# Wired & Mains Power

# Mains Power for Permanent Installations

## Mains Power for Permanent Installations

Where mains (AC grid) power is available, it is convenient and low-maintenance for routine operation: it provides essentially unlimited energy day-to-day, avoids battery-cycling wear, and simplifies the build. **But for emergency communications, this framing has a critical caveat: in a disaster the grid is usually the first thing to fail.** A node that depends solely on mains power will go dark in exactly the incidents the mesh exists to serve. For any node that must survive a grid-down event, treat mains as *primary-with-battery-backup at best*, and prefer solar + battery for nodes whose whole purpose is grid-down resilience. Mains is "reliable" only for normal-day uptime, not for disasters.

**Safety:** Any work on the 120/240 V AC side - adding a circuit, an outdoor outlet, or hard-wiring a supply - can be lethal and almost always requires a licensed electrician. Permit requirements vary by jurisdiction; check your local code. AC branch-circuit conductors must be sized per NEC (14 AWG for a 15 A circuit, 12 AWG for a 20 A circuit) regardless of the small load the node draws - never use thin wire on a branch circuit. The low-voltage DC guidance below applies only downstream of a listed AC adapter or power supply.

### When to Use Mains Power

- Rooftop or building-mounted nodes where a power run is feasible
- Nodes at locations with existing power (communications towers, buildings, facilities)
- High-power nodes like the Station G2 (requires 15V PD - impractical with solar)
- Room Server nodes that are expected to be always-on for message storage

For any of the above that has an emergency-communications role, pair mains with battery backup sized for the expected outage (see Battery Backup, below) - a node's value during a disaster is exactly when grid power is most likely gone.

### Power Supply Requirements by Device

Input requirements below follow each board's published documentation (Meshtastic hardware docs and the respective vendor datasheets, as of 2026-06-08). The current figures are minimums for a single node; confirm against your specific board revision.

<table id="bkmrk-deviceinputpower-sup"><thead><tr><th>Device</th><th>Input</th><th>Power Supply Needed</th></tr></thead><tbody><tr><td>Heltec V3, V4</td><td>5V USB-C</td><td>Any 5V USB-C charger, minimum 1A</td></tr><tr><td>LilyGo T-Beam, T-Deck</td><td>5V USB-C or Micro USB</td><td>Any 5V USB charger, minimum 1A</td></tr><tr><td>RAK WisBlock (RAK19007)</td><td>5V USB or battery</td><td>5V USB-A charger or 5V regulated supply</td></tr><tr><td>Station G2</td><td>15V USB-C PD</td><td>USB-C PD charger supporting 15V, ≥20W output (e.g. 15V/2A)</td></tr><tr><td>Any node with LiPo</td><td>Battery + charger</td><td>Power the charger circuit; see device documentation</td></tr></tbody></table>

### Station G2 Power Requirements

The Station G2 requires 15V USB-C Power Delivery. This is a specific PD negotiation - the charger must support 15V PD output, not just 5V. The manufacturer specifies a USB-C PD adapter that supports the 15V PD protocol with a maximum output power of 20W or more (i.e. ≥20W, e.g. 15V/2A). Compatible chargers include:

- Most 65W+ USB-C laptop chargers (verify 15V output in spec sheet)
- Anker 65W or 90W USB-C GaN chargers
- Any charger explicitly listing "15V/2A" or "15V/3A" in its PD output specs

A 5V USB charger plugged into the Station G2 will not provide enough power. The device may appear to power on but will behave erratically or fail to transmit at full power.

### Battery Backup for Mains Installations

For mission-critical nodes on mains power, a battery backup (UPS function) maintains operation during power outages. **Match the backup capacity to the outage you actually need to survive:** small UPS modules give only a few hours, which covers brief utility blips but NOT disaster-length outages, which routinely run days to weeks after major storms, wildfires, or earthquakes. For genuine grid-down resilience, size battery backup in *days*, or use solar + battery so the node self-recharges. Options:

