 PLUS Bronze certified, comes with a semi-modular PSU design and meets the ATX 3.0 standards, including a 12VHPWR connector for PCIe Gen 5.0 devices. With all the safety features you would expect, a high-quality Japanese main capacitor, and backed up by a competitive five-year warranty, it looks like a strong contender for budget-conscious system builders. Packaging & Accessories The box is great, with all the main specifications clearly labelled right on the front, as well as a large and clear photo of the power supply design. Around the back, you'll find even more features listed, such as the high amp single 12v rail design, Japanese main capacitor, and the efficiency graph. There's also a full rundown of every cable included in the box, so you know exactly what you're ordering. Inside, you'll find the PSU comes with some protective bubble wrap around it, and there's an additional bag for cables and a plastic bag around the main cable. The PSU is semi-modular, so it comes with the 24-pin and CPU headers are pre-installed, but there's a separate bag to store any extra cables. There's a 12VHPWR 600W cable, as well as the usual 6+2 for older (or AMD) GPUs, and 4+4 pin for the CPU and peripheral cables. The 12VHPWR connector looks decent enough and comes with thick braiding while the other cables are all a flat cable design. A Closer Look This is a pretty standard-looking PSU, but since it's "only" 850w it's also pretty compact with a design that's largely square and not much bigger than the 120mm cooling fan on the top. There's a lot of ventilation here too, which will allow heat to be exhausted. However, there's a hybrid fan mode allowing for zero RPM usage at lower loads and temperatures, so that airflow will allow for some passive cooling too. There are additional cooling vents on the sides too, which are pretty uncommon, but I think they look cool, and they'll certainly improve the cooling performance too. The design is tidy enough though, with a large product sticker on each side, and an all-black chassis, it'll blend into most PC builds easily enough. On the underside, you'll find the usual specifications sticker, showing you the capabilities of each of the rails. This is a pretty simplistic PSU design and with it being semi-modular, there as just connectors for the 12VHPWR, peripherals, and PCIe and that's about it. A Closer Look - Interior The fan is one of Thermaltake's own, a TT-1225 120mm DC Brushless design. This is a fairly compact PSU design, with the chassis being pretty packed full of hardware. Actually, it looks more cramped than usual, as the semi-modular design involves having the 24-pin and CPU cables being fed into the main compartment, where they're hard-wired to the main PCB. It looks like a good quality job though, with thick solder, and good quality colour-coded heat wrap around all the contact points. There also a number of cable ties in here, ensuring everything is kept neat and tidy. The AC line-in looks robust, using thick gauge cables, and some small amounts of adhesive to keep cable runs in place. The capacitors look pretty packed in here, with the 5v and 3.3v coils slotted between them and a fairly large heatsink. Actually, very large heatsinks for an 850W Bronze unit, but with the Hybrid Fan mode, these will certainly help with passive cooling too. There's a lot more of that rubber contact adhesive too, creating a barrier between that larger coil and the heatsink. It looks a bit messy, and it is, but it gets the job done. The main transformer is in the middle with another heatsink below, and there's plenty of space between the heatsinks to allow airflow to push through the PSU, and out the rear and side ventilation. The main capacitor is pretty hefty and is a Japanese-made Nichicon unit rated at 105c. It can deliver 820uF at 400V, so I have no doubt this will be able to push well above the rated 850W if needed, but we'll find out in our OPP test shortly anyway. Methodology & Testing At eTeknix we take the power supply testing procedure very seriously and have invested a lot of resources into acquiring the appropriate testing equipment. For all power supply reviews, we test the power supplies with dedicated power supply testing equipment. This means we can get the most accurate results from our testing as opposed to using software benchmarks (such as OCCT) or multi-meter readouts which are broadly inaccurate. Testing Hardware Sunmoon SM-8800 Active Load Tester Stingray DS1M12 USB Oscilloscope Voltcraft DT-10L laser tachometer What the eTeknix Test Procedure Involves Testing each power supply at 20/40/60/80/100% load (with load balanced across all rails) and measuring PFC (power factor correction), efficiency (actual power divided by power "pulled at the wall") which also uses a 50% load test, and voltage regulation (deviance from expected voltages of 3.3/5/12 on the main rails). Measuring ripple with an oscilloscope at 20/40/60/80/100% load. Transient loads taken with an oscilloscope are taken from 0% to 100% on the 12v raid, 3.3v rail, and then both