DJI Cold weather Info FW 1.6

[Droider]

Thank you for the valued comments. Seeing yellow is bad enough but seeing red “cells” is very bad. Please be careful! There will be hysteresis build in but red have to be very close to disconnect; your charge-up rate for cold weather should take to the account the extra battery cost that you definitely will incur.

FYI – the profiles that I published are for 6800 mAh battery cell but the 1100 mAh lesser capacity (6800 - 5700 mAh = 1100 mAh) would only marginally change the profiles and in absence of having the actual DJI profiles they are good for the explonation.

There is another way to explain: the temp profile applicable to the idling I1 current drain will be close to the C/2 (5700mAh/2 = ~2.85 A) and as soon you pull the power slowly at least 1C current will be drained (5700mAh/1= 5.7 A) and the Vol will drop to the lower level represented by the -30degC profile. The moment you will do sharp/quick manoeuvre a 2C (2x5700mAh = 11.4 A) will be drained for the duration of the manoeuver (red flashing) and the Vol will drop to the lower level represented by the -40degC profile > and if you keep it for long enough the battery cell or battery pack (or both) protection will activate …. So, be careful over your Scottish winter. DJI should really issue a white paper with all proper points that they must have as all of the above “is elementary” and was/is part of their battery pack design work. BTW I would NOT use the TB47 (4500mAh) battery in a cold temp environment.

Quality work there Waldermar54. Are there 6800 packs available? My issue is I have to fly to where I will be going and am limited to the 4500 packs unless I freight the bigger ones in advance which is possible but just another factor to go wrong!

 

[Scotflieger]

Thats what I started the thread with. Its says nothing what so ever about trigger point temps or just what happens like limp mode or motor shut down

I would not expect to get anymore information from DJI. If I am unsure of something I believe in doing my own testing to establish for myself what the limits and issues are. But that is the engineer in me...

 

[Waldemar54]

DJI is starting to open up.

My comments and interpretation of what they saying.

“ DJI: In extreme cases, a battery could drain below 3V, causing reduced thrust or even battery shutoff due to over-discharge protection systems designed to keep your battery healthy” > So that is definite acknowledgment that they will allow for I1 to drop in order to keep the battery healthy! But the battery will drop with I1 so it will expire anyway.
In my view it would be better in a emergency to allow for the battery to be damaged and the system should be designed to keep I1 healthy at all costs. The damaged battery in turn can be permanently disabled to protect the user from himself and ultimately the I1.

Hot Tips for Beating the Cold

1. Make sure batteries are fully charged before each flight. > No comments required.


2. Warm batteries to 25°C or more before flight. We recommend using a battery heater. > The battery heater will definitely heat-up all the cells, including the inner cells by making a current to flow but that is at an expense of the battery capacity = fly time; an extreme measure in my view.

Quick external heat will only warm the external cells however making a 30degC portable oven powered by 12V that the battery packs can be stored for say 3hrs or more before flying would be best; I think I would build myself and portable oven.


3. Hover the aircraft for around a minute to allow the battery to warm up. > That is basically using I1 as a battery heater; again extreme and costly but definitely very sound if none of other means are available.


4. Turn on “Show Voltage on Main Screen" on the "Aircraft Battery" page of the DJI Go app. > That is a must and that how I noticed one damaged cell of brand new battery pack that was replaced. That is especially important for few initial cycles.

“DJI: Do not continue flying if battery voltage drops below 3.2V” > there is most likely 0.6V margin so that makes the disconnect point 3.2V–0.6V=2.6V and for a good balanced battery pack that is 2.6V * 6 = 15.6V. It all follows the generic profiles.

 

[eldorado]

Hot Tips for Beating the Cold

1. Make sure batteries are fully charged before each flight. > No comments required.


2. Warm batteries to 25°C or more before flight. We recommend using a battery heater. > The battery heater will definitely heat-up all the cells, including the inner cells by making a current to flow but that is at an expense of the battery capacity = fly time; an extreme measure in my view.

