Lighthouse Mode

Through a power cut

Keeping the light on

The node has a second DC input. Plug a battery pack you already own into it — any 12 V pack, a lithium jump box, a sealed lead-acid brick, a USB-C power bank through a trigger cable — and the node runs on it when the wall does not. I do not ship cells and I never charge yours.

Both of those are deliberate. Cells are a consumable and the node is sealed to outlast them, so putting a battery inside would build in a failure date. And a device that charges someone else's pack owns the consequences of doing it badly. The node is a load, not a charger, and that is enforced in the wiring rather than in software.

There is also nothing to switch. Both supplies sit on the same rail behind ideal diodes and the higher one simply wins, so when the power drops the pack is already carrying the node. The transfer time is zero because there is no transfer.

Inside the node, a small reserve holds it up for seconds. That is its whole job: write down the moment it lost power and get one message out before it goes dark. It is the last thing the node does, whenever that turns out to be — the night the wall supply fails, or days later when your pack finally runs down.

That reserve is not a battery. It is a capacitor, which means there is no cell sealed inside the node to swell, fade or want replacing in five years. The part of this system that has to outlast everything has nothing in it that wears out.

Designed and decided, not built: the message that matters more comes from outside the house entirely. The controller checks in on a schedule, and when it stops, that silence is the alarm. We have not heard from your tank since 3:14am does not depend on your power, your router, or anything in the building still being alive.

Both answers below are the same two failures, told apart. Both answers below are designed and decided, not built — that network and Pharos Power go together, and neither is shipping.

The router goes down and the power stays on. Nothing in the control path was on your router to begin with. The controller carries a network of its own and the nodes and the outlets are both on it, so readings keep arriving, your limits keep being enforced, and an outlet still cuts a heater that will not stop. What you lose is the outside world: the app from somewhere else, and the alert.

The power goes. Now there is no mains to switch. The node runs on the pack you plugged in and keeps the twelve volt ports — the doser, the ATO, a CO₂ solenoid — and being able to stop those is worth more than being able to start anything. It will not run your return pump. Nothing will, because the wall is what failed.

Getting the alert out of the house is a separate problem, which is what the next block is about — and that part you buy somewhere else.

The screen, through the same cut

What the Pod does on a pack

The Pod runs from a 27 watt USB-C supply, so what holds it up is a power bank. It stays outside the box. Nothing sealed in, no cells of mine, and no part to buy from me.

Which pack is not settled. The two requirements are. It has to hold 5 V at 5 A, because below that the Pi limits its own USB ports and puts a warning on the screen. And it has to pass power through while charging. One that does carries the Pod across the cut without a blink, and one that does not will drop it. What is still open is which part meets both.

It will not last the way the node does, and that is the design, not a shortfall. A node is milliamps. The Pod is a computer with a lit screen. On the same 100 watt-hour pack that is around eight hours for the Pod against a couple of days for the node — roughly six to one. Both are calculated from published draws and not yet measured on the hardware, which is why they are quoted against a wattage. The ratio is the part that matters: the limits that stop a heater run on the node, and never needed a screen to work.

Designed and decided, not built: on a pack, the Pod stops being a dashboard. A lighthouse runs on its own power, does nothing but be visible, and says one thing clearly. The screen falls back to a single reading and the beacon, dimmed. A tap brings the rest back for a minute. You are never asked to diagnose your own power cut — you are shown what each choice costs.

One rule inside that. Acknowledging the power cut silences the power warning and nothing else. If the tank then drifts out of range, that is a new alarm at full brightness with no memory of the first. Yes, I know the power is out must never silence your tank is at 82 degrees.

That goes for the Pod as well as the node. And if you are only going to hold one thing up, hold up the node. It is the cheap one to keep alive, and it is the one actually stopping things.

Keeping the internet up

Buy this one from someone else

Start with what a power cut actually takes with it. Not just the tank — the lights, the return pump, the heater, and the router in the hallway along with them. One circuit if you are lucky, the whole house most nights.

A node on the pack you plugged in keeps watching through all of that. What it cannot do is shout. The router is dark, so nothing leaves the building — and what tells you instead is the silence: the check-in stops, and you are told the tank has gone quiet. That is a different message and it arrives differently. It comes late, by however long the check-in interval is, and it says we have not heard from your tank rather than naming what went wrong. A backup on your router buys the other version — the alert the moment it fires, saying which thing failed, and the app still working while you decide what to do about it.

A router averages about 8 watts and an all-in-one gateway about 15, which is nothing, so the box that holds one up is small. A DC unit runs the router straight from cells with no inverter in the path, and what you are buying is watt-hours rather than a brand.

The arithmetic is the whole thing. Divide the pack's watt-hours by your router's watts, then take off about a fifth for what the conversion costs. A 38 watt-hour pack is just under four hours on an average router. A 100 watt-hour pack is roughly ten, which is enough to sleep through most of what takes a street down.

There is no price here for one, and that is deliberate. I went looking, and the same stated capacity sells for wildly different money depending on which listing you land on, so the price tells you nothing about what you are getting. The watt-hour figure tells you everything, and plenty of listings do not print it.

It works the other way round too, and it catches people out: a backup on your router keeps your connection alive, not your controller. The reserve inside a node is seconds, not hours. Back only the router and the internet stays up while the tank goes unwatched. They are two different jobs.

I do not sell the router one, and I am not going to. That shelf is already full of the same few designs under a dozen different names, and putting my badge on one would be asking you to pay more for a box I did not make. Buy whichever you like. What I will do is tell you plainly that you need it, and say what to look for.