Best battery discharge method?

[Former Member]

If I have a drone query....It’s gotta be listen to our own Dr Thunderdrones every time.

I appreciate that very much. I am not always right, but when Im wrong, I try to fess up to it.

 

[Kilrah]

I would never trust the internal voltage meter in the Mavic battery when it gets to that low of a voltage. It is uncharted territory for the firmware and might relay incorrect data.

Sorry but that's total BS. It's designed to do it and there's absolutely no reason it would report wrong voltages.
The percentage reading is another thing but it's actually very smart and aggregates lots of info. If the capacity meter says there's 20% left but total voltage is lower than expected for this remaining capacity or a cell is lower than others the reported % will adjust itself down and the appropriate actions be taken automatically. Temperature and voltage drop under load are other things taken into account. That's why some people have been seeing fast drops from 50 to 10% and autolands.
And as said anytime something is at unacceptable levels it shows 0%.

It is foolish to run a battery that low while depending on the battery to report correct data. As you said, "0% is typically reached a little before that depending on how well the meter is calibrated." What if the calibration is off and the battery level is actually lower than what the battery is reporting? Disaster.

You seem to have forgotten the scenario. Of course don't do that in flight, but we are talking of an "intentional deep discharge" scenario that the manual told you to do, where you come back at 30% like normal then leave the aircraft in a hover 20cm above soft ground while looking at the battery page, then land at 3% or so as long as the battery status shows all cells are still within tolerance.

 

[Former Member]

Some people will read excerpts from this thread and think that it's ok for them to fly a battery that low because someone on Mavicpilots said so. Yes it might be their fault for not reading or simply misinterpreting the entire thread, but I just wouldnt want to plant the idea in anyones head that going below 20% is ok (unless you are an expert and know what you are doing).

 

[Kilrah]

Well then say that and go with "I wouldn't recommend it, but..." and educate people properly.
Regardless of how noble the goal is giving technically wrong info to get people to follow a train of thought is really low. There are enough politicians and media doing that already...

 

[jeplane]

@Thunderdrones

If you are getting frustrated with some posts this morning...

If you are thinking, “what the heck, screw it, I am leaving this board, life is too short”...

I just wanted to let you know that, by far, not everyone think you are spreading wrong info. And even if/when you do, we know that you will stand corrected.

I am a new drone pilot with only 100 flights, so your posts are always welcome, and I always devore the knowledge in them.

Well you and Soar104... you guys rock! Keep up the good work!

 

[Former Member]

@Thunderdrones

If you are getting frustrated with some posts this morning...

If you are thinking, “what the heck, screw it, I am leaving this board, life is too short”...

I just wanted to let you know that, by far, not everyone think you are spreading wrong info. And even if/when you do, we know that you will stand corrected.

I am a new drone pilot with only 100 flights, so your posts are always welcome, and I always devore the knowledge in them.

Well you and Soar104... you guys rock! Keep up the good work!

I appreciate that.

 

[Former Member]

I think someone just has a burr up his "you know what" today.

 

[Former Member]

Well then say that and go with "I wouldn't recommend it, but..." and educate people properly.
Regardless of how noble the goal is giving technically wrong info to get people to follow a train of thought is really low. There are enough politicians and media doing that already...

Not sure what your problem is, but telling people that it's OK to fly their drone down to 3% is Dangerous.

Btw, I don't know you, just from what you post on the boards which is usually rational and logical. Don't equate me with politicians and media and I'm not in this for the "nobility" of it all, I'm here to help people same as everyone else. Not sure why you have a problem with that.

 

[Garritynet]

Just out of curiosity why would you want to discharge your battery that low? I mean I read the part where the manual says to do it but specifically how does it help? I charge my devices when they get low and I've never worried about it beyond that but I have also never had to worry about something crashing so I'm curious what discharging batteries does that makes them last longer.

 

[tcope]

Just out of curiosity why would you want to discharge your battery that low? I mean I read the part where the manual says to do it but specifically how does it help? I charge my devices when they get low and I've never worried about it beyond that but I have also never had to worry about something crashing so I'm curious what discharging batteries does that makes them last longer.

It is a throwback to the battery software.

The software controls the maximum and minimum charge on the battery. If a lipo battery ever truly goes to 0% or very close, it will be difficult to ever charge it again. There are also obvious problems if it overcharges. So the software controls minimum and maximum charges. It also needs to know the batteries state in between these amounts. Two things to keep in mind... the battery really goes by voltage per cell and converts this to a percentage and the software needs to know the max and min charges but also where it is in between. A battery might be drained down to 30% and charged back up to 80%, drained to 50% and charged back to 95%. Under the old software is was possible that the the software would not know the correct lower and upper charge of the battery. Or at least DJI thought this might be an issue. Since that time, things have changed.

However, I can't think of any real harm this would cause. Perhaps for some people this caused a problem so DJI simply stop recommending it.

 

[WithTheBirds]

That’s the trouble with the internet. Everybody has an opinion/theory/experience whatever.
Try Googling symptoms of say, A sore knee into a health forum and you’ll probably end up with a diagnosis ranging from bone Cancer to housemaids knee.
Do you remember the wide ranging answers to, “should I fly with gimbal guard on or off?”
They were ranging from a flat ‘no’ to ‘I do it all the time and it hasn’t affected my drone, tho it did get very hot a few times!!’ Hmm.
If I have a medical question I consult and listen to a Dr.
If I have a drone query....It’s gotta be listen to our own Dr Thunderdrones every time.

