solentlife Posted at 2018-7-28 05:48
Oh dear ....

I agree with you till you get on the Memory wagon again ... time for that old item to go the way of the NiCd ..... it has no place here with any Lithium based cells.

Lithium-ion batteries are high performance energy storage devices used in many commercial electronic appliances. Certainly, they can store a large amount of energy in a relatively small volume. They have also previously been widely believed to exhibit no memory effect. That's how experts call a deviation in the working voltage of the battery, caused by incomplete charging or discharging, that can lead to only part of the stored energy being available and an inability to determine the charge level of the battery reliably. Scientists at the Paul Scherrer Institute PSI, together with colleagues from the Toyota Research Laboratories in Japan have now however discovered that a widely-used type of lithium-ion battery has a memory effect. This discovery is of particularly high relevance for advances towards using lithium-ion batteries in the electric vehicle market. The work was published today in the scientific journal Nature Materials.

Read more at:  https://phys.org/news/2013-04-me ... -ion-batteries.html

I've flown a couple of times with the batteries not fully charged.  But I also never went very high or very far.  And once it caused me to crash my P3S.  The battery was showing that it was at about 50%.  I was just going to test something in the app in my front yard.  The problem was that I let the drone fly over my house with only about 6 feet of clearance.  I had only been in the air for about 3 or 4 minutes when I got a Critical Battery warning and the aircraft began to land automatically.  The problem was that it went from 50% to Auto-land critical within about 3 minutes, and I was over my house.  It was Hell-bent on landing. I tried to stop it and was trying to maneuver it off the roof and over to the lawn.  In the process, I hit a vent pipe on the roof.  The repair cost me $250.00 at the DJI facility.

ATJ Posted at 2018-7-28 05:59
Lithium-ion batteries are high performance energy storage devices used in many commercial electronic appliances. Certainly, they can store a large amount of energy in a relatively small volume. They have also previously been widely believed to exhibit no memory effect. That's how experts call a deviation in the working voltage of the battery, caused by incomplete charging or discharging, that can lead to only part of the stored energy being available and an inability to determine the charge level of the battery reliably. Scientists at the Paul Scherrer Institute PSI, together with colleagues from the Toyota Research Laboratories in Japan have now however discovered that a widely-used type of lithium-ion battery has a memory effect. This discovery is of particularly high relevance for advances towards using lithium-ion batteries in the electric vehicle market. The work was published today in the scientific journal Nature Materials.

Read more at:  https://phys.org/news/2013-04-me ... -ion-batteries.html

1. This is the same as the Swiss Institutes claims for Wrinkle Face cream.

2. You have taken a LiFePo4 supposed study and applied to LiPo .... two completely different battery formats.

One of the reasons studies are conducted on LiFe .... (generic term for LiFePo4, A123 and so on) ... is that they have been identified BY TESTING and significant R&D by many companies to provide a battery system with high energy basis but able to remain fully charged indefinitely. Something a LiPo cannot do.

There is also a fundamental flaw in the report ... NiMh does not have same characteristics as NiCd ... and that I base on the information given to me by a Senior Battery Tech at Mallory - who specialise in all forms of battery tech.

Even if you take what this guy writes - it follows the similar course of increasing Internal Resistance and causing reduced voltage delivery ... overall Watts.

Nigel

solentlife Posted at 2018-7-28 06:17
1. This is the same as the Swiss Institutes claims for Wrinkle Face cream.

2. You have taken a LiFePo4 supposed study and applied to LiPo .... two completely different battery formats.

Thank You Nigel - Andy

ATJ Posted at 2018-7-28 02:57
Don't be fooled by Labroides people Lithium Batteries are prone to a memory as well (especially when they are hot).  Keep charging them at a 50% discharge and eventually you'll find out for yourself. In using Li ion and Li poly for years I have found this to be, VERY MUCH, the truth. You can lead a horse to water.

I've been reading posts from very experienced RC pilots since 2013 and I have not once read a post that stated that "Lithium Batteries are prone to a memory."  Can you link me to one?  Also, do you have a reference, a link, or anything anywhere that substantiates your claim?

Thanks.

Labroides Posted at 2018-7-27 08:43
But if you put a battery in that's been sitting around for a week or more, although it says it's at 50%, it's not and within a minute it could drop to critical low voltage levels.

I can't make it any clearer.

So the problem is batteries that have begun self-discharge.