- **Small UPS:** A compact DC UPS module (available from AliExpress for $10 - $20, price as of 2026-06-08) passes through 5V USB power and switches to battery automatically on outage. Battery runtime of a few hours is typical for small units - adequate for short utility interruptions only, not for a multi-day disaster.
- **Battery + charge controller:** Some boards with a battery connector and an onboard charge/power-path IC can charge a LiPo or 18650 from USB and run from battery when USB power is removed, giving automatic failover. **This is not universal:** many cheap boards cannot safely charge while running or may overcharge, so check your specific board's documentation before relying on it for UPS failover. Also note that on-board USB chargers (TP4056-class) have no temperature sensing - in a cold or hot outdoor enclosure they will happily charge a lithium cell below 0 °C or at high temperature, which causes lithium plating and a hidden fire risk. For an outdoor backup battery exposed to sub-freezing or high temperatures, use a charger or BMS with a low-temperature charge cutoff, put an inline fuse on the battery lead, and prefer LiFePO4 with a low-temp-cutoff BMS over a bare LiPo.
- **Full UPS:** For the Station G2 and other high-power nodes, a proper UPS with 15V PD output is required. These are less common but available from server hardware suppliers.

### Weatherproofing Mains-Powered Outdoor Nodes

If the node is outdoors on mains power, weatherproofing requirements are the same as for solar nodes:

- Use an IP65+ enclosure
- Route mains wiring through appropriate weatherproof conduit (AC wiring and connections should be installed by a licensed electrician per local code)
- Use a weatherproof outdoor power outlet or a sealed junction box for the power entry
- Keep the power supply (transformer/adapter) inside the weatherproof enclosure or in a separately housed waterproof enclosure. **Watch enclosure heat:** an AC adapter dissipates heat, and a sealed box traps it - co-locating a hot adapter against a lithium battery can drive internal temperatures into the cell's charge-derating range (typically above ~45 °C) or damage the cells. Separate the power supply from the battery, provide thermal mass or ventilation, and monitor enclosure temperature; do not press a hot adapter against a lithium pack.
- If using a standard USB charger adapter, note that most USB chargers are not rated for outdoor use - enclose them in an additional weatherproof housing or use an industrial-rated outdoor power supply

### Cable Run Considerations

For nodes mounted at height (rooftop, tower, pole), the cable run from power to the node may be significant. At 5V, voltage drop over long cables is a real concern. The voltage-drop figures below assume a modest node load of about 500 mA; drop scales with current, so a higher-draw node (e.g. ~1A during Wi-Fi/transmit) sees roughly double these values:

<table id="bkmrk-cable-runcable-gauge"><thead><tr><th>Cable Run</th><th>Cable Gauge</th><th>Voltage Drop at ~500mA</th><th>Action</th></tr></thead><tbody><tr><td>&lt;5m</td><td>24 AWG USB cable</td><td>Negligible (at ~0.5–1A)</td><td>Standard USB cable fine</td></tr><tr><td>5 - 15m</td><td>22 AWG or better</td><td>0.3 - 0.9V (at ~0.5–1A)</td><td>Use thicker cable or boost supply voltage</td></tr><tr><td>&gt;15m</td><td>18 AWG or higher, or 12V supply</td><td>Significant with 5V</td><td>Run 12V and use a 12V→5V DC-DC converter at the node</td></tr></tbody></table>

For long cable runs, running 12V DC (lower current for same power, less voltage drop) and using a small buck converter at the node end is more efficient than running 5V USB over a long distance. (This 12V/24V/18V guidance is for low-voltage DC runs only - not AC mains branch circuits, which must follow NEC conductor sizing.)

### Lightning Protection for Mains-Powered Sites

Mains-powered outdoor nodes are vulnerable to both direct lightning strikes and power line surges. Protect with:

- A quality surge protector or transient voltage suppressor (TVS) on the mains input
- A DC-grounded lightning arrestor on the antenna feedline
- Ground the enclosure and mast to an earth ground rod
- Consider a whole-circuit surge protector at the breaker panel for critical sites (installed by a licensed electrician)

# AC Mains Power for Permanent Node Installations

For fixed infrastructure nodes at permanent sites with grid power access, AC mains power is the lowest-maintenance power solution for routine uptime, eliminating battery replacement cycles and enabling higher-power configurations. It is **not** the most reliable option in an emergency, however — the grid is commonly the first thing to fail in a disaster. Pair any mission-critical mains node with battery (and ideally solar) backup sized for the outage length you must survive.

