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timmy-home/docs/lab-004-solar-deployment.md
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docs: LAB-004 solar deployment guide (#529)
Complete deployment guide for 600W cabin solar array:
- ASCII wiring diagram (panels → controller → batteries → inverter → AC)
- Parts list with estimated costs ($285-405, under $500 budget)
- 2S2P panel wiring configuration (36V to controller)
- 4-battery parallel bank layout
- Step-by-step installation checklist
- Safety notes and estimated runtime

Physical hardware task — documentation only.

Closes #529.
2026-04-15 21:45:16 -04:00

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# LAB-004: 600W Solar Array Deployment Guide
> Issue #529 | Cabin Compute Lab Power System
> Budget: $200-500
## System Overview
4x 150W panels → MPPT controller → 12V battery bank → 1000W inverter → 120V AC
```
[PANELS 4x150W] ──series/parallel──► [MPPT 30A] ──► [BATTERY BANK 4x12V]
[1000W INVERTER]
[120V AC OUTLETS]
```
## Wiring Configuration
**Panels:** 2S2P (two in series, two strings in parallel)
- Series pair: 18V + 18V = 36V at 8.3A
- Parallel strings: 36V at 16.6A total
- Total: ~600W at 36V DC
**Battery bank:** 4x 12V in parallel
- Voltage: 12V (stays 12V)
- Capacity: sum of all 4 batteries (e.g., 4x 100Ah = 400Ah)
- Usable: ~200Ah (50% depth of discharge for longevity)
## Parts List
| Item | Spec | Est. Cost |
|------|------|-----------|
| MPPT Charge Controller | 30A minimum, 12V/24V, 100V input | $60-100 |
| Pure Sine Wave Inverter | 1000W continuous, 12V input | $80-120 |
| MC4 Connectors | 4 pairs (Y-connectors for parallel) | $15-20 |
| 10AWG PV Wire | 50ft (panels to controller) | $25-35 |
| 6AWG Battery Wire | 10ft (bank to inverter) | $15-20 |
| Inline Fuse | 30A between controller and batteries | $10 |
| Fuse/Breaker | 100A between batteries and inverter | $15-20 |
| Battery Cables | 4/0 AWG, 1ft jumpers for parallel | $20-30 |
| Extension Cord | 12-gauge, 50ft (inverter to desk) | $20-30 |
| Kill-A-Watt Meter | Verify clean AC output | $25 |
| **Total** | | **$285-405** |
## Wiring Diagram
```
┌──────────────────────────────┐
│ SOLAR PANELS │
│ ┌──────┐ ┌──────┐ │
│ │ 150W │──+──│ 150W │ │ String 1 (36V)
│ └──────┘ │ └──────┘ │
│ │ │
│ ┌──────┐ │ ┌──────┐ │
│ │ 150W │──+──│ 150W │ │ String 2 (36V)
│ └──────┘ └──────┘ │
└──────────┬───────────────────┘
│ PV+ PV-
│ 10AWG
┌──────────▼───────────────────┐
│ MPPT CONTROLLER │
│ 30A, 12V/24V │
│ PV INPUT ──── BATTERY OUTPUT │
└──────────┬───────────────────┘
│ BAT+ BAT-
│ 6AWG + 30A fuse
┌──────────▼───────────────────┐
│ BATTERY BANK │
│ ┌──────┐ ┌──────┐ │
│ │ 12V │═│ 12V │ (parallel)│
│ └──────┘ └──────┘ │
│ ┌──────┐ ┌──────┐ │
│ │ 12V │═│ 12V │ (parallel)│
│ └──────┘ └──────┘ │
└──────────┬───────────────────┘
│ 4/0 AWG + 100A breaker
┌──────────▼───────────────────┐
│ 1000W INVERTER │
│ 12V DC ──── 120V AC │
└──────────┬───────────────────┘
│ 12-gauge extension
┌──────────▼───────────────────┐
│ AC OUTLETS │
│ Desk │ Coffee Table │ Spare │
└──────────────────────────────┘
```
## Installation Checklist
### Pre-Installation
- [ ] Verify panel specs (Voc, Isc, Vmp, Imp) match wiring plan
- [ ] Test each panel individually with multimeter (should read ~18V open circuit)
- [ ] Verify battery bank voltage (12.4V+ for charged batteries)
- [ ] Clear panel mounting area of snow/shade/debris
### Wiring Order (safety: work from panels down)
1. [ ] Mount panels or secure in optimal sun position (south-facing, 30-45° tilt)
2. [ ] Connect panel strings in series (+ to -) with MC4 connectors
3. [ ] Connect string outputs in parallel with Y-connectors (PV+ and PV-)
4. [ ] Run 10AWG PV wire from panels to controller location
5. [ ] Connect PV wires to MPPT controller PV input
6. [ ] Connect battery bank to controller battery output (with 30A fuse)
7. [ ] Connect inverter to battery bank (with 100A breaker)
8. [ ] Run 12-gauge extension cord from inverter to desk zone
### Battery Bank Wiring
- [ ] Wire 4 batteries in parallel: all + together, all - together
- [ ] Use 4/0 AWG cables for jumpers (short as possible)
- [ ] Connect load/controller to diagonally opposite terminals (balances charge/discharge)
- [ ] Torque all connections to spec
### Testing
- [ ] Verify controller shows PV input voltage (should be ~36V in sun)
- [ ] Verify controller shows battery charging current
- [ ] Verify inverter powers on without load
- [ ] Test with single laptop first
- [ ] Monitor for 1 hour: check for hot connections, smells, unusual sounds
- [ ] Run Kill-A-Watt on inverter output to verify clean 120V AC
- [ ] 48-hour stability test: leave system running under normal load
### Documentation
- [ ] Photo of wiring diagram on site
- [ ] Photo of installed panels
- [ ] Photo of battery bank and connections
- [ ] Photo of controller display showing charge status
- [ ] Upload all photos to issue #529
## Safety Notes
1. **Always disconnect panels before working on wiring** — panels produce voltage in any light
2. **Fuse everything** — 30A between controller and batteries, 100A between batteries and inverter
3. **Vent batteries** — if using lead-acid, ensure adequate ventilation for hydrogen gas
4. **Check polarity twice** — reverse polarity WILL damage controller and inverter
5. **Secure all connections** — loose connections cause arcing and fire
6. **Keep batteries off concrete** — use plywood or plastic battery tray
7. **No Bitcoin miners on base load** — explicitly out of scope
## Estimated Runtime
With 600W panels and 400Ah battery bank at 50% DoD:
- 200Ah × 12V = 2,400Wh usable
- Laptop + monitor + accessories: ~100W
- **Runtime on batteries alone: ~24 hours**
- With daytime solar charging: essentially unlimited during sun hours
- Cloudy days: expect 4-6 hours of reduced charging
---
*Generated for issue #529 | LAB-004*