The geek page

This is the page I wish existed when I was wiring up my own van. The kit page covers the stuff in normal English. This page is for people who already know what a Zigbee coordinator is and want to see what actually runs in my van. Home Assistant OS on a Pi, a Cerbo GX, ZHA with Sonoff sensors, a three-layer fridge thermal loop, and a five-view kiosk dashboard that lives on a rugged Samsung tablet bolted to the habitation wall.

The stack at a glance

The hardware

Raspberry Pi 4 (8 GB), fanless case, 256 GB SSD over USB3

Home Assistant OS, not Supervised. I went back and forth on this. HAOS gives you the appliance experience with the Supervisor and add-ons (MQTT broker, File editor, HACS, Terminal) all one-click, and that is what I ended up wanting. Supervised lets you run other Docker workloads on the host, but I already have an Unraid box at home for that and a second NUC for heavier lifting. The Pi should do one thing and be restorable in ten minutes if it dies. HAOS gets out of the way.

SSD rather than SD card is non-negotiable if you care about the thing surviving a year. SD cards and a write-heavy recorder database are a losing fight, and an appliance install writes constantly.

Sonoff Zigbee 3.0 USB Dongle Plus (ZBDongle-E)

Paired with ZHA, not Zigbee2MQTT. ZHA lives inside HA, one fewer moving part, and the Dreo / Victron / MQTT add-ons already give me plenty of other integrations to maintain. Mounted on a USB3 extension cable so it is not squeezed against the Pi's own Wi-Fi radio. Range across a motorhome is fine from a single coordinator; no routers needed at this distance.

The Zigbee fleet (what is actually paired)

Tuya, Sonoff, and eWeLink. No Aqara, I went off them after a couple of battery surprises on door sensors. Current devices:

• SONOFF SNZB-02D with the little LCD display, inside the habitation. The reference temperature for most automations.
• SONOFF SNZB-06P mmWave presence and illumination. Sensitivity turned down to "large movement only" so rolling over in bed does not trip the lights.
• eWeLink TH01 outside, in a vented housing under the skirt.
• SONOFF SNZB-02WD and eWeLink SNZB-02P as second and third temperature sensors, including one inside the fridge. The one inside the fridge doubles as a fridge-door-open sensor because the illuminance jumps when the interior light comes on.
• Tuya TS0503B single-channel dimmers driving the strip lighting, the fridge vent relay, and tap / step lights. These present to HA as Zigbee lights. One of them happens to switch a 12V fan circuit rather than an LED, which is slightly cursed but works.
• Tuya TS0044 four-button scene remote by the door for "lights up", "lights down", "all off".
• SONOFF S60ZBTPG smart plug with power metering, for an appliance that I keep meaning to remove.

Home Assistant to Cerbo: how the power stack actually talks

Not MQTT. Modbus TCP.

The Cerbo GX will happily publish over MQTT and that is the integration most guides point you at. I started there and swapped. The LaggAt ha-victron HACS integration connects over Modbus TCP on port 502, the Cerbo's native protocol, and gives you every vebus, solarcharger, system and ESS register as a typed HA entity. 268 sensors for my install, all with proper units and device classes, no YAML topic-juggling.

MQTT is still running on the Pi as a Mosquitto add-on. I use it for a couple of other things. But the Cerbo connection is not one of them.

The MultiPlus mode decision: CHARGER vs ON

This is the bit that took me the longest to think about and the bit most motorhome Home Assistant writeups get wrong.

The MultiPlus has three modes: OFF, CHARGER, and ON. Most guides assume you want ON permanently so that Power Assist is available. Power Assist is Victron's trick where the inverter tops up shore power from battery whenever your AC load exceeds the current limit you told the Cerbo the pillar could supply, so you do not trip a 6A campsite breaker with a kettle and a fridge running at the same time.

