Manually Discharging Batteries

[Wave Reflections]

Has anyone come up with a way to manually discharge a Mavic 3 battery without flying it? If I charge all 3 batteries for a shoot and come back with one or two still fully charged, I'd like to bring them down to ~50% or so for storage until the next flight. I understand that there is a built-in mechanism to discharge to a safe level when not in use for a period of time - just curious!

When I had my Inspire 1, someone had come up with a DIY solution to discharge the batteries using the rig pictured.



Thanks!

 

[BlairAir]

This is an important issue. I have 5 batteries, but I usually can't predict how many I will deplete on a given outing. I would also like a method to quickly get batteries to "storage" level of charge.

From observation, I see the 4c Mavic 3 battery discarging to 96% after several days. After which I don't see any additional discharge. To be fair, I rarely go more than 3 or 4 days without flying again and cycling through the set. I doubt there is additional cycles, at a longer interval: perhaps at 10 days? I feel like these cycles could be shorter, though the manufacturer knows a lot more than I do, but I certainly have more motivation to improve battery longevity than DJI does since the longer they last, the fewer replacement batteries DJI will sell over time.

Additionally, I would really like to have more control over the discharge process, or at the very least, have some options available.

A certain competitor let's you choose from 1-10 days before the first discharge cycle; and appears to do regular cycles every few days until it's somewhere between 50-60% charged. This is reassuring, particularly at the prices we pay for batteries. DJI would do well to provide similar options, or any options along with "Competitor A" Orange you glad I didn't say that name?

I autel watch myself though, or I'll slip up and then I'm in trouble again.

 

[SkywalkerFeng]

According to DJI, Mavic 3 battery is designed to automatically discharge to 96% after being fully charged for 3 days. It then discharge to 60% after 9 days of no operation.

DJI GO4 allows pilots to set a time between 1-10 days, for the battery to start self-discharge down to 60%. Unfortunately this option is never implemented for the notorious FLY app. We needs to ask DJI to add this option back.

 

[UAVquadman]

I charge my batteries to 60% if I know I will not be flying within 24 hours max. I invented a discharger for Nicad batteries using a relay, etc...

 

[ianwood]

Agree that a manual setting is best, like with GO4. All my Inspire 2 batteries begin slowly discharging after 3 days and settle somewhere around 3.9V per cell which is fine.

 

[UAVquadman]

Agree that a manual setting is best, like with GO4. All my Inspire 2 batteries begin slowly discharging after 3 days and settle somewhere around 3.9V per cell which is fine.

3 days? not a good practice if you want the best lifespan.

 

[Meta4]

3 days? not a good practice if you want the best lifespan.

If you didn't use the battery today, but might tomorrow or the day after, three could be the best option.
Don't like 3 days?
Pick a number from 1-10 for whatever suits your situation.

 

[UAVquadman]

If you didn't use the battery today, but might tomorrow or the day after, three could be the best option.
Don't like 3 days?
Pick a number from 1-10 for whatever suits your situation.

how long does it take for the battery to go from 100% to 60% once the discharge has started? and if the battery is at 10 to 20% after the flight is done.... it would be stupid to charge it to 100% knowing you will not use the battery in a day or two if you can help it! right? AND..... how much stress does it put on the battery when it's discharging on its own? I wonder what resister is used and if it fails, is the battery no longer usable. Not a good practice one would think versus charging it to 50 to 60% instead of 100% knowing you will not use the battery soon.

 

[ianwood]

how long does it take for the battery to go from 100% to 60% once the discharge has started? and if the battery is at 10 to 20% after the flight is done.... it would be stupid to charge it to 100% knowing you will not use the battery in a day or two if you can help it! right? AND..... how much stress does it put on the battery when it's discharging on its own? I wonder what resister is used and if it fails, is the battery no longer usable. Not a good practice one would think versus charging it to 50 to 60% instead of 100% knowing you will not use the battery soon.

Depends on your priorities. If you're serious about filming, you always aim to have more than what you need, just in case. When we go on set, we always charge enough batteries upfront to maintain a continuous rotation with whatever charging solution we plan to use. So we usually return with several sets unused.

Technically speaking, the discharge process puts zero stress on the battery. It's a trickle. And cycle count is far less important than time spent fully depleted or fully charged. The longer the time fully charged/depleted, the more the chemical construction changes and alters the ability of the battery to maintain high amp output.

Setting my TB50s to 3 days discharge has kept them healthy. Some are going on 6 years old with plenty of use.

 

[Meta4]

how long does it take for the battery to go from 100% to 60% once the discharge has started?

