Flyduino kindly sent us a set of the new KISS 24A ESC Race Edition (RE) to try out. In this post we will go through the key features, performance testing, and finally some guides on how to use these KISS 24A ESC.

Get your KISS 24A ESC Race Edition from Flyduino.

Also Check out my review on the KISS FC.

Overview of KISS 24A ESC Race Edition

In this review I will talk about the following topics, hopefully it will cover most of the stuff that a new user would normally ask.

Last Update: 28/02/2016

Many thanks to Artur Banach for taking some of the pictures for me! :)

Features and Specification

Here is a list of features from the product page. I added my own comment in green text.

32-bit processor

Allows 24A continuous current even with bad ESC cooling – I think they mean even mounting ESC’s inside the frame and not the arms, e.g. using their carrier PDB

2S to 5S LiPo – Even possible on 6S but not recommended

Telemetry capability: Voltage, Current, Temperature, Motor RPM – Only works with KISS FC at the moment

Over-current protection – ESC measures the current going through and limits it to 30A max (max current adjustable)

Over-temperature protection – when reached critical temperature, ESC power is reduced

Adaptive auto-timing – more efficient than fix timing

MAX RPM: 450,000erpm, 64,000rpm on a standard (14 magnet pole) motor

Accurate RPM control (~ 950 steps)

Active freewheeling – common in other ESC’s as well, helps ESC to run more efficiently

Supports normal PWM signal (25-500Hz), OneShot125 and OneShot42, protocol auto detected

Size and Weight

The size of the KISS 24A ESC is 19 x 27mm, which is smaller than the KISS 30A of 21x35mm. To be exact, the dimension is 19.55 x 26.94 x 4.19mm.

Weight of the ESC is 3.6g excluding any wires and soldering.

Hardware

KISS 24A ESC RE is currently one of the very few ESC‘s that runs on a 32-bit processor.

Majority of the ESC’s on the market at the moment are based on an 8-bit ATMEL or SiLabs MCU, such as the previous KISS 12A/18A/30A ESC’s (ATMEL), Littlebee 20A (Silabs F330), XM20A (Silabs F390). This reminds me how flight controllers evolved from 8-bit to 32-bit about 2, 3 years ago, same thing is probably happening on ESC.

The 32-bit MCU on the KISS 24A is an ARM Cortex STM32F051 microcontroller running at 48MHz. It allows faster communication and processing, also unlocks the potential for more complex and sophisticated functionality in future development.

No BEC

Just like other Opto ESC’s, the KISS 24A doesn’t come with a BEC, so you cannot power your flight controller directly from the ESC.

FET and Gate Driver

The FET’s are AON6512 N-FET which are actually rated for up to 150A, but in most cases heatsinks are required to run at high current like this. Using high current rated FET’s helps the overheat issue, especially in situations where we try to avoid heavy heatsinks.

Similar to the Littlebee 20A and KISS 18A ESC’s, the new KISS 24A Race Edition also use gate drivers for faster switching, which makes the motor braking especially fast.

Voltage Limit

The ESC is capable of 2-5S LiPo battery, but on paper it can take up to 25V so in theory you could run 6S with it. However it’s not recommended. Also Flyduino mentioned there is over-voltage protection that triggers at 26.5V.

Firmware

Say goodbye to BLHeli and SimonK, the new KISS 24A ESC runs on a custom firmware developed by themselves.

You will still have the same features like OneShot125, active braking (a.k.a damped light in BLHeli). It also support standard PWM signal and a new ESC protocol, OneShot42.

Old KISS users told me that they don’t normally get as many updates as BLHeli or SimonK. It could be a good thing if no one is complaining, means they tend to get things done right the first time. :)

One advantage on Flyduino’s part is they have the control of both hardware and software. I reckon it would make it easier to write the firmware which is specifically for that particular hardware they also designed. Not saying writing ESC firmware, and hardware design are easy, but it enables one to focus more on performance rather than compatibility.