combined. Measuring fan speed after a stabilisation period of five minutes at each loading scenario using the Voltcraft DT-10L laser tachometer and a reflective strip on the fan. Testing each power supply's OPP (Over Power Protection) mechanism and seeing how many watts each power supply can deliver before shutting down. Any deviation from this will be explained per review as appropriate on the respective testing pages, but this methodology page will remain unchanged. Other Things to Consider We recognise that a single 12-volt cable can provide only 6 Amps before overheating (which corrupts voltage regulation and efficiency) so we used an adequate number of cables for each power supply to ensure there is no efficiency loss from poor cable selection. If there is more than one 12VHPWR on a PSU, all will be used to test their combined loads. We use the same time scale and horizontal millivolt scale on our oscilloscope for all ripple tests, that is a 20ms T/DIV (horizontal) and a 0.02 V/DIV (vertical) meaning the scale is from -80mV to +80mV, ATX spec dictates that the 12v rail must fall within 150mv of ripple and the 3.3/5 within 50mv so that scale allows us to include both 150 and 50mV peaks. (Some older PSU reviews use different scales which were later ditched as the visual representation they give is inadequate, in these reviews written measurements are provided only). Deviance is the terminology used to represent the way voltages diverge from the expected values Voltage Regulation To test voltage regulation we load the power supply to five different load scenarios that give an equal spread of load across every single rail. So that means 20% on all rails, 40% on all rails and so on. We then calculate the average deviation of each rail from its expected voltage. Ideally, anything of +/- 2% regulation is seen as a very good result. Power Efficiency Power efficiency is measured by calculating the supplied wattage divided by the wattage drawn at the wall/plug, multiplied by 100 to give a percentage. We then compare that to the particular 80 Plus certification the company claims to see if it meets that. You can see the 80 Plus certifications below, we always test power supplies at 230v. Transient Loads Power Factor Correction Power Factor Correction is the ratio of the real power flowing to the load, to the apparent power in the circuit. PFC aims to make the load circuitry that is power factor corrected appear purely resistive (apparent power equal to real power). In this case, the voltage and current are in phase and the reactive power consumption is zero. The closer the number to one the better as this allows the most efficient delivery of electrical power (Source - Wikipedia). Ripple An oscilloscope can easily measure noise and Ripple. These show how much voltage fluctuation there is on a particular rail. We tested the rail stability of the 3.3-volt, 5-volt and 12-volt rails using an identical time and millivolt scale for all graphs. millivolt ripple is measured by the peak-to-peak size of the voltage curve. The latest ATX 12-volt version 2.3 specifications state that ripple from peak to peak must be no higher than 50 millivolts for the 3.3-volt and 5-volt rails, while the 12-volt rail is allowed up to 120 millivolts peak to peak to stay within specifications. Millivolt figures are stated to the closest increment of 5 given their variability. OPP Power supplies are often quoted as having various protection mechanisms and the most important of these is Over Power Protection. In our testing, we crank up the power draw until the power supply either shuts down (meaning the OPP mechanism is present and working) or blows up (meaning it is either not present or not working). We then note the maximum power consumption before the power supply shut down, or before it blew up. Fan Speed When testing in a power supply laboratory it is difficult to take fan noise readings as the noise from the Sunmoon test equipment and air conditioning corrupts everything. The next best thing in our circumstances was reading off the fan speed with a tachometer to get an idea of the noise. The ambient temperature during testing is held constant at 22 degrees, with 1 degree of variation. Each power supply had a consistent period of 5 minutes to stabilise between each load scenario. In my experience, the following general relationships apply between noise levels and fan speeds, though it can vary greatly between the type of fan used. Below 800 RPM - Inaudible/Silent 800 to 1000 RPM - Barely audible 1000 - 1200 RPM - Audible but still quiet 1200 - 1400 RPM - Moderately noisy 1400 - 1800 RPM - Noisy 1800 - 2000 RPM or above - Intolerable Internal Components This is just an example of what you can expect to see on a PSU interior. Efficiency In our first test, we see the efficiency does drop off at higher loads, however, this is only a Bronze-rated unit and it's certainly well within this rating, actually it started off at around Platinum at lower loads, moving through gold, and silver and ending up just on the top