Hello you wonderful IntoFPV members.

I've built my 5th custom 5" quad, and it flies amazing. However, this is the first time I am little puzzled about one thing, and it's about my battery readings in OSD, and LOW BATTERY notifications. I've tested this quad already yesterday, and got this same problem, so I kind of disregarded these warnings for a moment, just so I can record this video and show you what's happening.

To me it looks like battery is totally fine, and it should be, since it's almost brand new, with 5-6 flight sessions on its watch only. The other thing is, I've tried with another battery, also brand new, and I'm getting the same readings.

Again, battery was fully charged before the flight, each cell was showing 4.20V clean. When I plugged battery in my quad, Avatar HD Pro OSD displayed 4.13V - 4.14V right away. I repeat, I already performed one test yesterday, so today, second time I am flying it, I knew what I see in OSD is not the real representation of my battery level, so I continued to fly after couple of those LOW BATTERY warnings. I knew there is a lot more juice left for flying. After just 1 minute of flying, I was getting LOW BATTERY warning. OSD was showing total of 21.5V (3.58V per cell)... You can see all this in the attached video as well.

After just 1 minute and 19 sec of flying, I've got LAND NOW warning. OSD was showing total of 19.5V (3.24V per cell). Don't pay attention to my landing struggling please, I was dealing with 55km/h winds (with wind gusts up to 70km/h) for the last couple of days... My city is officially the windiest city in North America. I hate it!

End Battery Voltage on my OSD was showing as 21.87V, but when I got home, literally after 2 minutes after I landed, both my battery chargers (iSDT D1 and ToolkitRC M7AC) displayed 23.0V, and one little battery checker, showed 22.9V, so pretty close.

Inside the Betaflight, under the "Power & Battery", Amperage Meter Scale is set to 200, as per T-Motor's recommendation for this ESC (Velox V50A), and Voltage Meter Scale is set to 113 after I did calibration with full battery. BF was showing me accurate Voltage at the time, but I am still getting these LOW BATTERY, LAND NOW warnings.

I am totally puzzled and have no idea where to search for source of my problem. At first I thought I did not set those settings properly in Betaflight, but now I am not sure what to do anymore. Does any of you wonderful people have some advice as to what to look for? It would be greatly appreciated.

This is my video from today:


Components I used in this build are the following:

Frame: MOPAX, 5" frame designed by Rotor Village
ESC: T-Motor Velox V50A
FC: Rush Blade F722 HD
Video System: Walksnail Avatar HD Pro
Motors: iFlight Xing-E Pro 2306 1700Kv
Receiver: MatekSys R24-D, True Diversity, 2 antennas, one installed horizontally, another one vertically.
Buzzer: Vifly Finder v2

If anyone is interested, here is my build video. I believe it's clean build as it can be, I paid a lot of attention to get everything right:


Thank you all so much in advance!

What you're seeing is voltage sag. Anytime you pull amps from a power source that doesn't have unlimited output, the voltage will start to drop until you let the load off.

Plug the battery in? Tiny drop.
Punch the throttle? Big drop.

Your flight controller only knows to watch the voltage level at the moment, so during big spikes in amp draw, it may think the battery is getting too low for a moment. Just ignore it if you know it's not really dead.

Edit: Here's a video of me hitting the throttle to see how much speed I could achieve. Watch the amp draw in relation to the voltage reading.

(04-Nov-2023, 02:06 AM)Suros Wrote: What you're seeing is voltage sag. Anytime you pull amps from a power source that doesn't have unlimited output, the voltage will start to drop until you let the load off.

Plug the battery in? Tiny drop.
Punch the throttle? Big drop.

Your flight controller only knows to watch the voltage level at the moment, so during big spikes in amp draw, it may think the battery is getting too low for a moment. Just ignore it if you know it's not really dead.

Edit: Here's a video of me hitting the throttle to see how much speed I could achieve. Watch the amp draw in relation to the voltage reading.
...

But, I am doing the same with my other quads, and I know there is voltage sag involved with punchouts. But we are talking about 1 minute of pretty normal flying here with one or two rolls, nothing else. I am getting at least 3.5 minutes, 4 minutes with some other quads I've build (SpeedyBee F405 v3 stack, Diatone Mamba, etc.). All 6s configurations. After the voltage sag, it should slowly go back to normal, but have a look at my video again please... after just over a minute, cell were sitting at 3.6 and not going back up. When I see 3.6 on my other quads, that's when I land immediately, but it happens after at least 3.5 minutes of normal flying with couple of tricks here and there.