It takes around two days to discharge the battery to 65%

and if the battery is at 10 to 20% after the flight is done.... it would be stupid to charge it to 100% knowing you will not use the battery in a day or two if you can help it! right?

That's why experienced users only recharge to around 50% and top up before flying again.

 

[UAVquadman]

It takes around two days to discharge the battery to 65%

That's why experienced users only recharge to around 50% and top up before flying agthanks!

Depends on your priorities. If you're serious about filming, you always aim to have more than what you need, just in case. When we go on set, we always charge enough batteries upfront to maintain a continuous rotation with whatever charging solution we plan to use. So we usually return with several sets unused.

Technically speaking, the discharge process puts zero stress on the battery. It's a trickle. And cycle count is far less important than time spent fully depleted or fully charged. The longer the time fully charged/depleted, the more the chemical construction changes and alters the ability of the battery to maintain high amp output.

Setting my TB50s to 3 days discharge has kept them healthy. Some are going on 6 years old with plenty of use.

I wonder when you should stop using them. I have 4 Mavic 2 Pro/Zoom batteries between 350 and 400 charges that I have retired. I would think 400 would be the max but only if you take good care of them. I wonder how bad it is to always use them down to 10% remaining power. Something I don't like to do but I end up doing it so often because of all the action where I fly most of the time.

 

[GadgetGuy]

I wonder when you should stop using them. I have 4 Mavic 2 Pro/Zoom batteries between 350 and 400 charges that I have retired. I would think 400 would be the max but only if you take good care of them. I wonder how bad it is to always use them down to 10% remaining power. Something I don't like to do but I end up doing it so often because of all the action where I fly most of the time.

An upgrade to the M3 will give you 10 minutes more per battery, but if all the action continues, you'll just run them down to 10%, too, like I always do! I can always find something else interesting down to 10%, no matter the flight time!

 

[UAVquadman]

An upgrade to the M3 will give you 10 minutes more per battery, but if all the action continues, you'll just run them down to 10%, too, like I always do! I can always find something else interesting down to 10%, no matter the flight time!

same here except when it starts raining!

 

[ianwood]

Percentages are tricky as they may not represent what's actually happening with the battery. But since the Mavic 3 doesn't give you voltage, I would say 10% is very low and will shorten the overall life of the battery if you hit 10% regularly. It is better to land, swap in a new battery than to run batteries down that low regularly.

It also risks serious sagging as the battery gets older. Sagging can cause voltage to drop quickly to a point where the drone is at risk of not being able to fly.

On all other platforms, I watch the voltage. As soon as the voltage gets below 3.57 per cell under load, you are playing with "the cliff" where the voltage will drop much more quickly. As soon as it hits 3.6V per cell, I bring it in to land.

3.6V is likely somewhere between 20% and 30% but depends on C rating and current. Mavic 3 has such long battery life, I am almost always done by 30%.

 

[GadgetGuy]

same here except when it starts raining!

I'm sure @Phantomrain.org has a solution for that!
Coal?

 

[GadgetGuy]

Percentages are tricky as they may not represent what's actually happening with the battery. But since the Mavic 3 doesn't give you voltage, I would say 10% is very low and will shorten the overall life of the battery if you hit 10% regularly. It is better to land, swap in a new battery than to run batteries down that low regularly.

It also risks serious sagging as the battery gets older. Sagging can cause voltage to drop quickly to a point where the drone is at risk of not being able to fly.

On all other platforms, I watch the voltage. As soon as the voltage gets below 3.57 per cell under load, you are playing with "the cliff" where the voltage will drop much more quickly. As soon as it hits 3.6V per cell, I bring it in to land.

3.6V is likely somewhere between 20% and 30% but depends on C rating and current. Mavic 3 has such long battery life, I am almost always done by 30%.

View attachment 148395

Percentages are indeed tricky. DJI's 0% now still leaves two minutes of flight time in the tank. Mavic 3 does always display all cell voltages in the Fly app under Safety/Battery, and I carefully screenshot the individual voltages after landing, after first screenshotting the remaining battery, so I, too, am tracking the cell voltages religiously, but not under load. For a frame of reference, 3% remaining battery is still 3.65V per cell, as displayed in the Fly app. 10% remaining is well above that. Under load values will understandably be lower than that, but not dangerously so. The M2P displays voltage on the main screen under load in Go 4, and won't drop below 3.5V per cell until well below 0% remaining. M3 is likely very similar, but I will now start checking the M3 under load for comparison.

