With one 100 watt solar panel 10 gauge wire is adequate for up to 17.5 feet but position the controller as close as possible to the battery. Here’s the wire chart I use…
https://www.windynation.com/jzv/inf/choosing-right-wire-size
Winnebago 2101DS TT & 2022 Chevy Silverado 1500 LTZ Z71, WindyNation 300 watt solar-Lossigy 200 AH Lithium battery. Prefer boondocking, USFS, COE, BLM, NPS, TVA, state camps. Bicyclist. 14 yr. Army -11B40 then 11A - (MOS 1542 & 1560) IOBC & IOAC grad