Scary after critical battery, got questions!

[networth]

I was flying, I have it set to 30% critical and 10% last critical alarm.
It went to 30% and alarm started, but I kept flying as it was 30% still left.

Immediately after 5 minutes, it started saying the continuous beep sound about battery dying.
And it activated the RTH.
Since I have RTH set to 30M altitude, it started slowly going to very height of 30M.

I thought, it cannot make it to land, as 30M is very high.

And the alarm was continuous and scary.

I immediately switched off the RTH and enabled sports mode and rammed it into my hands.

Hand catched it safely, but now Im afraid about battery.
Will it really make it to home by itself by intelligently calculating the battery left power or will it crash from the sky ?

 

[CactusJackSlade]

I was flying, I have it set to 30% critical and 10% last critical alarm.
It went to 30% and alarm started, but I kept flying as it was 30% still left.

Immediately after 5 minutes, it started saying the continuous beep sound about battery dying.
And it activated the RTH.
Since I have RTH set to 30M altitude, it started slowly going to very height of 30M.

I thought, it cannot make it to land, as 30M is very high.

And the alarm was continuous and scary.

I immediately switched off the RTH and enabled sports mode and rammed it into my hands.

Hand catched it safely, but now Im afraid about battery.
Will it really make it to home by itself by intelligently calculating the battery left power or will it crash from the sky ?

It tries to do the calculations but I doubt it can predict excess wind or obstacles it may need to avoid in those calculations... yes the 10% final warning is very unnerving, I wish there was a way to silence it as it breaks my concentration... I have only gotten to this point once. Even having to disengage the batter low warning is a pain...

Also, Sport mode is the least efficient way to come back home, it eats even more battery power... just keep in GPS mode and go full stick forward to home and that is pretty close to maximum efficiency.

 

[networth]

I think I have to simply make it a point to land to home immediately after 30% critical warning.

So, basically to use only 70% always

 

[Robbyg]

I think I have to simply make it a point to land to home immediately after 30% critical warning.

So, basically to use only 70% always

I cannot think of anything I have ever flown that did not have roughly a 25-30% recommendation reserve for landing. As your own experience shows you can end up in trouble if you break that rule.

 

[Cyberpower678]

So let me enlighten you about my own experience in flying in high winds and flying on a calm day. Starting off with a calm day the RTH feature is pretty accurate. It takes your setting for critical battery, don't confuse it with low battery, and adds the amount of power needed to return home based on the current distance and altitude for the return trip. It made it home right as calculated.

For the windy day I flew 4km out, and I knew I was flying with the wind. I looked at the battery gauge and decided to return home despite having some green left before needing to come home. The return trip required sport mode to compensate for high speed wind. By the time the drone came back the battery remaining was less than the calculated amount need to return home and I dipped in to the critical part of the battery during this flight. Fortunately I was already landing when I hit the critical portion of the battery.


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[networth]

So basically land immediately at 30%

 

[Cyberpower678]

So basically land immediately at 30%

Not necessarily. You do need to periodically drain the battery to 8 percent to maintain it after 20 or so flights. I have 120km logged on my drone since I get it late December.

 

[DerekG]

Another thing to keep in mind is the further you discharge your batteries the more stress you put on them and the fewer cycles (on average) you will get out of them. For example, if you charge to 100% and fly to 50% two times then you've used 100% total capacity, however, it is WAY better to do this than discharge 100-0% one time. Without getting too much into the chemistry of the batteries basically unless you need to stay in the air it's a good habit to be landing by 50% (best) vs 30% (not bad) vs 10% (worst), as your batteries will last longer

 

[Neto]

I had only one experience of 10%-from-hell battery and I learned my lesson.
Did everything wrong.
Took off with 60% then went where I wanna go in a straight line and decided to come back when battery was at 30%.
OF COURSE it's impossible to come back home before the 10% RTH trigger.
The problem is that when my Mavic was close from home, with the 10% RTH active, it simply got crazy.
It hit a fence and fortunately only broke two propellers.

Untitled Project.mov

 

[Robbyg]

Without getting too much into the chemistry of the batteries basically unless you need to stay in the air it's a good habit to be landing by 50% (best) vs 30% (not bad) vs 10% (worst), as your batteries will last longer

100% Correct. My Mavic touches the ground at 30% or more charge.
Li batteries do not like deep discharges and having no reserves in the tank is dangerous..

 

[Cyberpower678]

Another thing to keep in mind is the further you discharge your batteries the more stress you put on them and the fewer cycles (on average) you will get out of them. For example, if you charge to 100% and fly to 50% two times then you've used 100% total capacity, however, it is WAY better to do this than discharge 100-0% one time. Without getting too much into the chemistry of the batteries basically unless you need to stay in the air it's a good habit to be landing by 50% (best) vs 30% (not bad) vs 10% (worst), as your batteries will last longer

You're supposed to discharge them to less than 8% every 20 charge cycles.


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[jerryss]

You're supposed to discharge them to less than 8% every 20 charge cycles.


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Where does it say that in the manual?

 

[Cyberpower678]

Where does it say that in the manual?

Somewhere, as part of the battery service, they need to be discharged after every 20 charges so the onboard software can stay properly calibrated to battery performance.

