My experiences with the FVT 120A 12S Dual ESC / Sleeping Lion

Hi everyone,

I would like to share my experience with the FVT 120A Sleeping Lion twin ESC, and give some troubleshooting tips for anyone who considers this ESC. image I got this ESC from alieexpress, however I saw there is also a version from APS. I chose to go with it since I was looking for a cheap and hopefully simple dual drive solution. I chose the 12s version, however I only used it with an 8s lipo battery. My setup was:2x6355 sk3@260kv, 15Tx36T, 12mm belts.

When I first hooked up everything , it seemed fine when riding. However I quickly noticed an array of problems:

  • Problem 1 - The ESCs were not synced up. One of the motors would start to spin earlier and have more throttle throughout. Individually calibrating the ESCs using the short wires would not solve this.
  • Problem 2 - The same ESC taht would start up late would stutter randomly when pushing the throttle at any speed. Those microstutters were really annoying and probably unsafe for unexperienced riders at high speed.
  • Problem 3 - I could not get the PC software to work properly with the ESC using the USB-link. I thought I was doing everything right, but I missed a tiny detail I guess…

Now after many emails and chats with the FVT support and my aliexpress seller, I think I finally have fixes for all these problems. I’d also like to add that while experimenting I tried different receivers, motors etc, so I am pretty sure these components were not the problem.

  • Solution to problem 1 When having this problem I was hooking up the long signal wire to the receiver. For some reason, this seemed to be the problem. When calibrating each of the ESCs individually using the short wires, they worked fine and had the same throttle response. So my solution was to make a Y cable for the signal wire and feed the signal to the ESCs using the short wires.
  • Solution to problem 2 After solving problem 3, the fix to this was to reset firmware back to 170818. The ESCs were shipped with 171103, which according to FVT support was the latest version. Weird :confused:
  • Solution to problem 3 While connecting the USB-link to the PC using the short wires, I always had the long signal wire hooked up to the receiver. Apparently that is not ok!

Another thing: FVT support confirmed that it is ok to use the ESC with only 1 motor attached. I was considering this before I found the fixes to my problems :smiley:

Now with everything solved, I finally have the ESC I expected to get. The throttle is similar to a car esc like HK X-Car Beast and the acceleration is immediate and a ton of fun. The brakes are pretty quiet and strong but take getting used to. At default settings, it builds up progressively for like 80% of the way , but if you push beyond that they get super strong and drag brake (I think), even if you have it turned off in settings.

In retrospect, I think it’s probably not worth it to get for about 150€ considering that you can get two HK VESCs for that price. However if you really like the feeling of a car esc, and want to pull a lot of amps and have a lower voltage battery setup I think it can be worthwhile to get this ESC. Let’s see how long it lasts for me, for now it only has around 150km on it :slight_smile: But I plan to ride it a lot more and ride it hard, my 12s single 6374 focbox setup feels tame compared to this one^^

Keep on riding!


Hello! Thank you for writing this. It’s very god, but I have a few questions: When you say short signal wires, do you mean the two wires which have only black and white? And do you now use these two wires for the signal from the remote control with a y-cable? Or do you use the long(glack,red,white) cable as the remote controll wire still?

And if you only use the small ones for the reciever, and for the programming, what do you use the long one for? :open_mouth:

Best regards, and thanks again.

When you say short signal wires, do you mean the two wires which have only black and white?


And do you now use these two wires for the signal from the remote control with a y-cable?


I use the 5v and ground from the long one to power the receiver.

Can you take a picture or two of how this is wired? It is a little hard to understand with words. Thanks for the reply.

I can’t, the board is for a friend… I will try to describe: Receiver pins:

  • Signal - Y cable that connects to the white cables of the short wires
  • 5v - red wire from the long cable
  • ground - black wire from long cable

Thanks alot for the reply! I’ve been so busy with work so that is why I haven’t responded.

It worked perfectly! I did as you said, and reset the controller limits and it now rotates at the same time.

Thanks for your time. Best regards.

I’m glad my post could help someone, I wanted to give back to the community that taught me so much in some way and I’m happy I could do so.

Thanks for posting this, I just got this esc. It looks like you used an anti spark key on your build. the esc has an on/off switch so I’m wondering if the anti spark is necessary? TIA!

Hey, sorry to potentially hijack things, but could you post a pic or two of your esc and also a link to where you bought it? I’ve had my eye on this thread and on the sleeping lion for my first build

I bought two on alibaba because there was a price break but I should only need one. I could sell you the other one with the usb link if your interested (no mark up lol) but I wouldn’t want sell it until I have my board up running so probably two weeks from now, which is about how long it took to get them from china. just let me know. I let the seller (Jenny) know that I was using it for an e-mtb so I’m hopping it has the right firmware flashed already and I don’t need to use y cable for the short leads… we’'ll see.

Hey! Thanks for getting back to me! Sounds like a plan… I’ll take it off you (I can wait a couple of weeks). I’ll drop you a pm, and if you could send over a couple an idea of price and a shipping cost to the uk that would be superb

There is some 2.0 something something firmware out on their website now, I tried it. The stuttering issue came back. For me, only 171103 works nicely.

I don’t think its necessary, but I’ve read somewhere around here that these switches arent fully reliable or can maybe die after getting used a lot. I have had a similar car ESC for a long while though, and it still works fine, so maybe it is ok.

Nice. Thanks for letting me know. Do you know where I could get the firmware that’s worked well for you?

its on their website under

Hello again! Altough my project evolves slowly, I’ve now started testing. I am having some trouble with the ESC. When It is hard at load, it suddently dies. I also have this power analyzer between the battery and the ESC. When the ESC stops under load, the power analyzer also shuts off, even though it is directly connected to the battery. I’ve tried without the power analyzer, and it still shuts off. Only a replug of the battery will fix it.

Because the power analyzer also blacks out, it leads me to believe that there is big voltage spikes from the motors occuring under load. (Under load means when accelerating from standstill when the motors are sort of “jiggeling” before i start to go forward, and when steep hills/tought terrain occur) Is there any way I can check for these spikes? And does anyone know how to fix it? The only Idea that came to my mind were bigger capacitors for the ESC, which I find a bit risky thinkering with.

Sorry for the long post. Best regards.

I’ve maybe had something similar. The ESC blocks both wheels for me when I accelerate really really hard. My only workaround is to be careful with the trigger.

Well, this doesn’t look like a block, but more like the ESC shorting out… What do you think?

Yes probably a short of some sorts, only occurs under very heavy load.

what remote do you use with it?