Section 1: Power Systems¶
System Overview¶
The Jeep LJ uses a dual-battery electrical system with intelligent power distribution and programmable power management.
Power Generation & Storage¶
- START battery: Odyssey PC1500 (850 CCA, 68 Ah) in driver rear wheel well - critical systems only
- AUX battery: Dakota Lithium 135Ah LiFePO4 (108 Ah usable, heated BMS) in passenger rear wheel well - accessories, winch (jump start capable)
- RedArc BCDC Alpha 50: DC-DC charger/isolator - batteries operate independently when isolated
- 270A Alternator: Charges START battery, BCDC charges AUX battery
See Power Generation for complete details on batteries, alternator, BCDC, and solar charging.
Power Distribution¶
Each battery uses a different distribution strategy:
- START battery Distribution: Inline CBs at battery (250A for PMU, 80A for BCDC input) — no local bus, direct stacked terminal lugs
- AUX battery Distribution: Inline CBs at battery (300A master forward feed + 150A SafetyHub local + 100A audio amp local) → Firewall CONSTANT Bus (Blue Sea 2105, 250A) feeds SwitchPros and BODY PDU at the firewall cluster; JL Audio MV800/8i amp fed direct from AUX battery via 100A CB
The system replaces the factory TIPM with modular programmable controllers:
- PMU24: 24-channel programmable power management - engine bay critical circuits
- BODY PDU: Cabin convenience circuits - radio, USB, heated seats, camera
- SafetyHub: High-current safety circuits - ARB compressor, winch contactor
Ground distribution architecture:
- Grounding Architecture: Battery grounds, engine bay ground bus, firewall stud bus, distributed grounding system
Wiring Standards¶
| Standard | Specification | Notes |
|---|---|---|
| Connections | Soldered + marine heat shrink | Waterproof, vibration-resistant |
| Connectors | Deutsch DT series (IP68) | Engine bay and exterior locations |
| Securing | Every 12-18" | High-vibration areas (engine bay, wheel wells, frame rails) |
| Securing | Every 24" | Low-vibration areas (cabin, trunk) |
| Loom | Split loom or braided sleeving | Abrasion protection where routed against metal |
| Grommets | Rubber with sealant | All firewall and body penetrations |
| Temp derating | 60°C for engine bay | Ampacity calculations must use derated values |
| Temp derating | 30°C for cabin/rear wheel well | Standard ampacity values acceptable |
See Wire Distance Reference for routing distances and gauge specifications.
Outstanding TBD Items¶
Auto-derived from this page's section (area/power-systems) — open GitHub issues only.
High (3)
- JL Audio amp feed: 100A CB exceeds 4 AWG ampacity (95A @ 20°C) (#149) — The amp's battery feed is 4 AWG (95A continuous @ 20°C per the project reference table) protected by a 100A CB. The amp's internal 80A fuse is downstream and does not protect the battery-to-amp run against a chafe/short. This violates the project's "CB protects the wire" rule and is NOT covered by STANDARDS-EXCEPTIONS (which only sanctions the SwitchPros/SafetyHub 150A-on-2-AWG case).
- START+ auxiliary distribution busbar + breakers for relocated fan / iBooster / TCU (#135) — Relocating the radiator fan, iBooster, and TCU from the PMU to START-battery-direct adds three breaker-protected feeds. All three loads are forward (engine bay / transmission) while the START battery is rear, so the chosen architecture mirrors the AUX forward-feed pattern: a single master-protected feed forward to an engine-bay busbar rather than three long runs or ~9 stacked lugs on the battery post.
- Dakota Digital Panel Mounting (#39) — HDPE sheet dimensions and location for the Dakota Digital panel.
📋 Medium (10)
- SwitchPros Output Wire Lengths (#107) — Wire lengths for the 12 SwitchPros SP-1200 output circuits (front/cabin/rear/roof fan-out from the firewall) are currently 'Various / TBD'. Determine once final load mounting locations are fixed.
- Radio Ground Routing (#82) — Path for 14 AWG ground wires from GMRS / Intercom (dashboard) to START battery negative (driver rear wheel well) - direct grounds required for RF noise isolation
- BODY PDU Metri-Pack Pinout (#69) — J301-J306 connector pinout (military TM or reverse engineering)
- Alternator Voltage Regulator Set Point (#68) — Verify 14.2-14.4V for AGM batteries
- Alternator Output Terminal Size (#67) — Terminal size for 1/0 AWG lug selection
- RF Power Grommet Location (#66) — Grommet 6 location near battery for radio power
- Roof/Roll Bar Routing (#64) — Light bars, dome lights
- Cab to Cargo Routing (#63) — Rear lights, compressor, lockers
- Dash to Console Routing (#62) — Switch panels, USB, radio
- Firewall Grommet Circuits (#61) — Complete wire bundle lists
📝 Low (1)
- AUX battery− chassis-bond (rear frame rail) peak return current (#124) — Peak current through the AUX battery− → rear frame rail 2/0 chassis bond needs a proper derivation.
🔍 Verify (2)
- ARB compressor feed length: reconcile 8/10/12 ft and measure (#154) — Three different lengths are documented for the SafetyHub → ARB twin compressor feed: ~8 ft (wire-distance reference), ~10 ft (harness inventory H6), ~12 ft (SafetyHub circuit table). The SafetyHub is in the passenger rear wheel well and the compressor under the seat, so the spread doesn't change the 6 AWG sizing materially, but the figure should be measured and unified across the three files.
- Measured cable distances: START battery → relocated radiator fan / iBooster / TCU (#136) — The radiator fan, iBooster main, and TCU now feed from the START+ forward distribution busbar (engine bay) via a single master feed from the START battery (driver rear wheel well). Provisional gauges: