In this edition of our buyers guide series, we will discuss electronic speed controllers. Specifically, we will talk about how they work, what you should look for when purchasing one, and offer a few of our favorite options on the market.
What does the ESC I choose affect?
The job of an ESC is relatively simple to understand – it controls the speed of the motor in response to commands from the flight controller. The faster the motor turns, the more thrust it generates, and the more speed you will get out of your miniquad. The way the ESC communicates with the motor can actually affect the amount of thrust that motor generates. In his bench tests on miniquadtestbench.com, QuadMcFly found that from the best ESC to the second worst on the market, there was actually a 20% variance in thrust produced from the same motor. Interestingly enough, this is pretty similar to the variance seen in testing different motor brands. This means you can gain just as much thrust performance from picking the right ESC as you can from picking the right motor.
The way the ESC talks to the flight controller matters as well. All of the ESCs on this list talk using Oneshot125, a communications protocol that ensures a reasonably low-latency communications link between the two devices. However, ESCs with faster processor chips are technically capable of talking to the flight controller more often. This is currently the bleeding edge of performance gains, but ultimately it will mean a smoother flying miniquad once they are realized.
Given that ESCs have just as much of an affect on thrust performance as motors, and that they have a huge effect on how smooth your miniquad flies, we believe that ESCs are the single most important component you can buy for your miniquad. Do not cheap out. There is no real reason to – there are great ESCs on the market for every price point – see our recommended pick below.
What makes a good ESC?
When looking at ESCs, you should pay attention to these factors:
- The power rating. This is measured in amps. For miniquad purposes, there are 3 general classes of ESCs: <18A, 20A and 30A. 20A is generally the way to go unless you are flying 6″ props on 4S batteries. <18A ESCs may be appropriate for smaller 180-sized quads. 30A ESCs are the way to go if you are going for a true powerhouse. The compromise with higher ratings is generally larger size and more weight.
- Burst power rating. This is the amount of power an ESC can handle for short periods of time. This is a convenient rating for miniquads because often time you will be hovering at very low power settings with spurts of high power usage.
- Battery support. All ESCs on this list will support 3S and 4S batteries, the most common used in miniquads. If you want to build a monster, you may be interested in 6S support.
- The form factor of the ESC. The most popular form factor for an ESC is that of a small chip that gets mounted to the arm of your quadcopter. This type of ESC is easy to work on and replace but does affect the looks and aerodynamics of your quadcopter. Recently, with smaller quadcopters becoming all the rage, 4-in-1 ESCs that mount underneath the flight controller in the main body of the quadcopter have become more popular. These are lighter and easier to wire, but carry the risk that a failure of a single ESC could warrant replacement of the entire board. Another option is going “in between” a 4-in-1 and separate ESCs with the X-Racer Quadrant – which are four small ESCs which can be assembled into a 35x35mm board. These can be individually replaced if any ESC fails. The best of both worlds for those needing a 4-in-1!
- The physical size of the ESC. As miniquads get lighter, the arms get thinner and shorter and the space for the ESC gets smaller in the process. Also, a smaller ESC generally looks much nicer.
- The weight of the ESC. Like motors, these weights are multiplied by four and generally bring the weight away from the center of mass of the miniquad. You want your ESC as light as you can get it.
- ESC firmware. This should appear in the specs for the ESC when you are buying them. Here are the most popular ones:
- BLHeli is the most common firmware being run on multirotor ESCs today. It’s popularity is pushed further by support for what is called “BLHeli passthrough” built into any CleanFlight based flight controllers. What this allows you to do is to program and update all of your multirotors ESCs from the computer connection to the flight controller. It is an amazingly convenient feature that pretty much assures that this is the firmware you want on your ESC.
- BLHeli_S is an variant of BLHeli written for BB2 and BB1 controller chips (see below).
- KISS is the closed-source (think Apple vs Google) offering on the market from Flyduino. They remained competitive through 2016 because they were the only ESC offering hardware PWM. It will be interesting to see how they compete now that BLHeli_S has hit the market.
- SimonK is a previously popular firmware that has fallen out of industry favor. We strongly recommend you do not buy a SimonK ESC if you are a beginner.
- ESC controller chip. You don’t need to know the nitty gritty details about controller design; just know that in bench tests, the BB2 chip > BB1 > F390 > F330 > Atmel in overall performance. You can generally identify the chip being used in the ESC you are looking at in the tech spec section. Chips can also have an effect on what type of motors you can run if you are building a smaller 150-sized quad. If you follow our recommendation and only buy a BB2 or BB1 ESC you do not have to worry about that though.
- Packaging. For the purposes of building a miniquad, the optimal ESC is one that has no wires. This is because using connectors adds weight and inefficiency into the system. You want to directly solder you power wires and motor wires to your ESC boards.
- Hardware PWM Driver – This is either a “have it” or “don’t” feature. Hardware PWM will make your quad noticeably quieter and slightly more efficient. It also affords more fine control, although we honestly are not sure humans can take advantage of this. Here are the technical details of this feature:Motor speed control is accomplished by raising or lowering the voltage sent to the motor. This, in turn, is accomplished by rapidly switching special chips called FETs on and off with a proportion of “on” time equivalent to the percent of power you want to apply to the motor. Up until recently, this switching was controlled entirely by the microchip that controls the ESC. KISS changed that on their models by adding a separate driver chip that was responsible solely for producing the switching signal. The miniquad community caught onto this and raved about how “smooth” KISS ESCs felt, despite the fact that they use outdated, arguably inferior technology elsewhere on-chip. With the release of BB1 and BB2 chip support with BLHeli_S, hardware PWM control is available on BLHeli ESCs as well.
Our Recommendation for Quadcopter Pilots
We realize that the above might not “clear the water” for you. If you just want to know what ESC represents the best all around value, you should check out our “Propwashed Best Value Pick” in the section below. We update this list regularly and our pick will always be the best combination of price, features and performance.
Realistically, you do not need to know all the above information to pick a miniquad racer ESC. It is, in fact, pretty simple: buy a BLHeli_S ESC from one of the manufacturers in the list below rated for 30A.
Recommended ESC Brands
|Brand||Amp Rating Options||Battery Support||Cost/pc (USD)||Firmware||Notes|
|Racerstar (Cicada)||20 / 30||4S||$12||BLHeli_S||Propwashed Best Value Pick – 4-in-1 options available|
|Littlebee_S||20 / 30||6S||$14||BLHeli_S||4-in-1 options available|
|X-Racer Quadrant||25 /30||6S||$12.99||BLHeli_S||Can be both 4-in-1 or singles|
– Special thanks to QuadMcFly for his excellent tests and research. I have learned a ton from his informative posts.
Like many of our articles, many of the links above are affiliate links. We urge you to shop around, but if you do decide to buy from the vendors above, we would really appreciate it. It doesn’t cost you a dime more, but it sends us a few cents every time a purchase is made. Thanks!
Updated 1/5/2017 to remove recommendations for non-BLHeli_S ESCs and add a few more options.
Updated 6/1/2016 to add BlHeli_S ESCs (EMax Lightning and Aikon SEFM)
Updated 7/6/2016 to add BlHeli_S section, and Cicada ESC. EMax Lightning removed because of recall.
Updated 9/3/2016 to remove a few older ESCs and add the Littlebee_s ESCs.