How low should I allow the battery to go before I stop flying?

[EpicFlight]

I know that HP over the last 2 years has had a heck of a time with their laptop batteries charging repeatedly to 100%. They pushed firmware out that generally maintains the battery at 80% for health reasons.

The charging and use pattern for laptop batteries is radically different, and totally abusive in all the bad ways mentioned here, as compared to DJI batteries.

If you left our drone lipos on a trickle charge keeping them topped off at 100% most of they time, they'd be goners pretty quick.

 

[slup]

Just a couple questions & comments to what you wrote ...

...the battery module is doing a better job managing all this than you can. Just fly until low battery RTH kicks in, then come home and land.

You do know that the DJI battery doesn't have a clue that you've flown a far distance with a tailwind & doesn't calculate in that extra need of battery percentage when deciding when it's time to go home?

The low battery RTH is only distance to HP dependent ... nothing more, so if pilots in general should follow your advice we should see a lot of cases where crafts go down before reaching back to HP.

Fully charge your batteries after each flight, so they're ready for tomorrow. If you go long enough without flying, they'll discharge on their own to 50%.

Have so far never seen that a DJI BMS auto discharge as far as 50% ... the majority of batteries go to 60% after X-days & some do it in 2 steps with a first let off from 100% just after one day.

DJI's lithium pouches inside the hard shell enclosure aren't of any special magic mixture ... they are identical to all other LiPo batteries ... meaning that electrolyte decomposition, increased internal resistance gassing & decrease of maximum capacity still will occur ... & it's well established that keeping LiPo & LiIon on max charge for a long time increase the wear substantially. Keeping them on full for a week compared to 2 days is a big difference.

Trying to improve on this is really a waste of time. I've got 6 (7?) year old P3 batteries that work seemingly as good as new...

Do you follow them up in any way ... I mean, as you claim that they are as good as new. Or do they just take charge, still keep your P3 airborne & aren't swollen? Lithium batteries doesn't last forever, eventually they will fail in some way ... if you're lucky they just fade away, give so short flight times so it isn't worth to use them anymore. Or they fail suddenly with massive cell failures dropping the cell voltages well below 3V ... which makes your craft start to critical low battery voltage force land on the spot, if you then is over something not suitable for landing (water for instance) it will be the end of that craft. Even though your P3 batteries seems to still take charge & can discharge without a drama ... do you actually know... if you've been on the verge to a critical low battery voltage auto landing?

...Which adds to the point of not obsessing over this: long before any noticeable degradation, you'll probably have upgraded to a newer bird.

What you're trying to mostly achieve by taking care of the batteries is to prevent them to suddenly fail completely ... instead get a predictable fading degradation where you actively can decide to take them off active flight duty. In order to achieve this, thing's as cell deviation, flight times, total capacity & voltage drops when pushing for amps must be followed trend wise.

THAT'S a far more realistic take on DJI batteries

Sorry, but that's just ... "-I don't care, I fly until something happens & deal with it then" ...

 

[EpicFlight]

I figured there would be nitpicking, and technical flexing. It means nothing to me.

I'm a retired EE. I've spent so much time reading specs for various batteries I'm virtually cross-eyed. Designing BMS circuits and selecting LiIon formulations and functional characteristics is something I'm very familiar with.

Throw all the jargon at me you wish. It doesn't impress.

Nitpicking over auto-discharge percentage is a good example. I don't know the exact percentage, and no one else here does either. it's not the point. This is a casual conversation among laypeople... 50% is a "rule of thumb" used almost universally as proper lipo storage level. You can't discuss lipos anywhere on the internet without running into the 50% storage rule of thumb almost immediately.

Others reading will make up their own minds, which is the point.

You are wasting your time and effort trying to eek a few more cycles out of your battery modules. You simply do not have sufficient direct control over the battery cells to meaningfully affect these issues – save making sure you charge them.

Finally, @slup please do not put words in my mouth. I can speak for myself. I meant what I said as it was written. You don't agree. That's fine with me. Insulting me by stating that I don't care is what pissing matches are made of.

For example, you keep making statements that scream ignorance on the subject. "DJI's lithium pouches inside the hard shell enclosure aren't of any special magic mixture ... they are identical to all other LiPo batteries".

Impossible, as all other lipos are not identical to each other, nor are their chemistries, nor their charge/discharge characteristics. In fact, these attributes vary widely, such that there are lipos that tolerate full charge without significant degradation for a year or more, others that operate at a higher charge voltage, and on and on.

You seem to know a lot about Li-Ion batteries that's wrong. Not opinion, but factually. like the idea that all lipos are the same.

 

[slup]

... It means nothing to me.

Totally up to you ...

 

[Dougcjohn]

I figured there would be nitpicking, and technical flexing. It means nothing to me.

I'm a retired EE. I've spent so much time reading specs for various batteries I'm virtually cross-eyed. Designing BMS circuits and selecting LiIon formulations and functional characteristics is something I'm very familiar with.

Throw all the jargon at me you wish. It doesn't impress.