My van runs in CHARGER mode as the default. Reasons:

• Every AC load I have (kettle, microwave, heater, shore chargers) only runs when I am plugged in. Off-grid I am on 12V DC: fridge compressor, LEDs, water pump, USB. The inverter does not need to be live.
• CHARGER mode is simpler and less surprising. Pass-through to AC-out when shore is present. Nothing when it is not. No phantom loads, no standby whine, no risk of the inverter running all night because a USB-C charger is left plugged in.
• Power Assist only helps if your input current limit is correctly set for the pillar you plugged into. Get it wrong and you either starve the van or trip the pillar before Power Assist engages. It is a manual-setup-every-site tax that I do not want.

What I do have instead is a Shore Power Breaker Alert automation that pings my phone when AC consumption crosses 2100W, roughly 9.1A at 230V, just under a typical 10A pillar limit. That is the "back off the kettle" warning. It is a substitute for Power Assist that puts a human in the loop, which is what I actually want because I am the one deciding between kettle and microwave on a 6A site.

When I want Power Assist, the kiosk has a tile that flips the mode. CHARGER is blue and says "Tap to Power Up". ON turns it green and reads "230V Sockets LIVE - Tap for Safe Mode". One touch in each direction. ESS is already configured in self-consumption mode, so when the MultiPlus goes to ON, the right behaviours come with it.

# The conditional tile on the Pilot view, verbatim from my dashboard
type: conditional
conditions:
  - entity: select.victron_vebus_mode_227
    state_not: 'ON'
card:
  type: custom:mushroom-template-card
  primary: Charger Only
  secondary: Tap to Power Up
  icon: mdi:battery-charging
  icon_color: blue
  tap_action:
    action: call-service
    service: select.select_option
    target:
      entity_id: select.victron_vebus_mode_227
    data:
      option: 'ON'

The fridge thermal loop

Why it matters on a retrofit

OEM motorhomes get a factory fridge chimney: a dedicated vent bay with a top and a side grill, sized for the fridge model. Retrofits do not. You stuff a compressor fridge into a kitchen cupboard and the cupboard cooks unless you help it. Home Assistant gives me a smarter version of the chimney: a differential thermostat, a hysteresis loop, and a battery-aware safety gate.

The vent itself

A plate vent on the side wall holds three 12V fans: two exhaust, one intake. The asymmetric ratio gives slight negative pressure in the cupboard, so any small leaks in the cupboard wall pull into the cupboard and out through the vent rather than pushing warm compressor air into the habitation. A Zigbee relay (a Tuya TS0503B presenting as a "light" to HA, which is mildly funny because it is a 12V fan circuit) switches the fans on and off.

The automation

Three layers of monitoring, one actuator:

• Active cooling loop - fans on when fridge rear temperature is more than 8 degrees above inside temperature; fans off when the differential drops to 4 degrees. Hysteresis stops it short-cycling.
• Parked fridge guard - alerts if the internal fridge temperature rises above 8 degrees while the van is marked as parked. That means the inverter or the fridge has died and I have not noticed.
• Driving fridge guard - a second, tighter alert at 6 degrees, gated on an input_boolean.fridge_monitoring_active toggle. The fridge naturally warms a degree or two when the inverter is off; the tighter threshold catches real problems without false alarms at home.

The active cooling loop also has a battery safety gate: fans will not run if leisure state-of-charge is below 30%. The fridge cupboard bleeding a few degrees to the habitation is a much smaller problem than running a set of fans flat for an hour and ending up at 15% SoC overnight.