Quick external heat will only warm the external cells however making a 30degC portable oven powered by 12V that the battery packs can be stored for say 3hrs or more before flying would be best; I think I would build myself and portable oven.


3. Hover the aircraft for around a minute to allow the battery to warm up. > That is basically using I1 as a battery heater; again extreme and costly but definitely very sound if none of other means are available.


4. Turn on “Show Voltage on Main Screen" on the "Aircraft Battery" page of the DJI Go app. > That is a must and that how I noticed one damaged cell of brand new battery pack that was replaced. That is especially important for few initial cycles.

“DJI: Do not continue flying if battery voltage drops below 3.2V” > there is most likely 0.6V margin so that makes the disconnect point 3.2V–0.6V=2.6V and for a good balanced battery pack that is 2.6V * 6 = 15.6V. It all follows the generic profiles.

Excellent!
Thank you for summing up the Cold Weather Flight manual!
For an oven–an insulated picnic bag with Hot Packs-Hot/water bottles works well if you are not out side for more than an hour or two. You have to work fast loading in the new batt as the temp can drop quickly. Especially if you need to calibrate the compass! So best to have a very tight SOP/checklist for take offs.
The warm-up hover is very valuable to test out the control links and overall performance.

 

[eldorado]

I agree DJI should publish ALL the changes that their firmware imposes, however the problem is lack of information from them and with pilot SOPs as we learn to fly in winter.
A cold battery doesn't have the same performance as a warm one. As others have noted a LiPo will degrade to useless in cold temps.

I flew yesterday in -2.5ºC on 1.6 firmware.

I kept the batteries in a warm insulated bag that was at 20ºC. The battery cooled to 16ºC before I had the AC started up. I took off to 2m and performed a quick rotate CW-CCW and left/right/back/forward check and watched the batt temp and voltage for ~60 sec. The batt (with insulators) quickly got up to 25ºC and all 4 flights were perfect. The biggest problem was keeping the light dusting of fresh snow on the ground from blowing up into the AC on landing ;-) and overcoming the new No Fly Zones I had to register for to take off!

If your battery is cold, say 15ºC, you probably shouldn't fly with it regardless of DJI's settings. Just keep them warm before you fly. Why not a battery vest inside your coat if you want to avoid the battery warmer? I just use a picnic cooler with hand warmers packs and a themometer.

I am waiting to hear back from DJI with my FW 1.6 questions:

1. Is 15ºC the trigger temp?
2. Does the battery reserve calculation change? (ie drop by x% thereby cutting down flight time overall before RTH conditions set in)
3. What is the percentage cut in propulsion performance so I can calculate safe wind conditions? (Standard wind max is 10m/s so what is the new value if the propulsion degrade kicks in?)

I hope this helps a bit.​

Eric, DJI-Support-LA said he'd get back to me via e-mail at the time of this original post, he has not as of today.

 

[Droider]

As so many people on here seem to have contacts at DJI it really surprises me there is no response from them. @eldorado the AC on 1.6 will fly in -2.5ºc no problem, the packs are fine if you keep them warm as has been displayed by DJI flying in the claimed -45ºc its just what happens when there cold weather protection kicks in and WHEN it kicks in. I know the battery parameters now its more what the FC does to protect the battier is and what triggers it. I am guessing its just battery temp over percentage but it would be nice to know from DJI just what the trigger points are.

 

[The Editor]

As so many people on here seem to have contacts at DJI it really surprises me there is no response from them. @eldorado the AC on 1.6 will fly in -2.5ºc no problem, the packs are fine if you keep them warm as has been displayed by DJI flying in the claimed -45ºc its just what happens when there cold weather protection kicks in and WHEN it kicks in. I know the battery parameters now its more what the FC does to protect the battier is and what triggers it. I am guessing its just battery temp over percentage but it would be nice to know from DJI just what the trigger points are.

Just because some individuals have contacts at DJI doesn't mean they actually answer!
In some instances I have waited weeks if not longer to get information out of them. If it is deemed slightly sensitive or something they may not be willing to share, there is a chain of command they have to follow before something can be said.

