Best battery discharge method?

[Steve L Reid]

I think you go all the way down to about Zero and recharge if your cells are uneven and to recycle you go down to about 5 % and recharge every 20 charges on the inspire 1 batteries and I would assume the Mavic would be the same.

 

[WithTheBirds]

I think you go all the way down to about Zero and recharge if your cells are uneven and to recycle you go down to about 5 % and recharge every 20 charges on the inspire 1 batteries and I would assume the Mavic would be the same.

You don't need to do it on any of the current DJI batteries. A deep discharge might seem to provide some improvement to an out of balance pack however any apparent improvement is almost always short lived. The fact you might have an out of balance cell simply demonstrates it has a different internal resistance to its neighbours, a condition it is unlikely to recover from.

 

[Steve L Reid]

You don't need to do it on any of the current DJI batteries. A deep discharge might seem to provide some improvement to an out of balance pack however any apparent improvement is almost always short lived. The fact you might have an out of balance cell simply demonstrates it has a different internal resistance to its neighbours, a condition it is unlikely to recover from.

Thank you for that info.

 

[deleted member 877]

So, in terms of getting the most out of the Mavic Pro LiPo 3S battery, there seem to be two distinct schools of thought. To fully discharge every 20 or so cycles or to never discharge below approximately 25%.

I would really like to know which one is correct. Does anyone have a link to a reputable, scientifically based document covering this topic?

 

[Cmeflydrone]

Fly those bartteries! You spent the money to enjoy the hobby but are diminishing the fun worrying about battery care. Golfers lose golf balls that cost 4-$5 each! Sometimes more than 1 a hole. We get peeved over some loss of battery capacity that equates to just nickels per flight? Are we not smarter than golfers? Our “golf ball” comes back with the push of a button? Enjoy. Just some perspective.

 

[WithTheBirds]

So, in terms of getting the most out of the Mavic Pro LiPo 3S battery, there seem to be two distinct schools of thought. To fully discharge every 20 or so cycles or to never discharge below approximately 25%.

I would really like to know which one is correct. Does anyone have a link to a reputable, scientifically based document covering this topic?

Google is your friend.....

Re 25% issue simply look at cycle life vs depth of discharge for LiION.

To understand why the deep discharge /20 cycles is a useless exercise have a look at the Texas Instruments white papers on "Fuel Gauging" and "Impedance Track" for LiION batteries (TI supplies the SOC micro controllers in all the current DJI batteries).

 

[Balko]

Every ten flights I run my batteries all the way to zero. Keep your drone running on the ground until it drains.

Won't that cause the MP to over-heat with the motors running while sitting still on the ground?

 

[deleted member 877]

Fly those bartteries! You spent the money to enjoy the hobby but are diminishing the fun worrying about battery care. Golfers lose golf balls that cost 4-$5 each! Sometimes more than 1 a hole. We get peeved over some loss of battery capacity that equates to just nickels per flight? Are we not smarter than golfers? Our “golf ball” comes back with the push of a button? Enjoy. Just some perspective.

Yeah, fair enough but it would be good to have accurate, proven information in regard to Battery Care best practices. How does typing a few paragraphs in a discussion forum in any way "diminish the fun" of flying our drones?? Your "golfing" analogy doesn't really make any sense.

 

[WithTheBirds]

Yeah, fair enough but it would be good to have accurate, proven information in regard to Battery Care best practices. How does typing a few paragraphs in a discussion forum in any way "diminish the fun" of flying our drones?? Your "golfing" analogy doesn't really make any sense.

The information is all out there. The reality is you get best performance and service life folowing a few simple practices. Store them in a cool place. Don’t fly them down below 25% unless you have a real need to. Don’t leave them at 100% charge for extended periods if you can avoid it. Let them cool before charging and don’t charge them at low temps. If they drop below 25% during long term storage put them on the charger to bring them closer to 50%. The quickest way to harm them is to let them sit empty or to keep them at 100% charge (higher temperatures fully charged is worst case scenario).Both can and will cause permanent changes in the chemistry that cannot be reversed.

 

[Donnie Frank]

I’m brand new at this and would like to know the best way to discharge or drain a battery? Can I just turn it on?, or do I need to put it in my MP? Thank you.

I fly the drone to about 8%, hover until it hit's 0%, and then leave it powered up until it dies. I've been doing that every 10 flights for my Inspire 1 batteries, and after 70-80 flights per battery, they're still running strong.

