how to avoid forced landing because of low battery
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Why would you want them to believe the misinformation you posted?
I have flight logs to prove it. Do you?
Droning on and on...
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Prove what? That the indicated SoC that DJI Fly displays is accurate?
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My last sentence: "You may in theory be able to do so, but the voltage drops too much during that last 5% (indicated), causing the drone to shut down."
You say this is "untrue". You base this on experience with healthy packs, and believe (erroneously) that, "Actually 10% Remaining Battery with DJI batteries means you have MORE than 10% of the battery's capacity remaining".
You're a lipos-are-gas-tanks guy. I explained why this is a false notion, and like I said, others can take your word, or mine. Designing and building custom powerbanks with cylindrical and lipo cells, I've learned quite a bit about how lithium chemistry multicell series packs work.
What you seem to be unwilling to understand is how packs fail, and can indicate plenty of charge, and then die when you put a heavy load on them. And how this marginal pack health can be entirely hidden until you run it down to 10% expecting it to work the same as it always has.
After all, it's the same as a gas tank, right? Your logs prove it!
I never said it was the same as a gas tank (unless your gas tank also has a 10% reserve tank!).
What I did say is that your statement, "but the voltage drops too much during that last 5% (indicated), causing the drone to shut down" is simply untrue, IF by 5% you mean the displayed Remaining Battery Percentage by the DJI Fly app.
I also KNOW that, "Actually 10% Remaining Battery displayed with DJI batteries in the DJI Fly app means you have MORE than 10% of the battery's capacity remaining."
If it were not true, the drone would otherwise do as you erroneously claim, and drop out of the sky before, or at the exact moment it displayed 0% Remaining Battery.
Instead, the battery continues to sustain controllable flight for at least 2 more minutes AFTER the Fly app displays 0% Remaining Battery.
Therefore, there MUST be MORE than 10% displayed Battery Remaining when it displays 10% Remaining Battery. QED.
You can quote all the theory you want, but the fact is that my almost 500 hours of DJI flight experience and over 1400 logged flights on AirData contradict your theory.
I have never had any DJI battery fail unless it was flown for more than 2 minutes after 0% remaining battery was displayed, and I have supposedly "abused" my batteries by regularly flying them down to well below 10% displayed Remaining Battery, and kept them at 100% as much as possible to be ready to fly immediately.
Clearly, what you refuse to accept is that DJI's current 0% Remaining Battery is deliberately misleading, leaving a Hidden Reserve Battery Capacity which will still sustain flight for two more full minutes before the drone shuts down from battery failure.
If I had to guess, I suspect DJI's currently displayed 0% Remaining Battery is actually closer to 5-10% TRUE Remaining Battery, which would be consistent with your experience, which is why what you postulate never happens from 10% to 0% displayed Remaining Battery on current DJI aircraft.
The declining voltage charts in Air Data also show no increase in power consumption until below 3.5V per cell, which is still 0% displayed Remaining Battery in the app. Once it reaches 3.3V per cell, it drops off precipitously, but that is not until 2 minutes after displaying 0% Remaining Battery.
No. What proof do you have that DJI's displayed 0% Remaining Battery is not deliberately inaccurate, for safety reasons, leaving two more minutes of usable flight time in an emergency?
How do YOU explain how the aircraft is still flying after having already reached 0% Remaining Battery, and will still consistently fly in N or P mode for another two full minutes at over 20mph on all P4P and Mavic 2 and Mavic 3 aircraft?
I'm sure that DJI intentionally sets the indicated battery SOC slightly below the actual value.
One has only to read comments on this and other forums to know that there are drone operators who callously disregard safety and good practice to squeak out the last seconds of flight from a battery. Every car or truck I've owned has a similar offset in the fuel gauge.
Droning on and on...
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Your repition of these assertions makes it clear you don't understand (and seemingly don't want to).
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Guys, there is so much misunderstanding going on here applying liquid fuel operational characteristics to series-cell lithium-ion batteries, and it's completely wrong.
I'll try to explain with an analogy. Imagine your car's gas tank was divided into 3 compartments, with an opening between them allowing gasoline to flow from one compartment to the next. At full throttle, these openings are big enough to allow sufficient flow to keep the levels in all 3 compartments the same.
