# Eltek DC power systems (-48 V)

A -48 V DC power system of rectifiers, controller, distribution and batteries for PBX rooms, base stations, transmission and fiber nodes. Promark uses Eltek Flatpack2 HE and Flatpack S systems in its solutions and sizes, installs and maintains them across Türkiye and in Turkmenistan.

Source: https://www.promark.tr/en/solutions/platforms/eltek-dc-guc

## What does it do?

A telecom DC power system converts AC mains to -48 V DC with rectifier modules, feeds the loads and keeps the battery bank on charge at the same time. Because the battery sits on the DC bus, the loads continue to run from the battery when mains fails. The ETSI EN 300 132-2 standard defines this interface as -48 V DC with the positive conductor connected to earth; the normal service range is -40.5 V to -57.0 V.

The system has four parts: hot-plug rectifier modules; a controller (Smartpack S) that monitors and manages the system over CAN bus; battery distribution with battery fuses and a battery disconnect contactor (LVBD); and load distribution with MCBs or fuses plus an optional load disconnect (LVLD). During a mains failure, when battery voltage drops to the set limit, the controller opens the LVD contactor; when mains returns and the output voltage reaches the reconnect limit, it closes the contactor again.

Eltek is the telecom power brand of the Delta Electronics group (Delta Group); current Flatpack S datasheets are published by Delta Electronics (Netherlands) B.V. Promark supplies Eltek rectifier systems and Exide VRLA batteries, and designs and installs the DC power infrastructure with the same team that handles PBX and transmission projects.

## Who is it for, and at what scale?

- **PBX room (OpenScape 4000):** OpenScape EcoServer and EcoBranch are available with a -48 V DC input power supply version, and the LUNA 2 power supply in AP shelves runs from -48 V DC input in DC systems. The PBX is fed from a single DC system together with the battery bank.
- **Base station and microwave site:** Flatpack S 1U system: controller, rectifiers, battery and load distribution in 19" 1U at 262 mm depth. It fits shallow site cabinets and delivers 40 A with 2 rectifiers or 100 A with 3 rectifiers at -48 VDC.
- **Transmission and fiber node:** Transmission, fiber/FTTx and broadband equipment fed from -48 V DC. Battery autonomy is sized to the site's access time, and alarms are carried to the central site via SNMP or relay outputs.
- **Central office, data center, utility site:** Flatpack2 HE: 2000 W and 3000 W modules, from 8 kW 2U racks to multi-cabinet systems. Applications listed in the datasheet include central office, data centers, and SCADA, control and protection at power utilities.

## Key features

- Flatpack2 HE rectifiers: 48V/2000W HE (41.7 A) and 48V/3000W HE (62.5 A); 96% efficiency at nominal input
- Flatpack S rectifiers: 48/1000 HE and 48/1800 HE; up to 95.5% and 95.8% efficiency; 72 × 41.5 × 217 mm, under 850 g
- Flatpack S 1U system: 19" / 1U / 262 mm; 40 A with 2 rectifiers, 100 A with 3 rectifiers at -48 VDC
- Hot-plug rectifier modules; on Flatpack S the controller can also be replaced in operation
- Output voltage 53.5 VDC default, adjustable from 43.5 to 57.6 VDC
- Smartpack S controller: 2.2" colour display, web interface over Ethernet, SNMP v3 (trap, set, get), Modbus TCP, email notification of trap alarms
- 6 programmable relay outputs and 6 multi-purpose inputs (digital or analog)
- Automatic battery monitoring and test; battery quality indication based on test results, event and battery test logs
- LVBD (battery disconnect) and optional LVLD (load disconnect); disconnect and reconnect voltages are set in the controller

