Current sensing (safely) for Heavy Octo?

Harry Courter October 12, 2017 at 6:57am

jbabio, I have a heavy Y6 built a few years ago and still in the air. In my case I have three parallel 5s, 5000mah batteries. It works for me and my Y6, but I would not recommend three parallel batteries as this creates battery issues you can not anticipate. Anyway, I use one AttoPilot 180A sensor attached only to one battery. In this setup the sensor will report the correct voltage, but reflect an incorrect current. In mission planner you can set a parameter to adjust Amps per Volt, or amps reported per volt from the sensor. Using an external battery monitor during flight the external battery monitor will report the max current during the flight, then find the AttoPilot max current recorded in the telemetry log and calculate a new setting for the Amps/Volt parameter. Repeat the process until the reported current equals the battery monitor results. Like I stated, it works in my case, but is not generally recommended as failure of one of the two non-monitored batteries will not be reported to the flight controller, and the voltage of the remaining operative batteries will drop like a rock, faster than the FC can anticipate.

Also, I have been educated by those knowledgeable that the available current from multiple parallel batteries IS NOT additive, in other words if each battery can supply 100 amps then two batteries DO NOT provide 200 Amps. My understanding is that this is due to the battery's internal resistance. In my case I switched form 20C Batteries to 50C Batteries and Im fine. In my case I have six 50 amp motors for a theoretical 300Amps, (5S) I hover at 80 amps and have never seen 200Amps reported.

On another note: Check the wicki, I believe I have seen reference to a second battery monitor, However I have not chased down that issue and I don't know how the FC uses the second sensor data.

MR60

Hugues October 12, 2017 at 4:23am

I designed with Nick Arsov and sell a hall effect current sensor (up to 200A), up to 8S

http://www.airbotservices.com/airbotpower.html

AirbotPower | Drones

daniel garrow October 10, 2017 at 6:39pm

I also already use mission planner software with my dragon link

daniel garrow October 10, 2017 at 6:35pm

I was thinking of getting a pixhawks cube but I'm wondering if I can make this dull current sensor thing work with my eagle tree vector too?????

daniel garrow October 10, 2017 at 6:15pm

How would I then wire that to my osd ? I have a vector eagle tree osd

Guy Tzoler October 9, 2017 at 5:10am

You can just use this:

http://www.mauch-electronic.com/apps/webstore/products/show/7594449

with 2 of these:

http://www.mauch-electronic.com/apps/webstore/products/show/7588549

and you are good all the way to 400A.

daniel garrow October 6, 2017 at 11:20pm

my X8 can pull up to 531 amps so can I even use a current sensor?

Harry Courter October 6, 2015 at 9:41am

In my case with parallel batterys, I used the Attopilot on only one battery feed. The voltage is correct, and I adjust the pixhawk parameter to adjust "amps per volt," to compensate for the additional current. With a little fiddling it seems to work.

On a similar, related subject, your max current is 200+ amps, so you expect to draw 1/2 that current from each battery? My situation is similar. However once in flight I am finding serious voltage lag triggering battery fail safe way to soon. This indicates I am pulling more current than the battery is capable of delivering.

I sent a message to the guys at AtomikRC and they responded that the parallel battery arrangement will deliver the current on ONE battery pack, and that with lipo battery you do not get to multiply the current C rating by the number of battery packs.

I'm doubtful of this response but I suppose that internal balancing of the cells between packs may be using current capacity. I'm considering a balance cable between the lipo packs.

Any thoughts?

1280MHz > Harry Courter April 3, 2016 at 3:54am

What is the correct way to connect the AttoPilot 180A ground wire without causing a ground loop when using two separately fed 6Ss into a PDB while only sensing one of the packs (I only want to monitor 1 pack)? Pixhawk is powered via the top power port using the original Pixhawk PM via a separate 3S (I’m not running the Pixhawk from the PDB).

I have hit a massive dead end after trawling the forums for hours, help greatly appreciated.

Thanks

Gerard Valade September 22, 2015 at 11:36pm

Warning, using attopilot with draw more than 180 can be dangerous because the power consumation grow wtih square of current :

P = I² * R

actual attopilot for 180A :

180*180*0.00025 = 8.1 watts

if you draw 272A

272*272*0.00025 = 18.4 watts

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Current sensing (safely) for Heavy Octo?

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