sync: Add Wrightstown Solar and Smart Home projects

New projects from 2026-02-09 research session: Wrightstown Solar: - DIY 48V LiFePO4 battery storage (EVE C40 cells) - Victron MultiPlus II whole-house UPS design - BMS comparison (Victron CAN bus compatible) - EV salvage analysis (new cells won) - Full parts list and budget Wrightstown Smart Home: - Home Assistant Yellow setup (local voice, no cloud) - Local LLM server build guide (Ollama + RTX 4090) - Hybrid LLM bridge (LiteLLM + Claude API + Grok API) - Network security (VLAN architecture, PII sanitization) Machine: ACG-M-L5090 Timestamp: 2026-02-09 Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
2026-02-10 18:44:35 -07:00
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+# Wrightstown Solar - Project Index
+
+**Project:** DIY Home Solar Battery Storage
+**Location:** Wrightstown (home)
+**Status:** Planning / Research Phase
+**Created:** 2026-02-09
+**Last Updated:** 2026-02-09
+
+---
+
+## Project Overview
+
+DIY 48V LiFePO4 battery storage system for whole-house UPS / backup power with generator failover. Designed for modular expansion from 5kWh to 20kWh.
+
+## Target System Specs
+
+| Spec | Value |
+|---|---|
+| Chemistry | LiFePO4 (LFP) |
+| Cell | EVE C40 (40135 cylindrical, 3.2V 20Ah) |
+| Configuration | 16S5P per 5kWh pack |
+| Nominal Voltage | 51.2V (48V system) |
+| Pack Capacity | 5.12kWh per pack |
+| Target Total | 20kWh (4 packs) |
+| Inverter | Victron MultiPlus II 48/5000 |
+| BMS | JK BMS B2A8S20P 150A (recommended) |
+| GX Device | Cerbo GX |
+| Existing Solar | Fronius IG Plus (grid-tie string inverter) |
+
+## Design Goals
+
+1. Seamless switchover when grid drops (<20ms, UPS-grade)
+2. Zero grid backfeed (physical relay disconnect)
+3. Generator input for extended outages
+4. Modular expansion (build one 5kWh pack at a time)
+5. Fronius solar continues working during outages via Victron micro-grid
+
+## Architecture
+
+```
+                    NORMAL OPERATION
+Grid -----> [Victron MultiPlus II] -----> House Panel
+                    |
+              [48V Battery]
+              (EVE C40 packs)
+
+Generator ---> [AC Input 2]
+
+                    GRID DOWN
+Grid --X    [Victron MultiPlus II] -----> House Panel
+             (relay OPENS, no backfeed)
+                    |
+              [48V Battery] (discharging)
+
+Generator ---> [AC Input] (if battery low)
+```
+
+---
+
+## Files
+
+### Documentation
+| File | Description |
+|---|---|
+| `documentation/system-design.md` | Full system architecture and component specs |
+| `documentation/bms-comparison.md` | BMS models compatible with Victron CAN bus |
+| `documentation/ev-salvage-analysis.md` | Analysis of salvaged EV packs vs new cells |
+| `documentation/parts-list.md` | Bill of materials and estimated costs |
+
+### Session Logs
+| File | Description |
+|---|---|
+| `session-logs/2026-02-09-session.md` | Initial research and planning session |
+
+---
+
+## Budget Estimate
+
+### Phase 1 (5kWh + Victron System)
+| Component | Est. Cost |
+|---|---|
+| Victron MultiPlus II 48/5000 | $1,400-1,800 |
+| Cerbo GX | $320-350 |
+| JK BMS B2A8S20P 150A | $80-150 |
+| 80x EVE C40 cells | $240-400 |
+| USB-UART cable | $15 |
+| Cell holders, bus bars, wiring | $60-120 |
+| Fuses, breaker, enclosure | $60-110 |
+| **Phase 1 Total** | **$2,175-2,945** |
+
+### Phases 2-4 (Additional 15kWh)
+| Component | Est. Cost |
+|---|---|
+| 3x additional 5kWh packs (cells + BMS + hardware) | $1,140-2,010 |
+| **Full 20kWh System Total** | **$3,315-4,955** |
+
+---
+
+## Decision Log
+
+| Date | Decision | Rationale |
+|---|---|---|
+| 2026-02-09 | EVE C40 cells over salvaged EV packs | Lower $/kWh ($190-282 vs $365-780), longer life, LFP safety, simpler build |
