Posts: 164 Threads: 10 Likes Received: 95 in 71 posts Likes Given: 172 Joined: Dec 2020 Reputation: 4 11-Feb-2021, 12:00 AM (This post was last modified: 14-Feb-2021, 03:40 AM by Joshua_A.) I’ve just started working on a “fix” (hopefully) for the “ Low Voltage Cutoff” problem that -seems- to only haunt 2s li-ion power systems... Disclaimer: I have NO idea what will happen... even if it works it will be relatively difficult to do successfully... do so at your own risk!! Well with that disclaimer why would one proceed??well...2-x cell AIO have (generally) have more uarts and higher rated ESCs then normal 1-2s AIOs. Research: I started my research with This post by Gray-w-Johnson. It got me thinking, is the NMOS (mosfet driver) starving for power at voltages lower than 6.00 volts? And is this the main/only cause of the LVC problem? I’ve done a few tests, and every test showed that the NMOS stopped working at <6.00v input (or ~3.75v at NMOS input). So can one remove the voltage regulator (-2.25v) and get longer flight times (or should I say; discharge your battery to 3.25v?). If you can, how is it to be done? I unsure, but that’s why I’m doing all this testing.  If this is to be done how does one find the right components?? I found it’s easiest to find the mosfet driver and work backwards. I’m using a Hifionrc F7 25A AIO so the mosfet drivers are Fortior Tech FD6288Q’s (a VERY common mosfet driver.) Power is supplied in pin 4 (Vcc, or positive) and pin 6 (Com/Gnd, or negative) see the data sheets page 6. So with this in mind, I worked back a found the voltage regulator... Sorry my phone is going to die, I’ll update this post soon. Posts: 1,529 Threads: 49 Likes Received: 720 in 531 posts Likes Given: 481 Joined: Oct 2020 Reputation: 93 11-Feb-2021, 03:13 AM (This post was last modified: 11-Feb-2021, 03:18 AM by V-22.) Joshua_A Wrote:Sorry my phone is going to die Ironic your post was interrupted by LVC!  Looking forward to seeing what you come up with  Posts: 359 Threads: 14 Likes Received: 163 in 126 posts Likes Given: 1 Joined: Jul 2020 Reputation: 12 I think your on the right track. That was my conclusion when I'd did some testing a while back with a voltage regulator, that some chip or component was not stable at the low voltages. But that data sheet shows Vcc 0.3-35v for that chip so I don't think you've located the right component. Assuming Vcc means the same here as wiring a drone.
Electronics components generally do have common design voltages. The 1s boards likely either use components stable at low voltages like 3.3 or use a step up regulator to maintain the right voltage. 2s and up just don't need this before li-ion anyway.
Maybe ill send an email off to an esc company and inquire. Posts: 164 Threads: 10 Likes Received: 95 in 71 posts Likes Given: 172 Joined: Dec 2020 Reputation: 4 (11-Feb-2021, 03:13 AM)V-22 Wrote: Ironic your post was interrupted by LVC! Yah, whoever’s behind LVC doesn’t want this out...  (11-Feb-2021, 03:55 AM)EVILsteve Wrote: I think your on the right track. That was my conclusion when I'd did some testing a while back with a voltage regulator, that some chip or component was not stable at the low voltages. But that data sheet shows Vcc 0.3-35v for that chip so I don't think you've located the right component. Assuming Vcc means the same here as wiring a drone.
Electronics components generally do have common design voltages. The 1s boards likely either use components stable at low voltages like 3.3 or use a step up regulator to maintain the right voltage. 2s and up just don't need this before li-ion anyway.