Certainly taking off twice on the same battery with 55% should not pose a problem, especially if the battery has not been removed from the AC and left in storage for days.

During training sessions with my wife and daughter, we made full use  of a charge. Landing the drone several times, taking off again, etc., until the battery was down to 28% or so.  No problems in that situation, but I gather that's not what you're referring to.

Absolutely without a second thought I would fly.

If you are at 70% you have plenty of time left.

I take off at 30% quite regularly if necessary.

Mark Weiss Posted at 2018-7-28 12:23
So the problem is batteries that have begun self-discharge.

Certainly taking off twice on the same battery with 55% should not pose a problem, especially if the battery has not been removed from the AC and left in storage for days.

The only problem that I have observed is that the % full indicator is not always accurate.  The reason that it is not accurate is that it is not a measure of how much power is in the battery since there is no way to measure this directly, instead it is 100% minus a count of how much power has been taken out of the battery since the last 100% charge plus any power that has been added.  So the only way to get it fully accurate is to charge to 100%, after that it will slowly loose accuracy until the next 100% charge.   The biggest loss of accuracy is due to the self discharge during which it is very hard for it to measure the loss of power accurately because it discharges very slowly so that it doesn't overheat when stored inside the packing case.

If you charged to 100% on the last charge, and it has not had a chance to self discharge, then you can make as many flights as you like and there is unlikely to be any problem.

This thread. It just keeps going, and going. So here’s my 2 cents. I’ve had a P4P for around 8 months. I only fly after charging to 100%. I might take 2 or 3 flights on a fully charged battery, over a couple hours. I won’t launch below 60% in that case. I don’t fly below 40%, unless I’m cycling the battery after 3 months of use. I always store the batteries between 40 and 50%. I average about 20 minutes of total flight time per charge. I’ve never stored the batteries at 100% charge for more than 24 hours. Over that 8 months on 3 batteries, I’ve got around 30 charges on each. All three seem healthy and balanced. Some of my behavior is based on what I’ve read from Labroides, some of it is based on what I’ve read from Mark the Droner. For the most part it’s a conservative approach to following the manual. Treat them with respect, for they must be healthy to carry your investment home to safety.

Jeff

Jeff Millard Posted at 2018-7-31 02:00
This thread. It just keeps going, and going. So here’s my 2 cents. I’ve had a P4P for around 8 months. I only fly after charging to 100%. I might take 2 or 3 flights on a fully charged battery, over a couple hours. I won’t launch below 60% in that case. I don’t fly below 40%, unless I’m cycling the battery after 3 months of use. I always store the batteries between 40 and 50%. I average about 20 minutes of total flight time per charge. I’ve never stored the batteries at 100% charge for more than 24 hours. Over that 8 months on 3 batteries, I’ve got around 30 charges on each. All three seem healthy and balanced. Some of my behavior is based on what I’ve read from Labroides, some of it is based on what I’ve read from Mark the Droner. For the most part it’s a conservative approach to following the manual. Treat them with respect, for they must be healthy to carry your investment home to safety.

Jeff

At 70% I'd fly - but I'd keep it close. Below 50% - no.
I fly a P3 Standard, and generally charge prior to each flight.

fans970acecf Posted at 2018-7-31 05:51
At 70% I'd fly - but I'd keep it close. Below 50% - no.
I fly a P3 Standard, and generally charge prior to each flight.

Case in point: You start out with 100% charge, You land and 60% and then, within minutes, takeoff again. (This is a scenario that happens to me: "aircraft disconnected" during Intelligent Flight modes, requiring me to land the AC, and power cycle all three devices, AC, RC and mobile device.) Should I presume that scenario is providing accurate battery charge data to the AC?

djiuser_hRZzv67dLdhW Posted at 2018-7-26 20:28
As an example, I needed a quick shot at one location, the next location was 15 miles across the valley.  45 minutes later, ready for the next shot.  Seems like it should be unnecessary to swap out a battery that has only been used for a few minutes.  j

I do that all the time, as long as start with a full battery Im happy to do three short flights on a battery . but never if battery has been charged 3 or 4 days previous ..  only after a fresh recharge night before

solentlife Posted at 2018-7-28 05:30
ALL batterys suffer usage .. and the term 'Memory' is a term that got abused and became accepted fact instead of reality ... Batterys do not actually get a memory as some claim ... NiCd days - this was a constant argument ... what actually happened was repeated partial discharge, it was nothing to do with charging, caused a chemical and physical limitation to be created that needed full cycling to break. LiPo's are resistant to this phenomena.

