3 Battery related failsafe settings

BraamMavic · May 9, 2017

Hi Guys,

Background
So after grounding myself for the first week after getting the Mavic to gain knowledge, I started flying this weekend. Love this toy. It really is a giant leap from my Syma x5c and Syma X8HG ( both of which taught me valuable cheap lessons in manual mode).

I'm currently driving out to a harvested crop field on a friend's farm 50km away from me (South Africa) to do my flying as it is far from all the WIFI and other interference of the City. I feel it to be a safe place (apart from the dreaded power lines) to learn about my mavic, test its functions & build my skills. I generally fly very high to make sure I can't hit anything (140m high) and have flown to 1.2km out over this property. Apart from having trouble calibrating the compass & two weird warning messages (auto switch to ATTI mode for 10 seconds despite 20 satellites & a "high wind" warning while the wind was perfectly still) which I will post the log of later in another thread, all is going well

Question

So the way I see it, there are 3 battery related failsafe settings. Is my interpretation correct ?

Low battery alarm. You can set this to 70% if you so wished. It has nothing to do with actual safe battery % left and is there so you can set your own preferred battery level % at which you would like to alerted of its current status. Default is 30 % I think.
Smart RTH. If this setting is activated, the aircraft will constantly automatically determine in flight how much battery power is needed to still make it to the RTH point safely. Thus this Smart RTH alarm / warning could in theory kick in at say 50% battery power if you were for example flying directly away from yourself all the time from the start of the flight.
Critical low battery alarm & auto landing. Default is set at 10% I think and you cannot set it lower than that. If this % is reached (you can set it higher than 10%), the aircraft WILL come down right were it is. You will have position control but it will continuously descend until it touches down.

Is my interpretation correct & are there any remaining failsafe & battery related setting I don't know of yet ?

Regards
Braam

rockydog · May 9, 2017

Regarding point 3 above, you do have the ability to pause the landing until you find a safe spot.

JoostGT3 · May 9, 2017

Only marginally related; be aware that there may be strong electromagnetic interferences around powerlines, messing with both the connection between controller and the bird AND with the compass...

Reigate · May 9, 2017

BraamMavic said:
Hi Guys,

Background
So after grounding myself for the first week after getting the Mavic to gain knowledge, I started flying this weekend. Love this toy. It really is a giant leap from my Syma x5c and Syma X8HG ( both of which taught me valuable cheap lessons in manual mode).

I'm currently driving out to a harvested crop field on a friend's farm 50km away from me (South Africa) to do my flying as it is far from all the WIFI and other interference of the City. I feel it to be a safe place (apart from the dreaded power lines) to learn about my mavic, test its functions & build my skills. I generally fly very high to make sure I can't hit anything (140m high) and have flown to 1.2km out over this property. Apart from having trouble calibrating the compass & two weird warning messages (auto switch to ATTI mode for 10 seconds despite 20 satellites & a "high wind" warning while the wind was perfectly still) which I will post the log of later in another thread, all is going well

Question

So the way I see it, there are 3 battery related failsafe settings. Is my interpretation correct ?

Low battery alarm. You can set this to 70% if you so wished. It has nothing to do with actual safe battery % left and is there so you can set your own preferred battery level % at which you would like to alerted of its current status. Default is 30 % I think.

Smart RTH. If this setting is activated, the aircraft will constantly automatically determine in flight how much battery power is needed to still make it to the RTH point safely. Thus this Smart RTH alarm / warning could in theory kick in at say 50% battery power if you were for example flying directly away from yourself all the time from the start of the flight.

Critical low battery alarm & auto landing. Default is set at 10% I think and you cannot set it lower than that. If this % is reached (you can set it higher than 10%), the aircraft WILL come down right were it is. You will have position control but it will continuously descend until it touches down.

Is my interpretation correct & are there any remaining failsafe & battery related setting I don't know of yet ?

Regards
Braam

My understanding and not very clear from the supplied manual: The two manual settings which are the two white dots on the horizontal flight time display only reflect the low battery and critical battery warnings and nothing else. The H icon is the point where the Mavic THINKS it can safely return home but can be inaccurate based upon the impact of wind velocity on the ground speed home. The misunderstood one is the red bar at the end which is where it will initiate an immediate landing. It appears to be set at 10% but is actually dynamic and will increase if you fly high to reflect the increased time and power required to land vertically.

BraamMavic · May 10, 2017

Thanks @rockydog & @Reigate. Didn't realise the pause option was functional during a critically low battery descend. The horizontal line is also something I haven't payed much attention too up to now - have just been paying attention to the distance & height vs battery.

