Battery discharge cycle for 3-month maintenance...down to 10%? 8%? 0%?

[scubaddictions]

All,

Have both a Mavic 2 Pro and a Spark. I've never deliberately fully discharged any of the batteries as outlined in DJI''s guidelines of a "full discharge every three months" and I'd like to rectify that. The problem is (as best as I can tell) DJI doesn't have specific CURRENT details about what the manufacturer considers "fully discharged". I gather in the past DJI had stated for particular models to not go below a certain percent.

When I search now, I only find a lot of forum opinions on the subject. Some saying NEVER take a LiPo battery below 12%, or 10, or 8, etc. Others say run it down gently (non-flying) either until it shows 0% or till it shuts itself off, then recharging fully after it has completely cooled. I've read that even while displaying 0% the modern batteries are hiding a significant reserve so the brief run to 0% does no harm and lets the cell balance and the software re-calibrate measured battery levels.

Is the whole argument just picking nits? Anywhere from 10% to 0% is just fine?

 

[bumper]

This one does all that. A great charger, I prefer it to the one that came with my Mavic 2 P.

https://www.amazon.com/gp/product/B07Y9V4GTR/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

 

[Thomas B]

This one does all that. A great charger, I prefer it to the one that came with my Mavic 2 P.

https://www.amazon.com/gp/product/B07Y9V4GTR/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

Couldn’t agree more. Love mine!

 

[scubaddictions]

Thanks for the recommendations, at the moment I'm not looking for another piece of hardware (especially since it'll only work on one of the two drones I own). I've got the time to run them down gently by leaving them on, just looking for recommendations on the amount to run it down to. Please advise if possible. Thanks!

 

[WithTheBirds]

If the intent is to provide any improvement in the accuracy of the fuel gauging let the AC sit idling until it powers down. That will be 0% reported capacity remaining- it is still above min cell voltage where irreversible damage is a likely.

I wouldn’t bother doing it at all unless you have a cell balance issue. All you are doing is throwing away a charge cycle and possibly putting the battery under unnecessary stress.

The battery management algorithms are well beyond simple coulomb counting, changes in cell parameters from new are constantly measured during charge and discharge and factored into the calculation of usable capacity. Accuracy within 1% for the life of the pack can be expected without a deep discharge calibration effort.

It is likely the routine deep discharge is a carry over from earlier recommendations that applied to less advanced fuel gauging schemes.

 

[bumper]

Thanks for the recommendations, at the moment I'm not looking for another piece of hardware (especially since it'll only work on one of the two drones I own). I've got the time to run them down gently by leaving them on, just looking for recommendations on the amount to run it down to. Please advise if possible. Thanks!

The recommendation I've read is to run it down to zero. Without additional hardware, with a programmed discharge function, your option is what, leaving the battery turned on? That won't work, as the battery switches itself off if not used for 20 minutes. Leaving the drone powered on, motors running with no props, has been recommended. Not sure if that will take the battery to zero, but it might - if the drone doesn't protect itself and battery by shutting down before hand. I would not use that method, if for no other reason than it's kluged at best, and why impose additional, non flight time, wear and tear on the drone?

Also, I'm not gonna sit wait and watch a battery being discharged to zero, I'd rather sit and watch railroad tracks rust. The previously recommended charger is $55 with shipping. Has 3 modes. Charges up to 4 batteries at once (when a battery nears full charge, the charge rate drops and continues slowly to function as a cell equalizing charge). Charges or discharges batteries, as needed to take them to 50% for storage. And discharges batteries to zero for the periodic recommended full discharge. All done automatically, while a digital display shows status, voltage and current for each battery.

As to whether or not to fully discharge batteries, see the last line on page 5 here:
https://dl.djicdn.com/downloads/Mav...igent_Flight_Battery_Safety_Guidelines_EN.pdf

 

[Jeff A]

This one does all that. A great charger, I prefer it to the one that came with my Mavic 2 P.

https://www.amazon.com/gp/product/B07Y9V4GTR/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

I have one of these as well. Getting to like it a lot. What do you guys who use this charger discharge to for the Deep Cycle Event?

 

[Jeff A]

<SNIP>
As to whether or not to fully discharge batteries, see the last line on page 5 here:
https://dl.djicdn.com/downloads/Mav...igent_Flight_Battery_Safety_Guidelines_EN.pdf

It says Printed in China. What am I missing?

 

[bumper]

It says Printed in China. What am I missing?

Scroll up to look at the last line of text . . . it's labeled page 4 (for some reason it says page 5 at the top of the screen on my computer).

 

[Thomas B]

Here is the pertinent text on batteries....

 

[Heijst]

The recommendation I've read is to run it down to zero. Without additional hardware, with a programmed discharge function, your option is what, leaving the battery turned on? That won't work, as the battery switches itself off if not used for 20 minutes. Leaving the drone powered on, motors running with no props, has been recommended. Not sure if that will take the battery to zero, but it might - if the drone doesn't protect itself and battery by shutting down before hand. I would not use that method, if for no other reason than it's kluged at best, and why impose additional, non flight time, wear and tear on the drone?