There's a float in each compartment to measure remaining full, the 3 values simply added together.
Now, at some point some crap partially blocks the opening from the middle and last compartment where the fuel exits to the engine. Starting full, there's no sign that anything's wrong. You can floor it and it responds with full power like you expect. Fuel Guage drops normally as you burn fuel. You seem to be getting normal mileage, after half the tank is gone.
Here's what you are completely unaware of while the tank is far from empty: Every time you floor it, that last compartment drains faster than the other two because of the partial restriction allowing fuel to pass from the middle compartment to the last. This only happens when you floor it... under less of a load, the necessary flow rate to the motor doesn't exceed the compromised orifice between the compartments. When you back off the gas, everything equalizes again.
Now, your gas gauge says you're at 10% remaining fuel. There's a shallow pool of gas in each compartment, filling the bottom 10% of the volume.
You floor it pulling a heavy trailer up a steep hill. The last compartment drains completely, the fuel in the other two compartments unable to flow in to the last fast enough because of the occlusion. Fuel stops flowing to the engine, and it quits.
Your gas gauge says you have 8% left. Because you do.
That is similar to how a series cell battery fails with a marginal cell that has developed high internal resistance compared to the other cells in series.The high resistance in analogous to an occluded opening between compartments in the example above.
The point of all this is that at the low end of charge, 10% can not be relied on to have a usable 10% accessible. More and more so the more cycles you have on a pack. Most of the time, you'll be okay. But the risk is MUCH higher you will drop your drone from the sky – we hear about it rarely but regularly – where it's pretty close to zero chance if you abide the limits engineered into the system.
The safety margin engineered into the system is there for one reason only: For minimal necessary maneuvering during a forced landing so you can do a controlled, safe landing. get out of the way of people and property.
And what's the best way to damage an already marginal cell and permanently increase it's internal resistance? Run it down to depletion.
I'll try to explain with an analogy. Imagine your car's gas tank was divided into 3 compartments, with an opening between them allowing gasoline to flow from one compartment to the next. At full throttle, these openings are big enough to allow sufficient flow to keep the levels in all 3 compartments the same.
There's a float in each compartment to measure remaining full, the 3 values simply added together.
Now, at some point some crap partially blocks the opening from the middle and last compartment where the fuel exits to the engine. Starting full, there's no sign that anything's wrong. You can floor it and it responds with full power like you expect. Fuel Guage drops normally as you burn fuel. You seem to be getting normal mileage, after half the tank is gone.
Here's what you are completely unaware of while the tank is far from empty: Every time you floor it, that last compartment drains faster than the other two because of the partial restriction allowing fuel to pass from the middle compartment to the last. This only happens when you floor it... under less of a load, the necessary flow rate to the motor doesn't exceed the compromised orifice between the compartments. When you back off the gas, everything equalizes again.
Now, your gas gauge says you're at 10% remaining fuel. There's a shallow pool of gas in each compartment, filling the bottom 10% of the volume.
You floor it pulling a heavy trailer up a steep hill. The last compartment drains completely, the fuel in the other two compartments unable to flow in to the last fast enough because of the occlusion. Fuel stops flowing to the engine, and it quits.
Your gas gauge says you have 8% left. Because you do.
That is similar to how a series cell battery fails with a marginal cell that has developed high internal resistance compared to the other cells in series.The high resistance in analogous to an occluded opening between compartments in the example above.
The point of all this is that at the low end of charge, 10% can not be relied on to have a usable 10% accessible. More and more so the more cycles you have on a pack. Most of the time, you'll be okay. But the risk is MUCH higher you will drop your drone from the sky – we hear about it rarely but regularly – where it's pretty close to zero chance if you abide the limits engineered into the system.
The safety margin engineered into the system is there for one reason only: For minimal necessary maneuvering during a forced landing so you can do a controlled, safe landing. get out of the way of people and property.
And what's the best way to damage an already marginal cell and permanently increase it's internal resistance? Run it down to depletion.
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As someone who Runs there Battery Down to Zero and Below for years now on almost every Flight in the Pouring Rain , as to Capture the most amount of Lightning in the sky, testing our Wet Suits , there simply has been zero issues with the batteries being run down.