**Safety warning — AC mains can be lethal.** Working on 120/240 V AC mains and breaker panels can kill you, and mistakes are unforgiving. AC mains and branch-circuit work should almost always be done by, or under the supervision of, a licensed electrician. Ensure proper equipment grounding/bonding of the enclosure and mast (NEC 250.x). This page describes the hardware involved, but it is not a substitute for a qualified electrician.

## Power Supply Selection

Most ESP32/nRF52 LoRa mesh nodes regulate to 3.3V internally and accept 5V via USB or 3.7V from a single lithium cell. For AC-powered installations, you need a reliable AC/DC converter:

### USB Wall Adapters

The simplest option for indoor nodes:

- **5V/3A USB-C adapter** - A basic 5V/3A USB-C adapter (full PD negotiation is not required) powers any USB-C node (Heltec V3, T-Beam Supreme). Roughly $10-20 for quality Anker or Baseus adapters (prices as of 2026-06-08).
- **Quality matters** - Cheap switching adapters can emit RF noise. Use a reputable brand with proper EMI filtering. Choose adapters that comply with FCC Part 15 Subpart B (Class B) emission limits (see 47 CFR 15.107/15.109).
- **UPS integration** - A small USB UPS (Anker PowerCore Fusion, Cyberpower CP685AVR with USB output) adds battery backup to any USB-powered node.

### DIN Rail Power Supplies

For professional installations in electrical enclosures or server racks:

- **Meanwell HDR-15-5** - 5V/2.4A (12W) DIN rail supply, ~$15-20 (as of 2026-06-08). Widely used in industrial automation, proven reliable.
- **Meanwell HDR-30-12** - 12V/2A DIN rail supply for nodes that accept 12V input (most PoE-powered nodes, some T-Beams with barrel jack).
- DIN rail supplies mount in standard electrical enclosures alongside circuit breakers and terminal blocks.

### PoE (Power over Ethernet)

For nodes at locations with Ethernet infrastructure (commercial buildings, outdoor fixtures with Cat5e runs):

- A PoE splitter converts standardized PoE (nominal 48V, range 44-57V) to 5V/12V for powering a node. Note that passive PoE may run at 24V or other voltages — match standard 802.3af/at gear to standard gear to avoid mismatch or damage.
- Enables remote power cycling via managed PoE switch (reboot a node from the office)
- Single cable for both data (if using an Ethernet-capable node or Pi-based room server) and power
- Requires Ethernet infrastructure - not practical for standalone outdoor nodes without network connectivity

## UPS Integration for Grid-Powered Nodes

Even grid-powered nodes benefit from battery backup:

- **Mini UPS modules** - IP UPS boards (Waveshare UPS HAT, PiJuice) that sit between the power supply and the Pi or node. Runtime depends on load and battery capacity (commonly 1-4 h for low-power loads).
- **Standard UPS** - A small APC BE425M (~$40, as of 2026-06-08) protects against power line surges and provides battery backup for a low-power node; runtime is load-dependent (commonly 30+ minutes for a sub-watt node). Verify the specific model's USB output before relying on it.
- **Lead-acid battery bank** - For extended outage protection (24+ hours), a 12V 7Ah SLA battery (84Wh) on a float charger provides long runtime — roughly 24-40 h at a 1-2W node load. SLA tolerates continuous float charging well (unlike lithium), though chronic overvoltage causes gassing/drying and shortens life. Self-discharge (~5%/month at room temperature) is comparable to or slightly higher than LiPo.

## Outdoor AC Power Runs

Running power to an outdoor enclosure requires weatherproof wiring:

- **Wire gauge:** AC branch-circuit conductors must be 14 AWG (15A) / 12 AWG (20A) per NEC 240.4(D), regardless of how little the node draws — a downstream fault must be cleared by the breaker before the wire overheats. **Do not run 18 AWG on a 15/20A AC circuit** — it cannot survive a 15A fault and is a fire hazard. 18 AWG belongs only on the low-voltage DC side, never as AC branch-circuit wiring.
- **Weatherproof conduit:** Schedule 40 PVC conduit is a common method for outdoor AC runs (NEC Article 352); other approved raceways include RMC and LFNC. Seal entry points with weatherproof conduit fittings.
- **GFCI protection:** The NEC requires GFCI protection for all outdoor outlets (NEC 210.8). Use a GFCI breaker or GFCI outlet at the first outlet in the outdoor circuit.
- **Permit requirements:** New AC circuit runs usually require an electrical permit, depending on your local jurisdiction (AHJ). Check local code — this is especially important for community networks working on public property — and have a licensed electrician perform the work.

