80 to 90% battery level takeoff is triggering outrage

rickray · Jan 9, 2016

Hi,

I'm a bit confused.There are literally dozens of posts on this forum about never taking off with less than a 100% battery charge. People with other kinds of malfunctions are blamed for taking off with 3 bars instead of 4, or with 91% or 88% battery power. Is this really a legit objection? Why can't someone takeoff and get a good 8 to 10 minutes of safe flying from an 88% battery charge? And yet several posts seem to indicate this is a wildly unsafe and crazy thing to do.

While I understand that a 100% battery charge is "ideal", I am often in the field with batteries charging on two car chargers, and lots of great photographic opportunities happening. I will, on occasion, fly before my battery has fully charged and I have not had issues. I won't do it at 2 bars or 50%, but why is it so awfully unadvisable to fly at 3 bars or when my reading is well above 80% if I just monitor my flight time closely?

msinger · Jan 9, 2016

The problem is that these people are taking off with a battery that is not fully charged AND neglecting to monitor the battery voltage. If you do the latter, all should be well.

alokbhargava · Jan 9, 2016

What's your objection? Please start taking off at 50% charge. Nothing bad will happen if you can ensure that your battery had 50% charge remaining and also start planning to take it down when remaining charge is about 25-30%. Don't base your planning on the charge shown on the controller. That's the secret.

On the serious note: to make everything work perfectly, the built in instrumentation should be accurate which is NOT. So what's the alternative with you: Safety first.

robinb · Jan 9, 2016

The problem is a bit deeper than that is that when the battery is in its automatic self discharge state the % shown is unreliable. All of a sudden you can go from 60% down to critical battery voltage warning.
(at least until the last firmware was supposed to fix this).

msinger · Jan 9, 2016

robinb said:
The problem is a bit deeper than that is that when the battery is in its automatic self discharge state the % shown is unreliable.

I think this is speculation based on theories from recent forum posts. How exactly could the battery be in its automatic self discharge state while it's powered on and being used?

doomclam · Jan 9, 2016

My understanding is that if you fly a battery from 100% to 60% or whatever, you're safe to use it again[provided you monitor voltage - ALWAYS ALWAYS ALWAYS monitor voltage] provided you use it again WITHIN 24 hours.

Another reason they drop when not fully charged [in my opinion] is due to cold weather and/or someone jamming the throttle to full up which sucks power down below 3.3volts, which causes the battery to auto-shutdown. Full throttle isn't a problem with 4volts, but when you're at 3.7v already, that full throttle could be the kiss of death.

DISCLAIMER: these are my opinions and theories, not necessarily facts.

rickray · Jan 9, 2016

robinb said:
The problem is a bit deeper than that is that when the battery is in its automatic self discharge state the % shown is unreliable. All of a sudden you can go from 60% down to critical battery voltage warning.
(at least until the last firmware was supposed to fix this).

rickray · Jan 9, 2016

doomclam said:
My understanding is that if you fly a battery from 100% to 60% or whatever, you're safe to use it again[provided you monitor voltage - ALWAYS ALWAYS ALWAYS monitor voltage] provided you use it again WITHIN 24 hours.

Another reason they drop when not fully charged [in my opinion] is due to cold weather and/or someone jamming the throttle to full up which sucks power down below 3.3volts, which causes the battery to auto-shutdown. Full throttle isn't a problem with 4volts, but when you're at 3.7v already, that full throttle could be the kiss of death.

DISCLAIMER: these are my opinions and theories, not necessarily facts.

This is all useful information. My question is how much of this is hearsay and how much is useful. Monitoring voltage is always a good idea and there is scientific data about low voltage causing total craft failure.

But these other allegations about false high charge readings after discharge - are they credible? Is there actual consensus on this problem and does the most recent upgrade - which I have yet to implement - actually fix this as a known issue? It's hard to separate hearsay from fact sometimes on here.

yawnalot29 · Jan 9, 2016

rickray said:
This is all useful information. My question is how much of this is hearsay and how much is useful. Monitoring voltage is always a good idea and there is scientific data about low voltage causing total craft failure.

But these other allegations about false high charge readings after discharge - are they credible? Is there actual consensus on this problem and does the most recent upgrade - which I have yet to implement - actually fix this as a known issue? It's hard to separate hearsay from fact sometimes on here.

