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>
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# Wrightstown Solar - System Design
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**Created:** 2026-02-09
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**Status:** Planning
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---
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## System Overview
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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.
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---
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## Cell Selection: EVE C40
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| Spec | Value |
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|---|---|
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| Chemistry | LiFePO4 (LFP) |
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| Form Factor | 40135 Cylindrical |
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| Model | EVE IFR40135 / C40 |
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| Nominal Voltage | 3.2V |
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| Capacity | 20Ah (20,000mAh) |
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| Energy per Cell | 64Wh |
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| Weight | 366g |
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| Max Continuous Discharge | 50-60A |
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| Pulse Discharge | 100A |
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| Standard Charge | 10A |
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| Fast Charge | Up to 8A |
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| Internal Resistance (DC) | <=8 milliohm |
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| Internal Resistance (AC) | <=3 milliohm |
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| Operating Temp | 0-55C |
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| Certifications | CB, UL1642, UN38.3 |
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### Why Cylindrical Over Prismatic
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- Individual cell failure is contained (easier thermal runaway management)
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- No compression hardware needed (prismatic cells need clamping)
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- Modular -- add capacity by adding parallel strings
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- Smaller units easier to handle
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- Trade-off: More connections to make, need cell holders
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---
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## Battery Pack Design
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### Per-Pack Configuration: 16S5P
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| Parameter | Value |
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|---|---|
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| Series cells | 16 (51.2V nominal) |
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| Parallel strings | 5 |
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| Total cells per pack | 80 |
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| Pack voltage (nominal) | 51.2V |
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| Pack voltage (full) | 58.4V (3.65V/cell) |
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| Pack voltage (empty) | 48.0V (3.0V/cell cutoff) |
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| Pack capacity | 100Ah / 5.12kWh |
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| Max continuous discharge | 100A (limited by BMS) |
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| Weight (cells only) | ~29.3kg (80 x 366g) |
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### Full System: 4 Packs (16S5P x 4)
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| Parameter | Value |
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|---|---|
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| Total cells | 320 |
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| Total capacity | 400Ah / 20.48kWh |
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| Packs in parallel | 4 (at DC bus) |
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| Total weight (cells) | ~117kg |
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### Expansion Plan
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1. **Pack 1** -- Build, test, run for 1 month to validate design
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2. **Pack 2** -- Parallel with Pack 1 (now 10kWh)
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3. **Packs 3 & 4** -- Build together once confident in process
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---
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## Inverter: Victron MultiPlus II 48/5000
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| Spec | Value |
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|---|---|
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| Model | MultiPlus II 48/5000/70-50 |
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| Continuous output | 4,000W |
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| Peak output | 9,000W |
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| Transfer switch | Built-in, <20ms switchover |
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| AC inputs | 2 (grid + generator) |
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| Battery voltage | 48V nominal |
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| Max charge current | 70A |
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| Transfer relay | Physical disconnect (no backfeed) |
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### Key Features for This Build
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- **UPS Function:** <20ms transfer time, seamless for all electronics
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- **Anti-Island:** Physical relay opens on grid loss, zero backfeed risk
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- **Generator Support:** AC Input 2 accepts generator, charges battery + powers loads simultaneously
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- **Micro-Grid:** Creates stable AC output that Fronius IG Plus can sync to during outages
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- **PowerAssist:** Supplements grid during high-demand periods
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### Parallel Option
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Two MultiPlus II 48/5000 units in parallel provide:
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- 8,000W continuous / 18,000W peak
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- Full whole-house coverage including AC units
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- Consider for future expansion if single unit isn't enough
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---
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## GX Device: Cerbo GX
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| Spec | Value |
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|---|---|
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| Price | $320-350 |
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| BMS-CAN Port | Yes (500kbit/s) |
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| USB Ports | 2 (for dbus-serialbattery driver) |
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| Display | Built-in touchscreen or HDMI |
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| Connectivity | Ethernet, WiFi, Bluetooth |
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| Remote Monitoring | VRM Portal (free) |
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### Functions
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- DVCC (Distributed Voltage and Current Control) -- lets BMS control charge/discharge