Were talking hundreds of Flights taxing the Drone to not force land , squeezing every last second out of the battery and never had a single issue with the battery.
That said , is it good Practice, no most likely not however it is good to know the limits and to practice with them so Panic does not set in or at least know the limits? Yes I think so.
Flying in Extreme Wind is scary but learning how to do it , is smart , again so you dont panic.
Flying with your controller turned off , not good practice , knowing how to negotiate it a good idea.
Being a good Seasoned pilots is about Limiting Risk, being able to negotiate it , being prepared for bad weather incidents and knowing the Limits of your drone . ,. an applying Commons sense .
Its not about pretending that battery cannot go down to below zero and keep flying or that the drone cannot really fly in the extreme wind or that birds are not a threat as we know they are the Biggest Threat to all of us.
Nothing wrong with flying safe , but also Safe is being prepared an knowing the limits of your drone.
Phantomrain.org
Gear to fly your Drone in the Rain and Capture the Storm.
Were talking hundreds of Flights taxing the Drone to not force land , squeezing every last second out of the battery and never had a single issue with the battery.
That said , is it good Practice, no most likely not however it is good to know the limits and to practice with them so Panic does not set in or at least know the limits? Yes I think so.
Flying in Extreme Wind is scary but learning how to do it , is smart , again so you dont panic.
Flying with your controller turned off , not good practice , knowing how to negotiate it a good idea.
Being a good Seasoned pilots is about Limiting Risk, being able to negotiate it , being prepared for bad weather incidents and knowing the Limits of your drone . ,. an applying Commons sense .
Its not about pretending that battery cannot go down to below zero and keep flying or that the drone cannot really fly in the extreme wind or that birds are not a threat as we know they are the Biggest Threat to all of us.
Nothing wrong with flying safe , but also Safe is being prepared an knowing the limits of your drone.
Phantomrain.org
Gear to fly your Drone in the Rain and Capture the Storm.
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You directly contradict yourself. Or perhaps indicate that you don't consider yourself a good, seasoned pilot?
You increase risk when you fly a battery down to 0% indicated SOC. You greatly further increase risk when doing so in the midst of a thunderstorm.
What could possibly be the justification for knowingly operating at risky battery levels, rather than landing and swapping batteries? You'll get far more flight time out of two batteries flown at reasonable SOC levels than one battery strained to the very last bit of power output.
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If you ever tried to capture lighting in a storm you realize that every second your capturing 60 Frames of those Lightning Strikes, thus every single second in the sky counts. If you land an Swap the battery by the time you go back up that show is over.
I think it fair to say that most people know what a seasoned pilot is compared to someone who flys on sunny days with no winds because everything else is risk not worth taking.
Phantomrain.org
Gear to fly your Drone in the Rain, and know that every second counts when the Lighting is biting.
Your spelling, capitalization, and logic complement one another well.
Droning on and on...
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@Phantomrain.org, the issue is risk and risk mitigation. If you're mitigating the increased risk when running to zero, I have no criticism. If the only thing at risk is your drone, it's your decision to risk it for the mission in question, and I and others might make the same choice given the mission.
Understand that mitigating risk means flying over space that, should you have a failure, the drone is the only thing harmed or damaged. If you follow the engineered limits (return when low-battery RTH tells you to, land where you are when FL kicks in, etc.) the risk of a sudden battery failure is very close to zero. We know this from the actual experience of millions of flights around the world for decades... DJI drones, protected by the safety margins and protocols engineered in (RTH, FL) don't get reported as suddenly losing power and free-falling. Just doesn't happen. Only time we hear of this usually turns out to be a poorly seated/latched battery that pops out.
Drones that have had FL turned off do. Rarely, but it does happen, and we hear about it.
It's not surprising you have not had a failure with a low probability risk like this. But that's the wrong way to analyze it. Risk analysis includes both the likelihood of an occurance, and the severity of outcome should an occurance take place. Even the tiniest risk must be mitigated if the risk is someone's life, for example. In such cases we usually implement redundancy, sometimes triple or more redundancy to push the risk of an incident vanishingly close to zero.
