================================================================================ SCHEMATIC: LiFePO4 Battery Pack with BMS TM-PWR-001 Rev A 12.8V Nominal (4S: 4 cells in series) | Capacity: 20–100 Ah BMS protection: OV, UV, OC, SC, temperature | Anderson Powerpole output ================================================================================ LiFePO4 CELL CHEMISTRY ──────────────────────── LiFePO4 (Lithium Iron Phosphate) is the safest lithium chemistry for ham field use: - No thermal runaway (cannot burn or explode under normal abuse) - 2000–5000 charge cycle life (vs. 300–500 for Li-Ion) - Flat discharge curve from 80% to 20% SOC (voltage stays near 3.2V) - Non-toxic iron-phosphate cathode CELL PARAMETERS: Nominal voltage: 3.2V per cell Full charge voltage: 3.60V (charge cutoff) Full discharge cutoff: 2.50V (discharge cutoff; do not go below) Optimal range: 2.8V–3.4V (80% of capacity, maximizes cycle life) 4S PACK (4 cells in series): Nominal: 4 × 3.2V = 12.8V Full charge: 4 × 3.60V = 14.4V Discharge cutoff: 4 × 2.50V = 10.0V VOLTAGE vs. SOC TABLE (4S pack, 20°C): 100% SOC: 14.2–14.4V (just after charge) 90% SOC: 13.4V 80% SOC: 13.2V 60% SOC: 13.1V ← very flat region 40% SOC: 13.0V 20% SOC: 12.8V 10% SOC: 12.5V 0% SOC: 10.0V (cutoff; never reach in normal use) Rest for 1 hour after charge before measuring OCV for accurate SOC. CAPACITY SELECTION: 20 Ah: QRP portable (< 5W TX; 4+ hour POTA/SOTA activation) 50 Ah: Mobile HF at 100W (2–3 hour operation without solar) 100 Ah: Base station portable (full day with 100W HF) ================================================================================ BMS (BATTERY MANAGEMENT SYSTEM) OVERVIEW ================================================================================ PROTECTION FUNCTIONS: 1. Overvoltage (OV): disconnect charge if any cell > 3.65V 2. Undervoltage (UV): disconnect load if any cell < 2.50V 3. Overcurrent Charge (OCC): limit charge current (set at 0.5C typically) 4. Overcurrent Discharge (OCD): limit discharge current (set at 1C–3C) 5. Short Circuit (SC): ultra-fast cutoff < 100 µs 6. Temperature: cutoff if < 0°C (charging) or > 60°C (any) 7. Cell balancing: equalize cell voltages during top-of-charge BMS TOPOLOGY: Common Port (single B− connector; charge and discharge share one path) OR Separate Port (dedicated charge port + discharge port — preferred for large packs) RECOMMENDED COMMERCIAL BMS: For 20–50 Ah, ≤ 50A continuous: Daly 4S 50A BMS ($15–$25) For 50–100 Ah, ≤ 100A continuous: JK BMS 4S 100A (active balancer, $30–$50) For custom discrete design: see Section "DISCRETE BMS CIRCUIT" below. ================================================================================ DALY BMS CONNECTION (COMMON PORT TOPOLOGY) ================================================================================ DALY 4S 50A BMS PINOUT AND CONNECTIONS: B+ ── Pack positive (direct to cell 4 positive) B− ── Pack negative (direct to cell 1 negative) C1 ── Cell 1 to Cell 2 junction (balance tap 1) C2 ── Cell 2 to Cell 3 junction (balance tap 2) C3 ── Cell 3 to Cell 4 junction (balance tap 3) GND ── Cell 1 negative (same as B−) P+ ── (same as B+ — common port design) P− ── Load/Charger negative OUT (switched by BMS MOSFET) FULL PACK WIRING DIAGRAM: [CHARGER]─────────────────────────────┐ (+) ──────────────────────────────── B+ (−) ───────────────────────── P− ← BMS ← B− ─── [CELL1−] [CELL1+]──[CELL2−] C1 balance tap ──────── BMS C1 [CELL2+]──[CELL3−] C2 balance tap ──────── BMS C2 [CELL3+]──[CELL4−] C3 balance tap ──────── BMS C3 [CELL4+] ─────────────────────────── B+ [LOAD(+)] ────────────────────────── B+ (or P+ on separate-port