# Centre-tapped battery bank

Canonical URL: https://eloragrid.ai/symbols/centre-tapped-battery-bank
Publisher: Elora Grid
Updated: 2026-10-28
Lookup label: GB ±
Drawing use: SLD, Schematic
Reference families: IEC, IEEE / ANSI

A battery bank with a mid-point connection that provides positive and negative rails about a common centre point.

## In plain English

### What does Centre-tapped battery bank mean?

A centre-tapped battery bank brings out a connection at the middle of the series chain, giving positive and negative rails referred to that point. It is used in some UPS rectifier-inverter designs, three-level converters and telecom or substation DC systems that need a symmetric supply or a defined midpoint for earth-fault detection.

### A simple example

Drawings show the battery symbol split into two halves with a lead taken from the junction, often labelled N, M or 0 V. The midpoint may be earthed, earthed through a resistance or left floating with an insulation monitor, and the drawing should state which.

### What the drawings help you do

The symbol does not show how the two halves are kept balanced. Unequal loading on the two rails discharges one half faster, and the midpoint earthing method changes how an earth fault on either rail behaves.

### This particular reference

A battery bank with a mid-point connection that provides positive and negative rails about a common centre point. A centre-tapped bank has a usable midpoint; an ordinary battery string presents only positive and negative terminals.

### Terms

- DC: Direct current: electricity flowing in one direction.
- Terminal: An identified point where a conductor connects.
- Schematic: A drawing showing function and connections rather than physical appearance.

Concept diagram: Identify the device and form → Read the connections and state → Check the equipment reference
A guide to reading this reference. The original symbol illustration and its drawing notes appear below; these boxes are not a wiring diagram.

- [IEC graphical symbols for diagrams](https://tc3.iec.ch/tc-activity/graphical-symbols-for-diagrams/)
- [Multilevel NPC converter application context](https://www.infineon.com/product-information/sic-modules-for-ups-design-and-efficiency-guide)


## What it represents

A centre-tapped battery bank brings out a connection at the middle of the series chain, giving positive and negative rails referred to that point. It is used in some UPS rectifier-inverter designs, three-level converters and telecom or substation DC systems that need a symmetric supply or a defined midpoint for earth-fault detection.
Drawings show the battery symbol split into two halves with a lead taken from the junction, often labelled N, M or 0 V. The midpoint may be earthed, earthed through a resistance or left floating with an insulation monitor, and the drawing should state which.
The symbol does not show how the two halves are kept balanced. Unequal loading on the two rails discharges one half faster, and the midpoint earthing method changes how an earth fault on either rail behaves.

## How to read it

- Identify how the midpoint is earthed or monitored.
- Check whether loads draw from one half only.

## Information to show or reference

- State voltage of each half and total.
- Show midpoint earthing or monitoring.
- Reference balancing and fault detection.

## Important distinction

A centre-tapped bank has a usable midpoint; an ordinary battery string presents only positive and negative terminals.

## Facts

- Terminals: Positive, midpoint, negative
- Common uses: UPS DC links, three-level converters
- Midpoint treatment: Earthed, resistance-earthed or floating
- Preview: Independent educational illustration; consult the applicable standard and project legend for the exact graphic

## Public references

- [IEC graphical symbols for diagrams](https://tc3.iec.ch/tc-activity/graphical-symbols-for-diagrams/) — IEC. IEC graphical symbol context for batteries.
- [Multilevel NPC converter application context](https://www.infineon.com/product-information/sic-modules-for-ups-design-and-efficiency-guide) — Infineon Technologies. Public three-level converter context requiring a DC midpoint.

## Graphic scope

Independent original educational concept illustration by Elora Grid. Not a certified standards graphic or manufacturer footprint. Unitless; not to scale. Original artwork licence: https://creativecommons.org/licenses/by/4.0/. Publisher material is linked only.