 

[eldorado]

As so many people on here seem to have contacts at DJI it really surprises me there is no response from them.

"Contacts at DJI" is easy:
+1 (818) 235 0789
http://www.dji.com/support/product/inspire-1

Ask them and they will try to help. However as The Editor mentioned they don't always have the answers (or permission to answer).

 

[Dave Stanton]

No - there appears to be a hard cut off (or non start threshold) of 15 degrees.
Above this the motors will start, below they won't and a warning message appears.
From my testing, once you get down into the 3.3 to 3.4 v per cell territory your throttle is limited to prevent a voltage drop under load into dangerous land!
This on itself is not a bad thing since this is no different to a lipo losing its 'punch' at nearly depleted levels.
Recreational RC fliers have known this for years and you really shouldn't be still up in the air at 3.3v per cell territory in any case.
This is more for the 'out of the box, I've never used a lipo and I dont want to read a manual gang'
It's idiot damage limitation.

Actually, three days ago I attempted to fly at a location here in East Texas. We are experienceingwhat we call "cold" weather here with lows in the upper 20's to low 30's. I did all my checks, compass calibrations, etc., pressed the two sticks down and to the center and got a warning message that the battery was too cold to fly. The motors did not start. I had just taken the fully charged battery out of a warm vehicle. So, I shut the aircraft down, took the battery inside a building for a few minutes and warmed it up. I came back outside and tried again. It still didn't start. I waited a few seconds, tried two more times to start it and finally it did. I flew for about 15 minutes until the battery got to 30%, landed, switched batteries and did not have the problem again even though I used the other batteries that were sitting in the now cold truck. Strange.

 

[The Editor]

Actually, three days ago I attempted to fly at a location here in East Texas. We are experienceingwhat we call "cold" weather here with lows in the upper 20's to low 30's. I did all my checks, compass calibrations, etc., pressed the two sticks down and to the center and got a warning message that the battery was too cold to fly. The motors did not start. I had just taken the fully charged battery out of a warm vehicle. So, I shut the aircraft down, took the battery inside a building for a few minutes and warmed it up. I came back outside and tried again. It still didn't start. I waited a few seconds, tried two more times to start it and finally it did. I flew for about 15 minutes until the battery got to 30%, landed, switched batteries and did not have the problem again even though I used the other batteries that were sitting in the now cold truck. Strange.

If it is confined to that one battery I would say it is more likely a faulty temperature sensor in that particular pack.

 

[eldorado]

Perhaps a view of the battery temp value at startup is very important, especially if possibly below 20ºC (68ºF) to allow for variance? Hopefully the sensors are more accurate than that but if we have to depend on them, best to stay well above?

For me, I try to keep a happy battery on startup near +24ºC (+72ºF) if the prevailing conditions are cooling.

In ºF (upper 20's to low 30's) fits this concern very well!

30ºF = -1ºC, way below the temperature a LiPo needs to perform.

In Fº the minimum safe temp would be = 59ºF for a flight under the new DJI stats?

...or did i figure this wrong?

 

[CCTPREZ]

I've been using the hand/foot warmers that go in your gloves/socks. They have double sided tape, and I use 3 of them around the outside of battery while flying. They do get start cooling off after about 15-minutes, but they're cheap, and keep the INSULATED battery temp at about 55-F +/-. Also note, that when its that cold, I'm usually flying from inside my vehicle with my other batteries sitting up on the dashboard defroster to have a good warm start. I figure by the time the warmers start cooling off, the batteries are maintaining a descent temp from flying anyway. I've not seen them at less than 53-F after landing, and that was when temp outside was +9-F AGL filming snowboarders.

Just my opinion, doesn't look great close up, but you can barely tell when it's up in the air.

 

[Mad_angler1]

Perhaps a view of the battery temp value at startup is very important, especially if possibly below 20ºC (68ºF) to allow for variance? Hopefully the sensors are more accurate than that but if we have to depend on them, best to stay well above?