# The real automation, exported from HA
alias: "Climate - Fridge Vent Differential"
description: "Only run fans if air behind fridge is significantly hotter than cabin air."
triggers:
  - entity_id: sensor.fridge_rear_temperature
    trigger: state
conditions:
  - condition: numeric_state
    entity_id: sensor.victron_system_battery_soc
    above: 30
actions:
  - choose:
      - conditions:
          - condition: template
            value_template: "{{ (states('sensor.fridge_rear_temperature')|float - states('sensor.sonoff_snzb_02d_temperature')|float) > 8 }}"
        sequence:
          - action: switch.turn_on
            target: { entity_id: switch.fridge_vent_fans }
      - conditions:
          - condition: template
            value_template: "{{ (states('sensor.fridge_rear_temperature')|float - states('sensor.sonoff_snzb_02d_temperature')|float) < 4 }}"
        sequence:
          - action: switch.turn_off
            target: { entity_id: switch.fridge_vent_fans }

The inverter cupboard gets the same treatment with a separate temperature sensor and a separate relay. The principle is identical; the thresholds are different because the inverter only cares when it is actually running.

The other automations worth calling out

Heater (Dreo) with a three-layer safety interlock

The Dreo Atom One S electric heater lives in the habitation. It only runs if all three of these are true:

• Inside temperature is below the setpoint (21C).
• Presence sensor says there is a person in the van.
• Shore power L1 voltage is above 200V.

If L1 drops below 100V (shore power pulled, pillar tripped, extension cable snagged) the heater cuts immediately. The point is not "polite shutdown". The point is that a 2kW heater quietly switching from shore to inverter is how you wake up at 4am to a flat battery and a pissed-off LiFePO4 BMS.

Shore power breaker alerts

Two automations, opposite directions:

• AC consumption > 2100W with grid L1 active fires a notification: "you are about to trip the pillar".
• Grid L1 transitions to on fires a notification: "shore power restored and charging". Useful when the site is on a rota and you want to know when your window is.

Low battery alert

SoC below 20% pings phone and tablet. Simple. Paired with the 30% fridge-fan gate so that by the time the battery alert fires, the active-cooling loop is already off.

Auto lights on presence

SNZB-06P presence plus its own illumination sensor. Lights on when someone walks in and the ambient is dark. Off 5 minutes after the van goes empty. The sensitivity is set to low so a sleeping person turning over does not wake the strip lights up at 3am.

Home zone follows the van

One of the most useful, quiet automations. The tablet runs the HA Companion app with high-accuracy GPS. A trigger on the tablet's location updates HA's zone.home to wherever the tablet currently is, every ten minutes. The van is the home zone. Arrive at a new aire, the home zone moves to that aire. All the presence and not-home logic keeps working correctly without manual intervention.

alias: "The Dusty Van: Update Location"
description: "Moves the Home zone to the tablet's GPS coordinates"
triggers:
  - entity_id: device_tracker.sm_t636b
    trigger: state
actions:
  - action: homeassistant.set_location
    data:
      latitude: "{{ state_attr('device_tracker.sm_t636b','latitude') }}"
      longitude: "{{ state_attr('device_tracker.sm_t636b','longitude') }}"

The kiosk dashboard

A Samsung Galaxy Tab Active4 Pro (SM-T636B, the ruggedised one) is bolted to the habitation wall, running Fully Kiosk Browser pointed at a dedicated Lovelace dashboard. Five views, each in full-screen panel mode so you can tap once and land anywhere in the stack.

The dashboard is built on two HACS components:

• Mushroom - the card system. Rounded tiles, colour accents, template support. Works beautifully on a 10-inch tablet.
• power-flow-card-plus - the animated Victron energy-flow diagram on the Energy view. Worth the install just for this one card.

Pilot view: the one you land on

Ten numbered pins on the image. Tap a pin or a card below to highlight the match.

/dusty-van/pilot - tap a pin or a card to highlight the match.

Energy view: one card does the whole job

power-flow-card-plus takes battery SoC, solar watts, consumption, and grid watts, and draws the canonical Victron four-pole diagram with animated flow dots. It is worth showing to anybody who asks "what's a Cerbo for" because it answers the question in about two seconds. The animated dots below are a CSS approximation of the real card's flow; the real one in the van is reactive to live state.

×

/dusty-van/energy - Flow dots are animated client-side as a CSS approximation. The real card updates with live state every few seconds.