Or- you can try googling the right source of information. In this case that would be Texas Instruments (they supply the BMS SOC's to DJI's battery manufacturers) and you would be looking at their fuel gauging and impedance track cell monitoring algorithms, the white papers make for interesting reading.

If you take the battery down to 0% depicted capacity the cell voltage is still above that where irreversible cell damage might occur. It definitely isn't good practice however if you are looking for long service life and a high cycle count.

 

[choo choo]

Just out of curiosity why would you want to discharge your battery that low? I mean I read the part where the manual says to do it but specifically how does it help? I charge my devices when they get low and I've never worried about it beyond that but I have also never had to worry about something crashing so I'm curious what discharging batteries does that makes them last longer.

Batteries are basically chemical reactions which produce electrical energy, I won’t go into the whole electron bit.
When you discharge a battery, it effectively ‘stirs up’ the chemicals (electrons and neutrons) inside the battery.
If you only discharge/use the battery to 80% of its capacity, then effectively only 20% Of the chemicals are receiving a fresh charge, the remaining 80% will hold a charge but eventually the chemicals will age and their effectiveness at holding any charge will deteriorate. With a result that you will only have a storage capacity of 20% or so. This used to be the ‘memory effect’ with a lot of the older type batteries such as Nicad (Nickel Cadmium). Lipo batteries don’t have such a bad memory effect, however they don’t like to be completely drained of power or it becomes difficult to ‘wake them up’.
So, in short, it’s good practice give the chemicals a stir up now and then to keep them in tip top condition...the batteries and cells last longer, which leads to safer flights.

 

[WithTheBirds]

I find the best way to discharge a battery is to fly it until it's down below 60%. If you cant fly it, the battery will self-discharge in a number of days according to the setting you have in DJI Go.

Can you set less than 10days in GO4 (for the M2)?

Hopefully its coming to a future update if it isn't there.

I find another good way to bring a pack down if your stuck with a full pack or two is to charge my controller, iPad, phone etc.

 

[WithTheBirds]

DJI's position has evolved and that recommendation was removed from newer instructions, obviously the printed one is from back when the aircraft was released and does not include any later changes.


You totally can, when it switches to "forced landing" it just shifts the zero vertical speed point to 50% stick up so all you need is hold the stick there. This summer I have been doing a cycle on my 4 Mavic batteries after several months of being unused and brought them down in flight to 3% (10cm high above grass of course) and then left the aircraft on until it turned itself off, which only took about 15 mins as a result.

The displayed % and time spent still on after landing on all 4 suggested this is indeed no more necessary.

Auto shutdown on DJI batteries is 3.2V/cell so still save damage wise. Note they're LiHV so you don't want to go as low as <3V on those.

HV lipo will safely tolerate a higher maximum terminal voltage- LVC settings are the same in most applications. Think about it- if what you say is true- that a HV LiPO cannot be taken down safely to the same minimum terminal voltage- it would offer no additional capacity and therefore no advantage over a standard LiPO.

 

[msinger]

Can you set less than 10days in GO4 (for the M2)?

No. That setting is hard coded to 10 days.

 

[sparkorc]

According to the Drone Valley guy the dji mavic battery has a built in low voltage protection, so you can never drain it completly, I think he states there is 10% left when it lands automatically due to a low battery, and he recommends doing this every 6 months to a year to recalibrate the built in battery sensors, I can't vouch if the content of his video is correct or not.

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[WithTheBirds]

According to the Drone Valley guy the dji mavic battery has a built in low voltage protection, so you can never drain it completly, I think he states there is 10% left when it lands automatically due to a low battery, and he recommends doing this every 6 months to a year to recalibrate the built in battery sensors, I can't vouch if the content of his video is correct or not.

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All DJI batteries that contain the Texas Instruments BMS will power down to protect the cells, its a programmable LVC. Many have said this to be 3.2V. I recall it being 3.0V under load for the phantom 3 on latest battery firmware, not sure about any of the others.

It is well known that the Mavic will commence auto land at 10% (as depicted as remaining capacity in the GO app).

 

[msinger]

the dji mavic battery has a built in low voltage protection, so you can never drain it completly

You got it. That's why the batteries are called "smart" batteries.

I think he states there is 10% left when it lands automatically due to a low battery

The drone will auto land when the battery reaches the critically low level. That battery percentage changes throughout the flight. The flight controller constantly calculates how much time it needs to land and triggers the critically low battery when that point is reached.

 

[WithTheBirds]

You got it. That's why the batteries are called "smart" batteries.


The drone will auto land when the battery reaches the critically low level. That battery percentage changes throughout the flight. The flight controller constantly calculates how much time it needs to land and triggers the critically low battery when that point is reached.

What seems to catch a lot of people out is that the auto landing will initiate when the % set for “critical low battery” is reached. You can’t set it below 10% so I think we might safely say they autoland will commence at 10% as the absolute min %.

 

[DanMan32]

I've gotten one of my P3A batteries down to 2.8v and it did not shut off. I really did want to go any lower. Admittedly that was just sitting there powered on, not in flight forced not to land. I immediately charged it back up of course