Power conversion module for a −48 V DC power system (the plug-in rectifier that feeds telecom equipment and charges the battery)
The plug-in rectifier module of a −48 V telecom DC power system · the −40.5 to −57.0 V normal service range at the equipment interface, 53.5 V default float, 43.5–57.6 V adjustment, current sharing within ±5%, 20 ms hold-up, ORing on the output and derating with temperature
In telecom sites and central offices, equipment runs from a −48 V DC bus held up by a battery. Plug-in rectifier modules convert the mains to that bus, share the load and keep the battery charged; modules are paralleled for capacity and redundancy. Their output setting has to suit both the battery and the voltage range the equipment is built for.
Plug-in AC-DC rectifier modules for −48 V DC power systems in telecom, broadband and utility installations. Hot-swap redundant modules for equipment chassis are covered on the Redundant power supply (hot-swap plug-in modules run N+1 in an equipment chassis) page; chassis-mount AC-DC supplies on the Power supply module: enclosed and open-frame AC-DC switching supplies mounted on a chassis or inside equipment page; DIN-rail supplies on the Industrial DIN-Rail Power Supply Unit page; high-current DC rectifier cabinets on the Power supply unit (high-current DC rectifier cabinet for electroplating, anodizing and electrolysis) page.
CNFX editorial research · Sources checked October 13, 2026 · 2 sources
The voltage range the −48 V equipment is built for
ETSI EN 300 132-2 V2.6.1 (2019-04) states that the normal service voltage range for the −48 V DC nominal supply at interface A "shall be from -40,5 VDC to -57,0 VDC", with no degradation of service in that range, verified by voltage steps between −40.5 V and −57.0 V. It notes that "In most cases" the nominal voltage is based on a 24-cell lead-acid battery. [1]
Between 0 V and −40.5 V, and between −57.0 V and −60.0 V, equipment "shall not suffer any damage" and must restore normal service automatically when the voltage returns, without operating breakers or fuses. For networks based on −60 V feeding, an annex gives −50.0 to −72.0 V as the normal range. [1]
State the equipment's interface standard and the battery (cell count, chemistry, float and boost voltages) so the rectifier output setting can be chosen inside the equipment's normal range.
02
Output setting, current sharing, hold-up and derating of one module
Eltek's Flatpack2 48/2000 rectifier module data sheet (Doc 241115.100.DS3, v12) gives a default output of 53.5 V DC, an adjustable range of 43.5–57.6 V DC, 2,000 W at nominal input and 41.7 A at 48 V, with "ORING PROTECTION ON OUTPUT" and a low output voltage alarm at 43.5 V DC. [2]
Eltek's adjustable output reaches 57.6 V, above the −57.0 V end of the ETSI normal range, so the setting, not the module's capability, keeps the bus inside that range. [2][1]
Other figures in the data sheet: current sharing within ±5% of maximum current from 10 to 100% load; static regulation ±0.5%; hold-up of more than 20 ms at 1,500 W with output above 43.5 V; input 185–275 V AC nominal, 85–300 V AC operating, with power falling to 850 W at 85 V AC; efficiency up to 92.5%; and derating above 45 °C to 1,350 W at 75 °C. The module lists ETSI EN 300 132-2 among its design standards. [2]
Eltek Flatpack2 48/2000
Value
Output voltage default / range
53.5 V / 43.5–57.6 V DC
Power, nominal input / 85 V AC
2,000 W / 850 W
Current sharing (10–100% load)
±5% of maximum current
Hold-up at 1,500 W
> 20 ms, output > 43.5 V
Ripple and noise
< 100 mV p-p, 30 MHz
Operating temperature
−40 to +75 °C, derating above 45 °C to 1,350 W
Give the supplier the load current, redundancy (N+1), battery recharge current, mains range and site temperature, and ask for module count, output setting and derated power at the hottest ambient.
03
−48 V rectifier module details
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Compiled and source-reviewed by the CNFX editorial team.
Each manufacturer above links to the page on that company's own website where the product is listed, with the date we checked it. How we source and review
· Page last updated 13 October 2026
Buyer questions
What voltage range must −48 V telecom equipment work over?
−40.5 to −57.0 V DC at interface A without degradation, per ETSI EN 300 132-2. [1]
What is the default output of a Flatpack2 48/2000 module?
Eltek gives ±5% of maximum current from 10 to 100% load. [2]
Does the module lose power in hot sites?
Eltek derates above 45 °C to 1,350 W at 75 °C. [2]
Sources and what still needs a direct check
Sources checked 2026-10-13. ETSI publishes EN 300 132-2 on the −48 V DC power supply interface; Eltek's Flatpack2 48/2000 rectifier data sheet is read from a copy hosted by a reseller.