Navigation, Weather, Spotify

Navigation is a map card centred on the tablet's device_tracker, which means it shows the van exactly where it is parked (recall: the Home zone follows the tablet, so "Home" and "where the van is" are the same marker). Weather is a stock weather-forecast card on met.no's forecast for the current location. Spotify is a media-control card on my Spotify Connect account.

Network and remote access

The van LAN

The GL-iNet X2000 (Spitz AX) broadcasts "The Dusty Van" 2.4 / 5 GHz plus a guest SSID, with a 4G modem bonded to whichever EU SIM I am on. LAN is 192.168.1.0/24. Everything the Pi controls (tablet, Cerbo, Sonos, Nest Mini, Broadlink, Dreo) sits on that LAN. AirVPN WireGuard clients for UK and Switzerland are configured on the router itself so any device on the van LAN can exit through a specific country if it wants. There is no mystery route: the X2000 is the gateway, every client is on the same /24, and Zigbee is the one thing that does not touch Wi-Fi.

The four ways to reach the van from outside

My current setup is Tailscale for me, Cloudflare Tunnel for anyone else. Tailscale on my phone and laptop means I can SSH into the Pi, load the dashboard, and reach the Cerbo's web UI at its LAN IP from a cafe in Perpignan. Cloudflare Tunnel is what I hand to my partner so she can check battery state from her phone without installing anything, and what I would hand to a friend-of-the-family in an emergency. The Tunnel is locked behind Cloudflare Access with her email on the allowlist.

I have not paid for Nabu Casa. If I did not already own a domain I probably would.

Cerbo on the tailnet without running Tailscale on the Cerbo

Victron's Venus OS cannot run Tailscale (no supported binary for the Cerbo's hardware, and I would not install one in a running energy system anyway). So the Cerbo is reachable over Tailscale via the Pi. On the Pi I enabled tailscale up --advertise-routes=192.168.1.0/24. Any tailnet peer with --accept-routes enabled can now curl the Cerbo directly at its LAN IP. The Pi is acting as a subnet router for the van LAN.

# On the Pi, once, to expose the van LAN to the tailnet
tailscale up --advertise-routes=192.168.1.0/24

# On any device that wants to reach the Cerbo directly
tailscale up --accept-routes

Backups and resurrection

Home Assistant snapshots (Supervisor → Backups) nightly to the SSD. The Google Drive Backup add-on pushes the latest snapshot off-site weekly. If the Pi melts on a French aire the recovery is: new Pi, flash HAOS, restore latest snapshot from Google Drive on first boot. That is the recipe. It has been done twice.

Known gotchas in this stack

• Fully Kiosk's HA integration gives you brightness, motion, screensaver, and current URL if you enable the REST API on the tablet. Worth doing; I have not yet on my tablet. (HA Companion is what is currently providing device_tracker.sm_t636b and battery level - Fully Kiosk-specific entities are absent until I switch the integration on.)
• Every HACS integration you add is another thing that can break on a core HA upgrade. Pin versions, restore from snapshot after upgrades, do not upgrade on a Friday.
• Zigbee presence is only as good as the device staying online. The SNZB-06P is an excellent presence sensor when it is happy, but mine has a habit of going unavailable when the mesh churns - a re-pair usually fixes it. The van_auto_lights_on_presence automation stays armed in the meantime and silently does nothing, which is worth knowing before you trust the lights to come on. I also keep it on the opposite side of the habitation from the X2000, because the SNZB-06P does not like being close to a Wi-Fi radio.

Whats next on this page

• The Broadlink RM4 pro config for IR-controlling the TV and the aircon.
• The inverter-cupboard fan automation YAML, which works the same as the fridge one with different thresholds.
• The Sonos + Spotcast chain that pushes Spotify to the Sonos Beam without requiring the Spotify app to be open.
• A Cloudflare Access policy walkthrough with screenshots, for the "how do I let my partner in without an install" use case.

If there is a specific corner of this stack you want me to document sooner, email [email protected]. I add whatever people actually want to read next.