# 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)