power system research: IP5389 series config, 3S2P cells, power budget, audio amp, display controller power
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@ -16,7 +16,7 @@ A cyberdeck built from salvaged ASUS K501U laptop components and Orange Pi 3B SB
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- [x] Case nomenclature and orientation defined
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- [x] Build approach: wooden case + salvaged lid canopy
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- [x] Input device: ThinkPad TrackPoint keyboard
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- [x] Power system: \[IP5389 board]? + 18650 cells
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- [x] Power system: IP5389 board + 3S2P 18650 cells
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- [x] Video output: mechanical HDMI A/B switch
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- [x] Port layout defined (10 ports + SD reader + Kensington)
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- [ ] ~~Case design~~ (postponed — board bring-up first)
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@ -31,10 +31,17 @@
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| Item | Specification | Source | Est. Cost | Status |
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|------|--------------|--------|-----------|--------|
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| IP5389 power board | USB-C PD, 3S, bare PCB | AliExpress | $8-15 | Preliminary selection |
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| 18650 cells | 3S or 3S2P, quality brand | User's pick | $12-24 | To purchase |
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| IP5389 power board | USB-C PD, 3S, bare PCB | AliExpress | $8-15 | Board model TBD |
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| 18650 cells (x6) | 3S2P, matched, 2500-3500mAh | Shopping | $12-30 | To purchase |
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| 5A blade fuse + holder | Automotive | Amazon | $2 | To purchase |
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### Audio
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| Item | Specification | Source | Est. Cost | Status |
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|------|--------------|--------|-----------|--------|
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| PAM8403 amp module | 3W+3W, 5V, Class D | Amazon | $3-5 | To purchase |
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| 4Ω 3W speakers (x2) | Small drivers, ~31×70mm | Amazon | $5-10 | To purchase |
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### Networking
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| Item | Specification | Source | Est. Cost | Status |
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@ -74,18 +81,19 @@
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|----------|------|
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| Storage (USB enclosure) | ~$12 |
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| USB hub (powered 10-port) | ~$22 |
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| Power system (board+cells+fuse+charger) | ~$44 |
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| Power system (board+cells+fuse) | ~$32 |
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| Audio (PAM8403 amp + speakers) | ~$10 |
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| HDMI switch | ~$10 |
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| Panel-mount cables + SD reader | ~$23 |
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| **Remaining** | **~$100** |
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| **Remaining** | **~$110** |
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### Total Project
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| | |
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|---|----|
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| Spent | $213 |
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| Remaining | ~$111 |
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| **Estimated total** | **~$313** |
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| Remaining | ~$110 |
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| **Estimated total** | **~$323** |
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---
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@ -106,6 +114,8 @@
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- Panel-mount cables (USB-A, USB-C, HDMI, Ethernet, audio)
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- Panel-mount SD card reader
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- Heatsink for RK3566
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- PAM8403 audio amp module
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- 4Ω 3W speakers (x2)
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---
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@ -17,34 +17,56 @@ All-in-one power management PCB. Replaces separate charger module, BMS, and boos
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## How It Works
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The IP5389 uses cells in **series** (2S to 5S), not parallel. A synchronous buck-boost converter handles all voltage conversion in one IC with a single inductor.
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```
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USB-C wall charger → IP5389 board → 18650 cells (3S or 3S2P)
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↓ (passthrough)
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USB-C PD output → OPi3B (5V) + peripherals
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USB-C wall charger → IP5389 board → 18650 cells (3S2P configuration)
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↓
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USB-C PD output → OPi3B (default 5V)
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USB-A output → Display controller (5V via micro USB)
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5V rail → USB hub, audio amp, fans
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```
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One board, one cell pack, one output cable to the SBC. No separate modules to wire together.
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One board, one cell pack, one inductor. No separate charger, BMS, or boost modules needed.
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## Key Specs (varies by specific board)
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### Why Series, Not Parallel
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- Cell config: 3S–6S (most common: 3S or 4S)
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- Output: 45W–100W USB-C PD
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- Input: USB-C (bidirectional port)
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- Protection: overcharge, overdischarge, short circuit, thermal
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- Price: $8–15 bare PCB
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| Config | Voltage range | Regulator mode | Efficiency |
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|--------|--------------|----------------|------------|
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| Parallel (1SxP) | 3.0–4.2V | Must **boost** to 5V | ~85-90% |
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| 3S (series) | 9.0–12.6V | **Bucks** down to 5V | **Up to 97%** |
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## OPi3B Power Context
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With a 3S pack, battery voltage never drops below 9V even at cutoff. The regulator is always stepping down — the easy, efficient direction. The IP5389's synchronous buck-boost handles 3.0V–21V input range and can output 5V/9V/12V/15V/20V via PD negotiation.