## Flatpack S and Flatpack2 HE compared

|  | Flatpack S | Flatpack2 HE |
|---|---|---|
| Architecture | Complete 1U system: controller + 2 or 3 rectifiers + battery and load distribution | Rectifier module; from 8 kW 2U racks to multi-cabinet, MW-scale systems |
| Size | System 19" / 1U / 262 mm; module 72 × 41.5 × 217 mm | Module 109 × 41.5 × 327 mm, 1.95 kg |
| Module power | 1000 W / 1800 W | 2000 W / 3000 W |
| Module max. current | 20.9 A / 37.5 A (Vout < 48 VDC) | 41.7 A / 62.5 A |
| Efficiency | Up to 95.5% / 95.8% | 96% (at nominal input) |
| System output | -48 VDC; 2R: 40 A, 3R: 100 A | -48 VDC; depends on rack/cabinet model |
| AC input, operating range (module) | 85–300 VAC / 85–305 VAC | 85–300 VAC / 85–305 VAC |
| Output voltage | 53.5 VDC default; 43.5–57.6 VDC | 53.5 VDC default; 43.5–57.6 VDC / 43.2–58 VDC |
| Battery distribution | 2R: 2 × 40 A, 3R: 2 × 80 A; LVBD as default | Depends on rack/cabinet model |
| Controller | Smartpack S (hot-plug, Ethernet) | Smartpack family, over CAN bus |
| Operating temperature | -40 to +85 °C; power derating above 45 °C | -40 to +75 °C; power derating above 55 °C |
| MTBF (Telcordia SR-332) | > 315,000 / > 300,000 hours | > 350,000 / > 300,000 hours |

Source: Eltek Flatpack S 1U Systems datasheet (CTOS0X01.DS3 v6, 2016 and v8, Delta Electronics), Flatpack S 48V Rectifiers 1000W HE & 1800W HE (241122.1x5.DS3 v1, 2013), Flatpack2 48V HE Rectifiers 2000W & 3000W (PEDM0000133197 v02, 2021), Smartpack S Controller (242100.410.DS3 v1) and Flatpack2 48/2000 (241115.100.DS3). Where a cell has two values, the order is smaller / larger module. Distribution and capacity of a Flatpack2 HE system rack are confirmed in the BOM for the selected rack model.

## Expansion and replacement

### Growing by adding modules

Because the rectifiers are hot-plug, a module is added to a free slot when the load grows, while the system keeps running. Unused slots are closed with blind panels. Rack and battery fuse capacity are checked during the site survey.

### Replacing an old rectifier system

With 262 mm system depth, Flatpack S fits most cabinets and its datasheet describes it as a replacement unit for older systems. The existing battery bank is kept or renewed depending on its age and test results.

## DC power or UPS?

**-48 V DC power system**

- Telecom loads with -48 V DC input: OpenScape 4000 (EcoServer, EcoBranch, AP shelf), base stations, transmission and fiber equipment
- Battery connected directly to the DC bus; longer autonomy is achieved by adding battery capacity
- Modular N+1: rectifiers run in parallel and the system grows by adding hot-plug modules
- Battery test, LVD and remote monitoring via SNMP in the controller

**[AC UPS](https://www.promark.tr/en/solutions/platforms/ups-aku)**

- IT loads with AC input such as servers, storage and network devices
- Backup for AC loads in a server room or cabinet
- When the equipment to be powered has no -48 V DC input
- Details on the UPS and battery page

## What Promark delivers

- Site survey: load list, existing DC system, battery condition, cabinet depth and mains supply
- Sizing: number of rectifiers (N+1) from load and battery charging current, battery capacity from required autonomy
- Datasheet-based design; BOM within 24–48 hours
- Installation: rectifier rack, battery bank, battery and load distribution, earthing
- Commissioning: LVD limits, alarm relays, SNMP and email notifications, battery test
- Periodic maintenance and battery tests; field service across Türkiye and in Turkmenistan

## Sectors

- [Energy & Industry](https://www.promark.tr/en/solutions/energy)
- [Public & Critical Facilities](https://www.promark.tr/en/solutions/public)

