Hi there,
Can you please recommend me the best brush less motor which has really low KV with low mass? I am trying to build a quad copter which has a payload of 2.5 kg. It needs to have a battery life above 30m. I am thinking about connecting 2 LiPo batteries parallel. Total weight might go over 5kg with all the parts. So I need to cut down maximum weight.
Thanks
Replies
Lots of info on the 'net, you can search for "duration quadcopter". For maximum duration the use of NCR18650b batteries is almost mandatory in the right combination of series and parallel. Lightest weight of each component is crucial too. RCTimer 5010 - 360Kv motors are often used with 17" props for duration quads.
Thanks very much graham. I read NCR18650b batteries has really low C value. Some people doesn't recommend it. What should I be careful about when using this battery?
They do have low C value so must be used in parallel to stay in within 2C so about 6.8A max per parallel cell. They are robust cells, can take some abuse and are safer and lighter than equivalent LiPo's, commonly used in laptops and electric cars. I use them in fixed wing application for 2 hours flying time. Whatever multirotor you use them must be optimized for low weight though and the motors for low current & large props. Getting long duration for practical multirotors is the holy grail currently. If your payload is 2.5kg you're going to have to calculate and choose very carefully your size and weight of multirotor, components will not be cheap, the batteries cells themselves are US$7-$10 each and you'll probably need 6S6P at least (if not more) so look at $360 per battery pack.
Thanks Graham.