BMS) [LOAD(−)] ────────────────────────── P− (switched by BMS MOSFET) ANDERSON POWERPOLE ─────────────────────────── to Load(+) and P− CELL BALANCE RESISTORS (for Daly passive balancer, optional improvement): Between each balance tap and B−: 33kΩ bleeder maintains BMS reference stability. Or: leave as-is; Daly balancer works without external bleeder. ================================================================================ JK BMS ACTIVE BALANCER (PREFERRED FOR FIELD USE) ================================================================================ The JK BMS uses an inductor-based active balancer that transfers charge from high-voltage cells to low-voltage cells during balancing. This is 80–90% efficient vs. passive (resistive) balancing which wastes energy as heat. JK BMS ADDITIONAL FEATURES: - Bluetooth LE: phone app shows cell voltages, temperature, SOC, current - RS485 / UART output: for ESP32 monitoring integration - Configurable protection thresholds via app - LCD port: optional remote display - 2× temperature probes (cell and MOSFET temperature) ESP32 INTEGRATION WITH JK BMS: JK BMS UART (115200 baud): Tx → ESP32 GPIO16; Rx → ESP32 GPIO17 Protocol: JK BMS protocol (documented on GitHub: jblance/jkbms) Read: cell voltages, pack voltage, current, temperature, SOC, fault flags. Display on CYD: see firmware psu_monitor_esp32.ino ================================================================================ DISCRETE BMS CIRCUIT (EDUCATIONAL — for custom/high-current designs) ================================================================================ For understanding the protection circuit (commercial BMS replaces all of this): CELL VOLTAGE MONITOR (per cell): Each cell voltage fed through a precision voltage divider to a comparator. OV comparator: fires if V_cell > 3.65V → latches cutoff relay UV comparator: fires if V_cell < 2.50V → latches cutoff relay Example for one cell OV detection: V_cell ──[R1: 36.5kΩ]──┬── (+) of comparator LM339 │ [R2: 10kΩ] V_ref = V_cell × R2/(R1+R2) │ At V_cell = 3.65V: V_ref = 3.65 × 10/46.5 = 0.785V GND (−) ──[0.785V Zener or resistor from 2.5V ref] Comparator output goes LOW when V_cell > 3.65V → triggers FET cutoff DISCHARGE MOSFET STAGE: Uses N-channel MOSFETs with low R_DS(on) for efficiency. For 50A continuous: 4× IRF1404 (40V, 162A, 4mΩ) in parallel. MOSFET dissipation: P = I² × R_DS = 50² × 0.004 / 4 = 2.5W total (excellent). SERIES MOSFET SWITCH: B− ──[Discharge MOSFET stack]──[Charge MOSFET stack]── P− (Two separate MOSFET stacks with anti-parallel body diodes allow charge-only and discharge-only cutoffs independently.) OVERCURRENT / SHORT CIRCUIT: Current sense resistor: 0.001Ω (1mΩ) 50W in the B− path. At 50A: V_sense = 50 × 0.001 = 50mV SC detect: fast comparator (LM393) with 100mV reference → fires in < 10 µs. OC detect: slower comparator with 50ms filter → fires at sustained 50A. ================================================================================ CHARGING AND ANDERSON POWERPOLE OUTPUT ================================================================================ CHARGE PROFILE FOR 4S LiFePO4: CC/CV (Constant Current / Constant Voltage): CC phase: charge at C/5 to C/2 rate until V_pack = 14.4V CV phase: hold 14.4V until current drops below C/20 → full charge Do NOT charge above 14.6V (cell damage; BMS will disconnect but don't rely on it) Do NOT charge below 0°C (lithium plating; permanent damage) RECOMMENDED CHARGER: Victron Orion 12/24V DC-DC or AC/DC LiFePO4 profile charger. Set absorption voltage: 14.4V Set float voltage: 13.5V (maintains without overcharging) DIY CHARGER using LM317 or