1.1.3 BCDC Alpha 50¶
Type: Battery Isolator and DC-DC Charger
Model: RedArc BCDC Alpha 50 (BCDC1250R)
Manufacturer: RedArc Electronics
Product Page: BCDC Alpha 50
Installation Guide: BCDC Alpha Installation Manual
Instruction Manual: BCDC Alpha Instruction Manual
Specifications¶
- Output: 50A DC-DC charging, multi-stage LiFePO4/AGM compatible (0.37C charge rate for 135Ah LiFePO4)
- Inputs: 9-32V primary (alternator), 9-48V solar (up to 350W)
- Features: Auto isolation, jump start assist, Green Power Priority, ignition-triggered
- Dimensions: 260mm L × 160mm W × 70mm H
- Full Specs: Installation Manual | Instruction Manual
Wiring¶
| Connection | Terminal Label | Terminal Size | Source/Destination | Notes |
|---|---|---|---|---|
| Start Battery (+) | Red | M8 | START battery positive | See START Battery Distribution for wire specs |
| Auxiliary Battery (+) | Brown | M8 | AUX battery positive | See AUX Battery Distribution for wire specs |
| Solar (+) | Yellow | TBD | Cascadia 4x4 80W panel | See Solar Charging |
| Ground (-) | Black | M8 | AUX battery negative | See AUX Battery Distribution for wire specs |
| Ignition | Blue | Spade | PMU ignition sense tap | 18 AWG - see PMU Inputs |
| Battery Temp Sensor | +/- (reversible) | 2-pin plug | AUX battery positive terminal | REQUIRED - LiFePO4 temperature-compensated charging |
See START Battery Distribution and AUX Battery Distribution for complete wire specifications (gauge, distance, routing, circuit breakers).
Critical: Verify solar input polarity before connection - reverse polarity damages unit.
Function¶
The BCDC manages charging and isolation between starter and aux batteries:
- Normal Operation: Charges AUX battery from START battery/alternator at up to 50A
- Solar Priority: Uses solar input first when available (Green Power Priority)
- Jump Start Assist: Parallels batteries if START battery voltage drops critically
- Isolation: Prevents AUX battery from draining START battery when engine off
AUX Battery Charging Impact¶
Upgrade from 25A to 50A BCDC provides significant improvement for high-draw scenarios:
| Scenario | AUX Draw | 25A BCDC | 50A BCDC | Improvement |
|---|---|---|---|---|
| Night Offroad (full lights) | 70A | -45A drain | -20A drain | 2.3× longer runtime |
| Airing Up Tires | 110A | -85A drain | -60A drain | 30% less battery impact |
| Recovery after air-up | - | 34 min to recover 10Ah | 17 min | Half the recovery time |
See AUX Battery Load Analysis for complete scenario details.
Mounting¶
- Location: Passenger wheel well near AUX battery (water-protected, accessible for LED visibility)
- Installation: See Section 1 Installation Checklist
Temperature Sensor Installation¶
The BCDC includes a battery temperature sensor (2-pin, polarity reversible) that is REQUIRED for proper AGM charging.
Sensor Specifications:
- Type: NTC thermistor with 2-pin connector
- Cable Length: ~6 ft (included with BCDC)
- Polarity: Reversible - either orientation works
Installation Location:
- Mount Position: AUX battery positive terminal
- Attachment: Ring terminal under battery terminal bolt
- Why Positive Terminal: Measures both voltage and temperature at the battery for accurate charge control
Why Required:
- AGM batteries are temperature-sensitive during charging
- Overcharging at high temps causes thermal runaway risk
- Undercharging at low temps leads to sulfation
- BCDC adjusts charge voltage based on sensor reading (temperature compensation)
Installation Notes:
- Install ring terminal on AUX battery positive terminal bolt
- Route sensor cable to BCDC (short run - both in passenger wheel well)
- Plug into BCDC temperature sensor port (2-pin connector)