Community Charge Kiosk — Solar Edition
PV → MPPT → 24 V bus → 4× USB-C PD (100 W), 2× Qi pads, 2× 12 V sockets, optional queue screen. Field-deployable; serviceable with basic tools.
What changes vs. the base kiosk
- Built-in **PV subsystem**: folding/rigid panels → **combiner** (fused) → **MPPT** → 24 V battery bus.
- Correct **connection order**: Battery → MPPT → PV (reverse to shut down).
- Charge profile set for **LiFePO₄ 24 V** (8 S): Absorb ≈ 28.4–29.2 V, Float ≤ 27.2 V (or off).
Target solar spec
| Array | 400–800 W (rigid or suitcase) |
|---|---|
| Controller | MPPT 100/30–100/50 (or 150/35) class |
| Combiner | String fuses/breakers per string |
| Cabling | 10 AWG PV cable (MC4), short runs |
Bill of Materials — Solar Add-On
| Part | Notes |
|---|---|
| PV Panels (400–800 W) | Two 200 W “24 V-class” in series (2S) per string; for 800 W use 2S2P |
| Combiner box | Outdoor-rated; string **fuse holders or breakers**; deadfront cover |
| Fuses / breakers | Per panel datasheet (often **15 A** max-series-fuse); one per string |
| Disconnects | PV DC disconnect; battery-side breaker on MPPT BAT+ |
| MPPT | 100 V/30–50 A class (e.g., 100/50) — must fit PV Voc (cold) and array current |
| PV wire & MC4 | 10 AWG PV cable; MC4 branch connectors if paralleling strings |
| Labels & placards | “PV DC”, “BATTERY”, “DISCONNECT” etc. |
| Re-use from base kiosk | Notes |
|---|---|
| 24 V battery bus + fuse (Class-T/MRBF) | Class-T at source; branch MRBF/ATO as sized |
| USB-C PD 100 W modules (×4) | 12–24 V input, PD 3.0; one **10 A** branch fuse each |
| Qi pads (×2) | 3–5 A branch fuses; FOD & thermal cutback |
| 12 V sockets (×2) | 15 A branch fuses, 12 AWG runs |
| SB50 inlet | 50 A quick-connect for battery box / alt-power |
Size wire by ampacity & drop; fuse **for the wire**, not the load.
Wiring Overview
PV+ (String 1) ─ Fuse ┐
├─── Combiner ─── PV Disconnect ─── MPPT PV+
PV+ (String 2) ─ Fuse ┘
PV− strings common to Combiner → MPPT PV−
MPPT BAT+ ─── Battery-side breaker ─── 24 V Positive Bus (Class-T at battery source)
MPPT BAT− ──────────────────────────── 24 V Negative Bus
24 V Bus → Branch fuses → { 4× USB-C PD, 2× Qi pads, 2× 12 V sockets }
Returns → Negative Bus → Battery −
Order of operations:
1) Connect Battery to MPPT (and close BAT+ breaker)
2) Close PV Disconnect to connect array
(Shutdown is reverse: open PV Disconnect first, then BAT+)
Check panel datasheet for **Max Series Fuse** and **Voc**; ensure MPPT **max PV voltage** isn’t exceeded in cold weather.
Step-by-Step Build (Solar path)
- Panel layout. For 400 W: use 2× “200 W 24 V-class” in **series** (2S1P). For 800 W: two of those strings in **parallel** (2S2P). Keep strings identical; same orientation/tilt.
- Combiner. Mount an outdoor PV combiner. Install **one fuse or breaker per string** sized to the panel’s **Max Series Fuse** (often 15 A). Land positives to fuse holders, negatives to the negative bar.
- PV disconnect & run. From combiner, route to a PV DC disconnect, then to the MPPT PV inputs with 10 AWG PV cable. Use strain reliefs and MC4 torque spec.