+| 2026-02-09 | 5kWh modular packs (not 10kWh) | Spread cost, manageable builds, fault isolation, one-person liftable |
+| 2026-02-09 | Victron MultiPlus II for inverter | <20ms UPS switchover, physical relay anti-backfeed, generator support, micro-grid for Fronius |
+| 2026-02-09 | JK BMS B2A8S20P (recommended) | 2A active balancing critical for cylindrical cells, best value, huge community |
+| 2026-02-09 | Keep Fronius IG Plus | Still functional; AC-couple via Victron micro-grid during outages |
+
+---
+
+## Next Steps
+
+- [ ] Finalize BMS selection (JK BMS vs REC BMS vs SEPLOS)
+- [ ] Source EVE C40 cells (Grade A, matched, with test data)
+- [ ] Order Victron MultiPlus II 48/5000 + Cerbo GX
+- [ ] Design cell holder / bus bar layout for 16S5P cylindrical pack
+- [ ] Plan sub-panel / transfer switch wiring
+- [ ] Build Pack 1, test for 1 month before expanding
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+# Wrightstown Solar - BMS Comparison (Victron CAN Bus Compatible)
+
+**Created:** 2026-02-09
+**System:** 16S5P, EVE C40 20Ah, 48V, Victron MultiPlus II + Cerbo GX
+
+---
+
+## Quick Comparison
+
+| BMS | Price | Current | Balancing | Victron Method | Complexity |
+|---|---|---|---|---|---|
+| **JK BMS B2A8S20P** | $80-150 | 100-200A | 2A Active | dbus-serialbattery (USB) | Moderate |
+| **SEPLOS V3/V4** | $150-250 | 100-200A | Passive | Native CAN | Easy |
+| **Overkill Solar (JBD)** | $280-320 | 100A | Passive | dbus-serialbattery (USB) | Moderate |
+| **123SmartBMS Gen3** | $300-400 | Configurable | 1A Active | Native USB to Cerbo | Easy |
+| **REC BMS Q16** | $559 | Varies | 0.9A Passive | Native CAN (plug & play) | Easiest |
+| **Batrium WatchMon** | $650-850 | High (shunt) | 28Ah/day | Native CAN | Complex |
+| **Daly Smart BMS** | $80-150 | 100A/50A charge | 30mA Passive | dbus-serialbattery | Moderate |
+| **Orion BMS** | $500+ | Configurable | Active options | Native CAN | Easy |
+
+---
+
+## Recommended: JK BMS B2A8S20P (150A Version)
+
+### Why This BMS for EVE C40 Cylindrical Cells
+
+- **2A active balancing** -- Critical for cylindrical cells which have more cell-to-cell variation than prismatic. With 5P strings, mismatches multiply. Passive balancing at 30-200mA takes days; JK's 2A active balancing corrects in hours.
+- **150A rating** -- 16S5P is 100Ah, so 150A provides headroom for inrush and peak loads
+- **$80-150** -- Best value in the market
+- **Huge DIY community** -- Every problem already solved on forums
+
+### Specs
+
+- Current ratings: 100A, 150A, 200A options
+- Balancing: 2A active (best in class at this price)
+- Communication: Bluetooth, RS485, CAN, UART
+- Monitoring: Real-time via smartphone app
+- Temperature: Multiple sensor inputs
+
+### Victron Integration
+
+```
+JK BMS --[USB-UART cable ($15)]--> Cerbo GX
+                                      |
+                                 dbus-serialbattery
+                                 (free open-source driver)
+                                      |
+                                 DVCC enabled
+                                      |
+                              Victron MultiPlus II
+```
+
+**Required:**
+1. USB-UART cable (~$15)
+2. dbus-serialbattery driver (free, install via SSH on Cerbo)
+3. DVCC enabled in Cerbo settings
+
+### [WARNING] Known Gotcha: Reversed CAN Pinout
+
+JK BMS has CAN-H and CAN-L SWAPPED compared to Victron's RJ45 pinout. Solutions:
+- Buy pre-made JK-to-Victron cable (AliExpress)
+- Make your own cable and swap pins 7 & 8
+- Use USB-UART connection instead (avoids CAN entirely -- recommended path)
+
+### Known Issues
+