Nitpicking over auto-discharge percentage is a good example. I don't know the exact percentage, and no one else here does either. it's not the point. This is a casual conversation among laypeople... 50% is a "rule of thumb" used almost universally as proper lipo storage level. You can't discuss lipos anywhere on the internet without running into the 50% storage rule of thumb almost immediately.

Others reading will make up their own minds, which is the point.

You are wasting your time and effort trying to eek a few more cycles out of your battery modules. You simply do not have sufficient direct control over the battery cells to meaningfully affect these issues – save making sure you charge them.

Finally, @slup please do not put words in my mouth. I can speak for myself. I meant what I said as it was written. You don't agree. That's fine with me. Insulting me by stating that I don't care is what pissing matches are made of.

For example, you keep making statements that scream ignorance on the subject. "DJI's lithium pouches inside the hard shell enclosure aren't of any special magic mixture ... they are identical to all other LiPo batteries".

Impossible, as all other lipos are not identical to each other, nor are their chemistries, nor their charge/discharge characteristics. In fact, these attributes vary widely, such that there are lipos that tolerate full charge without significant degradation for a year or more, others that operate at a higher charge voltage, and on and on.

You seem to know a lot about Li-Ion batteries that's wrong. Not opinion, but factually. like the idea that all lipos are the same.

Great posts, enjoy the direct approach... and I couldn't agree more.

 

[LCummings99]

Hi Slup!

Our maintenance section and recommendations were reviewed by DJI Services a couple of months back and we continue to work closely with DJI on this.

Please never discharge a battery all the way to 0% as it could indeed harm the battery. DJI still does recommend discharging and charging on a regular basis. Please see one example from the M300 maintenance manual, page 13/14, here: https://dl.djicdn.com/downloads/matrice-300/20200507/M300_RTK_Maintenance_Manual_v1.0_EN.pdf

AirData HD 360 Gold plan and higher can help you track all of this, as well as track DJI specific services for their Enterprise drones (performed by DJI services) please see AirData is Taking Its Drone Fleet Management Platform to the Next Level With the Integration of DJI Maintenance for more info.

I hope this helps!

What are your thoughts on the reasonably recent change DJI made regarding increase in time to discharge from 5 to 9 days in the Fly app? (Edit: This applied to the AIr2s, not sure if it applies to the Mini2, Air2 or M3 as well)

 

[slup]

What are your thoughts on the reasonably recent change DJI made regarding increase in time to discharge from 5 to 9 days in the Fly app?

Have yet to see any valid reason... & this with days to discharge isn't related to the FLY app ... it's usually craft specific. And it's not anything new either, the Mavic Pro & Mavic 2 could be adjusted regarding this ... all the way down to 2 days but the Mavic Air 1 had a fixed 10 days discharge. And none of these crafts have been spared from failing batteries.

So would be valuable with some hard fact to why it's prolonged & why it isn't adjustable by the user.

 

[mschaffer66]

You do know that the DJI battery doesn't have a clue that you've flown a far distance with a tailwind & doesn't calculate in that extra need of battery percentage when deciding when it's time to go home?

That's my concern. I've seen my batteries slowly discharge on a nice calm day and other times drop 5% every couple seconds on a tough into the wind flight on the way home. I don't trust that it will make it back if I am running it to the auto return to home cut off.

 

[slup]

That's my concern. I've seen my batteries slowly discharge on a nice calm day and other times drop 5% every couple seconds on a tough into the wind flight on the way home. I don't trust that it will make it back if I am running it to the auto return to home cut off.

Yep ... & that's why generalizing advices like stated earlier "fly until the low battery RTH starts" can be devastating to new pilots that not yet have figured out how it actually works ... and furthermore they also tend to fly out with tailwinds (don't know why though ... or it's only their incidents that turn up here )

When I was a newbie & trying to figure out how thing's worked (& admittedly didn't know enough regarding regulations )... I flew out on distance & up on height & below is the result.

The low battery RTH % is only distance dependent, & will not count in head or tail winds.

Here, distance from HP in red & low battery RTH % in green ... the outbound trip was with a headwind.



And here a chart showing how the critical low battery landing is dependent on the height above HP.

The red is height above HP & the green is critical low battery landing % ...

 

[EpicFlight]

@mschaffer66, @slup, you are spot on regarding the potential impact from asymmetric winds going out and coming back.

I wasn't considering distance flights with my comment, rather being within 1-2000' most of the time, which is what the vast majority of my flying tends to be, and I suspect most others.

In seven years, I've only had one forced landing, and that was when I canceled RTH and kept flying. For me, low battery RTH has been a completely reliable indicator for battery depletion.

YMMV

 

[LCummings99]

Have yet to see any valid reason... & this with days to discharge isn't related to the FLY app ... it's usually craft specific. And it's not anything new either, the Mavic Pro & Mavic 2 could be adjusted regarding this ... all the way down to 2 days but the Mavic Air 1 had a fixed 10 days discharge. And none of these crafts have been spared from failing batteries.