 

[WithTheBirds]

I fly the drone to about 8%, hover until it hit's 0%, and then leave it powered up until it dies. I've been doing that every 10 flights for my Inspire 1 batteries, and after 70-80 flights per battery, they're still running strong.

And- they would be running strong without that undue stress also..... Maybe stronger. 70-80 flights is nothing...

 

[deleted member 877]

The information is all out there.

Where? Can you provide a couple of links please?

 

[Fanjet]

I’m brand new at this and would like to know the best way to discharge or drain a battery? Can I just turn it on?, or do I need to put it in my MP? Thank you.

Always a lively discussion with, shall I say, fake news. The following link will provide you with more useful information on the care and feeding of your intelligent batteries than you will find here, and no, I'm not Roger.
A Guide to Understanding LiPo Batteries

 

[WithTheBirds]

Always a lively discussion with, shall I say, fake news. The following link will provide you with more useful information on the care and feeding of your intelligent batteries than you will find here, and no, I'm not Roger.
A Guide to Understanding LiPo Batteries

That’s a lot of information that either has limited application to the current smart batteries (connections, external chargers, etc) or isnt relavent. The general care instructions of course do apply, as they are universal to all LiION chemistry.

What are you saying is “fake news”?

 

[Fanjet]

That’s a lot of information that either has limited application to the current smart batteries (connections, external chargers, etc) or isnt relavent. The general care instructions of course do apply, as they are universal to all LiION chemistry.

What are you saying is “fake news”?

Ignorance is bliss... unless your drone comes down in flames. Too much knowledge is never a bad thing. Better to have too much than too little. I would not want to lose my drone for want of a $90 battery. Bad things can happen with these batteries. I especially liked the bit about Thermal Runaway. I don't know if that was thought to be of limited application or not, but it can lead to "a very hot and dangerous fire", which would make for some spectacular footage but limit the usefulness of a crash and burn drone. I live in Arizona where the ambient air temperature is routinely above the operating range of these batteries. If I can get 70-80 flights from a battery, I would consider that a batter life well lived.

 

[WithTheBirds]

Ignorance is bliss... unless your drone comes down in flames. Too much knowledge is never a bad thing. Better to have too much than too little. I would not want to lose my drone for want of a $90 battery. Bad things can happen with these batteries. I especially liked the bit about Thermal Runaway. I don't know if that was thought to be of limited application or not, but it can lead to "a very hot and dangerous fire", which would make for some spectacular footage but limit the usefulness of a crash and burn drone. I live in Arizona where the ambient air temperature is routinely above the operating range of these batteries. If I can get 70-80 flights from a battery, I would consider that a batter life well lived.

You might find this to be a source of enlightenment.... An easy read with all the basics covered.. How to Prolong Lithium-based Batteries - Battery University

 

[BJR981S]

Do you have evidence of the so called fall from sky incidents?

There have been numerous accounts detailed on various forums where forced landings at critical level and total battery shutoff have been reported. Later analysis revealed in these cases the battery was one that had been partially charged at the start of the flight (usually by having entered auto discharge) or was faulty (usually bad cell).

The microconriollers and associated electronics in our packs don't need a deep discharge to calibrate- basic coulomb counting is yesterdays method of SOC monitoring. Cell condition including age and use related degradation is measured in our batteries and used by the fuel gauging algorithm. No need to stress your batteries with an outdated procedure.

Er no. The batteries are not that smart they are not prescient. You must measure the Watt hours taken to charge the battery, then measure the watt hours that the battery can deliver. The difference determines the capability due to the battery age. You cannot determine the ageing without a full discharge as the watt hours from a partial change can not be used for this calculation.

As from falling from the sky you need to do the math on the battery C rating. These batteries are about 10C. The C rating is the amount of current that can be drawn from the battery based on the charge of the battery in mah without creating a voltage sag. As the charge is depleted from the battery its ability to deliver current gets reduced. The Fuel Gauge calibration takes this into account when displaying the battery % in the DJI Go 4 app. The 0% in the app does not represent 0% of the battery charge. 0% charge on a battery will not deliver any current so the reality is self evident.

The fall from Sky scenarios generally relate to those people that have initiated a RTH on low battery warnings (who have not calibrated the Fuel Gauge) panicked and then switches to sports mode. The additional current drag request in sports mode exceeds the C rating of the deleted battery and generates a voltage sag. Resulting in a Fall from the Sky.

I don't understand your reference to Coulomb's law. It does not play in any case of battery ageing scenarios.

 

[BJR981S]

You might find this to be a source of enlightenment.... An easy read with all the basics covered.. How to Prolong Lithium-based Batteries - Battery University

Thanks for posting this its a very good reference.

