Identifying a −48 V DC plant in two photographs

Everyone photographs the module. Almost nobody photographs the controller — and the controller is what decides what you are allowed to install next.

VOLT48 engineering desk · Published 24 Aug 2026

Key figures at a glance

Parameter	Value	Where it comes from
Photo 1	Label on the front or side of the rectifier module	VOLT48 intake
Photo 2	The whole shelf, including the controller	VOLT48 intake
Read from the controller	Model and firmware version, from its display menu	VOLT48 intake
Why photo 2 decides more	Controller generation gates configuration; the module rarely does	VOLT48 compatibility audit
Do not trust	The brand on the cabinet — it is often a different vintage from its contents	VOLT48 compatibility audit
Answer time on a part request	One business day, including requests we cannot fill	VOLT48 service commitment

Photo one: the module label

The rectifier module carries its part number silkscreened or on a sticker, on the front face or along one side once the module is withdrawn. That string is the entry point to everything else — a Flatpack2 48/2000 HE reads 241115.105, a Huawei module reads R4850G2 or R4875G1, a Vertiv or Emerson module reads R48-2900U. If the label is unreadable, photograph it anyway: the format, the connector layout and the front-panel arrangement narrow it down further than people expect.

Photo two: the whole shelf, controller included

This is the one that gets skipped, and it is usually the decisive one. Step back and photograph the entire shelf — all module positions, the empty slots, and the controller, which is the unit with the display. The reason is simple: the module tells us what you have, but the controller tells us what you can do. Its generation and firmware version determine whether the plant can hold a lithium configuration at all, and no amount of detail about the module answers that.

The third thing, which is not a photo

Walk up to the controller and read two values off its display menu: the model and the firmware version. Do not infer the firmware from the model — the same controller model ships across a range of versions and the version is what gates several of the settings a lithium retrofit needs. It takes a minute at the cabinet and it removes the single most common source of a wrong quotation.

What not to trust

Do not trust the brand on the cabinet door. Cabinets outlive their contents and get re-used, so a cabinet with one manufacturer's name on it routinely holds another's shelf. Do not trust the asset register either, for the same reason plus one more: registers record what was purchased, not what was swapped in at 3 a.m. during an outage four years ago. The label and the display are the only two sources that describe what is physically in front of you.

What happens after you send them

We identify the part, tell you whether it is an availability question or a configuration question, and answer within one business day — including the requests we cannot fill, which we would rather say quickly than slowly. If the question turns out to be a lithium retrofit rather than a spare, the two photos are also the first two inputs to the compatibility audit, so nothing you collect here is wasted.

Equipment this guide covers

Common questions about this family

The label on my module is unreadable. Is that a dead end?

Usually not. Send the photo anyway along with the shelf photo — the module format, the front-panel layout and the shelf it sits in narrow the candidates considerably, and the controller often names the plant family outright on its display. Our part number index also lists the designations we are asked for most, which is sometimes enough to recognise yours by description.

Why do you need the controller if I only want a replacement module?

For a like-for-like spare, often we do not — the part number is enough to start. We ask because the controller generation decides whether a module of a different revision will be recognised, and because most people who need one module this year need a battery decision next year. Collecting it once saves the second site visit.