Oneshot42 is a new ESC protocol developed by Flyduino, that is 3 times faster than Oneshot125.

Telemetry

The KISS 24A ESC is capable of sending telemetry data to the KISS FC, such as voltage, current, temperature and RPM. The telemetry data then can be forwarded from the FC to the OSD (MinimOSD) via serial port, and display it on your screen. (Note that it only works with MinimOSD that has to be flashed with their own custom firmware.)

This feature only works with KISS FC at the moment. However this KISS ESC telemetry protocol is open source, so it’s completely possible that other FC get supported in the future.

This opens the door for 2-way communication between ESC and FC, which could be used to improve flight performance of our multicopters in the future.

The Telemetry protocol can be found in this document.

Why ESC burns?

I see this question a lot when people discuss about this new ESC: “is this likely to catch fire like the old KISS 18A?”

So why ESC catch fire? Well, ESC gets hot when it draws current. If you have bad cooling and the heat cannot go anywhere, the MOSTET’s will overheat. At some extreme cases, the MOSFET’s get so hot it eventually melts the solder holding them in place. It will be able to move around on the PCB and causing shorts, which then burns the ESC and goes up in flame!

Flyduino Precaution

Flyduino introduced the intelligent current limiter and over-temperature protection. They basically reduce the power when either the current or temperature reach the max limit, to prevent ESC overheating and burning.

I saw this in action when I was doing thrust tests and I was well impressed: I was testing a fairly powerful setup with this ESC, current draw reached 30A at 80%, but as I continued to increase throttle, current draw just fluctuated around 30A and didn’t go above it. Of course if you wish to set a higher, or lower limit, you can change it in the settings (CLI Mode).

So far we have not heard any burning report on these 24A ESC’s yet.

Update 28/Feb/2016: We have our first burnt 24A ESC LOL – Link here. But really i think it’s just an user error! The prop and motor combo is drawing current way over the spec recommended. (with 5045BN it draws over 27A already, with Triblade 5045BN it will be over 32A for sure)

KISS Race PDB – Flyduino Kiss Carrier

There is a KISS ESC carrier you can get for the ESC and KISS FC. You can sit your ESC’s and FC directly on the PDB, and solder them together. It simplifies the wiring a lot and the build would look cleaner.

However the Kiss Race PDB doesn’t fit any of the frames that I have, so I don’t seen myself using it.

The dimension of the PDB is 99.5 x 45mm.

How to use KISS ESC 24A

For the most accurate and up to date instructions, please visit the manual provided by Flyduino.

What Flight Controllers does KISS 24A Support?

It will work on with every FC that supports 50-500Hz PWM, or Oneshot125. It’s doesn’t support Multishot yet.

Connection and Soldering

Typically any KISS ESC’s from Flyduino comes with no wires, you have to solder these on your own. Make sure you have the spare wires in hand or go and get some before ordering these ESC’s.

You can probably solder the motor wires directly on the ESC. So all you really need is two 16 or 18 AWG wires for power (voltage + ground), and two 24/26 AWG wires for signal (signal + ground). If you want ESC telemetry as well, then add one more 24/26 AWG wire. The AWG number depends on your current draw.

You should solder the signal wire to the pad bellow the PWM label and the ground wire on the left of the GND label. Not to the pad bellow the TLM label (TLM – Telemetry)! That’s the telemetry pad. you must solder both ground and signal, otherwise you might have desync/twitching issue.

There are 2 more solder pads labelled “TX” and “RX” on the other side of the ESC, they are used for talking to the ESC via serial port. There is also an open solder bridge labelled “BT”, which is the bootloader pin, is used for firmware flashing. I will explain how to use these later in the article.

Calibrate ESC

Flyduino suggests no ESC calibration is required for this ESC because of accurate resonators.

But if you want to calibrate it anyway, same procedure applies as you would do on other ESC. With Cleanflight and Betaflight you could still use the motor tab to do so.