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The Orange Pi 3B draws ~3-5W under load (vs OPi5's ~8W), which simplifies the battery system:
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## Power Budget
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- Lower peak current means the IP5389 board doesn't need to push its limits
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- A smaller cell pack (3S vs 3S2P) may suffice
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- Less heat generated, less thermal management needed
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- The OPi3B's 5V/3A input spec is well within what a USB-C PD board can provide
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Updated estimates with all components known:
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| Component | Voltage | Current (est.) | Power (est.) | Source |
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|-----------|---------|----------------|-------------|--------|
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| Orange Pi 3B | 5V | 2-3A | 10-15W | USB-C from IP5389 |
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| Display + controller | 5V | 2A | 10W | Micro USB from IP5389 or 5V rail |
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| USB hub (powered) | 5V | 2-3A | 10-15W | 5V rail via barrel adapter |
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| Audio amp (PAM8403) | 5V | 0.3A | 1.5W | 5V rail direct |
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| Cooling fans (x2) | 5V | 0.2A | 1W | 5V rail or GPIO |
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| **Typical total** | **5V** | **~3-4A** | **~14-20W** | |
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| **Peak total** | **5V** | **~7-8A** | **~35-40W** | |
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Note: Display controller and OPi 3B can share the IP5389's USB ports (USB-C + USB-A). The hub, amp, and fans tap the 5V distribution rail with a simple barrel-jack breakout.
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## Cell Configuration
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TBD — need to select specific board first. Likely 3S (3 cells in series) or 3S2P (6 cells, pairs in series). 3S2P with quality 3000mAh cells gives ~6000mAh at 11.1V nominal.
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**Decision: 3S2P** — 6 cells total, two parallel strings of three series cells.
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| Config | Cells | Weight (50g ea) | Energy (2500mAh cells) | Energy (3500mAh cells) | Est. runtime (~14W) |
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|--------|-------|-----------------|----------------------|----------------------|---------------------|
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| 3S1P | 3 | ~150g | 27.75 Wh | 38.85 Wh | ~2-2.5 hr |
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| **3S2P** | **6** | **~300g** | **55.5 Wh** | **77.7 Wh** | **~4-5.5 hr** |
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| 3S4P | 12 | ~600g | 111 Wh | 155.4 Wh | ~8-11 hr |
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**3S2P** (~300g, 55.5 Wh with standard cells) is the pick. Matches a typical laptop battery capacity. With quality 3500mAh cells (Samsung 35E, LG MJ1, or equivalent), the pack delivers **77.7 Wh** — enough for a full café session without recharging.
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**Important:** Cells in the same parallel group must be matched (same model, age, capacity). Label and pair them during assembly. Never mix old and new cells in the same pack.
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## Salvaged Battery: Not Usable
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@ -74,15 +96,20 @@ K501U battery (B31N1429, 4240mAh, 11.4V, 3S) assessed and rejected:
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## Safety Notes
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- Cells in a parallel group must be matched (same model, age, capacity). Mixing old and new is a fire risk.
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- Always use 18650 cells with matching capacity and age in parallel pairs
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- Fuse between board output and SBC (5A automotive blade fuse recommended)
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- No puffy, warm-at-rest, or sub-2.5V cells — ever
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- Match cell count to board specs (3S board = exactly 3S, don't mix)
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- IP5389 modules vary in quality — buy from reputable sellers, check reviews for "clone" ICs
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## TODO
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- [x] Cell configuration: 3S2P (6 cells, ~300g)
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- [ ] Select specific IP5389 board model with verified reviews
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- [ ] Confirm cell count (3S vs 3S2P)
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- [ ] Source matched 18650 cells (Samsung 35E, LG MJ1, or equivalent)
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- [ ] Verify passthrough charging on selected board
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- [ ] Order board + cells
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- [ ] Select PAM8403 audio amp module + small 4Ω speakers
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- [ ] Select powered USB hub with 5V DC barrel input (not AC wall wart)
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- [ ] Order board + cells + amp + hub
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- [ ] Test charging and output before case integration
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