LiPo's as with ALL batterys have Internal Resistance. This increases with cycles of use until eventually the battery cannot deliver the power asked of it ... temperature goes up ... it swells etc.

Thanks Nigel.  Someone finally fully explained.   I now have a full understanding, at lease all I need to know, and I intend to only begin my flights with a recent fully charged battery.

Al

Mark Weiss Posted at 2018-7-31 06:10
Case in point: You start out with 100% charge, You land and 60% and then, within minutes, takeoff again. (This is a scenario that happens to me: "aircraft disconnected" during Intelligent Flight modes, requiring me to land the AC, and power cycle all three devices, AC, RC and mobile device.) Should I presume that scenario is providing accurate battery charge data to the AC?

You are placing too much reliance on the displayed battery capacity. It is vital to understand that the displayed capacity is not a measured value, it is a calculated value, and it is not very reliable. For the same reason that pilots are told not to rely on fuel tank readings, but to visually confirm the level of fuel in the aircraft tanks, relying on the calculated value will eventually bite you in the a*se. Landing and going out again at 60% is not a good idea in case you see sopmething you wish to record for a longer period of time. I can't afford to keep buying Phantoms, so I don't take any chances with them.

Geebax Posted at 2018-8-1 16:05
You are placing too much reliance on the displayed battery capacity. It is vital to understand that the displayed capacity is not a measured value, it is a calculated value, and it is not very reliable. For the same reason that pilots are told not to rely on fuel tank readings, but to visually confirm the level of fuel in the aircraft tanks, relying on the calculated value will eventually bite you in the a*se. Landing and going out again at 60% is not a good idea in case you see sopmething you wish to record for a longer period of time. I can't afford to keep buying Phantoms, so I don't take any chances with them.

So you're saying that 60% at second takeoff is not the same as 60% point in one contiguous flight?
It happens that from time to time, it is necessary to reboot the AC/RC and mobile device in order to restore connection. Often there will be more than half battery remaining at landing.
Now I realize that launching with 60% means no long distance missions. I wouldn't do a mission like that on anything less than a full charge.
But in our case, flying around a soccer field at under 50' AGL, I don't see a problem with launching a second time on the same battery, if it's over half capacity. Also verified with the LEDs on the battery.

Mark Weiss Posted at 2018-8-1 19:31
So you're saying that 60% at second takeoff is not the same as 60% point in one contiguous flight?
It happens that from time to time, it is necessary to reboot the AC/RC and mobile device in order to restore connection. Often there will be more than half battery remaining at landing.
Now I realize that launching with 60% means no long distance missions. I wouldn't do a mission like that on anything less than a full charge.

It is your aircraft, your choice. Personally I don't trust the batteries as far as I could kick one.

Geebax Posted at 2018-8-1 20:17
It is your aircraft, your choice. Personally I don't trust the batteries as far as I could kick one.

That's fine if you carry a dozen batteries wherever you go to fly, but if you have one or two batteries, quitting just because your bird lost communication and you have to land it and reboot.

I know on previous version of Phantom 4 you can change how many days until discharge. Mine is set to 10 days. I also have purchase many extra batteries. You buy car charger for battery and have full charge battery all times.

Mark Weiss Posted at 2018-8-2 08:50
That's fine if you carry a dozen batteries wherever you go to fly, but if you have one or two batteries, quitting just because your bird lost communication and you have to land it and reboot.

I don't know what your aircraft does, but my P3 does not have to be landed to re-establish communications, it can be done in the air. But as I said, your aircraft, your choice.

Personally ... 100% at first take-off ... I can land and take off again ... without shutting down etc. - then battery % is reasonable indicator. You can land / take off as you like ... NOT powering off between.

If I fly and then land .. power off ... then decide to fly again with same battery ... I do it with my butt cheeks fluttering and praying nothing will go wrong. I keep close and VERY short flight. I work on the principle that battery indicator now is not worth trusting ... I fly close enough I can make out the LED's on the battery ... its surprising how far you can see those ...
I fly / drive / boat RC models of most configs / types ... and I make it a rule to not use partial batterys, (or fuel tanks for that matter) ... seen too many models go down because of it.  