(04-Nov-2023, 02:40 AM)Seii-FPV Wrote: But, I am doing the same with my other quads, and I know there is voltage sag involved with punchouts. But we are talking about 1 minute of pretty normal flying here with one or two rolls, nothing else. I am getting at least 3.5 minutes, 4 minutes with some other quads I've build (SpeedyBee F405 v3 stack, Diatone Mamba, etc.). All 6s configurations. After the voltage sag, it should slowly go back to normal, but have a look at my video again please... after just over a minute, cell were sitting at 3.6 and not going back up. When I see 3.6 on my other quads, that's when I land immediately, but it happens after at least 3.5 minutes of normal flying with couple of tricks here and there.

I think you're just pulling a lot of amps due to the wind. The mAh used showed less than half the pack used, and the resting voltage supports that. Doesn't seem like anything wrong to me. Another potential thing is that these batteries you're using could have a crap C rating. All the manufacturers lie about the C rating, and there's also the occasional crummy batch that hits the market. Personally, I'd just send it and put the mAh counter on your OSD.

(04-Nov-2023, 02:48 AM)Suros Wrote: I think you're just pulling a lot of amps due to the wind. The mAh used showed less than half the pack used, and the resting voltage supports that. Doesn't seem like anything wrong to me. Another potential thing is that these batteries you're using could have a crap C rating. All the manufacturers lie about the C rating, and there's also the occasional crummy batch that hits the market. Personally, I'd just send it and put the mAh counter on your OSD.

I understand that, and I so want to believe, but for some reason I'd love if at least my OSD shows proper Voltage (I still believe it's not showing the correct values). I have two other batteries, exactly the same as this one, and been flying with them for the last 6 months. None of my other quads was behaving like this, so kind of worried what is going on...

Anyway, this is my first (maiden) flight with this 5th custom build yesterday:
https://youtu.be/A_qDfM42NWs?t=249

You don't have to watch the whole video (probably boring for many), I've linked it to the time the important part starts. It's 4 minutes and 9 seconds into the video. It's when my maiden starts. Just after 20-30 seconds into the flight, LOW BATTERY appeared again. My flight was super, super short. OK, that was with 5s battery, but after that one, I did one with 6s and got exactly the same result. No wind at all yesterday (at the time I was flying, and I was surrounded with hills, at the bottom of the valley, where usually there is no that much of wind anyway.

And then please have a look at this video I've posted coupe of months ago, my 3rd custom build, SpeedyBee F405 v3 inside, also Walksnail Avatar. I've pulled its soul out there, and never ever got any sag not even remotely as I'm getting with this 5th build (T-Motor Velox V50A and Rush Blade F722 HD):

If you doubt the voltage setting, you could always put a multimeter to the back of your battery plug while it's on the bench and compare. Then just change the number and save until it's looking right. That's how I get mine calibrated if the manufacturer didn't provide a value or I think it could be better. As for current, I get close with a current clamp, then dial it in with the charger.

Also, I hope I'm not sounding dismissive of your observations. Had too much caffeine and I've got a bunch of plans I'm trying to make, so I'm a total scatterbrain right now.

(04-Nov-2023, 04:57 AM)Suros Wrote: If you doubt the voltage setting, you could always put a multimeter to the back of your battery plug while it's on the bench and compare. Then just change the number and save until it's looking right. That's how I get mine calibrated if the manufacturer didn't provide a value or I think it could be better. As for current, I get close with a current clamp, then dial it in with the charger.

Also, I hope I'm not sounding dismissive of your observations. Had too much caffeine and I've got a bunch of plans I'm trying to make, so I'm a total scatterbrain right now.

All good, I know I might sound like I don't appreciate the input, but I really do. I am just suspecting there must be something I did not set properly, and I'm getting these early notifications about such a low voltage. And it really looks like something is draining the battery at much faster pace than it should. I mean, 1 minute and I had to land... above all, I measured what's left in that battery, and it was just enough to complete the flight at around 3, maybe even 3.5 minutes... which is totally OK, almost the same like my other builds.

To me, it really looks like for some reason my OSD is not telling me the right voltage (FC, ESC, whatever is sending those information to the OSD). Today, I've landed when my OSD was showing battery at 21.87V (6s battery that is). But when I checked it on my chargers, it was 23V.

If there is a draw that big, something is probably getting extremely hot. You feeling any hot spots in the first few seconds of plugging in? Alternatively, maybe a short has been formed through the frame.

If you don't feel any excessive heat, get a multimeter on it while it's plugged in. Alternatively, if your battery charger has a power supply mode, rig up a cable with XT60 female endings on both sides and plug your quad in directly to the charger and check amp draw.

