1.1.5 Wire Distance Reference¶
Measured wire routing distances between major electrical components for voltage drop calculations and wire sizing.
Measurement Method
These distances represent actual measured cable routing paths (not straight-line distances) following frame rails, firewall passages, and avoiding obstacles. All measurements are one-way cable length.
Dual Rear Wheel Well Battery Configuration
Both batteries located in rear wheel wells for optimal wire routing:
- **Driver Rear Wheel Well** = START battery (critical systems)
- **Passenger Rear Wheel Well** = AUX battery (accessories)
Component Distance Matrix¶
| From | To | Distance | Notes |
|---|---|---|---|
| Alternator | START battery (driver rear wheel well) | 8 ft | Primary charging path |
| Starter | START battery (driver rear wheel well) | 6 ft | Cranking power |
| PMU24 | START battery (driver rear wheel well) | 7 ft | Critical systems power |
| BCDC Alpha 50 | START battery → AUX battery | 5-6 ft | Inter-battery charging (BCDC in passenger rear wheel well) |
| Winch (front bumper) | AUX battery (passenger rear wheel well) | 13 ft | Recovery system power |
| OEM Battery (engine bay) | Starter | 4 ft | Reference: original configuration |
| OEM Battery (engine bay) | Winch (front bumper) | 5 ft | Reference: original configuration |
| OEM Battery (engine bay) | Alternator | 4 ft | Reference: original configuration |
| Firewall (driver side) | Tail lights | 13 ft | Rear wiring runs |
| Steering column | Driver headlight | 6 ft | CT4 lighting control |
| Steering column | Passenger headlight | 9 ft | CT4 lighting control |
| Steering column | Driver tail light | 11 ft | CT4 lighting control |
| Steering column | Passenger tail light | 16 ft | CT4 lighting control |
| PMU (engine bay) | Steering column | 3 ft | PMU to CT4/controls |
| Passenger rear wheel well | A-pillar | 7 ft | AUX battery to front accessories |
| Passenger rear wheel well | Roof | 6 ft | AUX battery to roof-mounted equipment |
Optimized Wire Gauge Specifications¶
Wire gauges optimized for performance at measured routing distances:
| Circuit | Distance | Wire Gauge | Max Current | Voltage Drop @ Temp | Notes |
|---|---|---|---|---|---|
| Alternator → START battery | 8 ft | 2/0 AWG | 270A | 2.81% @ 60°C | Charging system - temp derating applied |
| PMU24 Power Feed | 7 ft | 2/0 AWG | 220A | 2.40% @ 60°C | Direct connection via 250A CB - upgraded from 1/0 AWG |
| Starter Motor | 6 ft | 2/0 AWG | 400-600A | <3% @ 20°C | Brief cranking load - minimal temp effect |
| BCDC Inter-Battery | 5-6 ft | 4 AWG | 50A | 0.94% @ 20°C | Rear wheel well to rear wheel well (H3 cross-cab, see Wire Routing) |
| Winch → AUX battery | 13 ft one-way (26 ft circuit) | 1/0 AWG | 250A typical, 409A peak | 4.9% @ 250A, 7.9% @ 409A @ 13.8V1 | Passenger rear wheel well to front bumper routing — see ⚠️ TBD #106 and Wire Routing |
| START+ Fwd Bus master feed | ~8 ft (⚠️ TBD #136) | 2 AWG | ~108A peak / ~68A cont | 1.3% @ 60°C | Single feed to engine-bay busbar; relocated fan/iBooster/TCU fan out on short load runs |
Temperature Derating Notes:
- Engine bay circuits (alternator, PMU) calculated @ 60°C ambient
- Wheel well circuits (starter, winch) calculated @ 20°C ambient
- Voltage drop percentages shown at maximum rated current (winch shown at both typical and peak)
Measurements Needed¶
Distances required for voltage drop calculations and wire purchases. Measure actual routing paths, not straight-line.
