How to Build Community Charge Kiosk

What you’re building

Outputs

USB-C PD: 4 × 100 W source ports (20 V × 5 A max each)
Qi wireless: 2 × 15–25 W pads (Qi / Qi2-ready)
12 V sockets: 2 × automotive panel receptacles (15 A each)

Inputs

24 V DC bus via SB50 quick-connect
Optional: solar/alternator upstream (handled by your battery box)

Brains (optional)

ESP32 soft-AP queue/token screen (joins people to a charging queue)
0.96″ SSD1306 OLED for “Now Serving” + slot count

Bill of Materials (buy list)

Part

Notes

Qty

Ref

USB-C PD 100 W DC-input module (12–24 V)

Industrial 12–24 V input, PD 3.0/PPS; 5/9/12/15/20 V up to 5 A; mountable

Coolgear CG-PD100C or CG-PDC100W-PCBA

Qi wireless TX modules, 15 W (Qi / EPP), Qi2-ready if available

Use 12–19 V input reference designs/pads; ensure FOD & thermal cutback

WPC Qi EPP-class TX

12 V panel sockets (marine)

15 A rated; watertight cap; 1-1/8″ hole

Blue Sea 1011

Anderson SB50 panel/lead set

50 A class DC quick-connect; #6–16 AWG contacts

SB50 (red/grey keyed)

Busbars (150 A, covered)

Positive & negative distribution, #8-32 screws + 1/4″ studs

Blue Sea 2300/2301

Main battery fuse (Class-T or MRBF per bank)

Install at battery per ABYC; choose rating for cable ampacity

Class-T (main) + MRBF branches

Branch fuses/breakers

Size for wire: PD modules ~10 A ea @24 V worst-case; Qi 3–5 A; sockets 15 A

6–8

ATO/ATC or DIN DC breakers

Enclosure (IP-rated) + panel plate

Powder-coat steel or polycarbonate, IP65–67 target

~12″×10″×5″

Wire & lugs

Per ampacity & run length: 10 AWG for PD feeds; 14–16 AWG Qi; 12 AWG sockets

as needed

Tinned copper + heat-shrink

ESP32 dev board + SSD1306 128×64

For queue/token (optional)

1 set

ESP32-WROOM + I²C OLED

Fans & grill (optional)

80 mm 24 V PWM + filter for thermal management

1–2

≥20 CFM

Sizing wires? Use DC ampacity & voltage-drop charts; fuse for the wire, not the load.

Wiring Overview

Topology:

SB50 inlet → upstream main fuse at battery → kiosk positive busbar
From busbar → branch fuses → four PD modules, two Qi TX modules, two 12 V sockets
Returns → negative busbar → SB50 return

Label every branch; leave a service loop; add grommets & strain reliefs.

Critical: At the battery, place over-current protection “as close as practicable,” respecting the 7″ / 40–72″ sheath exceptions. Use Class-T where fault currents are high; MRBFs can protect smaller branches.

Follow your battery maker’s fuse guidance.

Branch fuse starting points

USB-C PD 100 W modules (24 V side): 10 A each
Qi TX (15–25 W): 3–5 A each
12 V outlet: 15 A each (socket rating)

Adjust for cable gauge & run length per ampacity charts.

Suggested wire (short runs)

PD branches: 10 AWG (or 12 AWG if short & ventilated)
Qi pads: 16–14 AWG
12 V sockets: 12 AWG

Grounding & enclosure

Bond negative bus to chassis if system requires it
Target enclosure IP65+; filtered fan if Qi/PD heat builds

Step-by-Step Assembly

0) Prep & layout

Print the Quick-Start Card for the lid.
CNC/hand-cut panel plate: 4 × USB-C, 2 × Qi pad windows, 2 × 12 V sockets, status LED, service switch.
Bench-test each PD module with a known load/cable before mounting.

1) Power ingress & protection

Crimp SB50 contacts to your 24 V feed leads; verify polarity.
At the battery side, install the main fuse (Class-T/MRBF) per manufacturer guidance and ABYC distance rules.
Inside the kiosk, land positive/negative to covered busbars; torque per spec.

2) Mount converters & sockets

Panel-mount the four PD modules; ensure airflow paths. Keep coil-to-metal clearance under Qi pads.
Install 12 V sockets (1-1/8″ hole) with watertight caps oriented downward.
Adhere Qi TX coils under the panel windows; follow the TX vendor’s coil height & FOD notes.

3) Branch wiring & fusing

From positive bus → inline blade fuse or DIN breaker → PD module +VIN (10 A). Repeat ×4.
Qi: 3–5 A each; 12 V sockets: 15 A each (use 12 AWG).
Return all negatives to the negative busbar. Heat-shrink every crimp. Label both ends.

4) Optional queue/token display

Wire ESP32 3V3/GND → SSD1306 (I²C SCL/SDA). Mount OLED behind a window.
Flash the sketch below to host a captive “Join Queue” page; the OLED shows “Now Serving”.