+- Firmware updates frequently with no changelog -- check forums before updating
+- SOC can jump from 85% to 100% prematurely during fast charge
+- Battery capacity/consumed Ah data may not transmit to Cerbo via some driver versions
+- Inconsistent quality control between batches -- test thoroughly on arrival
+
+### Where to Buy
+
+- AliExpress: $80-120 (multiple sellers)
+- Amazon: $120-180 (JKBMS official store)
+- EEL Battery, SeLian Energy (resellers)
+
+---
+
+## Alternative: SEPLOS V3/V4 (Easiest Native CAN)
+
+### Why Consider
+
+- Native Victron CAN protocol -- no drivers needed
+- One CAN cable to Cerbo, auto-detects
+- Multiple units can chain on one CAN link (good for expansion to 4 packs)
+- $150-250 is reasonable mid-tier pricing
+
+### Drawbacks
+
+- Passive balancing only (slower than JK's active)
+- Less community documentation
+- Setup can be tricky initially
+
+### Where to Buy
+
+- Seplos.com (official)
+- AliExpress, Alibaba
+
+---
+
+## Premium Option: REC BMS Q16 (Zero Hassle)
+
+### Why Consider
+
+- TRUE plug and play -- one CAN cable, auto-detected, DVCC works immediately
+- Most reliable Victron integration available
+- Professional-grade, excellent documentation
+- SOC/SOH calculation, cell resistance measurement
+
+### Drawbacks
+
+- $559 -- nearly 4x the JK price
+- Passive balancing only (0.9A) -- slower for cylindrical cells
+- No active balancing option
+
+### Where to Buy
+
+- Off Grid and Marine Energy (OGM Energy): $559
+- REC-BMS.com (official)
+
+---
+
+## Budget Option: Daly Smart BMS [NOT RECOMMENDED]
+
+### Why to Avoid for This Build
+
+- 100A discharge but only **50A charge** -- will bottleneck solar charging
+- 30mA passive balancing -- useless for large cells (would take 200+ hours)
+- CAN speed mismatch: Daly defaults to 250kbit/s, Victron uses 500kbit/s
+- Developers of dbus-serialbattery specifically do NOT recommend Daly for new builds
+- Bad CAN communication implementation
+
+---
+
+## Victron Side Configuration
+
+### Hardware Required
+
+**Cerbo GX ($320-350) -- Recommended**
+- Native BMS-CAN port (500kbit/s)
+- 2x USB ports for dbus-serialbattery driver
+- Built-in display, Ethernet, WiFi
+- VRM remote monitoring portal
+
+**Budget Alternative: Venus OS on Raspberry Pi 4 (~$100)**
+- No native CAN bus -- needs USB CAN adapter ($20-40)
+- More complex setup
+- Works for USB-UART BMS connection (JK, Overkill)
+
+### CAN Cable Pinout (Cerbo GX BMS-CAN RJ45)
+
+| Pin | Function |
+|---|---|
+| 3 | GND |
+| 7 | CAN-H |
+| 8 | CAN-L |
+
+Only 3 wires needed. Always verify against your specific BMS datasheet.
+
+### Software Settings
+
+1. **Update firmware** on Cerbo GX, MultiPlus II, and any MPPTs to latest
+2. **Battery Monitor:** Set to BMS (not "Automatic")
+3. **DVCC:** Enable
+4. **DVCC Sub-settings:**
+   - Limit managed battery charge voltage: OFF (let BMS control via CVL)
+   - SVS (Shared voltage sense): ON
+   - SCS (Shared current sense): OFF
+   - STS (Shared temperature sense): Optional
+5. **BMS-CAN speed:** 500kbit/s (default, don't change)
+
+### dbus-serialbattery Driver (for JK/Overkill/Daly via USB)
+
+- Install on Cerbo via SSH
+- Edit `/data/etc/dbus-serialbattery/config.ini`
+- Set BMS type and serial port
+- Free, open source: https://github.com/Louisvdw/dbus-serialbattery
+
+### DVCC Explained
+
+DVCC allows the BMS to send real-time limits to the Victron system:
+- **CVL** (Charge Voltage Limit) -- max voltage the battery will accept
+- **CCL** (Charge Current Limit) -- max charge current right now
+- **DCL** (Discharge Current Limit) -- max discharge current right now
+
+The Cerbo relays these to the MultiPlus and any solar chargers, preventing overcharge, over-discharge, and overcurrent dynamically.