Here is what i can gather based on various postmortem analysis from forum members.

Unless your battery is just fully chatge, the % power remain reported is wrong. And couple this with a battery programming defects, it is causing the drone drop off sky.

Thats the bottom line.

That is why an earlier respobds said, as long as you are monitoring your voltage and know when to land ( which is reported accurately) and don't trigger the bug, you are ok to fly without a fully charged battery.

msinger · Jan 9, 2016

yawnalot29 said:
Unless your battery is just fully chatge, the % power remain reported is wrong.

I'm not ready to write off this theory yet. However, it would be nice to see proof that this is actually occurring.

yawnalot29 · Jan 9, 2016

msinger said:
I'm not ready to write off this theory yet. However, it would be nice to see proof that this is actually occurring.

I think it would be easy to test out. Pretty much simulate the situation, take the brid up 3 feet in air then land. Download the DAT file and perform analysis to see what's the actual battery percentage.

Most of the postmortem analysis seems to consistently report that the "victim" takes off with much less % battery than they thought (100%). So someone just needs to charge up a battery, leave it to auto drain, then put in bird, do a screen capture of the reported % power, take to air 3 feet (in case it crash), land, then download the DAT file for analysis.

LamboH · Jan 9, 2016

Screenshot from the dji go app

syotr · Jan 9, 2016

The problem is that the firmware shuts down the aircraft to save the battery! Does anyone think this is a good idea?

BVC · Jan 9, 2016

I think there is more old timers on here bloating the subject more so because it's something to talk about vs reality. It's very easy to remember a common issue but not the details tied to those common issue. No one has that capacity to remember/plot that data in their head.

Before I joined this forum I had NO IDEA I could see the average voltage of my battery. I've done close to 80 flights and only the last 3 I watched the voltage on my display. I've done MANY flights where I've taken off at 90,80.70,60,50,40%.

It's forums like this that cause more panic than what's really there. People come online onto forums to COMPLAIN & REPORT BAD EXPERIENCES. Sure there are a couple posts here and there bragging about how awesome their flight was today but 9 out of 10 threads regarding flight = bad situations.

I'll personally keep doing my thing and flying with half used batteries or batteries that were 100% 7 days ago but may sit on my shelf at 90%. That's not to say I'm not going to get more eye on the data I can display so I can maintain a safe flight but I sure won't let the panic of the forums get to me!

End of the day it's all a learning experience. Take what you read from all the sources, be an adult and make your own plan of action. Don't let fear take control. Otherwise you're not going to enjoy the hobby!

msinger · Jan 9, 2016

syotr said:
The problem is that the firmware shuts down the aircraft to save the battery! Does anyone think this is a good idea?

I don't think DJI meant for this to occur. The critical low battery feature is supposed to auto land the Phantom at its current location before the battery shuts off. It seems they just didn't foresee how some Phantom pilots were going to attempt to fly with a low battery.

snowghost · Jan 9, 2016

I have no problem with flying a 100% charged battery that sat a week. Been doing this for awhile and the battery life on all of mine show 100%. I do monitor the voltage on the main screen though.

IMHO those that set discharge to start at two days and then top them off a day later or so to fly are too conservative. YMMV.

syotr · Jan 9, 2016

msinger said:
I don't think DJI meant for this to occur. The critical low battery feature is supposed to auto land the Phantom at its current location before the battery shuts off. It seems they just didn't foresee how some Phantom pilots were going to attempt to fly with a low battery.

But the pilots think their battery has more charge than it does because the value is not reported correctly. With all of my multirotors which have dumb batteries, I can fly with a nearly dead battery. I will get red flashing lights and I have time to manually land or they will begin autolanding if I do not. In no case does the aircraft shut down and fall out of the sky to save a battery.

msinger · Jan 9, 2016

syotr said:
But the pilots think their battery has more charge than it does because the value is not reported correctly.

I don't think there are any cases where this was proven to be the cause. In almost every related case I've seen, the pilot always said something like "well, I thought it was at 100%... or at least 90% anyhow".

syotr · Jan 9, 2016

msinger said:
I don't think there are any cases where this was proven to be the cause. In almost every related case I've seen, the pilot always said something like "well, I thought it was at 100%... or at least 90% anyhow".

It shouldn't matter if it is 90, 60, 50%. It should not shut off and fall out of the sky.