How to deep discharge batteries

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I need to do a deep discharge of many of my batteries. I was wondering if I put the props on and just let them spin without taking off if this is ok for the motors. I was also thinking of getting a charger that would do this along with charging them.
On the Airdata maintenance log it looks like I need to do this since they have never had it done properly.
Battery Maintenance.jpg
 

BigAl07

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@Skyviewvt WELCOME to our forum :)

Our SOP is to Deep Discharge (like used to be suggested) approximately every 20 or so flights. We do this by flying the aircraft until it hits Critical Low and starts to descend. We then keep the props turning on the aircraft (on the ground) until we hit something below 10%.

This is how WE do it and may not be a process you should try. At this low level of charge if you make a mistake you can RUIN your batteries in a just a moment.
 
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I know i can do this by flying it. My question is can I just power it up and let the motors spin while monitoring the power? I don't see how this would hurt the motors but i am asking if anyone knows if it will. I am in Vermont and the weather has been pretty bad lately and I thought this would be something I could do while waiting for good weather or more work.
 

Meta4

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I know i can do this by flying it. My question is can I just power it up and let the motors spin while monitoring the power? I don't see how this would hurt the motors but i am asking if anyone knows if it will. I am in Vermont and the weather has been pretty bad lately and I thought this would be something I could do while waiting for good weather or more work.
I would question the need to deep discharge the battery at all.
Most flyers never do that and have no problem.
Have you found anything in your aircraft manual that says it's necessary?
 
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BigAl07

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No I have not seen anything in the manuel.


It's a good idea to follow the manual as if you don't you could be out of luck should you have a warranty claim.
 

msinger

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@BigAl07, any idea why your SOP is to deep discharge the batteries? Are you somehow benefiting from this procedure?
 

BigAl07

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@BigAl07, any idea why your SOP is to deep discharge the batteries? Are you somehow benefiting from this procedure?

We started doing this back when the DJI manual suggested it and it was "good practice" from Old School ways. I can tell you this much,the batteries seem to maintain their "Health" very well compared to others we've seen. Granted this could be more from "Gentle Care" compared to "Hard & Rough" care but it works for us.
 
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Forget deep discharging- it is unecessary and only puts charge cycles on your packs you could be flying with.

The currently implemented battery management SOC does not require deep discharging for fuel gauging calibration, battery health measurements are performed in real time during charge and discharge, including internal resistance measurement.

The only exception to this might’ve if your cells are significantly out of balance however any improvement you might realise will be short lived.
 
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My concern of running the AC to discharge the battery is cell reversal. As the DJI batteries are " smart" I am sure this might be unfounded. I have extensive experience with "real aircraft" NiCad battery servicing. We discharged to Zero V and charged/discharged 3 times. I feel discharging a LiPo DJI battery to 30% should suffice (maybe cycle 3x). If not sufficient maybe time to replace the battery. At only $150 I'd replace the battery
 
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So do you have an answer to my question. I realize i need to do maintenance on them.
Yes, you can discharge by just letting the motors run, but if you have a way to go to the target minimum 8% mark, I would suggest going outside, taking off and hovering at about 1' AGL until about 11 or 12% capacity. You might need to cancel the RTH to achieve this. At 11 or 12%, land then let the rotors run to discharge further. I found that the battery continues to discharge after landing. Must be because of the massive power load in flight so be careful to land well before you hit the target minimum.

The manual says leave the aircraft on "until there is less than 8%", but many people say not to discharge past 8% or your batteries will be ruined. Who is correct? I'll go with the manual and, in fact, I have accidentally allowed mine to get as low as 6% as a result of hovering too long during a deep discharge. I'm not recommending it, but it doesn't seem to have affected battery performance.

HIH
 
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Yes, you can discharge by just letting the motors run, but if you have a way to go to the target minimum 8% mark, I would suggest going outside, taking off and hovering at about 1' AGL until about 11 or 12% capacity. You might need to cancel the RTH to achieve this. At 11 or 12%, land then let the rotors run to discharge further. I found that the battery continues to discharge after landing. Must be because of the massive power load in flight so be careful to land well before you hit the target minimum.

The manual says leave the aircraft on "until there is less than 8%", but many people say not to discharge past 8% or your batteries will be ruined. Who is correct? I'll go with the manual and, in fact, I have accidentally allowed mine to get as low as 6% as a result of hovering too long during a deep discharge. I'm not recommending it, but it doesn't seem to have affected battery performance.

HIH
Thanks for your input. This is what I was waiting to hear. I have been using Nicad batteries for a long time and after charging them the charger gives a trickle charge until I use them again. I do know that their is a certain bit of maintenance they have to have and that is why I posted the questions.
 
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Contact Alex on this website link below and you'll have the very best in Phantom or Mavic battery maintenance. I've been using this device for more than a year now and I've never, ever had any issues with my batteries.

Phantom Angel

Bud


I have never left them go below 20%. All cells on my 4 batteries are equal.
 
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Best info I have is that only NiCd and NiMh batteries need or benefit from a deep discharge. Li-Ion and Li-Po batteries not only don't benefit but it harms them, reduces the total charges life and potentially ruins them if you go too low.
 
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All I can tell you is that Alex, the gentleman that builds the Phantom Angel units is technical genius when it comes to batteries and after more than a year using them they haven't harmed my batteries one iota. Not even an imbalance in any cell of any of my 8 batteries in over 30 charges on the Mavics, and 26 charges so far on my Phantom batteries. Four Mavis Pro batteries and four Phantom 4 Pro batteries.

I believe they've enhanced the life of my batteries and I'll keep on using them. Oh, and I use the Phantom Angels to discharge all my batteries that still have a charge in them after a flying session.

Thanks for your reply though, and I hope your batteries last a long time also.

Bud

Best info I have is that only NiCd and NiMh batteries need or benefit from a deep discharge. Li-Ion and Li-Po batteries not only don't benefit but it harms them, reduces the total charges life and potentially ruins them if you go too low.
 
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I dont ever deep discharge that way. Never have never will, never had a problem. Owned most of the dji line up. Used to caring for my bigger rc heli lipo's 600/ 700 size heli's always followed the 80/20 rule... served me well. Dji's way of deep discharging a lipo makes me cringe. If i did that to one of my 6s 5000 mah 70c lipos it would be toast along with my money...anyways my dji lipos are doing well so dont think this "deep discharge shananigans" is really needed.... I don't know how the Smartboard works but I just would never do that to a lipo
 
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Thanks for your input. This is what I was waiting to hear. I have been using Nicad batteries for a long time and after charging them the charger gives a trickle charge until I use them again. I do know that their is a certain bit of maintenance they have to have and that is why I posted the questions.
Just to be clear, P4 batteries are LiPo and they need some special treatment to get the best life span from them. They can be quite dangerous if they are badly treated and can pose quite a fire hazard if they become defective for some reason. I have no experience of problems but there are some horror stories floating around and even a video on YT as I recall. I always charge batteries the day before a flight and store the fully loaded batteries in ammo cans, just to be on the safe side.

The main things to watch out for are visible damage, swelling or contact with water. The LiPo chemicals react violently in contact with water.

This guy is quite a good source of info about many things DJI:
 

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