- MPPT battery side. From MPPT BAT+ add a **DC breaker** to the **24 V positive bus**; BAT− to negative bus. Close the **battery main fuse** near the source (Class-T/MRBF per your base box).
- Program MPPT for LiFePO₄ 24 V. Absorb ≈ 28.4–29.2 V, Float ≤ 27.2 V (or disabled). No equalize. Temperature compensation usually off for LiFePO₄—follow your battery doc.
- Bring up safely. **Battery → MPPT** first, then **PV**. Verify PV Voc < MPPT max, then close PV disconnect. Confirm charge current rises in sun.
- Thermals. With 600–800 W PV driving heavy charging plus users on PD/Qi, add a filtered 80 mm fan over PD modules if internal air exceeds 40 °C.
- Labeling. Placard combiner, disconnect, MPPT, and bus bars; update your lid quick-start.
String sizing tips
- Controller must support **PV Voc (cold)** and **array Isc**. Check panel temp-coeff for Voc and site min-temp.
- Long cable? Up-size wire to reduce voltage drop (especially on PV→MPPT).
- Parallel strings → fuse/breaker **each string** in combiner.
Hazards
- PV is a live source in sun. Use the **PV disconnect** before service.
- DC arcs are spicy. Tighten to torque spec; cover busbars.
- Battery OCP must be **near the source**; sheath exceptions apply but don’t stretch it.
Harvest & Runtime Estimators
Daily Solar Harvest
Get PSH from NREL PVWatts/NSRDB for your location.
Net Runtime from Battery
× PD @ W
× Qi @ W
W other (router/fan)
Quick-Start (print this for the lid)
- Plant panels; plug to **Combiner**; open PV Disconnect.
- Battery main fuse **closed** → MPPT **ON**.
- Close **PV Disconnect** (sunny? it’ll start charging).
- Use ports: 4× USB-C PD (100 W with 5 A e-marked cable), 2× Qi (15–25 W), 12 V sockets (15 A).
- Shutdown: open **PV Disconnect** → open MPPT BAT+ breaker → service.
Bill of Materials — Quick List (Solar bits only)
| Item | Spec | Qty |
|---|---|---|
| PV panels | 200 W “24 V-class”; 2 in series per string | 2–4 |
| Combiner | MNPV-class outdoor combiner with fuseholders/breakers | 1 |
| String fuses | Per module spec (often 15 A); one per string | 2–4 |
| PV disconnect | ≥ 150 VDC rated switch | 1 |
| MPPT | 100/50 (or 150/35) class | 1 |
| PV cable & MC4 | 10 AWG PV wire; MC4 branch sets if 2S2P | as needed |
| BAT+ breaker | On MPPT output to 24 V bus | 1 |
| Labels | PV DC / DISCONNECT / BATTERY | set |
Notes & Rationale
- Battery first, PV second: protects the MPPT; reverse on shutdown to avoid uncontrolled PV on a sleeping controller.
- LiFePO₄ setpoints: use 28.4–29.2 V absorb, ≤27.2 V float or disable float for mobile use to reduce idle cycling.
- String OCP & combiner: when paralleling strings, each string must have its own OCPD in a combiner; follow your module’s “Max Series Fuse.”
- Wire & fusing: size by ampacity/voltage drop; place source OCP near battery; sheath exceptions allow longer distance but don’t abuse it.
- Harvest math: Daily Wh ≈ PV_W × PSH × efficiency (≈0.7–0.8 for real life). Use site PSH from NREL.
Sources
- Victron SmartSolar manuals — battery/PV connection order & MC4 guidance.
- Battle Born (LiFePO₄) — 24 V charge voltages (absorb/float) and lithium charge basics.
- MidNite Solar MNPV combiner manuals — per-string fusing/breakers in combiners.
- Blue Sea Systems — DC ampacity & voltage-drop methods; ABYC E-11 OCP placement summary.
- NREL PVWatts & Solar Resource/NSRDB — site-specific sun hours and production estimation.