So disable FL and push your batteries past 0% remaining as much as you feel necessary for the missions you're flying. Just don't risk anything but your drone. If you're flying over populated terrain with buildings, cars, domesticated animals, and people, at 0%, hoping there's enough to make it back to you, you are flying recklessly.
Understand that mitigating risk means flying over space that, should you have a failure, the drone is the only thing harmed or damaged. If you follow the engineered limits (return when low-battery RTH tells you to, land where you are when FL kicks in, etc.) the risk of a sudden battery failure is very close to zero. We know this from the actual experience of millions of flights around the world for decades... DJI drones, protected by the safety margins and protocols engineered in (RTH, FL) don't get reported as suddenly losing power and free-falling. Just doesn't happen. Only time we hear of this usually turns out to be a poorly seated/latched battery that pops out.
Drones that have had FL turned off do. Rarely, but it does happen, and we hear about it.
It's not surprising you have not had a failure with a low probability risk like this. But that's the wrong way to analyze it. Risk analysis includes both the likelihood of an occurance, and the severity of outcome should an occurance take place. Even the tiniest risk must be mitigated if the risk is someone's life, for example. In such cases we usually implement redundancy, sometimes triple or more redundancy to push the risk of an incident vanishingly close to zero.
So disable FL and push your batteries past 0% remaining as much as you feel necessary for the missions you're flying. Just don't risk anything but your drone. If you're flying over populated terrain with buildings, cars, domesticated animals, and people, at 0%, hoping there's enough to make it back to you, you are flying recklessly.
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I agree , if you flying over any of that , battery or no battery that is a risk I would not take.
But Flying off my Deck in a storm straight up , I want every ounce I can get to stay in the air which is when I learned of the Battery being able to fly past Zero Percent as others have stated and doing it for years without issue.
To many threads turn into a Safety Check almost instantly , its just information that been confirmed by Seasoned flyers that battery can go past zero, Forced landing can be Negotiated. Why , where an how , is common sense .
For the Record I used to be Reckless years ago. I use to believe in the Easter bunny.
I believed in Long Distance Flights BVLOS I dont anymore
I believed with a Parachute and Waiver of flying over Populated areas < not anymore
I will take flying in the Storm, and in the wind any day over those risks.
I created the Rescue Jacket for the Drones to see the drone better as it a Safer Flight.
Phantomrain.org
Gear to Fly in the Rain, and Type from my car so spellsing is hit or miss. lol
But Flying off my Deck in a storm straight up , I want every ounce I can get to stay in the air which is when I learned of the Battery being able to fly past Zero Percent as others have stated and doing it for years without issue.
To many threads turn into a Safety Check almost instantly , its just information that been confirmed by Seasoned flyers that battery can go past zero, Forced landing can be Negotiated. Why , where an how , is common sense .
For the Record I used to be Reckless years ago. I use to believe in the Easter bunny.
I believed in Long Distance Flights BVLOS I dont anymore
I believed with a Parachute and Waiver of flying over Populated areas < not anymore
I will take flying in the Storm, and in the wind any day over those risks.
I created the Rescue Jacket for the Drones to see the drone better as it a Safer Flight.
Phantomrain.org
Gear to Fly in the Rain, and Type from my car so spellsing is hit or miss. lol
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Just a note on LiPo's, particularly in DJI aircraft. I've been flying these aircraft since the Phantom 2 days (still have it but no working batteries) 2 P3P's and now onto all the aircraft in my signature. I can honestly say I have experienced pretty much every battery quirk there is, from sudden voltage dropouts at safe reported battery levels, to the other end, where a battery refuses to quit at (an incorrectly reported zero percent). Sometimes the BMS gets confused, sometimes the battery is just wearing out. You simply can't fully trust the reported values and behaviors that will be triggered by them. Flying that close to wire is asking for trouble and poses an unnecessary risk to your aircraft and anyone nearby. The forced landing is a feature to try to mitigate disaster which has a higher priority (IMO) than being able to force my own control. And just to add, even during a forced landing, you still have enough control to at least aim for a decent landing spot. Same as you have when your manned aircraft runs out of fuel....
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