Which 4 awg is best for application? 4 THHN THWN-2?

[pablopablo]

need direction on which type of 4awg copper to buy.
context is an 85 foot run on bedrock carrying 50v/50a from solar panels to battery house. will be in plastic/metal conduit.

is there one type of 4awg that would be best?

it seems the cheapest is 4 thhn thwn-2 :

4 AWG THHN THWN-2 Stranded Copper Building Wire

4 AWG stranded THHN wire rated for 70A at 90°C dry, 75°C wet. Ideal for service entrance wiring, motors, and conduit. Buy now for fast delivery.

nassaunationalcable.com

is that a good choice?
any help appreciated.

 

[Avo Mk8]

Use THWN if it might get wet. These wires are not sunlight (UV) resistant unless marked as such.
If it was for mains voltage I gather it wouldn't be to code, even in conduit. But in your case it's for low voltage - I'm unclear if the NFPA70 Code applies to your situation?
If you put the wire in UV/sunlight resistant conduit, and none of it is exposed to the sun (eg at the transition from conduit to panels or at the other end, house), purely from a practical point of view, I think it would survive.

Edit: I'd meant to say also that with 4awg, I think you'd have about a 2.5V drop in the cable at 50A, ie 5%