But be advised that the voltages they use are for LiPo batteries. The DJI batteries are LiHv and have a higher charge voltage than LiPos. 4.4V rather than 4.2V

So don't get anxious over the fully charged cell voltages displayed in the battery status of the DJI Go 4 app. They are not overcharging. They are different chemistry.

Cheers

 

[BJR981S]

Hmm that's interesting.

I'm new to drone flying but a very old hat at software and hardware.

My question has always been why do they call these batteries 'intelligent'?

Presumably because they have a microprocessor (computer) inside ensuring that all the necessary battery safety features are not violated, one of which should be ensuring against being discharged by the drone when the voltage falls below a certain threshold. This would be dead easy to implement in software if the micro is in charge of a relay or electronic switch which is only open when the battery voltage is above a certain threshold.

Is this happening?

Don't think about the drone suddenly falling out of the sky scenario because by the time this voltage point is reached the drone would have long been forced to land by existing battery safety features.

They are called intelligent as there is circuitry in the battery that causes a discharge to storage voltage after a programmed delay setting, and they have an activate button to display the current charge %.

Unfortunately the intelligence circuitry monitors the battery voltage. The act of monitoring actually very slowly drains the battery. This is why the battery safety manual recommends a cycle every 3 months. Leaving the battery to discharge longer than this time will result in battery damage.

There is no absolute safety automation in the drone that auto lands that can not be overridden by the operator. The low battery RTH can be aborted by the operator. The "Must Land Now" auto landing can be overridden by the operator by holding the throttle stick up. Usually done to prevent an auto landing over water.

 

[WithTheBirds]

Er no. The batteries are not that smart they are not prescient. You must measure the Watt hours taken to charge the battery, then measure the watt hours that the battery can deliver. The difference determines the capability due to the battery age. You cannot determine the ageing without a full discharge as the watt hours from a partial change can not be used for this calculation.

As from falling from the sky you need to do the math on the battery C rating. These batteries are about 10C. The C rating is the amount of current that can be drawn from the battery based on the charge of the battery in mah without creating a voltage sag. As the charge is depleted from the battery its ability to deliver current gets reduced. The Fuel Gauge calibration takes this into account when displaying the battery % in the DJI Go 4 app. The 0% in the app does not represent 0% of the battery charge. 0% charge on a battery will not deliver any current so the reality is self evident.

The fall from Sky scenarios generally relate to those people that have initiated a RTH on low battery warnings (who have not calibrated the Fuel Gauge) panicked and then switches to sports mode. The additional current drag request in sports mode exceeds the C rating of the deleted battery and generates a voltage sag. Resulting in a Fall from the Sky.

I don't understand your reference to Coulomb's law. It does not play in any case of battery ageing scenarios.

I made no attempt to apply coulombs law- I referred to an industry accepted term being "coulomb counting" which is the simple calculation you reference, measuring Ah delivered and subtracting from the expected battery capacity.

I agree wth you that in the not too distant past frequent full charge cycles needed to be performed to calibrate that battery monitoring schemes.

The Texas Instruments SOC employed in the current DJI batteries have rendered this unnecessary.

The depicted battery % is the calculated remaining charge available.

The code running on the micro controller in our batteries might be smarter than you have given it credit for. Instantaneous and average current, total pack and individual cell voltages, temperature and internal resistance are all constantly measured and inform the algorithms which provide real time state of charge and estimated run time to empty data to the aircraft flight controller. The cells are profiled when first connected and the cumulative health constantly updated and applied in reporting current status. The pack does not be taken down to a state of deep discharge and monitored during recharge to reliably report available capacity. The micro controller can reliably allow for any deterioration in cell performance from that provided when first installed.

My observations re the unexpected battery failures seem more often than not to relate to instances where partially charged packs are flown, particularly those that have entered auto discharge. The resistors that are switched in for auto discharge are the same ones used to bleed off excess voltage during balance charging. They are not precision matched and load the cells independently (this is not an issue during charge as their action is regulated by FET's in the charge controller). This creates a slight difference in cell voltages during auto discharge which obviously provides discharge will be uneven with the pack flown in this state leading to one or more cells approaching LVC much earlier than expected. Essentially the issue you are describing but for a different reason. The cell imbalances during discharge and evident at or shortly after commencement of flight has been evidenced in many flight logs available from these problem flights.

If you have time look at the white papers from TI on fuel gauging and impedance track. It is incredible technology.