+
+---
+
+## Common Mistakes to Avoid
+
+1. **CAN speed mismatch** -- Victron is 500kbit/s, some BMS default to 250kbit/s
+2. **JK pinout reversal** -- CAN-H and CAN-L are swapped on JK BMS
+3. **Enabling DVCC without setting battery monitor** -- set monitor FIRST
+4. **SVS with disconnect BMS** -- if BMS disconnects on overvoltage, turn SVS OFF
+5. **Multiple BMS on CAN** -- only ONE BMS should control Victron via DVCC (use master/slave for multi-pack)
+6. **Charging below 0C** -- LFP cannot be charged below freezing; ensure BMS low-temp cutoff is configured
+7. **Passive balancing on large cells** -- 30mA on 20Ah cells takes forever; use active balancing
+
+---
+
+## Sources
+
+- [Victron Compatible BMS - DIY Solar Forum](https://diysolarforum.com/threads/victron-compatible-lifepo4-bms.47111/)
+- [Victron Community - Compatible BMS List](https://community.victronenergy.com/questions/13574/list-of-compatible-bms-vebus-or-canbus.html)
+- [JK BMS and DVCC - Victron Community](https://community.victronenergy.com/t/jk-bms-and-dvcc/29580)
+- [REC BMS Victron Integration Guide - OGM Energy](https://ogm-energy.com/community/ogm-user-forum/topic/154310/)
+- [dbus-serialbattery GitHub](https://github.com/Louisvdw/dbus-serialbattery)
+- [Victron DVCC Documentation](https://www.victronenergy.com/media/pg/CCGX/en/dvcc---distributed-voltage-and-current-control.html)
+- [VE.Can to CAN-bus BMS Cables](https://www.victronenergy.com/live/battery_compatibility:can-bus_bms-cable)
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+# Wrightstown Solar - Salvaged EV Battery Analysis
+
+**Created:** 2026-02-09
+**Decision:** New EVE C40 cells selected over salvaged EV packs
+
+---
+
+## Summary
+
+Salvaged EV battery packs were evaluated as an alternative to new EVE C40 LiFePO4 cells for the 20kWh home storage system. The analysis concluded that new cells are the better choice due to lower total cost, longer lifespan, better safety profile, and simpler integration.
+
+---
+
+## Cost Comparison
+
+| Option | Cost for 20kWh | $/kWh | Expected Life | Chemistry |
+|---|---|---|---|---|
+| **New EVE C40** | **$3,800-5,640** | **$190-282** | **3,000-6,000 cycles** | **LFP** |
+| Salvaged Tesla LFP | $8,500-15,600 | $415-780 | 500-2,000 cycles | LFP |
+| Salvaged Chevy Bolt | $9,800-14,000 | $490-700 | 500-1,500 cycles | NMC |
+| Salvaged Nissan Leaf | $7,300-10,000 | $365-500 | 500-1,500 cycles | NMC |
+
+---
+
+## Why Salvaged Packs Cost More Than Expected
+
+### Voltage Mismatch
+
+EV packs run at 350-400V. The system needs 48V. Options:
+- DC-DC converter (400V to 48V): $1,500-3,000
+- Complete pack disassembly and reconfiguration: 40-60 hours labor
+
+### Proprietary BMS
+
+OEM battery management systems are useless outside the vehicle. Aftermarket replacement (e.g., Orion BMS) costs $800-1,500 plus significant wiring work.
+
+### Cooling Systems
+
+Most EV packs are liquid cooled. At home storage discharge rates, passive cooling may suffice, but you're discarding a system the cells were designed around. Adding proper cooling: $500-1,500.
+
+### Unknown State of Health
+
+- No reliable way to verify remaining capacity without specialized testing
+- Packs from totaled vehicles have unknown fast-charge history and cycle count
+- Cells may be at 70% SOH when "retired" -- a 60kWh pack may only deliver 40kWh
+- Average EV battery loses 2.3% capacity per year
+
+### Chemistry Concerns
+
+Most salvaged packs are NMC (nickel manganese cobalt), NOT LiFePO4:
+- NMC thermal runaway: ~210C (410F)
+- LFP thermal runaway: ~270C (518F)
+- For home storage inside/next to a house, LFP is the responsible choice
+
+### Time Investment
+
+- Salvaged EV build: 40-100+ hours (disassembly, testing, rewiring, custom fabrication)
+- New C40 build: 10-20 hours per 5kWh pack with off-the-shelf parts
+
+---
+
+## When Salvaged DOES Make Sense
+
+- Tesla Model 3 Standard Range LFP modules at under $100/kWh with verified 85%+ SOH
+- Free/very cheap packs from personal connections
+- Educational/hobby project where learning is the goal
+- Electrical engineering background and high-voltage experience
+- However: LFP Model 3 was discontinued in US market due to tariffs, limiting availability
+
+---
+
+## Salvage Sources (For Reference)
+