ESP32 Queue (Soft-AP + OLED)

// Minimal ESP32 queue server + SSD1306 OLED (Arduino)
// Libraries: WiFi.h, WebServer.h, Adafruit_SSD1306, Adafruit_GFX
#include <WiFi.h>
#include <WebServer.h>
#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>

#define OLED_RESET -1
Adafruit_SSD1306 oled(128,64,&Wire,OLED_RESET);
WebServer server(80);
const char* ssid="ChargeQueue";
const char* pass=""; // open AP

volatile uint32_t nextToken = 1, nowServing = 1;

String page(){
  return String("<!doctype html><html><body style='font-family:sans-serif'>")
    + "<h2>Community Charge Queue</h2>"
    + "<p>Now Serving: <strong>"+String(nowServing)+"</strong></p>"
    + "<a href='/join'>Join Queue</a> • "
    + "<a href='/pop'>Advance (staff)</a></body></html>";
}
void draw(){
  oled.clearDisplay(); oled.setTextSize(2); oled.setTextColor(SSD1306_WHITE);
  oled.setCursor(0,0); oled.print("SERVING");
  oled.setCursor(0,24); oled.setTextSize(3); oled.print(nowServing);
  oled.display();
}
void setup(){
  WiFi.softAP(ssid, pass);
  Wire.begin(); oled.begin(SSD1306_SWITCHCAPVCC, 0x3C); draw();
  server.on("/", [](){ server.send(200,"text/html",page()); });
  server.on("/join", [](){
    uint32_t tok = nextToken++; 
    server.send(200,"text/html","<p>Your token: <b>"+String(tok)+"</b></p><p><a href='/'>Back</a>");
  });
  server.on("/pop", [](){ nowServing++; draw(); server.sendHeader("Location","/"); server.send(302); });
  server.begin();
}
void loop(){ server.handleClient(); }

ESP32 captive portal / AP patterns and SSD1306 library usage are documented by vendors and community guides.

5) Bring-up & test

Check polarity & continuity (no load). Close fuses/breakers.
Test each PD port with an e-marked 5 A USB-C cable and a PD analyzer or laptop; verify 20 V @ ≤5 A.
Verify Qi pads with a Qi phone; confirm FOD trips with a stray coin.
Load a 12 V socket with a 120–150 W car load; verify fuse trip point is appropriate.

6) Thermal & labeling

Add an 80 mm 24 V fan + filter if the panel gets >40 °C at full load.
Label: “USB-C PD 100 W MAX | E-marked cable required for 5 A”, “Qi 15–25 W”, “12 V 15 A”.

Hazards & Rules (read before use)

Fuse at the source. Main battery protection at the battery per ABYC; branch fuses sized to wire ampacity.
USB-C 5 A requires e-marked cable. Without it, compliant PD sources won’t deliver 5 A/100 W.
Qi pads heat metal. Keep ferritic objects off the pad; rely on FOD & thermal cutback.
DC arcs bite. De-energize before service; cover busbars; use torque spec and strain relief.
Ingress. If outdoors, target IP65+ panel geometry; drip loop your SB50 lead.

24 V Battery Runtime Estimator

Rough math; assumes 90% DC path efficiency and uses 80% of rated pack capacity for life.

Battery capacity (Ah @ 24 V)

System efficiency (%)

Usable fraction (%)

Loads

× PD @ W

× Qi @ W

W other (fans, router, etc.)

Result

—

Printable Quick-Start (panel lid)

Community Charge Kiosk — Quick-Start

Connect 24 V: SB50 to battery box (main fuse at battery).
USB-C PD (x4): Use e-marked 5 A cable for 100 W; otherwise limited to ≤3 A.
Qi pads (x2): Place phone centered; remove metal cases.
12 V sockets (x2): 15 A max each; do not exceed rating.
Join queue: Connect to Wi-Fi “ChargeQueue” → tap “Join”.
Shutdown: Unplug loads → open branch breakers → disconnect SB50.

Service: open panel; check for loose lugs, heat-discolored terminals, and blown fuses.

References

USB-IF — USB Power Delivery Rev 3.1 overview (240 W EPR; 100 W at 20 V×5 A requires 5 A-rated e-marked cable)
Wireless Power Consortium — Qi / Qi2 specs and 15–25 W capabilities (EPP & Qi2)
Blue Sea Systems — DC wire ampacity & wire-size selection
ABYC E-11 excerpt — battery fuse placement distance rules (7″ baseline; sheath exceptions)
Anderson Power — SB50 datasheet (ratings, wire sizes)
Coolgear — 12–24 V DC-input USB-C PD 100 W modules (industrial, mountable)
IEC — IP ratings (ingress protection)
ESP32 docs — captive portal/AP patterns; SSD1306 OLED library docs