## Related catalog products

- [Eltek Flatpack S — 1U Compact 48V DC Power System](https://www.promark.tr/en/products/eltek-flatpack-s)
- [Eltek Flatpack2 HE — 48V Telecom DC Power Rectifier System](https://www.promark.tr/en/products/eltek-flatpack2)
- [Exide GNB Sprinter P12V875 — 12V 41Ah VRLA AGM Battery](https://www.promark.tr/en/products/exide-12v-41ah)
- [Exide GNB Sprinter XP12V1800 — VRLA/AGM Battery (12V 56.4Ah)](https://www.promark.tr/en/products/exide-12v-56ah)
- [OpenScape 4000 EcoServer 2 — Mission-Critical Communications Platform](https://www.promark.tr/en/products/openscape-4000-ecoserver)
- [All products in the family](https://www.promark.tr/en/products/dc-power-rectifier)

## Frequently asked questions

### Why is the positive pole earthed in a -48 V system?

The ETSI EN 300 132-2 standard, which defines the DC power interface of telecom equipment, specifies the nominal voltage as -48 VDC with the positive conductor connected to earth; this conductor is also called the "DC return". Because telecom equipment is designed for this interface, the DC power system is built with the same polarity. Under the standard, the normal service range is -40.5 V to -57.0 V.

### How many rectifier modules are needed?

The total current required is the load current plus the battery charging current; dividing this total by the current of one module gives N. One more module is added so that capacity is not short when a module fails or is under maintenance (N+1). According to the datasheets, module current is 41.7 A for Flatpack2 48V/2000W HE, 62.5 A for 48V/3000W HE and 37.5 A for Flatpack S 1800 W; rack capacity (Flatpack S 2R 40 A, 3R 100 A) is checked separately.

### How is battery autonomy calculated?

The current the load draws over the required time is compared with the battery's current rating at that discharge time; the nominal Ah alone is not enough. For example, Exide P12V875 at 25 °C and 1.80 V/cell end voltage delivers 4.1 A for 10 hours (41 Ah) but 25.4 A for 1 hour. For -48 V, 12 V blocks are connected as a string of 4 in series, and parallel strings are added if the current is not sufficient; temperature, ageing and the LVD limit are also taken into account.

### Flatpack S or Flatpack2?

Flatpack S is a compact system that combines controller, rectifiers and distribution in 19-inch 1U at 262 mm depth, delivering 40 A with 2 rectifiers or 100 A with 3 rectifiers at -48 VDC. It suits base stations, fiber nodes and shallow cabinets. For higher loads, Flatpack2 HE with 2000 W and 3000 W modules is used; its systems range from 8 kW 2U racks to multi-cabinet installations.

### Can the DC power system be monitored remotely?

Yes. The Smartpack S controller is monitored and configured through a web browser over Ethernet; it supports SNMP v3 (trap, set, get) and Modbus TCP and can send trap alarms by email. Its 6 programmable relay outputs pass alarms to another system as dry contacts, and battery tests and events are logged in the controller.

### Can an OpenScape 4000 PBX be powered from DC?

Yes. OpenScape EcoServer and EcoBranch are available with a -48 V DC input power supply version, and the LUNA 2 power supply in AP shelves runs from -48 V DC input in DC systems and battery operation. In that case the PBX is fed from the DC system made up of the rectifiers and the battery bank. We size the PBX and the DC power system in the same project, within a single BOM.

## DC power system quote

Send us the list of equipment to be powered or the total load current, the required battery autonomy, the mains supply (1-phase / 3-phase) and the cabinet dimensions on WhatsApp. We return a BOM and quote within 24–48 hours. Across Türkiye and in Turkmenistan.

- Request a quote: https://www.promark.tr/en/contact
- WhatsApp: https://wa.me/903125440915?text=Hello%2C%20I%20would%20like%20a%20quote%20for%20an%20Eltek%20DC%20power%20system.
- Call: +90 312 544 0915
- E-mail: destek@promark.tr
- Promark Dijital Teknolojiler Limited Şirketi — İvedikköy Mah. İvedik Cad. No: 245/38 06378 Yenimahalle / Ankara