+- Currents Marketplace (currents.market) -- dedicated EV battery platform
+- Greentec Auto (greentecauto.com) -- premium second-life batteries
+- Second Life EV Batteries (secondlife-evbatteries.com)
+- AZLithium (azlithium.com) -- Chevy Volt, Leaf, BMW i3 modules
+- eBay -- wide selection, variable quality
+
+---
+
+## Decision Rationale
+
+New EVE C40 cells win on every metric that matters for this project:
+
+1. **50-65% cheaper** total system cost
+2. **3-10x longer lifespan** (known cycle life vs unknown remaining)
+3. **Safer chemistry** (LFP vs NMC)
+4. **Native 48V** configuration (no voltage conversion)
+5. **Standard BMS** compatibility (off-the-shelf 16S)
+6. **Known capacity** (no degradation mysteries)
+7. **5x less build time** (10-20 hours vs 40-100+)
+8. **Warranty coverage** from cell manufacturer
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+# Wrightstown Solar - Parts List & Budget
+
+**Created:** 2026-02-09
+**Status:** Draft -- prices are estimates, verify before purchasing
+
+---
+
+## Phase 1: First 5kWh Pack + Victron System
+
+### Inverter & Control
+
+| Component | Qty | Est. Unit | Est. Total | Notes |
+|---|---|---|---|---|
+| Victron MultiPlus II 48/5000/70-50 | 1 | $1,400-1,800 | $1,400-1,800 | 4kW continuous, 9kW peak, <20ms transfer |
+| Cerbo GX | 1 | $320-350 | $320-350 | System brain, DVCC, VRM monitoring |
+| GX Touch 50 (optional) | 1 | $150-180 | $150-180 | Touchscreen for Cerbo (or use HDMI) |
+
+### Battery Pack (16S5P)
+
+| Component | Qty | Est. Unit | Est. Total | Notes |
+|---|---|---|---|---|
+| EVE C40 20Ah cells (Grade A, matched) | 80 | $3-5 | $240-400 | Verify test data from supplier |
+| JK BMS B2A8S20P 150A | 1 | $80-150 | $80-150 | 2A active balancing, 16S |
+| USB-UART cable | 1 | $15 | $15 | JK BMS to Cerbo GX connection |
+| 40135 cell holders | Set | $20-40 | $20-40 | Cylindrical cell mounting |
+| Nickel/copper bus bars | Set | $20-40 | $20-40 | Cell interconnects |
+| Battery enclosure | 1 | $30-60 | $30-60 | Ventilated, insulated |
+| Class T fuse + holder (150A) | 1 | $20-30 | $20-30 | DC protection |
+| DC disconnect switch | 1 | $20-40 | $20-40 | Isolation between battery and inverter |
+| Battery cables (2/0 AWG or similar) | Set | $30-50 | $30-50 | Battery to inverter |
+| Terminal lugs, heat shrink, misc | Set | $20-30 | $20-30 | Assembly supplies |
+
+### Electrical / Installation
+
+| Component | Qty | Est. Unit | Est. Total | Notes |
+|---|---|---|---|---|
+| Sub-panel (if separating critical loads) | 1 | $50-100 | $50-100 | Or use existing panel |
+| AC breakers | 2-3 | $10-15 | $20-45 | Input and output protection |
+| AC wiring (10 AWG or per code) | Lot | $30-50 | $30-50 | Grid to Victron to panel |
+| Generator inlet (if adding generator) | 1 | $30-60 | $30-60 | NEMA L14-30 or similar |
+| Mounting hardware | Lot | $20-30 | $20-30 | Wall mount for Victron, battery shelf |
+
+### Phase 1 Total
+
+| Category | Low Est. | High Est. |
+|---|---|---|
+| Inverter & Control | $1,720 | $2,330 |
+| Battery Pack | $475 | $855 |
+| Electrical / Install | $150 | $285 |
+| **Phase 1 Total** | **$2,345** | **$3,470** |
+
+---
+
+## Phase 2-4: Additional 5kWh Packs (x3)
+
+### Per Additional Pack
+
+| Component | Qty | Est. Unit | Est. Total |
+|---|---|---|---|
+| EVE C40 20Ah cells | 80 | $3-5 | $240-400 |
+| JK BMS B2A8S20P 150A | 1 | $80-150 | $80-150 |
+| Cell holders, bus bars | Set | $40-80 | $40-80 |
+| Enclosure | 1 | $30-60 | $30-60 |
+| Fuse, disconnect, cables | Set | $40-70 | $40-70 |
+| **Per Pack Total** | | | **$430-760** |
+
+### All 3 Additional Packs
+
+| | Low Est. | High Est. |
+|---|---|---|
+| 3x additional packs | $1,290 | $2,280 |
+
+---
+
+## Full System Total (20kWh)
+
+| Phase | Low Est. | High Est. |
+|---|---|---|
+| Phase 1 (5kWh + Victron) | $2,345 | $3,470 |
+| Phases 2-4 (15kWh additional) | $1,290 | $2,280 |
+| **Complete 20kWh System** | **$3,635** | **$5,750** |
+
+### Cost Per kWh: $178-281/kWh (all-in, including inverter)
+### Battery-only cost: $86-153/kWh
+
+---
+
+## Supplier Notes
+
+### EVE C40 Cells
+
+- **Source Grade A matched cells** with test data showing capacity and internal resistance
+- Reputable suppliers: EEL Battery, SeLian Energy, direct AliExpress sellers with good reviews
