Weird Battery Voltage monitor

Hello guys, We build an octocopter with a 4s 10000mAh battery 10C, 3DR power module, U3 700kv motors, 40A AIR ESC. With these parts I know that I can only draw 100A continuous current from the battery while U3 8 motor max draw is 160A, So i dont plan on exceeding 60A current(60% throttle) since that's the 3DR pm's limit. The problem is during flight at full charge (16V) the battery voltage is going down so fast to 13.8V and triggers the failsafe rtl . The mission planner reads 95% remaining battery. After disaming I can see the battery voltage going up again until 15.8volts? I dont know whats happening so I set the Failsafe to a very low voltage like (6.0V) and relied on the current sense of 3000(30%) to trigger the battery fs. I had successful flights for days with this actually current mostly at 20-30A until I had a sudden crashed because the battery voltage sense in mp reached 8.0V and the mp was reporting a low battery (battery sense at hud colored red at 8.V) battery remaining was 37% at mp. Check with a multimeter voltage was at 13.3 critical so battery fs didnt actually worked, luckily I was at 10m and the sudden brownout didn't cause any serious damage. So the problem here is that the battery voltage goes down so fast during hovering and I think it steady's or normal senses during hovers. So like 16V goes down to 14-13V depends on the initial charge upon hover and from there it goes down normally and after disarming the motors it goes backup to its right voltage. Could this be a bad 3dr power module problem? or cause by the over powered motor? 

telemetry logs below had some problems with auto mode and compass interference though

2016-03-01-14-31-39.tlog

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Replies

  • Thanks bro. I've check the logs before and it was just mostly at 20-30A, I'll try calibrating the battery monitor again and check for any changes. I'm gonna try attopilot 180A hope it solves the problem :) What battery connector is best for this? is my XT60 fine? my current doesnt really exceeds 60A at 120m which is my operational altitude.

    • I used XT60 connectors on my drones and airplanes for a long time and had no issues with them. They are easy to solder and are rated for high current.

  • You have an Octocopter that's clearly drawing more than 60amps.. At hover each each of the motors will be drawing more than 10amps easily, so that's way over the 3DR power module rating of 60amps.


    If you really want to be sure of how much amps your whole copter is drawing, try using a power meter... There's a good chance that you may have damaged that power module....

    http://copter.ardupilot.com/wiki/common-using-a-current-sensor/

    • Thanks brought the attopilot 180A, what battery connector should I use for this? is XT60 limit only at 60A?

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