what awg of power cable should I be running from PDB to LiPo battery on a 210 size mini quadcopter? 
I'm flying 4s by the way

I run 14AWG but you could get away with 16AWG if it's all you can find (not recommended though)

I run 75c 1300mah 4s lipos and I pull full current load on my 5" triblades regularly.
I have never had my power leads come back even slightly warm.

I always suggest using the same size that is on the battery you are using or larger.. Also if it a long run then you will want to up size also.
The tattu batteries I fly are 12 awg, so I use 12AWG wires as well between PDB and Lipo.

If you have batteries of different AWG wires (e.g. 12, 14), Then use the larger of them all.. Its always ok to oversize, its never good to undersize. When you undersize the wire heats up and can cause a fire.

I agree with Thomasfpv and cche, 14 AWG would be the minimum I would use, and as cche said, if you can use 12AWG go for it.

And of course you can always have a look at this from Oscar.s blog. (has this man not ever been there done that on anything yet?..lol)

http://blog.oscarliang.net/wire-awg-char...copter-rc/

(14-Apr-2016, 11:08 PM)BigglesFPV Wrote: I agree with Thomasfpv and cche, 14 AWG would be the minimum I would use, and as cche said, if you can use 12AWG go for it.

And of course you can always have a look at this from Oscar.s blog. (has this man not ever been there done that on anything yet?..lol)

http://blog.oscarliang.net/wire-awg-char...copter-rc/

I need to learn how to google! Doh!
Thanks guys! I think I will go for 14AWG