Seasonal storage & winterization
The boat is on the hard, or the camper is winterized in a lot, from October to April. The water is off — now the risks are electrical, environmental, and slow. The point of monitoring is being told before spring, not discovering it in spring.
What can go wrong
The quiet months are when things fail unnoticed.
The battery bank dies over winter
Batteries self-discharge, or a trickle charger quietly fails. Come spring the bank is ruined and you didn't know until you tried to start.
Storage-yard power drops
The pedestal or shed circuit trips and nobody tells you. Your tender stops tending weeks before you'd ever notice.
Water gets in under the cover
Rain, snowmelt, or a failed cover puts water where it shouldn't be — for months, with no one walking the yard.
A hard freeze finds un-winterized plumbing
The classic burst-pipe surprise. A temperature/humidity sensor gives you an early warning, but it is never a substitute for properly winterizing the water system.
How Guardian covers it
Each risk maps to something that ships today, with the plan tier it needs called out honestly.
Watch the bank all season
The Shelly Plus Uni reports bank voltage right through the layup. On Basic, automatic remote telemetry (~5-min freshness) turns a failing charger into a notification, not a spring surprise. On Free you can still check whenever you think of it.
Know the instant storage power fails
The Shelly PM Mini flags shore-power loss the moment it happens — automatically on Basic+, visible on refresh on Free.
Catch water intrusion under the cover
A Shelly Flood Gen4 in the bilge or a low point catches leaks. It's battery-powered and deep-sleeps, so it lasts the whole season and still pushes events instantly when they matter — and the away push reaches you on any tier.
Add cheap freeze & humidity awareness
A Shelly Plus H&T (~$30) in the cabin gives you temperature and humidity readings through the layup — an early hint of a heater failure or damp that leads to mold.
See the whole-winter curve
Hosted history (~1 month on Basic, ~3 years on Premium) gives you the voltage trend across the entire layup — useful for deciding when a bank is finally due for replacement.
The setup
Off-the-shelf hardware, bought once. The core app is free.
Recommended hardware
- Shelly Plus Uni — battery bank voltage~$25
- Shelly PM Mini Gen3 — storage-yard power~$25
- Shelly Flood Gen4 — low point / bilge~$30
- Shelly Plus H&T — temperature & humidity~$30
About $100–110 without the valve (the water's off anyway). You'll need a trickle of internet at the yard — a cheap always-on option from the connectivity guide is ideal since the whole point is being told while you're not there.
Recommended plan
Basic — $3/mo · $12/yr per vehicle
For the winter, Basic is the sweet spot: automatic remote checks and a month of hosted history, so a dying battery or a dead pedestal reaches you without you thinking to look — and you can see the trend that led up to it. Cancel back to Free in season if you like — the plan is per vehicle and month-to-month.
A temperature sensor is an early-warning aid, not a guarantee — always winterize your water system properly.