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Multiple motors and amp Draw

Old 11-23-2015, 06:31 AM
  #1  
weakcreature
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Default Multiple motors and amp Draw

Just wondering: If I have a twin motor plane (or multicopter} and hook it up to a watt meter is the amp draw multiplied my number of motors or will I be reading total draw? For example I have a hexacopter that when hooked up to my watt meter says that im pulling 42a but my ESC are only 30a (not good). Motors are 380kv and battery is only 20c.
And as far as my plane goes I have a Canadair with Turnigy G60 500kv 70a esc and well havent decided on a battery yet... but should I use one or two batteries?

Thanks in advance
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Old 11-23-2015, 07:18 AM
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fhhuber
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Depends where you connect the wattmeter.

if you have one battery and the wattmeter is between battery and ALL escs, that is total.

if you connect it between where you Y to the ESCs and one ESC then you are just measuring that one ESC

Best to Y the ESCs to one battery so you get the same voltage to both and both should hit LVC essentially the same time
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Old 11-23-2015, 01:20 PM
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pmullen503
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You can use multiple batteries but you should run them in parallel (think of a jumper cable positive to positive, negative to negative. ) Multiple batteries give you more flexibility for placement in the airframe.
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Old 11-23-2015, 06:50 PM
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Flubber
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Your multirotor should have a power distribution board. So the battery runs to the board and all the esc's connect to the board. With this set up the connection at the battery will show all the load of esc's combined so your hexcopter is pulling 7 amps per motor.

For your multi-engine plane I would check each motor for static load separately and choose a battery to handle twice that load. Like pmullen says connect the batteries in parallel so each motor sees the same voltage.
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Old 11-24-2015, 12:08 AM
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weakcreature
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Default So what now?

So I guess my next question would be:
If Im pulling 42 amps from all my motors..... do I need to increase my C rating on my battery ( 6s 20c 5000mah
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Old 11-24-2015, 12:27 AM
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fhhuber
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That battery can take 20C * 5000 ma / 1000 (ma/A) current... = 100 amps
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Old 11-24-2015, 02:17 AM
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weakcreature
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You all have been a great help.... Ill be back to try to stump you later
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Old 11-24-2015, 02:35 PM
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At 42 amps your battery is working at 8.4 c. At this rate the battery should have a long life if you do not discharge it below 20%. This rating is why some multirotor batteries are going to 10c rating to save weight and be more compact.
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Old 11-24-2015, 03:19 PM
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Just one little point ...

When first setting up the twin or multi engines ... its best to throttle calibrate separately BEFORE adding the Y lead.

You can calibrate via a Y lead but it's a bit hit or miss. My Concorde needed separate but my Tu144 worked via the Y.

To be honest at end of day I took out the Y adaptors and now run my Concorde and TU144 with batterys separated to their own motors. Why ? Got fed up squeezing the extra wiring in the battery bay !! Its stiff wire.

Nigel
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