Nigel

I do believe that the responses here got away from the original post...  Nowhere was it stated that he was sitting on discharged batteries for a week to 10 days where the auto-discharge starts to take affect, just a "few" days.  Soooo... if he stopped a flight at 70% which would be in the neighborhood of 3.8 volts and auto discharge is set for 7 to ten days then 3 days later if he decided to use that 70% battery he would still have 70% charge.. 3.8 or so Volts., he could easily get 10 to 12 minutes of flight to get a few shots.
Now if that battery sat "Uninterrupted" for over 10 days and the battery starts to auto discharge then of course the battery will have less power than when it was put away, and extreme caution would need to be used if you decided to fly.
All of my batteries are set for 10 days and I think that in the past 20 months that I've been flying my P4 I can count on one hand how many times a battery started auto discharge.  I fly as often as I can and I have on several occasions inserted a battery into my P4 with 60 to 70% charge and it continued flying just fine, just like if it had been in from start to finish, being the sum of the 2 flights equaled one complete flight (plus or minus a minute or two for a second IMU warmup period).

Thank you 'Oldman...' for re-establish the point of my original question. This is exactly what I wanted to hear. If I put the craft in the air, use 30% of battery or so, then next day or two I go again with remaining 70%. I fly having this in mind and never drain such battery to the critical point. And thanks to other who explained the technology of batteries in detail.
It is interesting and useful.
Andy

I mean...not to state the obvious. But it depends how long/far. Would I fly 4000' away for 20 min until 10% left? No. Would I fly within say, 500' until there was 20% left? Absolutely.

<sigh>

I don't know how many different ways it can be said.  

"Always launch with a fully charged battery."  

There it is.  Simple.  Seven words.  That's really all there is to it.  

...

After a while, you just give up...

We've done what we can.  Let 'em learn the hard way, I guess.  

Mark The Droner Posted at 2018-8-7 07:31
I don't know how many different ways it can be said.  

"Always launch with a fully charged battery."  

That's correct.
Always launch with a fully charged battery is just too complicated for some.
And you have to read to learn from the unpleasant discoveries of others that found out the hard way.

Or they get their short video, a few prized pics capturing the scenery, and land. ;-)


Now the real question is, how hard was the landing. Hahaha


RedHotPoker

Mark Weiss Posted at 2018-7-31 06:10
Case in point: You start out with 100% charge, You land and 60% and then, within minutes, takeoff again. (This is a scenario that happens to me: "aircraft disconnected" during Intelligent Flight modes, requiring me to land the AC, and power cycle all three devices, AC, RC and mobile device.) Should I presume that scenario is providing accurate battery charge data to the AC?

Thats always been classed as one full flight, a quick land to say change the lens or like you a disconnect, then take off again, is just one flight as far as the battery is concerned, been told this before on here, read it before on here and i will always go by that on here.

I have been charging a battery in the car before now and it got to all 4 lights flashing (97% in ac) and used it till it got to 30%, i always land at 30% or very close to it!!

I should add that i would NEVER land with 70% put it away and go out again the next day with that 70% not a cat in hells chance, hell, i wouldnt even do that later on the same day

With 70% I would definitely. Personally I wouldn't take off with 45% or less

Oldmaninwva Posted at 2018-8-7 03:39
I do believe that the responses here got away from the original post...  Nowhere was it stated that he was sitting on discharged batteries for a week to 10 days where the auto-discharge starts to take affect, just a "few" days.  Soooo... if he stopped a flight at 70% which would be in the neighborhood of 3.8 volts and auto discharge is set for 7 to ten days then 3 days later if he decided to use that 70% battery he would still have 70% charge.. 3.8 or so Volts., he could easily get 10 to 12 minutes of flight to get a few shots.
Now if that battery sat "Uninterrupted" for over 10 days and the battery starts to auto discharge then of course the battery will have less power than when it was put away, and extreme caution would need to be used if you decided to fly.
All of my batteries are set for 10 days and I think that in the past 20 months that I've been flying my P4 I can count on one hand how many times a battery started auto discharge.  I fly as often as I can and I have on several occasions inserted a battery into my P4 with 60 to 70% charge and it continued flying just fine, just like if it had been in from start to finish, being the sum of the 2 flights equaled one complete flight (plus or minus a minute or two for a second IMU warmup period).

Sorry -wrong for good reason ...

"if he stopped a flight at 70% which would be in the neighborhood of 3.8 volts and auto discharge is set for 7 to ten days then 3 days later if he decided to use that 70% battery he would still have 70% charge.. 3.8 or so Volts., he could easily get 10 to 12 minutes of flight to get a few shots."