It could be a bad cell in the battery, the FC voltage sensor needs calibrating, or there is unusual current draw in the build.

If there is a bad cell, it will may show the normal high voltage, but as soon as you add any load it sags quickly. Sometimes there are no apparent signs of physical damage. If your charger measure internal resistance, that may give you some clue. Otherwise did you try another battery and was it the same, or try this battery on another build.

Calibrating voltage meter is relatively easy. If you have an accurate battery tester, just connect it to the lipo at the same time you are connected to BF and check the reading. If you use one full pack and one discharged pack, that will give you a good two points to verify the settings.

For unusual current draw, as Suros mentioned this will manifest itself in excess heat. Check all components after you fly, motors, ESC, battery, connects, (WS VTX will be very hot, but that is normal). I don't fly 6S, and most likely your current meter is not calibrated, but your video showed around 20A cruising and 60A max for what looked like not very aggressive flying (you don't have the throttle setting on OSD so not sure). You might compare to your other builds if that is roughly the same.

(04-Nov-2023, 03:04 PM)mstc Wrote: It could be a bad cell in the battery, the FC voltage sensor needs calibrating, or there is unusual current draw in the build.

If there is a bad cell, it will may show the normal high voltage, but as soon as you add any load it sags quickly. Sometimes there are no apparent signs of physical damage. If your charger measure internal resistance, that may give you some clue. Otherwise did you try another battery and was it the same, or try this battery on another build.

Calibrating voltage meter is relatively easy. If you have an accurate battery tester, just connect it to the lipo at the same time you are connected to BF and check the reading. If you use one full pack and one discharged pack, that will give you a good two points to verify the settings.

For unusual current draw, as Suros mentioned this will manifest itself in excess heat. Check all components after you fly, motors, ESC, battery, connects, (WS VTX will be very hot, but that is normal). I don't fly 6S, and most likely your current meter is not calibrated, but your video showed around 20A cruising and 60A max for what looked like not very aggressive flying (you don't have the throttle setting on OSD so not sure). You might compare to your other builds if that is roughly the same.

I am sure it's not the bad cell, only because I've tested this today too, with another battery (fairly new, maybe 2-3 months old, and I do take great care of them, as much as it's possible). It's GNB 1350mAh, and the same thing is happening. I do however believe that something unusual draws current for some reason. And it's only in this build with T-Motor Velox V50A, and Rush Blade F722 HD. All my other custom builds are either SpeedyBee F405 v3, or Diatone Mamba stacks. These same batteries perform amazingly on other quads.

I did Voltage Meter Scale calibration and ended up setting it to 113 (from original 110). In Betaflight it showed my fully charged battery, nicely as 4.20V - 4.16V. Not sure if that's what you meant by "Voltage sensor needs calibrating", but if that's not it... then I have probably never done it

I will measure internal resistance with this battery and post the results here, just to get that too out of the way, and try to narrow down what is really happening here. Thank you so much for leading me through this, greatly appreciated!

To answer your other question - about the excess heat - absoultely cold motors after that minute and a half flight session. It wasn't even cold outside, there was just that crazy wind. With wind I was dealing yesterday, but my other flight, maiden, two days ago... no wind at all, and even though you can see some snow outside, I was in my hoody. It was so warm outside. Motors super cold, I touched them with my lips, not even warm. Other components, all perfectly fine, Avatar HD Pro unit only warm to the touch. This is killing me.

UPDATE: here is a link to my video where I just measured resistance of this battery's cells (just so we have that archived and for future reference):


Another little question - I just remembered I completely forgot to do DISCOVER SENSORS when I've created new model for this quad in my Radiomaster Boxer. Could this have something to do with my problem? I am grasping for the straws here, I know I sound desperate   I just looked inside, and it looks like there is 90% of sensors discovered already, but just to be sure, I clicked on Discover New Sensors again. At the moment, here on the bench, inside of those options where the sensors are, it looks like it's showing pretty close to what the real status of this battery voltage is. I've plugged one of those small battery checkers to the balance plug, so I can see the current values (for all individual cells, as well as for total of 6 cells). Also, checked what I see in goggles (OSD), and it looks quite close. I will test it later today (weather permitting) and see what's really happening when I start flying. I won't do any tricks, nothing, simple easy flying, just to see when will this Low Battery warning pop-up again.