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- Battery monitoring and SOC display
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- Remote monitoring via Victron VRM portal
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- Generator auto-start/stop control
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- System configuration interface
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---
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## Existing Solar: Fronius IG Plus
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- **Type:** Grid-tie string inverter (NO battery port)
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- **Status:** Keep as-is
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- **Normal Operation:** Feeds solar to grid, offsets electricity bill
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- **During Outage:** Victron creates micro-grid, Fronius syncs to it and produces solar to charge battery and power loads
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- **Future:** Replace with hybrid inverter when Fronius reaches end of life
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---
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## System Architecture
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### Normal Operation (Grid Available)
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```
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Solar Panels
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[Fronius IG Plus] ---> Grid (net metering)
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[Victron MultiPlus II] ---> House Panel
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| (pass-through)
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[48V Battery Bank]
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(trickle charge / standby)
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```
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- Fronius produces solar, feeds grid
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- Victron passes grid through to house
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- Battery maintains float charge
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- Victron can charge battery from grid if configured
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### Grid Down (Battery Mode)
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```
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Solar Panels
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[Fronius IG Plus] ---> [Victron MultiPlus II] ---> House Panel
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(syncs to | (relay OPEN, (powered from
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Victron | grid isolated) battery)
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micro-grid) |
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[48V Battery Bank]
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(discharging)
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```
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- Transfer relay opens (grid physically disconnected)
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- Battery powers house via Victron
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- Victron creates AC micro-grid
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- Fronius detects stable AC, resumes solar production
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- Solar charges battery + powers loads
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### Extended Outage (Generator Mode)
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```
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[Generator] ---> [Victron MultiPlus II] ---> House Panel
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[48V Battery Bank]
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(charging from generator)
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```
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- Generator connects to AC Input
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- Victron simultaneously powers loads AND charges battery
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- When battery full, can signal generator to shut down
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- Battery takes over, generator restarts when battery low (auto-start capable)
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---
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## Runtime Estimates (5kWh Single Pack)
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| Load Scenario | Consumption | Runtime |
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|---|---|---|
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| Essentials (fridge, lights, internet, outlets) | ~500W | 8-10 hours |
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| Moderate (+ TV, computers, fans) | ~1,000W | 4-5 hours |
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| Heavy (+ AC or electric cooking) | ~2,000W | 2-2.5 hours |
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| Full house (everything) | ~4,000W | 1-1.25 hours |
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### At Full 20kWh (4 Packs)
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| Load Scenario | Runtime |
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|---|---|
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| Essentials only | 32-40 hours |
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| Moderate use | 16-20 hours |
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| Heavy use | 8-10 hours |
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---
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## Installation Plan
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### Electrical Work Required
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1. **Critical Loads Sub-Panel** -- Move essential circuits to new sub-panel (or use whole panel)
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2. **Victron Placement** -- Between grid and sub-panel
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3. **Battery Location** -- Garage, basement, or utility room (ventilated, temperature controlled)
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4. **Generator Connection** -- Dedicated inlet with proper gauge wiring
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5. **Grounding** -- Victron system ground per local code
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### Safety Requirements
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- DC disconnect between battery and inverter
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- Proper fusing on each battery pack (class T fuse recommended)
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- Breaker on AC output
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- Ventilation for battery area
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- Fire extinguisher (Class D) nearby
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- Temperature monitoring on cells
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---
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## Cell Voltage Reference (LiFePO4)
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| State | Voltage/Cell | Pack Voltage (16S) |
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|---|---|---|
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| Full Charge | 3.65V | 58.4V |
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| ~90% SOC | 3.35V | 53.6V |
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| ~50% SOC | 3.30V | 52.8V |
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| ~20% SOC | 3.20V | 51.2V |
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| Low Cutoff | 3.00V | 48.0V |
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| Absolute Min | 2.50V | 40.0V |
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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.
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