Maybe ill send an email off to an esc company and inquire. Firstly I believe your right; the FD6288Q (mosfet driver) is probably NOT the problem, I’m was thinking it’s the voltage regulator (possibly outputting a unstable voltage at lower battery voltages, resulting in less power at the motors (because the FD6288Q is getting “PWM” input), my testing shows that this might be the case, but I could be completely wrong.) And secondly, if you get a reply from a manufacturer, your more than welcome to share the email on this thread, in fact I welcome it; if you find something share in here! On a side note: This AIO would be interesting to use for 2s li-ion packs... this might be the perfect board for the “Maverick mini Challenge” If it had a current sensor!! ![[-]](https://intofpv.com/images/collapse.png) • Posts: 5,967 Threads: 47 Likes Received: 2,798 in 2,259 posts Likes Given: 7,777 Joined: Jul 2019 Reputation: 97 Hi Joshua, Using a voltage regulator is a very good idea; just have to be sure that it can handle the current...probably need something around 20A for my builds; it would need a boost regulator set higher than maximum battery voltage. If the regulator was set at about 9V that would probably work. A more minor (maybe) consideration is the weight of the regulator. Now, a small 5V BEC doesn't weigh much, but the amp rating is also pretty small. In my mind, a regulator as you suggest would need to be rated at 20 Amp {at least} given that it is also driving the motors. Now, you might say that a 13 Amp is sufficient, but I use higher rated boards in most of my builds. Also, I don't know how much they weigh or how big it would be. The one caveat would be that you would loose battery voltage information in the OSD as it would always show 9V {full battery} even when it was almost empty. You might be able to use the mAh drawn information to judge how much battery is left, but I am not sure about that...maybe. So, a lot of experimental flights to determine how long {in time or mAh used} the quad would fly before just dropping out of the sky...perhaps without any warning. All of this said, I am willing to give it a try...or at least look into it a bit more. Keep us informed.  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Hi EVILsteve, I have looked at that AIO, but it is not sufficient for my needs. Most F4 processors don't have enough UARTS for me. I need at least 3 UARTS in order to run the Rx Receiver, SmartAudio, and the GPS unit. I have also moved up to boards rated for at least 20 amps which gives me more latitude for motors. Consider that a board with a decent Amp rating can be used in pretty much anything that I build or moved to different size quads with no problems. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ • Posts: 164 Threads: 10 Likes Received: 95 in 71 posts Likes Given: 172 Joined: Dec 2020 Reputation: 4 Hi ifly, I was referring to the internal voltage regulator, although it seem that your thinking of an external voltage regulator (I great idea, although I would only use it on a 16x16 stack, so the 4in1 will get the regulated power, but the fc would still receive the “real” voltage value.) To collect; I was considering the removal of the internal linear voltage regulator powering the mosfet drivers (it cuts 2.25volts, no matter the input voltage, well down to ~6volt  ), although requires a little more testing... • Posts: 5,967 Threads: 47 Likes Received: 2,798 in 2,259 posts Likes Given: 7,777 Joined: Jul 2019 Reputation: 97 12-Feb-2021, 07:41 PM (This post was last modified: 12-Feb-2021, 07:47 PM by iFly4rotors.) Hi Joshua, I am not brave enough to go tinkering with the tiny components on an FC/ESC board. On the other hand, if you do then let us know how it works out. Now, let me refine my though about the external regulator a bit. Since I would only use this with an 18650 pack, I would make a battery connector with the voltage regulator between the male and female XT30 connectors. With this method, I could use standard LiPo batteries and everything should work per the manufacturer's design specs. When I want to run an 18650 pack, I just plug the regulator in and then the battery: Male XT30 on the quad -> Female XT30 on regulator -> Male XT30 on regulator -> Female XT30 on Battery The entire system would be getting 9V all the time until the battery went belly up. To the FC/ESC it would look like a full battery until it didn't. No voltage drop as long as the battery continues to supply power. Then...when it is done, it is done. At least, that is the way I envision implementing it. • Posts: 1,435 Threads: 123 Likes Received: 1,440 in 748 posts Likes Given: 1,147 Joined: Jun 2019 Reputation: 42 Interesting thread guys! I would look at the voltage regulator that powers the FC controller first. Does that operate at the lowest Vcc you’re trying to operate at. Also look at the forward voltage ON value for the mosfets as well. The minimum voltage that is allowed across the drain/source junction,Vds? I think?