For me, I try to keep a happy battery on startup near +24ºC (+72ºF) if the prevailing conditions are cooling.

In ºF (upper 20's to low 30's) fits this concern very well!

30ºF = -1ºC, way below the temperature a LiPo needs to perform.

In Fº the minimum safe temp would be = 59ºF for a flight under the new DJI stats?

...or did i figure this wrong?

Something to take into account is most temp sensors are ntc and whilst they are very accurate they take time to give stable readings, sometimes a few minutes to stabilise when you have large temp shifts


Also the sensor is buried rite in the centre of the pack of cells so if the battery is cold soaked it could take far longer for the the heat to reach the middle cells and sensor.

One observation from looking at the layout of the I1 pack along each side is 2 cells. As these 2 cells on each side are on the outside they could loose heat rapidly compared to the rest of the pack , also Blade strike pointed out that as they are up against the metal that surrounds them and this could also act as a heat sink compounding the issue more, as the temp sensor is located in the centre of the pack the temp in the app could look ok but the outer cells could be loosing heat and be begin to sag in voltage.

As the battery is fully exposed this could be a real issue and make sense why DJI released the insulation pads.

In the coldest conditions starting flight with a battery as close to operating temp as possible will make a huge difference and the pack should not loose to much.

Just some thoughts

 

[Waldemar54]

Something to take into account is most temp sensors are ntc and whilst they are very accurate they take time to give stable readings, sometimes a few minutes to stabilise when you have large temp shifts


Also the sensor is buried rite in the centre of the pack of cells so if the battery is cold soaked it could take far longer for the the heat to reach the middle cells and sensor.

One observation from looking at the layout of the I1 pack is its 6S2P setup, along each side is 2 cells. As these 2 cells on each side are on the outside they could loose heat rapidly compared to the rest of the pack , also Blade strike pointed out that as they are up against the metal that surrounds them and this could also act as a heat sink compounding the issue more, as the temp sensor is located in the centre of the pack the temp in the app could look ok but the outer cells could be loosing heat and be begin to sag in voltage.

As the battery is fully exposed this could be a real issue and make sense why DJI released the insulation pads.

In the coldest conditions starting flight with a battery as close to operating temp as possible will make a huge difference and the pack should not loose to much.

Just some thoughts

Hi, Are you sure about the 6S2P configuration? That would be 12 cells!?

 

[Mad_angler1]

Hi, Are you sure about the 6S2P configuration? That would be 12 cells!?

Some more info [emoji106]


These packs are setup in 2 pairs of cells parallel that are in series to 6S configuration the packs are 10c rated. the cells in the TB47 are 8.32wh each compared to the TB48 that are 10.38wh each.

Cells are manufactured by Amperex Technology Limited, ATL are believed to be a major supplier of battery cell to Apple as well as many other tech giants.

 

[Waldemar54]

Some more info [emoji106]


These packs are setup in a 6 Series and 2 Parallel configuration the packs are 10c rated. the cells in the TB47 are 8.32wh each compared to the TB48 that are 10.38wh each.

Cells are manufactured by Amperex Technology Limited, ATL are believed to be a major supplier of battery cell to Apple as well as many other tech giants.

Thank you! That makes all the battery packs mislabelled and that a very last what I would expect to see.

I will pull one apart myself tomorrow to see if they are 6S2P or in deed 2P6S. It looks more like 2P6S.

 

[Mad_angler1]

Thank you! That makes all the battery packs mislabelled and that a very last what I would expect to see.

I will pull one apart myself tomorrow to see if they are 6S2P or in deed 2P6S. It looks more like 2P6S.

Sorry you mean the cells are arranged in pairs then series up then yes.

I was reading what you were saying and agreeing but writing it wrong every time, Sorry My brain was using traditional lipo terminology as 2P6S is uncommon , I edited to correctly reflect as you say.

Sorry my bad , thinking one thing and writing something else.