Worlds Best ESC - Making it Better

That's a bold statement ... Worlds Best. But it's even larger than that. Not just Worlds Best, but best for most all applications less than 30 Amps (limit of the tests). That means:

- duration ships that only pull 2 to 8 amps per rotor

- most all 6S and smaller ships (exception of nano-ships)

- any-size FPV racer

- any other ship in between

Why almost any size? Shouldn't a small FPV racer use a smaller and lighter ESC for response? Yes, if it does better on a net-lift response test. In other words, when you penalize the ESC for it's weight, is it still better and faster? What i continue to see is ESC manufacturers downsizing critical components of the ESC at a net loss. They weight savings is lost because of greater thrust loss and response. In other words, this heavier ESC will out accelerate, in the real world, a smaller and lighter ESC.

Why post this? To move technology forward, we need to report to industry what works and what doesn't. For some reason (i don't know why), this ESC works better than all others tested:

- for generating maximum thrust from the motor***

- for net-lift efficiency or the grams of weight it can lift (after it lifts the rotor) per watt

- for response (how fast it can generate targeted lift)

These tests were conducted on multiple days on multiple rotors of highly variant size, always being immediately compared back to another DYS 40A multicopter test to ensure that the baseline wasn't changing.

The ESC that dominated is a DYS 40A OPTO Multicopter using SimonK. The photo is included because there are two others that carry a similar or same name.

- Not the white cover DYS BLHeli 40A

- Not the one that is says "Programmable" versus "Multicopter" in the blue/purple band across the front


Have i tested all ESCs? No, but if you are convinced you know of one that would work better, let me know. I've tested most all of the following and one or more of their variants:


- Multistar

- Turnigy

- T-Motor

- Afro

- Motortron

- Quattro

- 3DR

- Spider



- Aris


- AutoQuad

- Exceed

- HobbyWing

- Lumenier

To do a test like this, a highly repeatable and finite test stand is needed. It took a while to develop one but what works is one that:

- measures (at a minimum) volts, amps, thrust, motor temp (shoots IR up the aft end of the motor)

- eliminates harmonics between the rotor and load sensor (this proved difficult but achievable)

- is calibrated and proves repeatable within 1.5%

- controlled by a system that can precisely repeat a rotor test (uses a Audurino Mega)

- directly feeds the data into Excel for analysis (uses DATAQ)

- uses a test script that produces repeatable results

- uses a test procedure that minimizes repeatability error (used average of multiple tests)

How much better is this ESC?  On average:

- 4.4% higher net lift (after it lifts itself)

- 2.3% more net-lift efficient (usually the larger the better)

- from more than twice the response or the same response as other ESCs (usually the larger the better)

                                                       So how to make it better?

Step 1: Strip it naked. See photo below.

           ... remove the cover

           ... remove the heat plate (better to locate the ESC under prop wash to run cooler, see below)


Step 2: Right-Size the bullet connectors or wires (see above where heavy wires are replaced by 2mm bullets)

           ... remove the large bullet connectors or wires

           ... replace them with ones that are the most net-lift efficient (where heat loss = weight loss)

Step 3: Seal the ESC. Seal it with Electrical Sealant to protect from moisture and conductive dust

           ... tape or plug connectors and wires

           ... repeatedly spray each side from different angles

           ... a mistake i made was not sealing the bullet connectors and solder

               - don't tape them off like i did

               - insert a male connector into the end of bullets so sealant doesn't get inside them


Step 4: Locate ESCs under Prop Wash. See photos below. The turbulence generated by the prop does not adversely affect lift when the ESC is placed on edge to the prop wash.

           ... Use something non-conductive like hot glue to bond the ESCs to the motor mast or spar

           ... Face the FETS (the little square warehouses or Fire Emitting Transistors) to open air

           ... Protect the ESCs from below from ground contact (not needed here because of clearance)

back-side with hot glue


front-side with FETs completely exposed to open prop wash


Step 5: Tie up wiring. Use dental floss to secure wiring away from the prop.