Also, I'm not gonna sit wait and watch a battery being discharged to zero, I'd rather sit and watch railroad tracks rust. The previously recommended charger is $55 with shipping. Has 3 modes. Charges up to 4 batteries at once (when a battery nears full charge, the charge rate drops and continues slowly to function as a cell equalizing charge). Charges or discharges batteries, as needed to take them to 50% for storage. And discharges batteries to zero for the periodic recommended full discharge. All done automatically, while a digital display shows status, voltage and current for each battery.

As to whether or not to fully discharge batteries, see the last line on page 5 here:
https://dl.djicdn.com/downloads/Mav...igent_Flight_Battery_Safety_Guidelines_EN.pdf

I use this (DJI approved) charger for my mavic Air.
Far more convenient than the original DJI charger.
I am 100% satisfied!

 

[Kilrah]

I wouldn’t bother doing it at all unless you have a cell balance issue. All you are doing is throwing away a charge cycle and possibly putting the battery under unnecessary stress.

The battery management algorithms are well beyond simple coulomb counting, changes in cell parameters from new are constantly measured during charge and discharge and factored into the calculation of usable capacity. Accuracy within 1% for the life of the pack can be expected without a deep discharge calibration effort.

That is not what the multiple cases of "battery fell from 50% to 0% in a second" events suggest.
Granted it seems to be less frequent with the newer models but it was a well known occurrence with the MP.

Still better do a preventive calibration cycle when the batteries have been sitting unused several months that find out about it in flight.

 

[WithTheBirds]

That is not what the multiple cases of "battery fell from 50% to 0% in a second" events suggest.
Granted it seems to be less frequent with the newer models but it was a well known occurrence with the MP.

Still better do a preventive calibration cycle when the batteries have been sitting unused several months that find out about it in flight.

It seems the notable failures (cell collapse shortly after launch) have been with packs that have commenced auto discharge. Auto discharge switches in the resistors used to balance during charge and, given they vary slightly in value and load the cells individually they will, in most cases, take the cells down to slightly different voltages. Starting a flight with a battery in this condition is obviously a bad idea.

If you look at the Texas Instruments white papers on impedance track and gas gauging it is clear why the now dated procedure of having to do a calibration deep discharge isn’t of any significant benefit with our current flight packs.

 

[Jeff A]

The fact that we are having this discussion at all indicates that DJI has not given us a definitive procedure for discharging our batteries. There is too much conflicting information floating around.

 

[sar104]

The fact that we are having this discussion at all indicates that DJI has not given us a definitive procedure for discharging our batteries. There is too much conflicting information floating around.

There is conflicting information from DJI?

 

[Squire330]

I treat my MM batteries just like I do my lithium-powered car, my lithium-powered tools, my lithium-powered RC aircraft and my lithium-powered robovacuum - I use them and recharge. I trust the makers to program their products to work without me having to constantly worry about if I’m doing everything to prolong the life of their batteries. Are the batteries really at 100% when they quit charging? I doubt it - the maker knows it’s best not to. I quit using a battery when I get a low voltage warning, as with the MM, or it quits, as my cordless drill or leaf blower does. My biggest investment is my car. I charge my Chevy Bolt to 100% when it gets to around 25%, or if I want it full for a longer trip the next day. There is nothing in the owner’s manual about not charging to 100% or periodically discharging to a specific level. Chevy doesn’t want to have to replace a multi-thousand dollar battery under warranty, so it makes sense they set every parameter to make sure, regardless of how the consumer treats it, the battery will last as long as possible. So if you want to get down in the weeds, create a spreadsheet, and develop a charge/usage matrix on each battery, more power to you. Me, I’m just going to fly, rotate my three batteries, charge them when they’re low, and have fun.

 

[Elude]

I store my battery at 50% for long-term storage.

 

[Kilrah]

Auto discharge switches in the resistors used to balance during charge and, given they vary slightly in value and load the cells individually they will, in most cases, take the cells down to slightly different voltages.

This makes no sense, as you mentioned yourself the point of these is balancing, so it would be very stupid if the discharge process didn't take care of also balancing if needed.

 

[WithTheBirds]

This makes no sense, as you mentioned yourself the point of these is balancing, so it would be very stupid if the discharge process didn't take care of also balancing if needed.

Stupid or not that is how it works. During charging the balance resistors are switched in to bleed off the higher voltage cell(s), as is the case for pretty much all LiION charging schemes for series connected cells. There is no attempt to balance cells during auto discharge.

 

[GadgetGuy]

Stupid or not that is how it works. During charging the balance resistors are switched in to bleed off the higher voltage cell(s), as is the case for pretty much all LiION charging schemes for series connected cells. There is no attempt to balance cells during auto discharge.

Therein lies the biggest risk when flying with partially auto-discharged batteries. The cell voltage discrepancies can produce unpredictable results under load. Topping off before flight, if it will allow you to (newer batteries like the M2 and P4 batteries can't be topped off to 100% unless below 97%), or setting a longer auto-discharge time period you know you have not exceeded, protects you from flying with unbalanced cells.