+- Verify cells are genuine EVE (counterfeits exist)
+- Order 5-10% extra cells for replacements and matching
+
+### JK BMS
+
+- Amazon (JKBMS official store) for faster shipping, slightly higher price
+- AliExpress for best price, slower shipping
+- Specify 150A version, 16S, with Bluetooth + RS485
+
+### Victron Equipment
+
+- Authorized Victron dealers for warranty
+- Signature Solar, altE Store, Battery Hookup (US dealers)
+- Check for bundle pricing (MultiPlus + Cerbo)
+
+---
+
+## Tools Needed
+
+| Tool | Purpose | Own/Buy |
+|---|---|---|
+| Multimeter | Cell testing, wiring verification | Essential |
+| Spot welder or compression fittings | Cell connections | Depends on bus bar choice |
+| Wire crimper (hydraulic for large lugs) | Battery cables | Essential |
+| Torque wrench | Bus bar connections | Recommended |
+| Heat gun | Heat shrink tubing | Essential |
+| Insulated tools | Working near battery | Essential for safety |
+| Class D fire extinguisher | Lithium battery safety | Essential |
+| Safety glasses, gloves | Assembly PPE | Essential |
--- a/projects/wrightstown-solar/documentation/system-design.md
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+# Wrightstown Solar - System Design
+
+**Created:** 2026-02-09
+**Status:** Planning
+
+---
+
+## System Overview
+
+Whole-house UPS using DIY 48V LiFePO4 battery packs with Victron MultiPlus II inverter. Seamless grid-to-battery switchover with generator backup for extended outages.
+
+---
+
+## Cell Selection: EVE C40
+
+| Spec | Value |
+|---|---|
+| Chemistry | LiFePO4 (LFP) |
+| Form Factor | 40135 Cylindrical |
+| Model | EVE IFR40135 / C40 |
+| Nominal Voltage | 3.2V |
+| Capacity | 20Ah (20,000mAh) |
+| Energy per Cell | 64Wh |
+| Weight | 366g |
+| Max Continuous Discharge | 50-60A |
+| Pulse Discharge | 100A |
+| Standard Charge | 10A |
+| Fast Charge | Up to 8A |
+| Internal Resistance (DC) | <=8 milliohm |
+| Internal Resistance (AC) | <=3 milliohm |
+| Operating Temp | 0-55C |
+| Certifications | CB, UL1642, UN38.3 |
+
+### Why Cylindrical Over Prismatic
+
+- Individual cell failure is contained (easier thermal runaway management)
+- No compression hardware needed (prismatic cells need clamping)
+- Modular -- add capacity by adding parallel strings
+- Smaller units easier to handle
+- Trade-off: More connections to make, need cell holders
+
+---
+
+## Battery Pack Design
+
+### Per-Pack Configuration: 16S5P
+
+| Parameter | Value |
+|---|---|
+| Series cells | 16 (51.2V nominal) |
+| Parallel strings | 5 |
+| Total cells per pack | 80 |
+| Pack voltage (nominal) | 51.2V |
+| Pack voltage (full) | 58.4V (3.65V/cell) |
+| Pack voltage (empty) | 48.0V (3.0V/cell cutoff) |
+| Pack capacity | 100Ah / 5.12kWh |
+| Max continuous discharge | 100A (limited by BMS) |
+| Weight (cells only) | ~29.3kg (80 x 366g) |
+
+### Full System: 4 Packs (16S5P x 4)
+
+| Parameter | Value |
+|---|---|
+| Total cells | 320 |
+| Total capacity | 400Ah / 20.48kWh |
+| Packs in parallel | 4 (at DC bus) |
+| Total weight (cells) | ~117kg |
+
+### Expansion Plan
+
+1. **Pack 1** -- Build, test, run for 1 month to validate design
+2. **Pack 2** -- Parallel with Pack 1 (now 10kWh)
+3. **Packs 3 & 4** -- Build together once confident in process
+
+---
+
+## Inverter: Victron MultiPlus II 48/5000
+
+| Spec | Value |
+|---|---|
+| Model | MultiPlus II 48/5000/70-50 |
+| Continuous output | 4,000W |
+| Peak output | 9,000W |
+| Transfer switch | Built-in, <20ms switchover |
+| AC inputs | 2 (grid + generator) |
+| Battery voltage | 48V nominal |
+| Max charge current | 70A |
+| Transfer relay | Physical disconnect (no backfeed) |
+
+### Key Features for This Build
+
+- **UPS Function:** <20ms transfer time, seamless for all electronics
+- **Anti-Island:** Physical relay opens on grid loss, zero backfeed risk
+- **Generator Support:** AC Input 2 accepts generator, charges battery + powers loads simultaneously
+- **Micro-Grid:** Creates stable AC output that Fronius IG Plus can sync to during outages
+- **PowerAssist:** Supplements grid during high-demand periods
+
+### Parallel Option
+
+Two MultiPlus II 48/5000 units in parallel provide:
+- 8,000W continuous / 18,000W peak
+- Full whole-house coverage including AC units
+- Consider for future expansion if single unit isn't enough