But if you are using the KISS FC firmware/configurator, you can follow these steps.

CAUTION: Remove Props before you start!!!

Unplug Lipo battery

Move transmitter throttle stick to max

Connect Lipo

Wait at least 5 seconds, for one long beep

Move throttle stick back to 0, wait for ESC to restart (long short long beeps)

Disconnect Lipo

Reverse Rotation

You can reverse the motor rotation by swapping 2 of the motor wires, but a much cleaner way is to bridge the two solder pads on top of the ESC (next to status LED).

Running 5S/6S, or 3D mode

If you want to run 5S, (or even 6S – not recommended), or 3D mode, it’s recommended to solder a capacitor across the voltage input of the ESC, because these put a lot of stress on the ESC.

Adding capacitor also helps when you have long power wires. Typically a 220uF on each ESC should be enough.

CLI Mode

You can connect and talk to the ESC with CLI mode (command line) to perform many useful tasks.

A FTDI cable (USB to UART Adapter) is required to connect the KISS ESC to a computer (same tool you use to flash the CC3D). You don’t need to connect the 3.3V or 5V power, only TX, RX and Ground is needed. The ESC will be powered by LiPo battery. To get the computer recognise your ESC and detect serial full duplex mode, you need to connect the USB UART first then the LiPo.

You need to wait 5 seconds after connected LiPo for it to enable CLI mode.

Then you can talk to the ESC with any serial monitor such as the Arduino Serial monitor, or Putty using 115200 baud rate.

There are currently 4 commands:

help - list all the available commands and explain what they do tlm - print ESC telemetry data reset - restore all settings back to default info - system information CLxx - set max current limit, xx should be 01-30A

For more detail about KISS ESC CLI, refer to this document.

Flash KISS ESC Firmware

You can download the firmware from Flyduino’s site, by entering your ESC serial number there. This way you should get the firmware that is exactly written for your ESC.

To get the serial number, go into CLI mode described above, and enter “info” in the serial monitor. You should get something similar to the following returned.

info KISS ESC24A Version: 1. 100 Manufacturer: Flyduino.net Dev.: Felix Niessen S/N: 20323931-42335719-001C004A Max. used Voltage: 1503 Current limit (A): 30

Once you downloaded the firmware, simply use the STM32 Flash Loader Demo program to update the firmware as shown in the manual. If you have trouble getting the STM program to read the MCU, try again on a different computer.

Detail instructions of flashing ESC firmware can be found here.

Reading ESC Telemetry Data

There are more than 1 way of reading ESC telemetry data.

OSD

Serial Monitor

Chrome Configurator

Apart from feeding the FC the ESC telemetry data, then displaying it on OSD, you can also see the telemetry data on the serial monitor by entering “tlm” in CLI mode described above.

If you have the KISS FC, you can also read the data from the GUI too. If the FC detects the ESC’s you can use the drop down menu over the gyro & acc graph to choose what you want to see.

To have the FC detect the ESC’s you will need to power them at the same time, e.g. with LiPo battery connected, the GUI save button will be ignored. (Remove your props)

ESC killing VTX?

If you are using these ESC’s, I strongly recommend using LC filter / voltage regulator in between your FPV gear and the LiPo. The fact that these ESC’s are working so well with active braking, it’s going to cause some serious voltage spikes, which might be enough to damage your video transmitter or OSD.

Even just some capacitor soldered to the power inputs of the ESC’s would help!

In fact I recommend doing this moving forward on any mini quad. ESC and motors are getting more and more powerful, we have heard a lot of reports on the Littlebee now killing FPV gear.

Performance Testing

Hopefully I would be able to test these ESC’s soon on a quad, but before that here are some static thrust test results, from a few different motors, props setup comparing the performance between Littlebee 20A, DYS SN20A and KISS 24A ESC.