@JoostGT3 - Thanks for your valued input. I will post a seperate thread with the log tonight. Some food for thought in the interim :

Also Read: Overhead power lines | EMFs.info.

I was flying around 140m high & my calibration was done at least 100m from the power lines so I'd be surprised if the lines actually had an affect. More on this in the "to be created" thread.

NPuter · May 10, 2017

Reigate said:
My understanding and not very clear from the supplied manual: The two manual settings which are the two white dots on the horizontal flight time display only reflect the low battery and critical battery warnings and nothing else. The H icon is the point where the Mavic THINKS it can safely return home but can be inaccurate based upon the impact of wind velocity on the ground speed home. The misunderstood one is the red bar at the end which is where it will initiate an immediate landing. It appears to be set at 10% but is actually dynamic and will increase if you fly high to reflect the increased time and power required to land vertically.

This is how I interpret it as well. As you stated, the manual does not make this clear

JoostGT3 · May 10, 2017

Thanks man. I have a buddy who works for an electricity firm and every time we get to talk about my mavic, he mentions that his company uses two big professional drones to inspect power lines. I'll have a chat with him about those and the provisions that were taken to take into account the EM interference.

LINK

JAREOP2017 · May 10, 2017

1. Low battery alarm setting - alarms the pilot that the preset low bat has been reached and gives pilot 10secs to cancel RTH. If not cancelled, AC automatically executes Low Bat RTH. Yes you can set this to any value, even 70% if you don't mind the beeping noise and the extra effort of cancelling the RTH procedure.
2. Smart RTH has nothing to do with battery levels. Smart RTH is activated by pressing the RTH button on the RC or tapping on the RTH icon on the app.
3. If your remaining battery level is just enough to return to HP as calculated by the app, you will be alerted by the app and reminded to start returning. But RTH procedures will not be automatically activated. You have to press RTH button, tap RTH icon or fly home manually.
4. Critical Low Bat alarm - when reached, pilot will be alerted by app, then AC will start descending at current location. You can pause the AC from descending by pushing throttle stick all the way up. Then you can use positioning sticks to move AC to safe landing spot. When you release throttle stick, AC will continue to descend.

Logger · May 11, 2017

JAREOP2017 said:
1. Low battery alarm setting - alarms the pilot that the preset low bat has been reached and gives pilot 10secs to cancel RTH. If not cancelled, AC automatically executes Low Bat RTH. Yes you can set this to any value, even 70% if you don't mind the beeping noise and the extra effort of cancelling the RTH procedure.
2. Smart RTH has nothing to do with battery levels. Smart RTH is activated by pressing the RTH button on the RC or tapping on the RTH icon on the app.
3. If your remaining battery level is just enough to return to HP as calculated by the app, you will be alerted by the app and reminded to start returning. But RTH procedures will not be automatically activated. You have to press RTH button, tap RTH icon or fly home manually.
4. Critical Low Bat alarm - when reached, pilot will be alerted by app, then AC will start descending at current location. You can pause the AC from descending by pushing throttle stick all the way up. Then you can use positioning sticks to move AC to safe landing spot. When you release throttle stick, AC will continue to descend.

If you believe smart RTH has nothing to do with the battery , you might want to take a look at this...

There are two Smart RTH entries in the the DJI app. One relates to obstacle avoidance (android app: advance vision settings > Turn on smart RTH) and the other on both platforms, shown above, relates to Battery remaining.

BraamMavic · May 11, 2017

Logger said:
If you believe smart RTH has nothing to do with the battery , you might want to take a look at this.

...My thoughts exactly Logger. Thanks for clearing that up.

Logger · May 11, 2017

You a welcome.

I will have a crack at correcting some the other erroneous assertions. Happy to stand corrected.

Low battery warning and Critical battery warning have no bearing on when smart RTH will trigger. If enabled, it is dynamically calculated by the firmware as a function of distance from the home point, not taking account any wind effect.

No you cannot set the low battery warning value to 70%. The maximum is 50%.

Low battery warning and Critical battery are audible and visual warnings that are customisable. They do nothing more than warn (or distract) you depending on our POV in flight. Again they have zero effect on RTH battery warnings. However it is co-incidental that the lowest possible user setting for the critical battery warning of 10% also happens to be the minimum setting at which critical battery autoland typically commences. (edit) Critical battery auto-land accounts dynamically for height above take off, so can be higher than 10%.

