Have you tried to do a voltage calibration again? I know you mentioned that you did it with full battery. But put some different voltage packs and check it against the multimeter.

Dang, I was so hopeful that you'd be able to just swap sensors and have the problem solved at the press of a button.

(07-Nov-2023, 05:01 PM)voodoo614 Wrote: From the photos of the ESC, it looks like only onboard ADC is supported. So ESC telemetry will not give you voltage or current.

Even though that's not the best news, I so appreciate you wonderful people taking your precious time trying to help me. It's so greatly appreciated! Too bad, this option with ESC's telemetry won't work for me then... 

(07-Nov-2023, 05:10 PM)voodoo614 Wrote: Have you tried to do a voltage calibration again? I know you mentioned that you did it with full battery. But put some different voltage packs and check it against the multimeter.

I've tried couple of times, even thought of "faking it", and punch in some numbers that would fool my FC thinking it's reading higher values (while they actually are the true Voltage readings). I am pretty positive at this point that all my battery chargers and my little battery checker are 100% correct... I mean, three devices with super close readouts. I believe that my combo ESC/FC is giving me some false information when it comes to battery Voltage for some reason. Every single time I complete my flight, I do that when OSD is screaming at me with 3.6V, even 3.5V. I do that only because I am positive it's false information I am getting there. As soon as I land, I check my battery and it's around 3.7V or in most cases 3.8V per cell. I've tested 4 different batteries so far, and each one of them is giving me amazing flights with other setups (all 6s).

When I do calibration in Betaflight, readings are quite accurate, I get it to as close as possible to what I see on connected Battery Checker (on the balance lead). But for some reason, all that looks different in my OSD when I start flying and during the flight. I will post another video I've recorded yesterday. I flew little bit more aggressively this time, and I've included stick animation as well (BlackBox data). I remember, in one of the previous posts, mstc mentioned it would be easier to understand what's going on with voltage sag, if we see stick animation. Bear in mind I am total beginner when it comes to flying, and started actual flying just couple of months ago (not counting my whoop Mobula 7 1s). When I say "aggressively", I mean I pushed it little harder on the throttle, did couple of very basic tricks, etc. I will post that video as soon as it's up on YT. I truly hope I am not bugging anyone with these links (never monetized, nor I have a lot of subscribers... not my goal anyway, I use YT just as an archive for my build videos, flights, some findings when it comes to FPV, etc.)

EDIT: here is the above mentioned video:


But, thank you so much for your advice. I will pull out two more batteries and attempt some more calibrating with full, and even with not so full batteries, just to confirm if the same will happen. For some reason, I get good, accurate Voltage displayed in Betaflight when I complete calibration, but that for some reason changes when I get to fly. It's simply not showing me the actual Voltage at that moment, and it's showing me for example 3.5V per cell when it's actually 3.7V. Not a huge difference, but when we fly and our flights are already quite short, that difference in Voltage numbers is quite important.

(07-Nov-2023, 05:12 PM)Suros Wrote: Dang, I was so hopeful that you'd be able to just swap sensors and have the problem solved at the press of a button.

Haha, me too... Well, I won't give up. I am so interested what is going on here. I've ordered another SpeedyBee F405, but this time v4, the latest one. I have couple of quads with v3, and can't believe how good they are. I love how everything performs way better than my Diatone Mamba MK2 which is F722. I could simply replace this T-Motor Velox V50A + Rush Blade F722 HD with this new SpeedyBee F405 v4 that's arriving in a day or two... but that's an easy way, and I can't let it go   It's itching me so much, even more now... I will start scratching my head like my puppy does 

I just noticed something. Not sure how I missed that in the first place, probably because my ESC (T-Motor Velox V50A) came with it in the box. Capacitor that's on this quad is 35V, but it is 470uF. I've read somewhere (I believe it was Oscar's article about 6s requiring at least 1000uF, so very reputable source I trust with my life). I just glanced over that quad's stack, and I see that small 470uF capacitor inside, haven't even paid attention before.

Could that give me problems, if not these ones I am having at the moment, but maybe in a long run? I do have tons of 1000UF 35V capacitors though, ready to be used (shipment arrived yesterday).


The thing is, this frame is fairly tight, and have no idea where to squeeze that bigger 1000uF capacitor. It wouldn't be a problem if I could extend its legs for some 6-7cm, but I've watched tons of videos where they do comparison, and saying it's always the best to solder it the closest possible to the device you want to protect, so in this case, directly to XT60 pads on the ESC. What do others to in order to fit these larger capacitors inside?

On a 6S, 1000uF is recommended. I thought we talked about this and you were going to buy some.

If I don't have room to place it close to the batt pad, I usually extended it with good wire solder closest to the base of the cap.

Yeah man, I have about that much of an extension on all of my caps. Just zip tie it to a standoff or an arm or something. Use a little shrink tube if you worry about it getting scratched up.

(08-Nov-2023, 07:51 PM)voodoo614 Wrote: On a 6S, 1000uF is recommended. I thought we talked about this and you were going to buy some.

If I don't have room to place it close to the batt pad, I usually extended it with good wire solder closest to the base of the cap.

I've received a bag of Panasonic 1000uF, 35V yesterday. When I put together that 5th custom build, I wasn't even looking, simply connected capacitor that came with T-Motor Velox V50A inside the packaging, and it appears that they are shipping them with 470uF, and not 1000uF. How come they don't know it should be at least 1000uF? At least that's recommended. Now, I have 1000uF and planning to replace this one that came inside the original packaging (470uF), with one of these.