Lighting Circuits (Priority: High)¶
| From | To | Wire | Distance | Purpose |
|---|---|---|---|---|
| CT4 (steering column) | Driver headlight | 14 AWG | 6 ft ✓ | Low/high beam voltage drop |
| CT4 (steering column) | Passenger headlight | 14 AWG | 9 ft ✓ | Low/high beam voltage drop |
| CT4 (steering column) | Left fender turn signal | 14 AWG | 6 ft ✓ | Same as driver headlight |
| CT4 (steering column) | Right fender turn signal | 14 AWG | 9 ft ✓ | Same as passenger headlight |
| CT4 (steering column) | Driver tail light | 14 AWG | 11 ft ✓ | Turn signal rear |
| CT4 (steering column) | Passenger tail light | 14 AWG | 16 ft ✓ | Turn signal rear |
| PMU (engine bay) | Rear tail lights | 16 AWG | 13 ft ✓ | Brake/reverse/marker (Out 21/22/23) |
| SwitchPros (firewall) | Roll bar dome lights | 16 AWG | ~8 ft | Low current, estimated |
| PBS-I PURPLE START | Cole Hersee 24213 coil | 16 AWG | ~10 ft ✓ | Via firewall Pin 15 |
| CT4 SW3 output | PMU In 7 | 18 AWG | 3 ft ✓ | Same as steering column → PMU |
Offroad Lighting (Priority: Medium)¶
| From | To | Distance | Notes |
|---|---|---|---|
| SwitchPros (firewall) | A-pillar ditch lights | 7 ft ✓ | Via Baja harness |
| SwitchPros (firewall) | Roof | 6 ft ✓ | Roof-mounted lights |
| SwitchPros (firewall) | Rear rock lights (2) | 2-3 ft | Low current, voltage drop negligible |
| SwitchPros (firewall) | Front rock lights (4) | ~10 ft | Estimated via frame rail |
Air System (Priority: High)¶
| From | To | Wire | Distance | Purpose |
|---|---|---|---|---|
| SafetyHub (passenger rear wheel well) | ARB compressor (under seat) | 6 AWG × 2 | ~8 ft ⚠️ TBD #154 | Compressor power (8/10/12 ft conflict — issue #154) |
| ARB compressor | Chassis ground | 6 AWG | ~2 ft | Local ground |
| SwitchPros (firewall) | Compressor control terminal | 14 AWG | ~6 ft | Control signal |
| Air manifold (under seat) | Front axle locker | Air line | ~6 ft | Custom air line |
| Air manifold (under seat) | Rear axle locker | Air line | ~6 ft | Custom air line |
Communication (Priority: Low)¶
| Location/Route | Purpose |
|---|---|
| STX intercom mounting | ✓ Dash/behind dash |
| GMRS radio mounting | ✓ Dash (~6 ft to A-pillar antenna) |
| Ham antenna position | ✓ Passenger A-pillar (~4 ft to dash) |
| Rear camera cable path | ~11 ft (windshield → A-pillar → rear center) |
Mounting Locations (Priority: Medium)¶
| Component | Status |
|---|---|
| SwitchPros power module | ✓ Firewall (cabin side, passenger area, with BODY PDU + Firewall CONSTANT Bus) |
| SwitchPros control panel | ✓ Dash mounted |
| SwitchPros control cable length | 5 ft (firewall to dash, short run) |
| Firewall CONSTANT Bus | ✓ Firewall (cabin side, passenger area) |
| Firewall CONSTANT Bus feed | 2/0 AWG, ~13 ft from AUX battery+, 300A CB at battery |
| CT4 GPS antenna | ✓ Integrated in CT4 unit |
| Rear cargo rocker switch | ✓ Blue Sea 4160 on rear wheel well top |
| Rear seat dome override switch | ✓ Blue Sea 4160, rear passenger accessible |
Related Documentation¶
- Batteries - Battery specifications and mounting locations
- BCDC Alpha 50 - Inter-battery charging system
- Alternator - Charging system specifications
- PMU24 - Power management unit
- Starter System - Starter power requirements
- Recovery Systems - Winch specifications
- START battery Distribution - Driver rear wheel well battery terminal connections
- AUX battery Distribution - Passenger rear wheel well battery terminal connections
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1/0 AWG flexible cable, ~0.103 Ω/1000 ft; 26 ft circuit (13 ft supply + 13 ft dedicated ground return) = 0.00268 Ω. At 13.8 V (engine running during winch ops): 250 A → 0.67 V (4.9%), 409 A → 1.10 V (7.9%). Calculated @ 20°C — winch is a brief peak load (seconds), so no engine-bay temperature derating per build standard. Winch feeders are not held to the 3% rule (brief, intermittent); 1/0 AWG is a deliberate upsize over WARN's 2 AWG service-lead spec — see Winch. ↩