You are prevented from taking off with your battery level lower than whatever you set your Critical battery warning level at.

So for kicks here is a flight with warnings set as high as possible....

Lets take off

Notice the two white dots in the green battery bar beneath the word Positions representing the two warning levels.

Go check the cows

Shock horror the battery has passed my Low Battery Warning of 50%. Audible Warning, Low Battery Warning at top left. Cows don't even look up.

A bit later I pass the critical battery warning level I set at 45%. Have not fallen out of the sky. But the audible warning is like a siren now and "Critically Low Battery" is in RED. Notice the Yellow H point RTH trigger point is still miles off, safely to the left.

Now I am bored the cows are bored, Mavic is bored and I think I will pack up and go home. Before I do, notice the battery bar turns red under the "a" in the word Critically. That is the level where critical battery autoland commences. Typically 10% but increasing dynamically with altitude.

So I land at 26% battery having not had the Smart battery RTH trigger even though I had maxed out all the warning settings. This of course because I never reached the dynamic yellow H trigger. But I can no longer take off because current battery level is below my user set Critical Battery Warning of 45%.

Set thing back how I like..

Go flying...

The two white dots for the nuisance alarms have moved to the left. The Critical Warning dot coinciding with the Critical Battery Auto land red bar so I will never hear the siren until it starts to critical battery autoland. Happy to live with the battery beep form 20%. Smart RTH for low battery is still active and the Yellow H tells me I am protected in that regard. So all good.

Here endith... HTH

BTW someone PLS correct me if the "Cannot take off" battery trigger is actually user low battery level and not user critical battery level as I suggest.

BraamMavic · May 11, 2017

Thank you @Logger ! What a fantastically informative & brilliantly explained post ! This kind of explanation if what one would expect in the manual in the first place Thumbswayup

(Ps: How insensitive of the cows indeed...)

Reigate · May 12, 2017

Logger said:
You a welcome.

I will have a crack at correcting some the other erroneous assertions. Happy to stand corrected.

Low battery warning and Critical battery warning have no bearing on when smart RTH will trigger. If enabled, it is dynamically calculated by the firmware as a function of distance from the home point, not taking account any wind effect.

No you cannot set the low battery warning value to 70%. The maximum is 50%.

Low battery warning and Critical battery are audible and visual warnings that are customisable. They do nothing more than warn (or distract) you depending on our POV in flight. Again they have zero effect on RTH battery warnings. It is however co-incidental that the lowest possible user setting for the critical battery warning is 10% which happens also to be the fixed setting at which critical battery autoland commences. You are prevented from taking off with your battery level lower than whatever you set your Critical battery warning level at.

So for kicks here is a flight with warnings set as high as possible....

View attachment 12616

Lets take off

View attachment 12617

Notice the two white dots in the green battery bar beneath the word Positions representing the two warning levels.

Go check the cows

View attachment 12618

Shock horror the battery has passed my Low Battery Warning of 50%. Audible Warning, Low Battery Warning at top left. Cows don't even look up.

View attachment 12619

A bit later I pass the critical battery warning level I set at 45%. Have not fallen out of the sky. But the audible warning is like a siren now and "Critically Low Battery" is in RED. Notice the Yellow H point RTH trigger point is still miles off, safely to the left.

View attachment 12620

Now I am bored the cows are bored, Mavic is bored and I think I will pack up and go home. Before I do, notice the battery bar turns red under the "a" in the word Critically. That is the fixed level where critical battery autoland commences.

View attachment 12621

So I land at 26% battery having not had the Smart battery RTH trigger even though I had maxed out all the warning settings. This of course because I never reached the dynamic yellow H trigger. But I can no longer take off because current battery level is below my user set Critical Battery Warning of 45%.

Set thing back how I like..
View attachment 12622

Go flying...

View attachment 12623

The two white dots for the nuisance alarms have moved to the left. The Critical Warning dot coinciding with the Critical Battery Auto land red bar so I will never hear the siren until it starts to critical battery autoland. Happy to live with the battery beep form 20%. Smart RTH for low battery is still active and the Yellow H tells me I am protected in that regard. So all good.

Here endith... HTH

BTW someone PLS correct me if the "Cannot take off" battery trigger is actually user low battery level and not user critical battery level as I suggest.

Great work but just want to expand on one of your comments. The red part of the bar is where the immediate landing will occur and is normally at 10% but is actually dynamic and will rise above that value as altitude is increased to make allowance for the increased time to descend.