Also, could bad capacitor give me these problems? Because I am done with this one, I've had so many problems with my 3rd custom build where I've had this same combo inside, and I just transferred it here to my 5th build, hoping it will finally work. I've posted about those troubles in this forum couple of months ago. This 5th custom build quad flies perfect now, no de-syncs, nothing, absolutely buttery smooth flights... except for this crazy battery drain for some reason. I never replaced that original capacitor, only because this is 6s setup (Velox V50A ESC and Rush Blade F722 HD), and this current capacitor is 1000uF, and the only ones laying around I have available at the moment, are three brand new units, but they are 470UF 35V - LOW ESR (these ones: https://rotorvillage.ca/voltage-capacito...w-esr-1pc/ ). Not sure if these would be OK so I can swap this old one (at least until I get Rubycon 1000uF delivered, just ordered full box of them).

Thank you so much once again!

By hot spots, I'm talking more like stuff that just heats up really fast with it sitting there. As in burning hot. As for the sensor detection, that's just for your radio controller to figure out what telemetry data is being sent back to it, so that can't be it.

Honestly, if it's not a short, I'm not really sure what it could be at this point. I looked over your build video and it looked like a good job. About the only thing I could possibly guess at is maybe a battery wire went on too cold, but that's a longshot. You actually probably build cleaner than me.

(04-Nov-2023, 07:00 PM)Suros Wrote: By hot spots, I'm talking more like stuff that just heats up really fast with it sitting there. As in burning hot. As for the sensor detection, that's just for your radio controller to figure out what telemetry data is being sent back to it, so that can't be it.

Honestly, if it's not a short, I'm not really sure what it could be at this point. I looked over your build video and it looked like a good job. About the only thing I could possibly guess at is maybe a battery wire went on too cold, but that's a longshot. You actually probably build cleaner than me.

Thank you so much for taking your precious time to assist here. You have no idea how grateful I really am. Well, you might think you can't help enough, but I need you here, just like any other member in this amazing, incredible forum! Please stick around, even if you don't have any other possible ideas. We can all learn something from this, I am 100% sure. And I tried searching about this all over the internet, before posting my questions, and bothering all of you amazing people... but to no avail.

I really need to find out what is going on with this, it's like an itch I can't get rid of now   No, joke aside... but I really want to find out what it causing this behavior. And yes, I've checked every single possible thing for shorts with my multimeter. It's just in this video, my 5th build, I did not record those parts for some reason... all my other builds (videos are available up on my YT channel), I've recorded when I'm checking with my multimeter, every single little thing after connecting it, and before plugging my quad for the first time. Even then, I use Vifly Shortsaver v2... you can never be too sure with these things.

Now, the only thing that comes to my mind at this point, would be that capacitor. Could it be if it's bad one, that things like this might happen? I have some 470uF laying around, but I thought I am supposed to use 1000uF or maybe just a little less, and not as far as 470uF. Am I wrong when I say this?

THANK YOU SO MUCH ONCE AGAIN! I am sure we'll solve this eventually  

Oh, I'll certainly be waiting to see if you get it figured out. Problem solving is something I greatly enjoy, and I too know the "itch" of having something unsolved.

Not sure if your cap could be doing that. Could always pull it off and see if the behavior changes. Might swap to a safe filter/PID profile first though, just in case. The one time I had a bad cap, I let too much heat get to it and it exploded when I plugged in. Got electrolyte goo all over the place and made me jump.

(04-Nov-2023, 07:39 PM)Suros Wrote: Oh, I'll certainly be waiting to see if you get it figured out. Problem solving is something I greatly enjoy, and I too know the "itch" of having something unsolved.

Not sure if your cap could be doing that. Could always pull it off and see if the behavior changes. Might swap to a safe filter/PID profile first though, just in case. The one time I had a bad cap, I let too much heat get to it and it exploded when I plugged in. Got electrolyte goo all over the place and made me jump.

I just swapped the SupaflyFVP preset with the UAVtech one for this type of quad with GoPro on it (I used Supafly one on all my quads, but I get it that not all configurations will equally accept it and behave nicely with it). I will do a test later this afternoon, just to see if that helps any.

As for the capacitors, they are super helpful but they are no joke. The thing I still don't understand (and want to learn), how do I know which one exactly is suitable for my setup (6s, F722, 50A ESCs etc. Is there a calculation of formula that should be used when it comes to the right, or at least acceptable capacitor size?

I usually just go with 10ish volts over the max charge of what the battery can provide, then just choose a capacity based on physical dimensions that look sane. It's not very scientific, but my power has always been pretty darn clean. Helps to get them from a reputable brand too. Panasonic tends to be good. Just make sure they're proper low-ESR capacitors so they can effectively soak that voltage ripple.