So would be valuable with some hard fact to why it's prolonged & why it isn't adjustable by the user.

Interesting that it's different for each AC. Go4 allows adjustment from 1-5 days to start discharge. I set mine to 2, which isn't perfect but LiPo's don't typically like to be left fully charged or deeply discharged for more than 24hrs so unless there is some new tech in the Air2s or any other AC using the Fly app that allows for a longer period to start discharge without being detrimental to the battery it doesn't make any sense to me.

 

[slup]

...some new tech... that allows for a longer period to start discharge without being detrimental to the battery it doesn't make any sense to me.

Don't think DJI have invented something regarding Lithium batteries that vastly differs regarding how/why they degrade during it's life time compared to generic LiPo packs. Furthermore their Smart batteries often contain high voltage (HV) cells which within other high amp draw RC areas so far have been proven to not be worth the extra $ as they degrade faster than non HV.

The main drivers for DJI, I think... is keeping the sales volume up, & cut the warranty costs ... and give the "photography" drone flyers what they want ... a minimum of maintenance, a battery always ready for a flight & for DJI, a battery that will last during the warranty period.

I fly much more often with amp hungry FPV quads ... which pushes the battery much more than drones, I usually, just by using them, can give a verdict regarding health status just out from how the battery performs ... voltage sag, internal resistance, total capacity, heat & swelling. All these factors immediately show up as bad performance as you always uses the battery to the very limit to what they can deliver. A drone battery is usually just idling in comparison & you will not feel a performance difference ... instead it shows up as a sudden swelling that pushes the battery out of the drone (Mavic 2's) or low battery voltage auto landings when a cell fails airborne crashing below 3V during a short Sport mode burst in colder ambient temperatures for instance.

As a recent poll here at the forum showed ... the vast majority of drone flyers classify them self as "Photographers that happens to have a camera on a drone" ... and it's very few that say "I'm a pilot of a drone that happens to have a camera". This makes the battery, in peoples mind, the same as all other stuff, ND filters, beacons, props ... the batteries are just another component that is expected to always work & be prepared for a flight ... that's why DJI marketing them as "charge & forget". And all this leads to ignorance when it comes to one of the most important components that keeps the drone airborne.

As LiPo batteries don't live forever ... how we treat & care, effects in what way they die, either it will be "fast & furious in a disaster" ... or they slowly fade away after several charge cycles & don't quite deliver enough flight time anymore, & gets retired.

 

[LCummings99]

Don't think DJI have invented something regarding Lithium batteries that vastly differs regarding how/why they degrade during it's life time compared to generic LiPo packs. Furthermore their Smart batteries often contain high voltage (HV) cells which within other high amp draw RC areas so far have been proven to not be worth the extra $ as they degrade faster than non HV.

The main drivers for DJI, I think... is keeping the sales volume up, & cut the warranty costs ... and give the "photography" drone flyers what they want ... a minimum of maintenance, a battery always ready for a flight & for DJI, a battery that will last during the warranty period.

I fly much more often with amp hungry FPV quads ... which pushes the battery much more than drones, I usually, just by using them, can give a verdict regarding health status just out from how the battery performs ... voltage sag, internal resistance, total capacity, heat & swelling. All these factors immediately show up as bad performance as you always uses the battery to the very limit to what they can deliver. A drone battery is usually just idling in comparison & you will not feel a performance difference ... instead it shows up as a sudden swelling that pushes the battery out of the drone (Mavic 2's) or low battery voltage auto landings when a cell fails airborne crashing below 3V during a short Sport mode burst in colder ambient temperatures for instance.

As a recent poll here at the forum showed ... the vast majority of drone flyers classify them self as "Photographers that happens to have a camera on a drone" ... and it's very few that say "I'm a pilot of a drone that happens to have a camera". This makes the battery, in peoples mind, the same as all other stuff, ND filters, beacons, props ... the batteries are just another component that is expected to always work & be prepared for a flight ... that's why DJI marketing them as "charge & forget". And all this leads to ignorance when it comes to one of the most important components that keeps the drone airborne.

As LiPo batteries don't live forever ... how we treat & care, effects in what way they die, either it will be "fast & furious in a disaster" ... or they slowly fade away after several charge cycles & don't quite deliver enough flight time anymore, & gets retired.

I didn't have that thought at all. A LiPo is still a LiPo. I wasn't aware an HV's actually had less life expectancy over a std, thanks for the info. My assumption was it is purely a revenue grab for them but still frustrated that the Fly app doesn't allow for adjustment. I sold my Air2s and hadn't updated firmware or the app from the release date so it was still at 5 days. My solution, charge them to storage voltage after use and to heck with their revenue grab. I have my M2P batteries set to discharge after 1 day, hoping to be able to get the most life out of them as possible sinc ethey aren't available from DJI without also purchasing a FMC. The cost of them across the retail market is increasing so I have been obtaining what I can find as far as low-time used and some new as well. I intend to fly my M2's for many years to come and batteries is one of the requirements for that to be possible.