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1.3 AUX battery Distribution (Passenger Rear Wheel Well)

Overview

The AUX battery (Dakota Lithium 135Ah LiFePO4) in the passenger rear wheel well provides power for high-current accessories and cabin systems via five direct terminal connections:

  1. Direct high-current → Winch (recovery system, no CB per manufacturer spec)
  2. Direct charging input → BCDC Alpha 50 output (no CB - charging path)
  3. Inline 300A CB → 2/0 AWG forward feed → Firewall CONSTANT Bus (SwitchPros, BODY PDU)
  4. Inline 150A CB → 2 AWG short feed → SafetyHub 150 (local in rear wheel well)
  5. Inline 100A CB → 4 AWG short feed → JL Audio MV800/8i Amp (mounted under rear seat)

Two-Stage Distribution Architecture

The AUX battery has no local CONSTANT bus — protected feeds run from inline CBs at the battery to two distribution points: the firewall CONSTANT bus (most loads) and SafetyHub (local). This places distribution near the loads, minimizes the cabin trunk to a single heavy cable, and keeps the rear wheel well compartment uncluttered.

See Firewall CONSTANT Bus for downstream distribution, SafetyHub for fused recovery circuits, and Circuit Breakers for full CB list.

Single Source of Truth

This page is the authoritative source for all AUX battery wire specs (gauge, distance, voltage drop). Component pages reference here. For battery specs see Section 1.1. For ground bus bars see Section 1.5.

AUX battery Positive Terminal (5 stacked ring lugs)

Circuit Destination Wire Gauge Distance Current Voltage Drop Protection
BCDC Alpha 50 output Local (rear wheel well) 4 AWG Short 50A Negligible None (charging)
Firewall CONSTANT Bus Firewall (cabin side, passenger) 2/0 AWG ~13 ft ~152A max 1.3% @ 20°C 300A CB at battery (<7")
SafetyHub 150 Local (rear wheel well) 2 AWG ~2 ft ~100A max <0.5% @ 20°C 150A CB at battery (<7")
JL Audio MV800/8i Amp Under rear seat 4 AWG ~3-4 ft 80A max (fuse) <0.5% @ 20°C 100A CB at battery (<7")
Winch Front bumper 1/0 AWG 13 ft 250A typ, 409A peak 4.9-7.9% @ 20°C None

AUX battery Negative Terminal (5 connections)

Circuit Destination Wire Gauge Distance Current Voltage Drop
Rear Frame Rail Local (chassis) 2/0 AWG ~3 ft 654A peak <0.1V @ 20°C
BCDC Alpha 50 Local 4 AWG Short 50A Negligible
JL Audio MV800/8i Amp Under rear seat 4 AWG ~3-4 ft 80A max (fuse) <0.5% @ 30°C
START Battery Driver rear wheel well 1/0 AWG 5-6 ft 75A max <0.05V @ 20°C
Winch Front bumper 1/0 AWG 13 ft 250A typ, 409A peak 4.9-7.9% @ 20°C