Hi everyone! I would like to list two ideas (none novice or mine) which I hope will gain the attention of our community and result in 3dr introducing some new products and functions in the apm code. 

1. 3dr made hall-effect sensor based power module which will have no limitations on voltage. Sensors for this module already exist with more than acceptable price points and can be DIY implemented but I think community will appreciate a professionally made unit. 

    reason:  many photography and mapping drones require 6s+ voltages with pick amp draw exceeding                    90amp. 

2. 3dr made batt voltage sensor communicating with apm/pixhawk via i2c capable of single cell monitoring + support for multiple such sensors (for people using multiple packs as well as separate non-flight packs and/or measuring voltage going to your various equipment, camera, gimbal, Vtx, etc.)

    reason:  I think many people had the scenario when the voltage would drop below critical in just 4-5                    seconds due to an individual cell failing.

my example from today's flight: flying for about 7min (always getting 14-15min) and hear lipo alarm going off, telemetry voltage shows 10.9 volts and about 1100 mah used of usual ~2400. Thinking that maybe lipo alarm got disconnected from the pack or having a bad contact. In about 4-5 seconds I am badly surprised when the tricopter starts dropping like a stone, looking at the telemetry -shows 8.6 volts!  well one might point out to use better quality lipo and always checking pack's internal resistance. all valid arguments, but there are already multiple things to check before the flight and a human might miss something. it would be a good option to setup a failsafe to trigger on individual cell failure.... the reason why my copter dropped so fast is because I used 3s , with a 6s and reasonably weighted copter it is possible to say that an operator will have more time to find a place to land in such an event as long as he knows that one of the cells failed. this will be a valuable option which could potentially help avoid damage to and by the copter.  

my 5c. 

please respond with critics or support! 

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I think we all agree that we need a power supply that works for more than 4s. If I remember correctly, 3DR said they were going to make this in one of their "technology previews" several months ago... I remember something about a 4 in 1 esc as well? Was I imagining that?

I agree with your proposal for having a profesionnally sourced Voltage & current sensor that is preconfigured Harware and software Wise for Pixhawk (&APM, although APM is end of life).

Why is this so important ?

-Voltage and current measurements are a critical for a safe flight (cf the number of accidents/crashes happening because of bad batteries and/or discharged batteries)

-Not everyone has the hardware/soldering skills to create reliable custom cables. This is even more true with the tiny DF13 connectors of pixhawk (which makes it even harder for the hobbyist/Diy)

-Not everyone has the electric/electronic background to understand how to hack résistors/dividers and the like.

-Not everyone has the IT background to understand how to configure/program Arducopter's code to measure and interpret ADC values.

However all of these people will fly APMS and PixHawks, putting themselves and others in danger.

I think it is fair to assume 3DRobotics wants to increase safety elements to the maximum with their own hardware (APM, PixHawk); therefore Voltage & current measurments are critical and should be put at the top priority list of Pixhawk hardware/software developments

Alternatively, 3DRobotics could sponsor selected skilled peoples to do this development... Just an idea.

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one more thing to add

the reason i suggest using separate sensors outputting only i2c is to safeguard apm/pixhawk from that sensor's failure. protocol can be i2c/can/uart whatever, but not a simple voltage divider to the pixhawk pins. In my opinion, safety measures, such as isolating controllers from the main powers, single cell voltage battery monitoring and pack temperature, are must for professional equipment flying over people and property. 

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