***Note: The T-motor Air 40 in high-timing mode (an option) generated higher thrust, but at the sacrifice of efficiency and motor temp. Also, the T-Motor Air 40 was 2nd best and close in performance. If you are using an Air40, it probably isn't worth switching.

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    • Race ESCs use 16ga for 40A, 16-18ga for 30A, and 18-20 ga for 20A versions. Wire gauge depends directly on run length; typically these ESCs will have BATT leads less than 100mm long. If you need longer than they come with, always step up to the next larger ga wires than come on the ESCs.

      We recommend for racing to mount ESCs as close to the motors as possible, directly under propwash with motor leads in the 15-30mm range if possible as it helps eliminate desync with smaller, high-speed props, and to never extend the wires longer than the manufacturer ships the motor with. Always solder motor leads directly to the ESCs without bullets; RACE ESC vendors know you will be doing this so it will not void your warranty.

      If you're not racing... meh. It's a matter of preference. Bullets are okay, and convenient to replace ESCs & motors in the field. I use 'em on my AP rigs. On the other hand, I've NEVER, EVER, had to replace an ESC on my AP rigs; I usually overbuild by a factor of at least 2X. The only times I've ever needed to replace a motor, I was already replacing a lot more than just a motor, so soldering was the least of my worries. ;)

      Yes, it's a PITA to have to re-shrink-wrap your ESCs, but it's part of racing. And you can change the colors while you're at it, if you care about such things. A couple of the latest model ESCs now come with a snap-together nylon shell so you can do away with all that mess; it looks more finished than heat-shrink and weighs less too.

      I'm not that sure I believe they'll hold up as well as polyolefin heat-shrink, but they will probably hold up better than the thin PVC heat-shrink we usually re-wrap in to shave a few grams and improve heat transfer for cooling.

      With modern FETs cooling is typically a moot point anyways; their on-resistance is so low, and they spend so little time switching states in the commutation phase that very little heat is generated even at maximum load.

      Typical heat-sinking provided by the copper pour is multiple times what they need anyways; the mounting in the propwash thing is really more to make us feel better because we know we're abusing our ESCs. ;)



    • MR60

      it depends on amps. fly in hover or if a FPV racer, at race speed. check your log and see what your typical ship amps are.  Then enter that value into the attached worksheet in cell E4.

      The color area will immediately change. pick the lowest number (the most green) and look back across at column D for the wire size.

      • Forrest,
        Sorry I hadn't read the whole thread and had you re-post your wire size spreadsheet. Would you consider smaller wires for the AC side of the ESC? These wires would be very short since the ESC resides under the props, the wires themselves get better cooling, and there are 3 wires to carry the current rather than 2.
        • MR60

          i apologize ... saw the question before and forgot to answer it.

          wires need to be the same size. only two wires between the ESC and motors carry DC current at any given time so same as the input side of the ESC.  

          interesting point on the cooling. you are right, cooler would result in lower wire temp and thus less resistance. The difference, however, would be less than a fraction of one wire size. So keep them the same size.

          to save weight, i use magnetic motor wire. it is epoxy coated and thus weighs quite a bit less than the thick silicone or rubber insulation. on a FPV ship, however, use regular insulated wire as they take a lot of abuse and the distances (weight) doesn't result in much savings.

          • Another question. I don't want to mount my ESCs vertically. What do you think about mounting them FETs facing down against the aluminum arms, with heat conductive tape between, and the shrink wrap around the ESC and arm. The ESC will be mounted outside of the propeller arc, but the aluminum arm will get lots of cooling.
            I am concerned that some of the FETs on the edge will not touch the aluminum since the ESC is wider than the 20mm arm. I also need to be careful about shorting out the ESC on the arm.

