Backup starts before the backup: in the protection that goes in front.

As well as the backup unit, this house comes from the world of electrical protection: what sits upstream of the cabinet. That matters because a backup unit protects you from the power going away, and there are two things it does not solve that also shut a video system down: a big surge —the classic one from a storm nearby— and a badly made earth.

That is where surge protection comes in, fitted in the panel and on the lines that leave the building, and it is what saves the outdoor cameras and the equipment at the end of a long run. In an industrial unit with cameras on masts, that is not an extra: it is the difference between a storm nobody notices and a morning spent replacing electronics.

In backup, the catalogue covers everything from the cabinet unit to the modular one, where capacity is added by putting modules in instead of changing unit. And almost all of the professional range have two things worth asking for: network monitoring and a way of changing the batteries without leaving the load unprotected.

Batteries are consumables: they wear out in a few years, they give half the runtime long before they fail completely, and they have to be changed. The practical question is how. On a small unit they are changed from the front without switching anything off. On a large one you have to look at whether there is a way of bypassing it so you can work on it with the load fed straight from the mains: without that, changing batteries means switching the video system off, and that is a planned shutdown nobody wants to plan.

The other question is when. A professional unit can run a scheduled runtime test and leave the result on record, and that turns the state of the batteries into a fact you can look at instead of a guess. With that, the replacement goes into next year's budget; without it, it arrives on the day of the cut.

And it is worth knowing that heat shortens a battery's life more than use does. A backup unit inside a closed, hot cabinet gets through its batteries at a surprising rate, and that is one of the reasons the cabinet temperature and the power backup are decided at the same time.

Runtime only means anything when it is measured: everything switched on, at the busiest hour, pulling the power and timing it. And «everything» is the whole chain: cameras, the switch that powers them, the recorder, the storage if it is separate, and the workstation somebody watches from. Backing up the recorder and not the switch is the most repeated mistake in the trade, and it leaves a recorder switched on recording nothing.

Orderly shutdown is the other half, and it protects you from something worse than losing minutes of video: a server cut off dead can damage the database that says where each recording is. With a program watching the battery, the system shuts itself down before the power runs out and starts itself up when it comes back, in the right order.

And the boundary has to be said: this is not a generator. If the installation has to keep running through a cut lasting hours, you need a generator set, and then the battery backup covers the minute that set takes to start and settle. Promising two hours of batteries for a four-hour cut is a sum that gets found out on the bad day.

A large unit in a closed, hot cabinet, no: it eats its own batteries. If there is no ventilation, the unit goes outside the cabinet or the cabinet gets sorted out first.

Nor would we fit it without network monitoring at a site where there is nobody. Backup that does not report the state of its batteries is not backup: it is a box that will be worn out on the day it is needed and nobody will know.

And we would not fit it as the only electrical measure in an installation with outdoor cameras and long runs. There you also need surge protection and an inspected earth; the backup unit does not protect you from a nearby lightning strike, and that is exactly what takes out the electronics of a perimeter.

What is done over the network IT handles without difficulty: the state of the unit, an alert when it goes onto batteries, an alert when the batteries are worn out, and all of it inside the alerting system they already have. If there are managed power strips, the remote restart of a hung piece of equipment too, which saves journeys.

What has to be assigned to a person is the physical maintenance: the annual runtime test and the battery replacement by calendar. The client's own maintenance team can do it with a written procedure, or we can do it under a contract. What does not work is it being on nobody's list, which is the most frequent case.

And there is a two-minute check anybody can do today: look at what is plugged into the backup unit. If a large monitor, a printer or something nobody decided on turns up, you have already found part of the missing minutes.