1. Go into Plugins\Trinity\Combat\Abilities\BarbarianCombat.cs with notepad.
2. Find "unitsInFrontOfBestTarget >= 3"
3. Change it to "unitsInFrontOfBestTarget >= 1" (this will probably make the bot charge suboptimally though)
4. Go into Trinity settings, Combat-Barbarian tab, check "Furious Charge OOC"
Hopefully that will work.