Will your plant actually charge a lithium bank?
Most lithium retrofits on −48 V plants fail for one of two reasons: the plant is left with temperature compensation enabled, or the controller firmware is below the version that lets you set the charge voltage the battery needs. Neither is discovered on the day of commissioning if somebody checked first.
The window everything turns on
Telecom equipment on a −48 V bus is specified to a normal service range of −40.5 V to −57.0 V. Every compatibility question below is really a question about staying inside it.
| What | Value | Source and meaning |
|---|---|---|
| What the equipment guarantees | −40.5 V to −57.0 V | ETSI EN 300 132-2, normal service range |
| What the rectifier can deliver | 43.5 V to 57.6 V | Flatpack2 48/2000 HE — the top of this range is outside what the equipment guarantees |
| Factory default of the rectifier | 53.5 V | A lead-acid number, and where most plants are still sitting |
| Lithium setpoint guidance | 52–55 V | Float and equalize at the same value |
| 15S LiFePO4 at full charge | 54.0 V | 3.60 V per cell — inside the window |
| 16S LiFePO4 at full charge | 57.6 V | 3.60 V per cell — above the −57.0 V limit |
Cell-level figures are calculated from the declared cell counts. Window limits and the factory default are the equipment manufacturer's published values. Always confirm against the datasheet of the specific model.
Find what you have
Type a part number, a brand or a controller name. This is an identification table: it tells you which family your equipment belongs to and what has to be determined on your site. It does not declare your plant compatible — that answer comes from reading the plant, not from a web page.
| What you have | Brand | Typical controller | What has to be determined |
|---|---|---|---|
| Flatpack2 48/2000 HE · 241115.105 | Eltek | Smartpack / Smartpack2 | Output adjustable roughly 43.5–57.6 V. Factory default 53.5 V. Confirm which HE variant is in the shelf: the wide-range 48-60/2000 covers a different span entirely. |
| Flatpack2 48/3000 HE · 241119.105 | Eltek | Smartpack / Smartpack2 | Same 1U format at a higher rating. Mixing ratings in one shelf changes plant capacity and protection sizing — both have to be re-checked, not assumed. |
| Flatpack S 48/1800 · Flatpack 1ª gen. | Eltek | Legacy Smartpack / era Valere | End-of-life generation. Mounting and controller interface differ from Flatpack2, so a similar-looking module may not seat or may not be recognised. |
| R48-2900U (Emerson o Vertiv) | Vertiv / Emerson | NetSure NCU · serie M | Same lineage under two names: Emerson Network Power was renamed Vertiv in 2016. Read the controller firmware version — it gates the charge-current limit and the walk-in setting. |
| NetSure 701 / 501 | Vertiv | NCU | On this plant the lithium parameters have NCU names: temperature compensation sensor, automatic equalize, battery thermal runaway management, string capacity, charge current limit, low-voltage disconnect, walk-in. |
| R4850G2 · R4875G1 | Huawei | ETP48 · integrado | Different current ratings — 50 A and 75 A classes. They share a slot but not a rating, so load sharing, controller capacity configuration and breaker sizing all have to agree before mixing. |
| ETP48100 y plantas embebidas | Huawei | Integrado | Compact plants where the controller is not a separate unit. Determine how the charge profile is set and whether the BMS can be read at all before promising monitoring. |
| ESR-48/56 y familia ESR | Delta | DC power controllers de Delta | Delta owns both the ESR line and the Eltek brand, so a Delta-group cross-reference sometimes resolves a Flatpack shortage that looks unsolvable on the Eltek side. |
| APR48 y variantes | Eaton | Controladores de planta Eaton | Common in older transmission and utility sites. Read the module part number from the module itself — the cabinet brand is frequently a different vintage from what is inside it. |
| ZXDU68 · familia ZXD | ZTE | Controladores ZTE | Determine the exact plant variant before quoting: the ZXDU designation covers a range of cabinet and shelf configurations rather than a single product. |
| Controladores y unidades de monitoreo | Multimarca | NCU · Smartpack · equivalentes | The controller and its firmware version decide more about compatibility than the rectifier marking does. Firmware below the minimum is a condition of entry: it is quoted as an upgrade, not worked around. |
Nothing matches that. Send us a photo of the label instead — most legacy 48 V plants are identifiable from the sticker.
Two things we will not tell you on a web page
That your specific plant is compatible, and that a 51.2 V rack battery is a drop-in for a −48 V string. The first needs the parameters above read off your equipment. The second is arithmetic: a 16-cell pack at full charge asks for 57.6 V, which is above the −57.0 V your equipment is specified for.
The twelve things a compatibility audit determines
This is the document the audit produces, filled in and signed for your site. A supplier who only lists part numbers cannot fill this table in. Every completed sheet also feeds a compatibility database organised by rectifier, controller and firmware version — which is the one asset in this business that improves with time.
| Point to determine | Why it matters | Reference value |
|---|---|---|
| Rectifier module part number | The number printed on the module, not the brand on the cabinet. | e.g. 241115.105 · APR48 · R48-2900U |
| Controller model and firmware version | A condition of entry, not a detail. Below the minimum version, the settings you need are simply not available. | Read it in the controller display menu |
| Output voltage range of the module | The adjustable minimum and maximum the module can actually deliver. | 43.5–57.6 V on a Flatpack2 48/2000 HE |
| Charge profile | Float and equalize at the same value. Lithium is not equalized. | Typically 52–55 V, from the battery datasheet |
| Temperature compensation | Disabled. Sensor selection set to None — not merely unplugged. | Compensation sensor = None |
| Plant thermal runaway management | Off. Thermal protection belongs to the BMS, which measures cells directly. | BTRM off |
| String capacity | Module amp-hours × number of modules, entered in the controller. | 4 × 100 Ah → 400 |
| Charge current limit | Enabled and set. A plant sized for VRLA will otherwise push more current than the pack wants. | 0.1C to 0.5C depending on the battery |
| Low-voltage disconnect | At least 0.5 V above the battery's own disconnect, so the BMS is not what opens first. | ≥ battery LVD + 0.5 V · practical floor 38 V |
| Rectifier walk-in and default voltage | Soft start enabled, so a plant returning after a long outage does not slam full current into a cold bank. | Walk-in enabled · module default voltage set |
| Communications and alarm mapping | Protocol, cabling and BMS version. Without this there is no state of charge or state of health in the controller, and monitoring cannot be sold. | RS485/Modbus · CAN on the rectifier bus |
| Mechanical fit | Rack height in U, frame depth, terminal type and torque, cable cross-section, breaker. | Confirmed per site, from the shelf photo |
Not sure what you have? Send the label.
A phone photo of the sticker on the module is usually enough for us to identify it. Send two pictures: the module label, and the whole shelf including the controller. The shelf photo is the one people forget, and it is often the decisive one — the controller generation drives compatibility more than the module marking does.