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Old Jan 01, 2011, 03:16 PM
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Why so serious?
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United States, FL, Cape Coral
Joined Dec 2007
5,972 Posts
Originally Posted by Commander Crash View Post
what size battery can i use with a 30 amp esc on a BEV sky surffer V2 with a 6x4e prop ?
You can use any size 3cell battery that fits.(brushless motor right?) The mAh ratings on batteries are basically "the size of your gas tank" A 2200mAh will give you longer flight time then a 1500mAh. The c rating is how many amps it can deliver. A 20c battery is plenty with the stock brushless. The batteries pavcon mentioned are good choices.
The esc size is is determined by the amp draw of the motor/prop combination, not the battery size.

Here's how it all works..Copied from a post I did on the EasyStar thread. The motor listed is a brushed but still applies to a brushless set up.

It's all pretty simple.
You start with the motor. Most have specs you can check to see what voltage and amps they are made for. Your permax is a 6 volt motor which works fine on 8.4 volts. Lets say with a 6x4 prop it draws 10 amps max. (You found this out from a friend who has one with a watt meter).
So your going to draw 8,4 volt at 10 amps max to keep the motor happy. You need a brushed esc that can deliver a minimum of 10 amps that can take a 2 cell lipo (8.4 fully charged though listed as a 7.2) So a 15, 20, 30amp or better will work fine as long as it's more then 10. It's a good idea to get the esc a bit bigger then the actual draw.
Now you need a battery to supply 8.4 volts and a minimum of 10 amps. The C rating tells you the max safe amps a battery can deliver. Take the C rating and times it by the mAh capacity of the battery and devide by 1000.
A 20C 1500 battery would be 20x1500=30,000/1000=30. So that battery can safely provide up to 30 amps its usable voltage.
Basically you can be bigger with the esc(amp rating) and battery(c rating)and mAh) without any issues. They will only provide what the motor/prop combination draw. Batteries and esc don't push current. They only try to provide what the motor/prop combination draw.

I hope that made sense.
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Last edited by 2500GENE; Jan 01, 2011 at 03:24 PM.
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