Siemens 6EP1931-2DC21 SITOP DC UPS module

Siemens 6EP1931-2DC21 is a SITOP DC UPS module that buffers a 24 V DC control load at up to 6 A with a compatible battery module.

System function

Rebuilt from individual evidence

Evidence and limits

6EP1931-2DC21 is documented by Siemens as a 24 V/6 A SITOP DC UPS module without an interface.

It occupies the battery-backed point between the 24 V DC source and downstream control loads, with buffer behavior dependent on battery and load current.

The captured sources document the 24 V DC/6.85 A input and 24 V DC/6 A output.

Unknown: the connected battery capacity, downstream load, runtime, wiring, service status, and installation compatibility.

Exact reference: 6EP1931-2DC21
Category: PLC / CPU
Evidence checked: 2026-09-12

System role

This section explains what the product does and where it acts in the surrounding system.

Function: Buffers a 24 V DC control bus at up to 6 A during a supply interruption when paired with a documented battery module.
System position: Sits between the 24 V DC supply and its battery branch and the downstream control loads.
Upstream / inputs: A 24 V DC supply and a compatible SITOP battery module feed the DC UPS.
Downstream / outputs: The module supplies the downstream 24 V control load in normal and buffer operation.
Limitations: Unknown: the connected battery capacity, downstream load, runtime, wiring, service status, and installation compatibility.

Evidence ledger

Facts, inferences, and unknowns are kept separate.

Facts

Siemens identifies 6EP1931-2DC21 as a SITOP DC UPS module rated 24 V/6 A without an interface, with 24 V DC/6.85 A input and 24 V DC/6 A output.
Confidence: high
- mall.industry.siemens.com — retrieved 2026-09-12; high confidence
- support.industry.siemens.com — retrieved 2026-09-12; high confidence
The Siemens manual documents operation with connected SITOP battery modules for energy storage.
Confidence: high
- support.industry.siemens.com — retrieved 2026-09-12; high confidence
The Siemens manual documents normal and buffer operating modes, with bridging time dependent on the connected battery and load current.
Confidence: high
- support.industry.siemens.com — retrieved 2026-09-12; high confidence

Inferences

The DC UPS sits between a 24 V DC supply with its battery branch and downstream control loads.
Confidence: high
Rationale: The exact product page provides the DC input/output ratings, while the Siemens manual documents the connected battery and buffer modes.
- mall.industry.siemens.com — retrieved 2026-09-12; high confidence
- support.industry.siemens.com — retrieved 2026-09-12; high confidence

Unknowns

Unknown: the connected battery capacity, downstream load, runtime, wiring, service status, and installation compatibility.
Confidence: low
Missing evidence: No installation-specific battery, load, runtime, wiring, service, or compatibility record was captured.

System position diagram

A 24 V DC supply and compatible SITOP battery module feed the 6EP1931-2DC21 DC UPS, which supplies a downstream control load at up to 6 A. — The Siemens manual documents the battery-backed buffer path and load-dependent bridging behavior.

View Mermaid source

flowchart LR
  supply["24 V DC supply"] --> ups["6EP1931-2DC21 SITOP DC UPS"]
  battery["Compatible SITOP battery module"] -->|stored energy| ups
  ups -->|24 V DC, up to 6 A| load["Downstream control load"]

View diagram labels

Nodes: 24 V DC supply; 6EP1931-2DC21 SITOP DC UPS; Compatible SITOP battery module; Downstream control load
Edges: 24 V DC input; Stored energy; 24 V DC, up to 6 A

Next action

The captured Siemens product page and manual support a concrete battery-backed 24 V control-bus role for this exact article.

Confirm the compatible battery module, load current, and required bridging time before replacement.

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