Hello once again. My problem is that I am using an apm 2.8 with copter 3.2.1 firmware and it achieves radio failsafe but never achieves battery failsafe. I am using 3S 3300mah lipo battery and set the failsafe limit as 10.3V and reserved capacity as 1050mah. Still it does not performs RTL. I am using M7N Ublox GPS. What should I do now?
This diagnosis is pretty much spot on.
Upgrade to a newer flight controller with current firmware, even a 40$ F4 FC will outperform your apm by Miles (as we have told you in the other thread already).
You can find a list of supported autopilots here.
In the meantime post a .bin log file of the flight in question. Battery failsafe not triggering can have a number of reasons, without the log file it’s a game of chance to get it right.
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Ok. So actually, I am getting all suggestions to just change my apm 2.8.
I am just wondering, is apm 2.8 so bad flight controller?
Nevertheless, I will upgrade to some other flight controller…
The APM2.8 by itself isn’t that bad, the main problem with it is that it isn’t supported with a current firmware (i.e. 4.4.4).
But let’s try to fix the battery failsafe anyway, we could learn something on the way.
Upload a .bin log file from the flight where it didn’t trigger and I will have a look.
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Actually I am not that much PRO in the field of UAVs and thus, I don’t know what is this .bin log file and how I can share it??
In your flight controller you should have a micro SD card. On it there should be the folders ‘APM’ and in it ‘LOGS’. In that folder your flight controller saves the logging data of the flights it is doing. These are the .bin log files we are talking about.
These files are usually too big to upload them here directly, so you have to share them through a filesharing service, for example Google Drive, Dropbox, WeTransfer, etc. Keep in mind to share them as public, otherwise we can’t access them 
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Not on that old dog of an FC. Have to download it via Mission Planner.
Not all of this applies to the APM:
Downloading Logs
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Oh well, thanks for the correction.
Another reason to switch off of the apm I guess xD
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Yes, for sure.
Assuming that battery monitoring is configured there are only 3 parameters for battery failsafe in V3.2.1.
These are default from an old parameter file I have:
FS_BATT_ENABLE,0
FS_BATT_MAH,0
FS_BATT_VOLTAGE,10.5
So, not much to go wrong if Bat voltage is being read and these are set.
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Ok. So can you please tell me the differences between Pixhawk 4 and Pixhawk 6C. I personally like them very much and thinking to buy Pixhawk 4. So, if you know, can you tell me what are the major differences in Pixhawk 4 and Pixhawk 6C? This will leave my apm 2.8 in dust…
You can determine that for yourself. Link to the 6C on this page.
Pixhawk 4
Then go the Arducopter Changelog and starting at the top page down until you reach V3.2.1 (FEB2015). You will be paging and paging and paging some more. These are the additional features and enhancements that modern Flight Controllers allow:
Arducopter changelog
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After reading all this, I think that most of us might be using only less than 50% of those extras in version 4.5 . Most of us just need stability in our multirotor, that’s all. So why is this upgrading firmware, selecting a nice flight controller so important?
But apm 2.8 doesn’t has a micro SD card… From where should I read the logs then? The ‘messages’ section of Mission planner also doesn’t shows much things…
It is described here on the wiki page Dave already linked.
You don’t need the ‘Messages’ tab but the ‘Dataflash Logs’ tab instead.
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I’ll try to explain it with an example from another field of aviation:
Imagine the APM 2.8 is a Douglas DC-10, a plane from the 1960s that, even today, will most likely bring you safely where you want to go. Maybe you arrive with only two of three engines working, but you probably arrive. When you only ever knew the DC10 for your whole life, you don’t think you’d need another plane.
Now let’s say a current H743 FC is an Airbus A350, a modern passenger plane of similar size. It will also bring you safely where you want to go but it will do it so much better. That it is quieter, faster and more comfortable are only the features that you notice as passenger. But there are lot’s of features passengers don’t even know/notice: it is not just faster, it is more fuel efficient per km at the same time and it has instruments and flight computers utilizing the lastest aviation navigation technology and safety standards.
In the end it comes down to the question
Do you want a drone that flies, or a drone that flies great?
If you want a drone that flies, your APM propably works.
If you want a drone that flies great (today’s interpretation of ‘great’), the APM just doesn’t cut it.
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OMG!!! You explained it so well!!! Thanks! Thanks alot!!! You don’t know but you people have solved a bulk of my doubts in this group discussion… Something which I always wanted… Thanks! 
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