Mike Swanson
aaf4172b3c
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>
84 lines
3.2 KiB
Markdown
84 lines
3.2 KiB
Markdown
# Wrightstown Solar - Session Log 2026-02-09
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**Session:** Initial Research and Planning
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**Machine:** ACG-M-L5090
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---
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## Work Completed
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### 1. Cell Selection Research
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- Researched EVE C40 (IFR40135) cylindrical LiFePO4 cells
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- Specs: 3.2V, 20Ah, 64Wh per cell, 366g, 50-60A continuous discharge
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- Selected for home solar battery pack build
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### 2. Pack Design
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- Determined 16S5P configuration for 5kWh packs (80 cells each)
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- 48V nominal system, 51.2V actual
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- Modular design: build in 5kWh increments up to 20kWh (4 packs)
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- Chose 5kWh over 10kWh packs for: cost spreading, manageable builds, fault isolation, single-person liftable weight
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### 3. Inverter Selection
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- Existing solar: Fronius IG Plus (grid-tie only, no battery port)
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- Selected Victron MultiPlus II 48/5000 for:
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- <20ms transfer (UPS-grade seamless switchover)
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- Physical relay disconnect (zero backfeed)
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- Generator input support
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- Creates micro-grid for Fronius to sync during outages
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- Architecture: whole-house UPS with generator failover
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### 4. Salvaged EV Battery Analysis
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- Evaluated Tesla LFP, Chevy Bolt, Nissan Leaf salvage options
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- Conclusion: New C40 cells are cheaper ($190-282/kWh vs $365-780/kWh for salvage)
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- Salvage has hidden costs: voltage conversion, custom BMS, cooling, unknown SOH
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- Most salvage is NMC chemistry (less safe than LFP for home use)
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- Decision: Proceed with new EVE C40 cells
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### 5. BMS Research (Victron CAN Bus Compatible)
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- Comprehensive comparison of 8 BMS models
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- Recommended: JK BMS B2A8S20P 150A ($80-150)
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- 2A active balancing (critical for cylindrical cells)
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- Victron integration via dbus-serialbattery driver + USB-UART cable
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- Known gotcha: CAN pinout reversed (use USB-UART path instead)
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- Alternatives: SEPLOS V4 (native CAN, $150-250), REC Q16 (plug & play, $559)
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- Cerbo GX ($320-350) selected as GX device
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### 6. Budget Estimates
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- Phase 1 (5kWh + full Victron system): $2,175-2,945
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- Full 20kWh system: $3,635-5,750
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- Battery-only $/kWh: $86-153
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---
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## Decisions Made
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| Decision | Chosen | Over | Why |
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| Cell type | EVE C40 (new) | Salvaged EV packs | Cost, safety, lifespan, simplicity |
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| Pack size | 5kWh modules | 10kWh modules | Modular, manageable, fault isolation |
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| Inverter | Victron MultiPlus II 48/5000 | Other options | UPS switchover, relay disconnect, generator support |
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| BMS | JK BMS B2A8S20P 150A | REC, SEPLOS, Daly | Active balancing, price, community support |
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| GX device | Cerbo GX | Raspberry Pi | Easier setup, native BMS-CAN port |
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---
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## Files Created
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- `projects/wrightstown-solar/PROJECT_INDEX.md`
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- `projects/wrightstown-solar/documentation/system-design.md`
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- `projects/wrightstown-solar/documentation/bms-comparison.md`
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- `projects/wrightstown-solar/documentation/ev-salvage-analysis.md`
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- `projects/wrightstown-solar/documentation/parts-list.md`
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- `projects/wrightstown-solar/session-logs/2026-02-09-session.md` (this file)
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---
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## Next Steps
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- [ ] Finalize BMS selection
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- [ ] Source EVE C40 cells (Grade A, matched, with test data)
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- [ ] Order Victron MultiPlus II + Cerbo GX
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- [ ] Design physical cell holder / bus bar layout for 16S5P cylindrical pack
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- [ ] Plan sub-panel / transfer switch wiring
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- [ ] Build Pack 1, test for 1 month before expanding
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