end of Bronze, so the overall efficiency is generally higher than Bronze, but it's rated on its lowest point score. PFC (Power Factor Correction) PFC is very good, the closer to 1.000 the better, and largely from 60% onwards, the PSU is very consistent and this should result in significantly lower heat production at common gaming loads. Voltage Regulation The voltage stability is fantastic, anything under 3% is very good and this is closer to 1.5% overall. Ripple Ripple is very good too, with the rating being under 120mv for 12V and under 50mv for the rest, and we're clearly a lot lower than that throughout all the rails, which is great to see. 3.3V 5V 12V 5VSB Over Power Protection and Max Wattage I was expecting this PSU to pull over 1000W for a short period, but much to my surprise, it hit nearly 1500W for a few seconds before the OPP kicked in, so dealing with any big power spikes shouldn't be an issue. However, keep in mind the PSU isn't designed to exceed 850W for long periods. Transient Loads These results measure the power supply from 0% load to 100% load on various rails to simulate a power spike from your system. Typically, we would like to see as small a spike as possible relative to the requested voltage. With modern GPUs being notorious for power spikes, this is becoming more relevant in modern PSU design. The transients aren't the fastest I've seen, but they're smooth and clean and level off at their expected targets with no under or overshoot, so again, very good overall. 0-100% 3V 0-100% +5VSB 0-100% 12V Cross-Loads With the 3.3 and 5v rails loaded, or just the 12v loaded, things are very consistent, with the 3.3v running a little hot, and a little drop in the 5v and 12v, but all are still well within the 3% target we require, so again, a big thumbs up here, no issues. Fan Speed Unfortunately, the fan mesh on this PSU had quite small holes, so my laser was struggling to get a consistent reading on the fan, so these are simply predicted fan speeds based on what I observed and the fan specifications, but overall, it ran very quiet, as it doesn't take much cooling given the lower wattage design, plentiful ventilation, and it can use a zero RPM mode at lower loads and temperatures too. How Much Does it Cost? The Thermaltake Smart BM3 850W Semi-Modular Power Supply is available now for £104.99 at Scan.co.uk, which is a fair price given the overall power output and efficiency. If the efficiency or wattage were higher, the cost would go up. However, at little over £100, this is more than enough for many mid-to-high-end gaming PC builds. An RTX 4070 Ti Super needs around a 700W CPU, so paired with a good CPU from AMD or Intel, 850W is plenty. Overview Thermaltake has been making some fantastic PSUs over the years, but admittedly, their top units are pretty expensive if you want something with high-end efficiency, a fully digital design, fully modular cables, and massive power outputs. However, not everyone needs such a beast of a PSU, and while efficiency is important, it's fair to say it's not important to everyone. If we could all afford to invest in the most efficient power supplies, I'm sure we would, but with 80 Plus Bronze efficiency, the BM3 850W holds up well, and as I saw in my testing, it's largely Gold or Silver efficiency and mid-loads and only Bronze at around 100% load. The power output, the good PFC results, and the excellent amount of ventilation in the PSU chassis allow this PSU to run surprisingly quietly. It comes with two fan modes, a hybrid mode where the fan stops at lower loads and temperatures, meaning for your daily work it's silent and only spins up while you're doing something like gaming. However, even in active fan mode, I found it to run very quietly anyway. While the unit is rated for 850W, the PSU deploys a good quality main bulk capacitor, and we actually exceeded the rated power by a staggering 75% before the OPP kicked in. I wouldn't be surprised if the PSU was happy to pull around 1000W consistently, but honestly, I don't recommend it as it would stress other components too. However, if you have any sudden power spikes that pull anywhere from 850W-1400W for just a few moments, it'll handle it without shutting your PC down. I'm a big fan of fully modular PSUs, but honestly, semi-modular just makes so much sense, as not only is it cheaper, but you're going to need the 24-pin and CPU 4+4 pin cables in virtually any PC you build, so having those hard-wired isn't that big of a deal. Should I Buy One? Thermaltake has hit a nice sweet spot with the Smart BM3 850W Semi-Modular Power Supply, as it delivers a good amount of power for a decent gaming PC, reasonable efficiency, and a decent form factor that will be suitable for more compact ATX-compatible cases, and still runs cool and quiet. However, best of all is the price, at around £105 it's on par with similar products from the big name rivals, and while some budget-branded units are promising similar specifications they're typically made with cheaper components too, so you get what you pay for.