ALL batterys suffer self discharge .... you can prove this to yourself ... there wouold not be 70% left in that pack in your example.

Charge up full a battery - any battery ... DJI or not. Disconnect. Go back 1/2 or 1 day later and try charge again ... (DJI you need to switch on battery first before connecting charger as it defaults OFF over 93%) .. what happens ?? OH yes - it charges ....

Do not be fooled by the LED's on the front ... they are +/- 12.5% flashing / solid ... even 4 solid LED's can be anywhere in the 90% and up ...

Reluctantly I would agree to second short flight of LESS than calculated time same day - but certainly not use it if left standing till next day or so - regardless of auto discharge setting.

Nigel

solentlife Posted at 2018-8-8 04:03
Sorry -wrong for good reason ...

"if he stopped a flight at 70% which would be in the neighborhood of 3.8 volts and auto discharge is set for 7 to ten days then 3 days later if he decided to use that 70% battery he would still have 70% charge.. 3.8 or so Volts., he could easily get 10 to 12 minutes of flight to get a few shots."

Nigel....  I decided to do an experiment to prove one way or the other to myself about what I was getting at on these Phantom batteries...  Now I only did this on one battery, over 1 year old, it had 60 recharge cycles and was very healthy. Set for auto discharge at 10 days.  I charged this battery up on a Sunday afternoon (8/5/18) and on Thursday morning I inserted it into the P4 and turned the screen recorder on before turning the P4 on.  I have these recordings but do not have the time to edit them down just yet.
The battery level on immediate startup when it showed was at 99%, total voltage of 17v, cells had 4.27, 4.27, 4.26 and 4.26.  At this point I decided to just turn the motors on and let them spin to run the battery down, after 20 some minutes I returned to find the remaining battery level at 80%, with total voltage at 16.3v and cells at 4.08, 4.08, 4.08 and 4.07.
I removed the battery and set it aside from that Thursday morning to this morning, about an hour shy of a full 3 days in a partially discharghed state.  Once again I turned on my screen recorder and inserted the battery.  When the battery level displayed it still showed a level of exactly 80%, however the one cell that showed 4.07v now shows 4.08.   The battery did NOT drain in any way.  I then proceeded to FLY the P4 at that point and had over 12 minutes of flying around before landing it at 36% charge.  I would have flown it a while longer except I needed to answer the phone and I do not like distractions when I’m flying. There was also no abnormal power level loss while flying like was suggested would happen by several others.

So....  I’m not sure what YOUR batteries are doing to make you say the things you and several others do concerning the original posters desire to fly on a partially discharged battery, but MY battery works JUST like I had stated several times in all of that dialog.
I will state one thing again that I had earlier, I KNOW what’s my equipment is doing as I fly ALL the time.  I know when a battery is not up to par so I start looking at cell deviations to see if I have the beginnings of a failure.
So I stand behind my original statement that for the purpose of what the original poster wanted to do, IF he has healthy batteries then he would have NO problem taking a partially charged battery and put his bird in the air for a quick shot or 2.
No it’s not considered something you would want to do all the time, but in MY opinion the risk for a great shot could be VERY well worth it.

Not trying to prove anybody wrong really because all you guys might be having some battery issues, what I did was for myself, cementing the fact that what I said is true...  for MY batteries

Oldmaninwva Posted at 2018-8-12 15:27
Nigel....  I decided to do an experiment to prove one way or the other to myself about what I was getting at on these Phantom batteries...  Now I only did this on one battery, over 1 year old, it had 60 recharge cycles and was very healthy. Set for auto discharge at 10 days.  I charged this battery up on a Sunday afternoon (8/5/18) and on Thursday morning I inserted it into the P4 and turned the screen recorder on before turning the P4 on.  I have these recordings but do not have the time to edit them down just yet.
The battery level on immediate startup when it showed was at 99%, total voltage of 17v, cells had 4.27, 4.27, 4.26 and 4.26.  At this point I decided to just turn the motors on and let them spin to run the battery down, after 20 some minutes I returned to find the remaining battery level at 80%, with total voltage at 16.3v and cells at 4.08, 4.08, 4.08 and 4.07.
I removed the battery and set it aside from that Thursday morning to this morning, about an hour shy of a full 3 days in a partially discharghed state.  Once again I turned on my screen recorder and inserted the battery.  When the battery level displayed it still showed a level of exactly 80%, however the one cell that showed 4.07v now shows 4.08.   The battery did NOT drain in any way.  I then proceeded to FLY the P4 at that point and had over 12 minutes of flying around before landing it at 36% charge.  I would have flown it a while longer except I needed to answer the phone and I do not like distractions when I’m flying. There was also no abnormal power level loss while flying like was suggested would happen by several others.