(08-Nov-2023, 08:35 PM)Suros Wrote: Yeah man, I have about that much of an extension on all of my caps. Just zip tie it to a standoff or an arm or something. Use a little shrink tube if you worry about it getting scratched up.

Sorry, I didn't lay out my question the best way. Finding space inside the frame alone is not that big of a problem, my camera cage is usually pretty empty, so there is tons of space in there, and sometimes I even manage to have my buzzer and the capacitor next to each other. But my concern was more about the fact that it's not the best to have capacitor legs so extended. I was watching quite a number of videos where they compare how they perform if there is some current spike, when they have short legs and they are close to the ESC, and how much they actually protect electronics if they are on extended wires. I use motors wires and ends (close to the capacitor itself) I always protect with heat shrink tubes.

Here is one of my quads, where there is tons of room inside the camera cage, but the problem is, those extension wires are around 6-7 cm.

This video shows the comparison:


And this is the photo of one of my quads, just to see where I mounted capacitors on two of my quads...

Not all quads are equal of course. Sometimes you will get away with a smaller cap just because the starting ripple isn't as big due to less noisy components. There's also a lot that's either preferring overkill for the sake of being sure it's enough, or manufacturers doing silly things. Unfortunately, there's also a lot of people who talk out their rear end or play telephone. I'm no pro, but I try to stick to what has either worked for me, or worked for somebody who I'm certain knows what they're doing.

I mean heck, sometimes I add a capacitor to a low power build just to eat the spike from plugging in. A lot of Mobula 7s were getting cooked when swapping to XT30s for their 2S setup as the connector and wire could move more power a lot faster. A tiny little cap on the connector soaks it up and saves the AIO.

I'd appreciate if someone could have a quick look at this wiring diagram and tell me if I connected everything correctly. It should be, but since I have no idea where to search anymore (checked all my batteries with other quads, and have zero issues, every single one flies 3.5, up to even 4 minutes of clean flight with some tricks thrown in, here and there). This is the only one that I'm having these battery drain issues, and want to double-check the very first thing I've done when putting that custom quad together.

And yes, in case you missed my post with a short video clip where I checked my batteries for internal resistance (shows just one battery, but I did the same with all the others, and all numbers are pretty much the same or very similar). Here is that video again (batteries are in great condition, and I know that because I fly them with other quads on a daily basis, and have zero issues with wrong Voltage displayed in my Avatar or Dji goggles v2, depending on the system each quad uses):


Since I did not use pre-made stack (like Diatone or SpeedyBee in my other quads), I had to connect two units from different manufacturers. ESC is T-Motor Velox V50A, and FC is Rush Blade F722 HD. Of course, the original connector was made for connecting Rush Blade FC to Rush Blade ESC, so some re-organizing of wires needed to be done.

I'd appreciate if someone could have a peek and tell me if this little cable that connects T-Motor ESC to Rush Blade FC is OK. I put that question mark on the light blue line because I did not know where that TX3 connection should go, but I believe someone from T-Motor FB group told me, it's not really supposed to go anywhere (?).

Those lines marked in different colors, are showing how I connected pins on my cable. Hope this is OK. Thank you so much in advance!

looks correct. tx3 does not need to be hook up.

(10-Nov-2023, 04:38 AM)voodoo614 Wrote: looks correct. tx3 does not need to be hook up.

Thank you. At least, I can erase that one from my narrow-down list 

Oh, BTW, earlier today I replaced that 470uF 35V with Panasonic 1000uF 35V. Just to be sure that's done correctly now. I was lucky because in this frame, there was plenty of room at the back, so this fairly large capacitor nicely fits inside without even touching anything else, and I did not have to extend its legs, kept it as short as possible.

(10-Nov-2023, 04:38 AM)voodoo614 Wrote: looks correct. tx3 does not need to be hook up.

OK, don't want to bother anyone with my findings, but just wanted to update this thread so anyone with possible similar problems can maybe help themselves too.

Anyway, we talked about ESC telemetry and possibility to read Voltage/Current from the ESC, instead of FC. I've got in touch with T-Motor engineers and they confirmed I could get those readings from my ESCs (4-in-1) instead of the FC. I went back to Betaflight and under the Power & Battery tab, for Voltage Meter Source I've picked ESC Sensor, and for Current Meter Source, I left it as Onboard ADC.

When I connected my battery, Voltage value shows 24.50 - 24.6 at the moment. I have that little battery checker plugged and it shows 24.6V. I've also checked with SpeedyBee Adapter 3, and exactly the same reading. Not sure if this is a sign of solution on the horizon, but at least reading is correct in Betaflight now.

I will have to do a flight (as soon as weather clears out) and check how it's behaving. I just wanted to post an update. It looks like Velox V50A I own, indeed supports Voltage telemetry. If this works, and I get correct readings in my OSD, what does that mean when it comes to my FC (Rush Blade F722 HD)? Does it mean, something is definitely wrong with how it reads Voltage values?

Oh, so it does work! That's exciting news! If this gives you acceptable readings, I would bet that the other monitoring hardware is just defective. Rush tends to make really nice stuff, but everyone gets a bad egg now and then.

Only mstc mentioned about proper settings for Warning Voltage and Minimum Voltage in the Power and Battery tab of Betaflight. If those numbers are too high, you will get flashing on the screen earlier than needed. It will drive you crazy. Yes, batteries sag when loaded.

For 1S I set those numbers to 3.2 (Low Voltage) and 3.1 (Land Now) volts. For 2S and up I set them at 3.5 and 3.3 volts. Since the voltages go quickly back up to 3.5 to 3.7 volts per cell after disarming, I know I am not damaging the batteries.

You can tweak these two numbers to get the best flight times with safe landings and no battery damage.