adjustable PSU: set output to 14.4V, current limit to C/2. For 50Ah pack: charge at 25A maximum; full in ~2.5 hours from 50% SOC. ANDERSON POWERPOLE CONNECTORS: Standard ham radio DC connector (ARRL/ARRL standard, shared with ARES/RACES). RED = positive, BLACK = negative. Housings stack: red on top-right, black on bottom-left (Powerpole convention). Contact sizes: 15A contact (20–18 AWG): small housing — for QRP (< 5W rigs) 30A contact (16–12 AWG): medium — standard HF station (100W rigs) 45A contact (10 AWG): large — high-power amplifier or battery bus INTERNAL WIRING TO POWERPOLE: Battery B+ ─── main fuse ─── Powerpole RED (+ lug) Battery P− ─────────────── Powerpole BLACK (− lug) Fuse size: 1.25× continuous maximum current. 50Ah pack, 50A BMS: use 60A ANL fuse (bolt-down type; not blade) 20Ah pack, 30A BMS: use 40A ANL fuse POWERPOLE DISTRIBUTION BLOCK (1 in, 4 out): One Powerpole battery feed → 4-port distribution with individual fuse per outlet. Each outlet: 15A automotive fuse + Anderson Powerpole pair. Provides independent protection per load (radio, charger, accessories). POWERPOLE WIRING DIAGRAM: [Battery B+] ──[60A ANL FUSE]──────────────────┬─── PP(+) to radio │─── PP(+) to accessories BMS CONTROL ────────────────────── MOSFET ──── ┘ [Battery B−] ──[BMS P−]────────────────────────┬─── PP(−) to radio └─── PP(−) to accessories ================================================================================ BATTERY ENCLOSURE AND SAFETY ================================================================================ CELL ARRANGEMENT (4S prismatic cells, 20–100Ah): Cells oriented with terminals on same side. Compression: use threaded rod + aluminum plates to maintain 15 psi on cells. (Prevents cell swelling, maintains capacity, improves cycle life.) Cell interconnects: copper bus bar, M6 bolts, anti-corrosion washers. THERMAL MANAGEMENT: LiFePO4 optimal temperature: 15–35°C. Below 0°C: charging prohibited; discharging OK down to −20°C at reduced rate. Above 45°C: reduce charge rate. Temperature monitoring: NTC thermistor (10kΩ at 25°C) attached to cell body. Wired to BMS temperature input AND to ESP32 ADC for display. VENTILATION: LiFePO4 does not emit significant gas under normal operation. However: if a cell is damaged or overcharged, small amounts of gas may vent. Install a 1/4" vent hole at top of enclosure with activated carbon filter. Never seal a LiFePO4 enclosure completely airtight. LABELING REQUIREMENTS: "LITHIUM BATTERY — 12.8V [capacity] Ah" "DO NOT SHORT CIRCUIT" "DO NOT CHARGE BELOW 0°C" "DISCONNECT BEFORE SERVICE" ================================================================================ PARTS LIST — LiFePO4 PACK WITH BMS ================================================================================ Item | Qty | Description | Source ----------|-----|------------------------------------------|------------------- CELL | 4 | 3.2V 50Ah LiFePO4 prismatic (EVE 50E) | AliExpress, Basen BMS | 1 | JK BMS 4S 100A active balancer | AliExpress, JKBMS FUSE_ANL | 1 | 60A ANL bolt-down fuse + holder | Amazon, Blue Sea PP_30A | 4 | Anderson Powerpole 30A red+black pair | PowerWerx, DX Eng PP_45A | 2 | Anderson Powerpole 45A (battery bus) | PowerWerx BUS_BAR | 2 | Copper bus bar 6× 25 × 150mm | Metal supplier BOLT | 8 | M6 × 20mm SS hex bolt + nut + washer | Hardware NTC | 2 | 10kΩ NTC thermistor (cell temp) | Mouser ALM_PLATE | 2 | 3mm aluminum compression plate | Metal supplier ROD | 2 | M8 × 300mm threaded rod + nuts | Hardware ENCL | 1 | Pelican 1510 or 3D-printed ASA box | Pelican/print ================================================================================