+
+---
+
+## GX Device: Cerbo GX
+
+| Spec | Value |
+|---|---|
+| Price | $320-350 |
+| BMS-CAN Port | Yes (500kbit/s) |
+| USB Ports | 2 (for dbus-serialbattery driver) |
+| Display | Built-in touchscreen or HDMI |
+| Connectivity | Ethernet, WiFi, Bluetooth |
+| Remote Monitoring | VRM Portal (free) |
+
+### Functions
+
+- DVCC (Distributed Voltage and Current Control) -- lets BMS control charge/discharge
+- Battery monitoring and SOC display
+- Remote monitoring via Victron VRM portal
+- Generator auto-start/stop control
+- System configuration interface
+
+---
+
+## Existing Solar: Fronius IG Plus
+
+- **Type:** Grid-tie string inverter (NO battery port)
+- **Status:** Keep as-is
+- **Normal Operation:** Feeds solar to grid, offsets electricity bill
+- **During Outage:** Victron creates micro-grid, Fronius syncs to it and produces solar to charge battery and power loads
+- **Future:** Replace with hybrid inverter when Fronius reaches end of life
+
+---
+
+## System Architecture
+
+### Normal Operation (Grid Available)
+
+```
+Solar Panels
+     |
+[Fronius IG Plus] ---> Grid (net metering)
+                          |
+                    [Victron MultiPlus II] ---> House Panel
+                          |                     (pass-through)
+                    [48V Battery Bank]
+                    (trickle charge / standby)
+```
+
+- Fronius produces solar, feeds grid
+- Victron passes grid through to house
+- Battery maintains float charge
+- Victron can charge battery from grid if configured
+
+### Grid Down (Battery Mode)
+
+```
+Solar Panels
+     |
+[Fronius IG Plus] ---> [Victron MultiPlus II] ---> House Panel
+     (syncs to            |   (relay OPEN,         (powered from
+      Victron              |    grid isolated)        battery)
+      micro-grid)          |
+                    [48V Battery Bank]
+                    (discharging)
+```
+
+- Transfer relay opens (grid physically disconnected)
+- Battery powers house via Victron
+- Victron creates AC micro-grid
+- Fronius detects stable AC, resumes solar production
+- Solar charges battery + powers loads
+
+### Extended Outage (Generator Mode)
+
+```
+[Generator] ---> [Victron MultiPlus II] ---> House Panel
+                       |
+                 [48V Battery Bank]
+                 (charging from generator)
+```
+
+- Generator connects to AC Input
+- Victron simultaneously powers loads AND charges battery
+- When battery full, can signal generator to shut down
+- Battery takes over, generator restarts when battery low (auto-start capable)
+
+---
+
+## Runtime Estimates (5kWh Single Pack)
+
+| Load Scenario | Consumption | Runtime |
+|---|---|---|
+| Essentials (fridge, lights, internet, outlets) | ~500W | 8-10 hours |
+| Moderate (+ TV, computers, fans) | ~1,000W | 4-5 hours |
+| Heavy (+ AC or electric cooking) | ~2,000W | 2-2.5 hours |
+| Full house (everything) | ~4,000W | 1-1.25 hours |
+
+### At Full 20kWh (4 Packs)
+
+| Load Scenario | Runtime |
+|---|---|
+| Essentials only | 32-40 hours |
+| Moderate use | 16-20 hours |
+| Heavy use | 8-10 hours |
+
+---
+
+## Installation Plan
+
+### Electrical Work Required
+
+1. **Critical Loads Sub-Panel** -- Move essential circuits to new sub-panel (or use whole panel)
+2. **Victron Placement** -- Between grid and sub-panel
+3. **Battery Location** -- Garage, basement, or utility room (ventilated, temperature controlled)
+4. **Generator Connection** -- Dedicated inlet with proper gauge wiring
+5. **Grounding** -- Victron system ground per local code
+
+### Safety Requirements
+
+- DC disconnect between battery and inverter
+- Proper fusing on each battery pack (class T fuse recommended)
+- Breaker on AC output
+- Ventilation for battery area
+- Fire extinguisher (Class D) nearby
+- Temperature monitoring on cells
+
+---
+
+## Cell Voltage Reference (LiFePO4)
+
+| State | Voltage/Cell | Pack Voltage (16S) |
+|---|---|---|
+| Full Charge | 3.65V | 58.4V |
+| ~90% SOC | 3.35V | 53.6V |
+| ~50% SOC | 3.30V | 52.8V |
+| ~20% SOC | 3.20V | 51.2V |
+| Low Cutoff | 3.00V | 48.0V |
+| Absolute Min | 2.50V | 40.0V |
+
+Note: LFP has a very flat voltage curve between 20-90% SOC (~3.2-3.35V). This makes SOC estimation from voltage alone unreliable -- coulomb counting via BMS is essential.