Cheers,
ph2t. • Posts: 164 Threads: 10 Likes Received: 95 in 71 posts Likes Given: 172 Joined: Dec 2020 Reputation: 4 (13-Feb-2021, 03:24 AM)ph2t Wrote: Interesting thread guys! I would look at the voltage regulator that powers the FC controller first. Does that operate at the lowest Vcc you’re trying to operate at. Also look at the forward voltage ON value for the mosfets as well. The minimum voltage that is allowed across the drain/source junction,Vds? I think?
Cheers,
ph2t. I’ll have to check into that, it really piles up...  Unfortunately I haven’t found anything, yet. I’ll talk to a few of my friends, to see what they think...  . • Posts: 1,435 Threads: 123 Likes Received: 1,440 in 748 posts Likes Given: 1,147 Joined: Jun 2019 Reputation: 42 How about powering the FC via the USB? Use a good LDO voltage regulator or even a BUCK/Boost DC to DC convertor to supply the 5V Vcc for the MCU and other logic components. Still use the V+,V- pads on the FC to power it as a whole from the li-ion 2S pack.
I know you said in the OP that you're looking at the mosfet drivers, I guess I wanted to ask what were the symptoms during your testing? Did you find once you hit that low voltage that the FC rebooted? Did that behavior occur at the really low voltage on the 2S li-ion pack? If so then it could be the FC power system that is faulting first? • Posts: 164 Threads: 10 Likes Received: 95 in 71 posts Likes Given: 172 Joined: Dec 2020 Reputation: 4 Hello ph2t,
In my testing; the ESCs gets no power from the usb plug (for safety, I guess, although the usb could hardly supply enough amperage anyway), so I don’t believe that would be a possible solution.
The “FC section” doesn’t seem to do anything odd until extremely low voltages (eg. much lower than I’d want to discharge a 2s li-ion pack).
I’m seriously considering the removal of the voltage regulator at this point, I’ll talk to a few of my friends to see what they think first.
We’ll see what happens... • Posts: 164 Threads: 10 Likes Received: 95 in 71 posts Likes Given: 172 Joined: Dec 2020 Reputation: 4 Update:
I’ve removed the voltage regulator from a fried board (the cpu was fried only, so the test should be good, also I notice the total voltage drop was due to cap AND the voltage regulator, but if my initial theory is correct then I’d only need to remove the regulator to rectify the problem anyway.)
The voltage drop is now only 0.75 volts (compared to 2.25 volts), so I should be able to discharge the battery an extra 1.5 volts (or in my case to 5.5 volts), AND if I’m right about the “PWM input at low voltage” then the discharge should be even further... • Posts: 164 Threads: 10 Likes Received: 95 in 71 posts Likes Given: 172 Joined: Dec 2020 Reputation: 4 14-Feb-2021, 03:28 AM (This post was last modified: 14-Feb-2021, 03:35 AM by Joshua_A.) Success!! Ok I did it on the LEAP 4”, but this time instead of removing the voltage regulator, I shorted the regulator with large success. The motors arm and everything else I’ve tested has been good. I’ll check the voltage readout to see if that’s still good and do a test flight tomorrow!! Edit: The voltage readout is right, now for the test flight! Posts: 5,967 Threads: 47 Likes Received: 2,798 in 2,259 posts Likes Given: 7,777 Joined: Jul 2019 Reputation: 97 • Posts: 164 Threads: 10 Likes Received: 95 in 71 posts Likes Given: 172 Joined: Dec 2020 Reputation: 4 14-Feb-2021, 05:05 PM (This post was last modified: 06-Apr-2021, 06:35 PM by Joshua_A.) (14-Feb-2021, 02:05 PM)iFly4rotors Wrote: Hey Joshua,
Congratulations Good Job
Post some detailed pictures and maybe annotate them. 
Thanks Thanks ifly, So far everything works as I wanted, although I haven’t had the chance to do a test flight (its 13 F degrees ,with a windchill of -3, and snowing  ), if the test flight is successful I’ll post all the details EDIT: all good, heres the mod . |