Testing Condition:

The tests were done using the Turnigy Thrust Stand

LiPo Voltage 16.0-16.4 V – Turnigy Nanotech 1800mAh 4S

Both SN20A and LB20A are flashed with 14.4 BLHeli firmware, Activate braking enabled

KISS 24A ESC Race Edition performed really well, very efficient and generate more thrust than the other 2 ESC’s in most cases. The Littlebee 20A is surprisingly close in terms of performance, given how cheap it is.

Cobra 2204 1960KV

Gemfan 5030

ESC Peak Thrust – g Peak Current – A Max Power – W Efficiency – g/W DYS SN20A 531 9.4 152.3 3.49 Littlebee 20A 615 10.8 175.0 3.52 KISS 24A Race 635 10.7 173.3 3.66

HQ 5045 BN

ESC Peak Thrust – g Peak Current – A Max Power – W Efficiency – g/W DYS SN20A 698 19.5 315.9 2.21 Littlebee 20A 744 21.1 341.8 2.18 KISS 24A Race 787 21.6 349.9 2.25

HQ 6045

ESC Peak Thrust – g Peak Current – A Max Power – W Efficiency – g/W DYS SN20A 962 22.0 356.4 2.70 Littlebee 20A 989 22.3 361.3 2.74 KISS 24A Race 1032 23.5 380.7 2.71

Cobra 2204 2300KV

Gemfan 5030

ESC Peak Thrust – g Peak Current – A Max Power – W Efficiency – g/W DYS SN20A 684 13.6 220.3 3.10 Littlebee 20A 734 14.5 234.9 3.12 KISS 24A Race 718 14.3 231.7 3.10

HQ 5045 BN

ESC Peak Thrust – g Peak Current – A Max Power – W Efficiency – g/W DYS SN20A 790 25.4 411.5 1.92 Littlebee 20A 879 28 453.6 1.94 KISS 24A Race 862 27.2 440.6 1.96

HQ 4045 BN

ESC Peak Thrust – g Peak Current – A Max Power – W Efficiency – g/W DYS SN20A 555 16.5 267.3 2.08 Littlebee 20A 570 18 291.6 1.95 KISS 24A Race 588 18.2 294.8 1.99

Emax RS2205 2600KV

Gemfan 5030

ESC Peak Thrust – g Peak Current – A Max Power – W Efficiency – g/W DYS SN20A 837 20 324.0 2.58 Littlebee 20A 1002 22.3 361.3 2.77 KISS 24A Race 990 21.7 351.5 2.82

HQ 4045 BN

ESC Peak Thrust – g Peak Current – A Max Power – W Efficiency – g/W DYS SN20A 707 24.5 396.9 1.78 Littlebee 20A 720 25.3 409.9 1.76 KISS 24A Race 776 27 437.4 1.77

Gemfan 4045

ESC Peak Thrust – g Peak Current – A Max Power – W Efficiency – g/W DYS SN20A 498 12.2 197.6 2.52 Littlebee 20A 518 14 226.8 2.28 KISS 24A Race 529 13.5 218.7 2.42

Conclusion

At this moment, I don’t have much to complain about (yet) :) Just before I got the ESC, there was some sync issues with running high KV motors (e.g. 2700KV motors) with 2Khz mode. It was due to an input processing problem with Oneshot high refresh rates. But it was quickly fixed by the team in firmware update. (impressed by the quick responds)

So only a few minor things:

Better manual translation

Maybe allow users to reverse rotation from GUI like BLHeli?

Firmware flash is still not simple enough, maybe that can be done from a GUI like BLHeli. What’s even better would be auto detect version and update reminder

And most importantly, more stock :)

I never own any previous KISS ESC’s , so it’s hard for me to say how much better this is and whether you should upgrade or not.

But if you want to get the new features on the 24A, that aren’t offered by the 18A or 30A, then you should consider it :) That’s because these ESC’s are using totally different MCU (i.e. STM32 vs ATMEL), so the capability and firmware would be different as well.

Any questions or comment please let me know.