--- a/projects/wrightstown-solar/session-logs/2026-02-09-session.md
+++ b/projects/wrightstown-solar/session-logs/2026-02-09-session.md
@@ -0,0 +1,83 @@
+# Wrightstown Solar - Session Log 2026-02-09
+
+**Session:** Initial Research and Planning
+**Machine:** ACG-M-L5090
+
+---
+
+## Work Completed
+
+### 1. Cell Selection Research
+- Researched EVE C40 (IFR40135) cylindrical LiFePO4 cells
+- Specs: 3.2V, 20Ah, 64Wh per cell, 366g, 50-60A continuous discharge
+- Selected for home solar battery pack build
+
+### 2. Pack Design
+- Determined 16S5P configuration for 5kWh packs (80 cells each)
+- 48V nominal system, 51.2V actual
+- Modular design: build in 5kWh increments up to 20kWh (4 packs)
+- Chose 5kWh over 10kWh packs for: cost spreading, manageable builds, fault isolation, single-person liftable weight
+
+### 3. Inverter Selection
+- Existing solar: Fronius IG Plus (grid-tie only, no battery port)
+- Selected Victron MultiPlus II 48/5000 for:
+  - <20ms transfer (UPS-grade seamless switchover)
+  - Physical relay disconnect (zero backfeed)
+  - Generator input support
+  - Creates micro-grid for Fronius to sync during outages
+- Architecture: whole-house UPS with generator failover
+
+### 4. Salvaged EV Battery Analysis
+- Evaluated Tesla LFP, Chevy Bolt, Nissan Leaf salvage options
+- Conclusion: New C40 cells are cheaper ($190-282/kWh vs $365-780/kWh for salvage)
+- Salvage has hidden costs: voltage conversion, custom BMS, cooling, unknown SOH
+- Most salvage is NMC chemistry (less safe than LFP for home use)
+- Decision: Proceed with new EVE C40 cells
+
+### 5. BMS Research (Victron CAN Bus Compatible)
+- Comprehensive comparison of 8 BMS models
+- Recommended: JK BMS B2A8S20P 150A ($80-150)
+  - 2A active balancing (critical for cylindrical cells)
+  - Victron integration via dbus-serialbattery driver + USB-UART cable
+  - Known gotcha: CAN pinout reversed (use USB-UART path instead)
+- Alternatives: SEPLOS V4 (native CAN, $150-250), REC Q16 (plug & play, $559)
+- Cerbo GX ($320-350) selected as GX device
+
+### 6. Budget Estimates
+- Phase 1 (5kWh + full Victron system): $2,175-2,945
+- Full 20kWh system: $3,635-5,750
+- Battery-only $/kWh: $86-153
+
+---
+
+## Decisions Made
+
+| Decision | Chosen | Over | Why |
+|---|---|---|---|
+| Cell type | EVE C40 (new) | Salvaged EV packs | Cost, safety, lifespan, simplicity |
+| Pack size | 5kWh modules | 10kWh modules | Modular, manageable, fault isolation |
+| Inverter | Victron MultiPlus II 48/5000 | Other options | UPS switchover, relay disconnect, generator support |
+| BMS | JK BMS B2A8S20P 150A | REC, SEPLOS, Daly | Active balancing, price, community support |
+| GX device | Cerbo GX | Raspberry Pi | Easier setup, native BMS-CAN port |
+
+---
+
+## Files Created
+
+- `projects/wrightstown-solar/PROJECT_INDEX.md`
+- `projects/wrightstown-solar/documentation/system-design.md`
+- `projects/wrightstown-solar/documentation/bms-comparison.md`
+- `projects/wrightstown-solar/documentation/ev-salvage-analysis.md`
+- `projects/wrightstown-solar/documentation/parts-list.md`
+- `projects/wrightstown-solar/session-logs/2026-02-09-session.md` (this file)
+
+---
+
+## Next Steps
+
+- [ ] Finalize BMS selection
+- [ ] Source EVE C40 cells (Grade A, matched, with test data)
+- [ ] Order Victron MultiPlus II + Cerbo GX
+- [ ] Design physical cell holder / bus bar layout for 16S5P cylindrical pack
+- [ ] Plan sub-panel / transfer switch wiring
+- [ ] Build Pack 1, test for 1 month before expanding