You left your battery sitting for three days and it flew OK.
That's great for you but it doesn't mean that people can leave their battery sitting for several weeks and fly safely.
There is way more than enough evidence to show that it has caused the loss of plenty of Phantoms.

Labroides Posted at 2018-8-12 15:37
You left your battery sitting for three days and it flew OK.
That's great for you but it doesn't mean that people can leave their battery sitting for several weeks and fly safely.
There is way more than enough evidence to show that it has caused the loss of plenty of Phantoms.

Ok...  BACK TO THE ORIGINAL POSTERS QUESTION....

No where did HE nor I state that several weeks were going by between  taking a partially discharged battery out and expect it to perform like it was only out a few hours or even a day or so...  
I easily understood his post as meaning a day or 2 when away from a way to charge his batteries.

Oldmaninwva Posted at 2018-8-12 15:54
Ok...  BACK TO THE ORIGINAL POSTERS QUESTION....

No where did HE nor I state that several weeks were going by between  taking a partially discharged battery out and expect it to perform like it was only out a few hours or even a day or so...  

I'm way past caring to continue this stupid discussion.
Every week there are reports of Phantoms that fell from the sky and investigation shows the cause to be launching with a partially discharged battery.
If your battery has been discharging a day or two, it's probably going to be fine.
If it a month or more it might be that Phantom's last flight.
If you want to take a ticket in the is-my-battery-too-discharged lottery to see which number of days does/doesn't work go ahead.
Knock yourself out.

C'mon guys ... lets ease off ...

No-one is against any flight with a partial battery if kept short and for that one-time shot. But it appears that the general consensus is that a serious prolonged flight is not a good idea.

I look upon it as like the car journey ... my Brother is one who doesn't like spending money and drives on minimum gasoline tank content ... and he's paid the price for that more than once, where he's run out of gasoline before reaching destination. Myself - I like a full tank so I know I have enough to complete the trip without worry.

As regards self-discharge - it is a fact and as I have said many times - is a very low rate of discharge - but it is there.

Nigel

Nope! Gotta lift off with full power. You wouldn't want to be over the ocean and have a power down issue.

solentlife Posted at 2018-8-12 18:54
C'mon guys ... lets ease off ... No-one is against any flight with a partial battery if kept short and for that one-time shot.

< ------------------ At least one person is.  

Mark The Droner Posted at 2018-8-13 02:36
< ------------------ At least one person is.

This Battery discussion really comes down to Common Sense.

If you are not intentionally storing your batteries then:

First push the power button and check the battery level. You've read the manual and know what the LEDS indicate.  Plug the battery in and check the battery percentage indicator on your DJi Go app, it's usually pretty accurate. If it shows 90-100% then you should be able to get a good long flight. If it shows 75-90% fly it, just don't go to far. If it shows 50-75% fly it, maybe do little bit of practice around the your yard, keep it close. If it shows below 50% then you make the decision (common sense), maybe use this power to set up or make adjustments to your drone or app.

I know Nigel disagrees, but I like to table discharge my batteries to between 5 and 10% before I charge them, I BELEIVE this adds to the life of the batteries. (Like I said I purchased my a P4 in January 2017 and the batteries still show a 80% battery capacity)

ATJ Posted at 2018-8-13 03:50
This Battery discussion really comes down to Common Sense.

If you are not intentionally storing your batteries then:

If it shows 50-75% fly it ...
If it shows below 50% then you make the decision
What part of only fly with fully charged batteries is too hard to understand?
You don't sound like someone to take advice from.

I like to table discharge my batteries to between 5 and 10% before I charge them,
A complete waste of time and effort.
How often do you calibrate the compass?

ATJ Posted at 2018-8-13 03:50
This Battery discussion really comes down to Common Sense.

If you are not intentionally storing your batteries then:

Common sense is the LAST thing you'd want to rely on.  Common sense is why all these new folks are launching with partially charged batteries and losing their aircraft due to unexpected drops.

Knowledge and experience beats common sense in this case.