the Sub · system
About 3.7 kWh across three battery banks, plus an independent survival battery, watched cell by cell — fused at every source, with a supervisor-driven master cut.
14 *active* days ≈ ~9–10 kWh (~2.5–3× the current pack); a *dormant/monitor* profile (sleep ~3–6 W, brief daily tasks) fits in far less. The 4″ hull is modular, so more energy = add a 4th bank / longer 400 mm tubes later — a bolt-on upgrade, not a redesign. Build v1 at 3.7 kWh, size the bus/charger/structure for +1–2 banks now, measure real draw in the reservoir, then scale. Hibernation + DVL nav are the enablers.
| Power module | Holybro PM08-CAN (DroneCAN, 2-14S / 200A, dual 5.2V BEC) | Arrived |
| Pressure tubes ×6 | WTE Locking Tube 4in aluminum — 1x 300mm (electronics) + 1x 400mm (supervisor) + 3x 400mm (battery banks) + 1 spare (deferred VBS) | Arrived |
| Power switch ×2 | M10 switch 5A | Arrived |
| Battery cells ×198 | Samsung INR21700-58E — 5330 mAh min, 10.7 A cont, flat top. 4S16P per bank x3 = 192 cells + 6 spares; ~3.7 kWh total. See docs/POWER-BUDGET.md. | Arrived |
| BMS ×6 | 4S 60/80A Li-ion BMS, 61x42mm (Create idea, 2-pack) | Arrived |
| Survival battery | Bioenno BLF-1206A 12V 6Ah LiFePO4 | Arrived |
| Spot welder | Glitter 801D capacitive | Arrived |
| Nickel strip ×2 | Pure nickel strip 0.15mm x 8mm (~15m needed) | Arrived |
| Pack materials | Pack materials — fish/barley paper, Kapton tape, cell-top insulator rings (cell holders are 3D-PRINTED, not purchased) | Arrived |
| Connectors/wire | XT90-S anti-spark (pack/bus trunk) + XT60 (thruster & accessory branches); silicone 10 AWG trunk + 12-14 AWG branches + 16-22 AWG signal; JST-GH | Arrived |
| 5V regulators ×2 | Pololu D24V50F5 | Arrived |
| 12V regulators ×2 | Pololu D36V50F12 | Arrived |
| Ideal diodes ×4 | LTC4359CS8 (8-lead SO) + IRFB7430 TO-220 N-FET (same as the thruster cut, #111) — one per bank, BUILD not buy | Planned |
| Fuses & holders | Fuse kit — 4x ANL/MIDI holders (3 banks + main bus) + 6-8 way blade fuse block (low-current branches) + assorted ANL (60A, 80-100A) & blade (10A) fuses + spares | Arrived |
| Thruster-cut (solid state) | Solid-state high-side thruster disconnect — 4x IRFB7430 (40V ~1.3 mOhm) paralleled + high-side charge-pump gate driver (LTC7000/LTC7001 class) + TVS | Arrived |
| Magnetic arm switch | Waterproof magnetic reed switch (NO/NC, 2-pack) — external magnet arms/disarms through the hull | Arrived |
| Bus capacitors ×2 | 35V 1000uF low-ESR filter capacitor (XT-lead) — mount on the ESC bus | Arrived |
| Charge port | CNLINKO 6-pin bulkhead connector (~15-20 A) — INTERNAL charge interface, no sealing needed | Arrived |
| 3.3V regulator (LDO) ×2 | 3.3 V LDO, 250-500 mA, fed from the 5 V rail — supplies the RM3100 compass (VDD + I2CEN) and any future 3.3 V logic | Arrived |
| Pack collectors | 0.5mm (24ga) C110 copper sheet, 300 x 600mm | Arrived |
| Cell checker ×2 | 1-8S LiPo/Li-ion balance-lead voltage checker | Arrived |
| Thruster-cut gate passives | C_B 2.2uF 50V X7R (225) x5 | C_G 47nF 50V+ (473) x5 | 10 ohm 1/4W x10 | 100k x10 | 0.1uF (104) x5 | Arrived |
| Thruster-cut catch diode ×3 | Schottky 40-60V, >=5A (SB560 axial or MBR1045G TO-220) | Arrived |
| Thruster-cut INP pulldown FET ×10 | 2N7000 (TO-92 through-hole) — BS170 equivalent | Arrived |
| Timer release | DIY: ATtiny + coin cells, potted | Planned |
| Pack/joint temp ×20 | DS18B20 1-Wire sensors (TO-92) + 4.7k pull-up | Arrived |
| Cell-group voltage ADC ×3 | ADS1115 16-bit I2C ADC breakout (4-ch) | Arrived |
| Precision divider resistors ×50 | Vishay Dale RN55E, 0.1%, 25 ppm/C — 300k x30 (two in series = 600k top leg) + 100k RN55E1003BRE6 x20 | Arrived |
| Bank current shunts ×6 | Stackpole CSSK3637FTL500 — 500 uOhm, 1%, 3W, 50ppm/C, 4-terminal Kelvin, 3637 SMD | Arrived |
| Pack-side 3.3V LDO ×6 | LM2936Z-3.3 — TO-92, ultra-low Iq, wide Vin (one per battery tube + spares) | Arrived |
| 1-Wire bus master ×4 | DS2482-800 I2C-to-1-Wire bridge (MIKROE-1892 'I2C 1-Wire click' - 8 channels) | Ordered |