## Related Pages

This topic overlaps with the "Mains Power for Permanent Installations" page, which focuses more on mains-install practices and USB failover via JST battery. Treat this page as the AC supply-hardware reference; consult that page for installation practices, and follow whichever gives the more conservative safety guidance.

# Power-over-Ethernet for Outdoor Node Deployments

Power over Ethernet (PoE) is an excellent choice for outdoor nodes at sites with structured cabling infrastructure. It combines power delivery and network connectivity in a single cable, simplifying installation and enabling remote management.

## PoE Standards

<table id="bkmrk-standardmax-powertyp"><thead><tr><th>Standard</th><th>Max Power (at PSE)</th><th>Typical Use</th><th>Common in</th></tr></thead><tbody><tr><td>IEEE 802.3af (PoE)</td><td>15.4W</td><td>IP cameras, VoIP phones</td><td>Most infrastructure</td></tr><tr><td>IEEE 802.3at (PoE+)</td><td>30W</td><td>PTZ cameras, APs</td><td>Modern switches</td></tr><tr><td>IEEE 802.3bt (PoE++)</td><td>Type 3 = 60W; Type 4 = 90W (≈71W delivered at the powered device)</td><td>Laptops, high-power APs</td><td>Newer switches</td></tr><tr><td>Passive PoE (non-standard)</td><td>Varies</td><td>Low-cost IP cameras, some APs</td><td>Ubiquiti older hardware</td></tr></tbody></table>

The 802.3bt maximum is 90 W at the power-sourcing equipment (Type 4), not 100 W — "100 W PoE" is a marketing rounding, not the IEEE spec figure.

For mesh nodes, IEEE 802.3af is more than sufficient. Most nodes consume 1-5W.

**Active vs. passive PoE — not interchangeable.** Standard (802.3af/at/bt) PoE negotiates voltage between the switch and the device (roughly 44 - 57 V) and is safe for compliant gear. Passive PoE simply puts a fixed voltage (often 24 V or 48 V) on the cable with no negotiation, and can damage equipment if mismatched. Match injector, splitter, and node carefully — a passive 24 V injector paired with a splitter that expects active 48 V may deliver no power or fry the node.

## Maximum Cable Run Distance

PoE follows the Ethernet 100m (328 ft) cable run limit. Choose by distance:

- **Single run ≤100m:** a standard PoE run works directly.
- **~100 - 200m:** use a PoE extender (repeater) at the 100m mark to extend another ~100m.
- **Beyond ~200m:** use a fiber optic run with a media converter.
- Use cellular or WiFi for power-independent remote nodes.

Note: independent of distance, a fiber optic break between the building and the node is also the strongest *lightning* isolation option (see below) because fiber is dielectric — consider it on any outdoor run in a high-lightning area, not only for long runs.

## Lightning Protection for PoE Runs

An Ethernet cable run to an outdoor node creates a lightning risk - the cable can couple surge energy into your equipment:

- **Ethernet surge protector:** Install a PoE-compatible Ethernet surge protector (e.g. Ubiquiti ETH-SP-G2, ~$15 as of 2026-06-08 — confirm current price on the [Ubiquiti store](https://store.ui.com/)) at both the building entry and the outdoor node enclosure. This is essential for any outdoor Ethernet run.
- **Fiber optic break:** Insert a fiber optic run between the building and the outdoor node. Fiber is dielectric - it cannot carry surge current. Best protection option.
- **Grounding:** Properly ground your outdoor enclosure and the surge protectors. The surge protector's ground and the enclosure ground must be bonded to the **same grounding electrode system as the building's AC ground** (per NEC 250.94) — bonding to a separate, isolated ground rod creates dangerous ground-potential differences during a strike. Tie all ground connections into that single building grounding electrode system.