 

[DerekG]

Somewhere, as part of the battery service, they need to be discharged after every 20 charges so the onboard software can stay properly calibrated to battery performance.

Yes, however, this should be done under a low-altitude hover (which has a stable, easily-calculated power draw). You are right that this is needed every once in a while to re-calibrate the "fuel gauge" (I'd argue every 20 times is too frequent... Once every 3 months is the most I would do), however, it's still hard on the cells to run them that low. All this does (for those curious) is to ensure that 50% is ACTUALLY 50% as opposed to 60% or 40%... If the battery reports 30% left but it's actually 10% you can see how this could become a problem. If you have the voltage displayed on the main screen a good indicator that you should land is the voltage displayed is around 3.50-3.55V or so (It displays the voltage of the lowest cell as well as the total pack voltage). I trust the voltage more than a percentage

A lot of people get into battery trouble when they notice their battery is low while they are far away, they punch the throttle, and as a result pull a huge load from a battery that's already pretty depleted. As the voltage drops the battery has to provide more current to produce the same power, which further drops the voltage (and so on). The best way to squeeze as much energy as you can out of the batteries (if you really need to get back) is to keep your forward speed at 15-20 mph while slowly descending (if terrain allows). A lot of people fly back as fast as they can in Sport Mode (which is less power efficient), then need to take a minute or so just to get the drone down from 400ft. Much better if you're coming in at a power efficient speed and are already low enough that you can land in a few seconds

If you only plan on keeping your Mavic for a year then taking good care of your battery / batteries may not be that important to you, however, these batteries can easily last 2-3 years if well taken care of. I have a few Phantom 3 Pro batteries that are almost 2 years old now with no puffing and still 95%+ of original capacity

 

[Cyberpower678]

Yes, however, this should be done under a low-altitude hover (which has a stable, easily-calculated power draw). You are right that this is needed every once in a while to re-calibrate the "fuel gauge" (I'd argue every 20 times is too frequent... Once every 3 months is the most I would do), however, it's still hard on the cells to run them that low. All this does (for those curious) is to ensure that 50% is ACTUALLY 50% as opposed to 60% or 40%... If the battery reports 30% left but it's actually 10% you can see how this could become a problem. If you have the voltage displayed on the main screen a good indicator that you should land is the voltage displayed is around 3.50-3.55V or so (It displays the voltage of the lowest cell as well as the total pack voltage). I trust the voltage more than a percentage

A lot of people get into battery trouble when they notice their battery is low while they are far away, they punch the throttle, and as a result pull a huge load from a battery that's already pretty depleted. As the voltage drops the battery has to provide more current to produce the same power, which further drops the voltage (and so on). The best way to squeeze as much energy as you can out of the batteries (if you really need to get back) is to keep your forward speed at 15-20 mph while slowly descending (if terrain allows). A lot of people fly back as fast as they can in Sport Mode (which is less power efficient), then need to take a minute or so just to get the drone down from 400ft. Much better if you're coming in at a power efficient speed and are already low enough that you can land in a few seconds

If you only plan on keeping your Mavic for a year then taking good care of your battery / batteries may not be that important to you, however, these batteries can easily last 2-3 years if well taken care of. I have a few Phantom 3 Pro batteries that are almost 2 years old now with no puffing and still 95%+ of original capacity

Makes sense. I'm an electrical engineer and the power used is ultimately watts which is essentially volts and amps multiplied. I tend to start descending as the drone approaches the landing spot. Uses even less power in the end.


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[triumphrider]

Somewhere, as part of the battery service, they need to be discharged after every 20 charges so the onboard software can stay properly calibrated to battery performance.

Where in the manual does it say you need to discharge the battery to 8% every 20 charges? If this is something you personally do because you want to, that's fine, but I wouldn't be giving false information based on personal preferences.
Li Po batteries have come a long way and doing these complete discharge/recharge cycles aren't as necessary as they used to be.

 

[Cyberpower678]

Where in the manual does it say you need to discharge the battery to 8% every 20 charges? If this is something you personally do because you want to, that's fine, but I wouldn't be giving false information based on personal preferences.
Li Po batteries have come a long way and doing these complete discharge/recharge cycles aren't as necessary as they used to be.

I believe I saw a recommendation from DJI somewhere to ensure the power levels remain calibrated with the battery's firmware.


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[Woody67]

Set low battery at 30% - critical at 22% at low battery warning. If you are out pass what the drone police say is hard to see start getting your *** back home. That's your comfortable reserve. As said above drain batt every 20 are so for the memory board in batt to learn it's parameters.

 

[Cyberpower678]

Set low battery at 30% - critical at 22% at low battery warning. If you are out pass what the drone police say is hard to see start getting your *** back home. That's your comfortable reserve. As said above drain batt every 20 are so for the memory board in batt to learn it's parameters.

Setting your critical to 22% is dangerous. The drone force lands when it hits the critical range. Your drone may end up landing some where you don't want it to.


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[Woody67]

I stand corrected. I generally start back at low warning. Being it's always LOS I've never been forced to the critical point. I will readjustment my settings. Thanks for the heads up......are should I say drone down.