 

[UAVquadman]

Percentages are indeed tricky. DJI's 0% now still leaves two minutes of flight time in the tank. Mavic 3 does always display all cell voltages in the Fly app under Safety/Battery, and I carefully screenshot the individual voltages after landing, after first screenshotting the remaining battery, so I, too, am tracking the cell voltages religiously, but not under load. For a frame of reference, 3% remaining battery is still 3.65V per cell, as displayed in the Fly app. 10% remaining is well above that. Under load values will understandably be lower than that, but not dangerously so. The M2P displays voltage on the main screen under load in Go 4, and won't drop below 3.5V per cell until well below 0% remaining. M3 is likely very similar, but I will now start checking the M3 under load for comparison.

The Mavic 2 Battery will not take a charge at times if you let it drain until it shuts off on it's own. Happened to me when I couldn't make it home in the wind and was about 20 feet above the ground when the power was to low for it to fly anymore and just crashed before I could land the drone. I fly over the ocean 99% of the time so I can't just set the drone down anywhere!

 

[GadgetGuy]

The Mavic 2 Battery will not take a charge at times if you let it drain until it shuts off on it's own. Happened to me when I couldn't make it home in the wind and was about 20 feet above the ground when the power was to low for it to fly anymore and just crashed before I could land the drone. I fly over the ocean 99% of the time so I can't just set the drone down anywhere!

Correct. Once the voltage of any cell drops below 3.0V, the battery will shut off in midair in flight, and is then most likely damaged beyond repair, even if it survives the crash. The statement above that the M2P can be flown for two minutes past 0% remaining is solely to recover the aircraft, where landing short isn't feasible, such as over water. If you end up pushing it to complete exhaustion, the battery will be toast. Anything less than two minutes past 0%, where it can still maintain flight (the less the better!), the battery will survive, and take a charge. It will, however, reduce future maximum flight times, by 5% or so (losing 1-2 minutes on the M2P). Use those extra two minutes past 0% only in an emergency. My goal is always to land between 5% and 10%, which still gives me a margin of safety, should I encounter unexpected headwinds on the return, or run into a GEO glitch that prevents returning to the launch point! My batteries are an item of consumption, and when flight times start degrading sufficiently, I buy new batteries for the initial flights, and save the degraded ones for additional flights.

 

[ianwood]

Anything below 3.5V under load is playing with fire. It ages the battery quickly and once you've done it enough times, your battery's voltage will sag when you don't expect it.

 

[UAVquadman]

Percentages are tricky as they may not represent what's actually happening with the battery. But since the Mavic 3 doesn't give you voltage, I would say 10% is very low and will shorten the overall life of the battery if you hit 10% regularly. It is better to land, swap in a new battery than to run batteries down that low regularly.

It also risks serious sagging as the battery gets older. Sagging can cause voltage to drop quickly to a point where the drone is at risk of not being able to fly.

On all other platforms, I watch the voltage. As soon as the voltage gets below 3.57 per cell under load, you are playing with "the cliff" where the voltage will drop much more quickly. As soon as it hits 3.6V per cell, I bring it in to land.

3.6V is likely somewhere between 20% and 30% but depends on C rating and current. Mavic 3 has such long battery life, I am almost always done by 30%.

View attachment 148395

I

Correct. Once the voltage of any cell drops below 3.0V, the battery will shut off in midair in flight, and is then most likely damaged beyond repair, even if it survives the crash. The statement above that the M2P can be flown for two minutes past 0% remaining is solely to recover the aircraft, where landing short isn't feasible, such as over water. If you end up pushing it to complete exhaustion, the battery will be toast. Anything less than two minutes past 0%, where it can still maintain flight (the less the better!), the battery will survive, and take a charge. It will, however, reduce future maximum flight times, by 5% or so (losing 1-2 minutes on the M2P). Use those extra two minutes past 0% only in an emergency. My goal is always to land between 5% and 10%, which still gives me a margin of safety, should I encounter unexpected headwinds on the return, or run into a GEO glitch that prevents returning to the launch point! My batteries are an item of consumption, and when flight times start degrading sufficiently, I buy new batteries for the initial flights, and save the degraded ones for additional flights.

I flew past the point I decided to make the emergency landing but the wind was too strong to make any forward motion... lesson learned to set her down and not chance it. So I turned around and flew with the wind and was seconds from making a successful landing but my battery still would had been toast I guess! lol.... in other words.... lucky to even get my drone back because I was over the ocean at 0%!!!! well if I had landed at the same place.... right away my battery would had been fine.... lesson learned after making thousands of drone flights this was a first... well second but not with this drone! lol but the drone landed fine. Air 2s