            PS. Did you test the stock 20A 3DR ESCs? I have ten of them and they could also be stripped down. I'm wondering if the efficiency savings is significant enough to warrant swapping them out.
            • MR60

              Brilliant to put the heat tape between the FETs and the Al arm and then wrap in shrink tape. just make sure nothing conductive on the FET side contacts the metal. I'd go the extra mile and put electrical tape around the arms under the ESC leads.

              The 3DR ESCs are good. Use them. Unless you are trying to set a world record, you won't notice a difference.

              P.S. I love it when people think outside the box. You put a big smile on my face.

      • @Forrest, thank you for that fantastic spreadsheet, a very useful tool.

        Can I divert this conversation away from racing quads for a moment to ask a question I haven't gotten a good answer to?

        I'm rebuilding a 3DR X8 and considering swapping out the eight ESCs that weigh 21g each with the tiny miniquad ESCs that weigh 4g each. Both are rated at 20A with a burst to 30A. This would save me 136g! (Not including the single additional ubec I will need since these are opto.
        An example of the ESCs I'm considering are the LittleBees or tiny DYS 20A.

        Does anyone see a problem with using a BLHeli miniquad ESC on a big X8? I know it isn't designed for a platform like this, but does it matter? There must be some disadvantage to loosing so much mass. Will I lose efficency to undermine my weight savings? Are they less robust in the long run? Do they handle low KV motors as well?
        The 3DR copters use aluminum arms which can act as a heat sink if I shrink wrap over the whole arm.

        Thanks for your opinions.
        • MR60

          Let's say you have two cases. You tell me, which is the better ship (endurance and response). Because the following is exactly your question:

          Case 1: The ship weighs 2 kg and generates 4 kg grams of thrust.

          Case 2: the ship weighs 2.136 kg and generates 4.4 kg of thrust.

          Hint:  F (force) = m (mass) x a (acceleration) or a = F/m

          P.S. An important note. Most of the weight of ESC is the wire, heat sink, and shrink wrap. If you run ESCs naked, then the wires on both are the same and there isn't a heat sink (not required when putting the ESC under the prop wash). So the difference in ESC weight of the BLheli miniquad and DYS 40A Multicopter ESC is 11 grams x 8 = 88 grams on a X8. The difference in thrust is over 400 grams more with the heavier ESC and far higher reliability.

        • I've been flying the DYS BL20As on a number of miniquads; they hold up well and perform well under pretty heavy loading with 6045 props on 1806-2300 & 2204-2300 motors and 3S. I get awesome runtimes; 30 min from a 30C 3S-4000 on my G10 Flying Brick build at approx 680 grams in LOS mode with a Mobius and 27 minutes at 760 grams with SJ4000 in a hardcase the same configuration and weight as a GoPro. The Xiaomi Yi and ABS holder are right in the middle at around 720 grams and 28 minutes.

          You're running in the neighborhood of what; 8x 2216-850-950KV? 4 kilos AUW? 

          Your peak current draw from an octo will likely be considerably less per ESC, particularly since you're not flying acro with stall-induced LRA current draw to worry about. But constant current may be higher (aside from the FFF adrenaline junkies I know who only know ZERO and FULL THROTTLE).

          If you're concerned with longevity, you may prefer to go with the XM30A for a couple $$ and 3 grams more. IIRC, it comes in at 7-8 grams with the motor wires removed.

          BLHeli has one quirk; it will only cal up to 2020ms. If your FC sends PWM that exceeds 2020ms, it considers it a corrupt signal and shuts down, so you need to make sure your upper limits are less than that in the motors tab. This manifests most obviously in the fact that you can only go up to about 80% rotation of the knob when testing with a servo tester.



          • Paul, thank you for the pilot report. I'm running 8x 2216-850 at about 4KG like you said. It should only pull about 10A per motor but need headroom to continue in the event of a motor failure.
            My goal here is efficency and reliability. I know you don't agree with Forrest's assessment of ESCs for racing, but for endurance he seems to make a solid argument that the 100g extra thrust from the subject ESC outweighs it's extra mass.

            Are there any changes that should be made in BLheli to accommodate for low KV motors?
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