1.8.1 Combined Scenarios¶
Multi-battery load analysis for realistic operating conditions where both START and AUX batteries are under significant load.
Scenario: Night Offroad (Worst Realistic Case)¶
Both batteries under significant load simultaneously:
START Battery (Alternator):
| Circuit | Load |
|---|---|
| Radiator Fan (max) | 53A |
| HVAC Blower | 15A |
| GMRS Radio (TX) | 5A |
| Oil/PS Cooler Fans | 30A |
| Dakota Digital | 25A |
| CT4 (headlights) | 10A |
| iBooster + Ignition | 7A |
| STX Intercom | 3A |
| BCDC (charging AUX) | 50A |
| START Total | 198A |
AUX Battery (BCDC-Charged):
| Circuit | Load |
|---|---|
| Roof Lights (8x) | 18A |
| Ditch + Fog | 14A |
| Rock + Chase | 4A |
| Lockers | 4A |
| Camera + USB | 4A |
| AUX Total | 44A |
Analysis:
- START: 198A / 270A = 73% alternator utilization
- AUX: 44A - 50A BCDC = +6A net charge
Verdict: With corrected XL Sport specs (2.2A/pod), full night offroad lighting is now fully covered by BCDC. Battery maintains charge even in worst realistic case.
Scenario: Recovery Operation¶
Winch recovery with engine idling:
START Battery:
| Circuit | Load |
|---|---|
| Radiator Fan (idle) | 25A |
| Dakota Digital | 25A |
| CT4 | 10A |
| iBooster + Ignition | 5A |
| BCDC | 50A |
| START Total | 115A |
AUX Battery:
| Circuit | Load |
|---|---|
| Winch Motor | 250A |
| Winch Trigger | 10A |
| Camera | 2A |
| AUX Total | 262A |
Analysis:
- START: 115A / 270A = 43% alternator
- AUX: 262A - 50A = -212A net discharge
- 30-sec pull: 212A × (30/3600)h = 1.8Ah (3% of battery)
Verdict: Brief winch pulls have minimal impact. Multiple recoveries possible.
Scenario: Extended Camp (Engine Off)¶
Overnight camping with minimal power:
AUX Battery Only (engine off):
| Circuit | Load |
|---|---|
| Dome/Rock Lights | 7A |
| Radio (music) | 8A |
| USB Charging | 10A |
| Camera | 2A |
| Total | 27A |
With Solar (daytime): 27A - 6A = -21A net
Without Solar (night): -27A net
Runtime:
- Day: 34Ah / 21A = 97 minutes to 50% SOC
- Night: 34Ah / 27A = 76 minutes to 50% SOC
Recommendations:
- Minimize lighting to essentials
- Idle engine every 60-90 minutes to recharge
- Use solar panel during daytime
- Consider lithium upgrade for extended camping
Scenario: Airing Up After Trail¶
ARB compressor running with engine idling:
START Battery:
| Circuit | Load |
|---|---|
| Radiator Fan (idle) | 25A |
| Dakota Digital | 25A |
| CT4 | 10A |
| iBooster + Ignition | 5A |
| BCDC | 50A |
| START Total | 115A |
AUX Battery:
| Circuit | Load |
|---|---|
| ARB Compressor (both motors) | 90A |
| Compressor Control | 15A |
| Camera + USB | 4A |
| AUX Total | 109A |
Analysis:
- START: 115A / 270A = 43% alternator
- AUX: 109A - 50A = -59A net discharge
- 10-minute air-up: 59A × (10/60)h = 9.8Ah (14% of battery)
Verdict: Standard air-up has minimal battery impact. Battery recovers in ~12 minutes of driving.
Summary¶
| Scenario | START Load | START % | AUX Net | AUX Duration | Status |
|---|---|---|---|---|---|
| Night Offroad | 198A | 73% | +6A | N/A (charging) | Excellent |
| Recovery | 115A | 43% | -212A | 30-sec pulls | Brief OK |
| Extended Camp | — | — | -27A | 76 min | Limited |
| Airing Up | 115A | 43% | -59A | 10 min | Excellent |
Key Insight: With corrected XL Sport specs (2.2A/pod), the dual battery architecture now provides net positive charging even during full night offroad lighting. The 50A BCDC fully covers all lighting loads with margin to spare.
Related Documentation¶
- Load Analysis Overview - Methodology and system architecture
- START Battery Load Analysis - Individual START battery scenarios
- AUX Battery Load Analysis - Individual AUX battery scenarios
- PMU ARB Load Shedding - Load management during compressor operation