# Bidirectional inverter-charger

Canonical URL: https://eloragrid.ai/symbols/bidirectional-inverter-charger
Publisher: Elora Grid
Updated: 2026-10-28
Lookup label: INV/CHG
Drawing use: SLD, Schematic
Reference families: IEC, IEEE / ANSI, Manufacturer

A battery converter that charges from an AC source and inverts back to AC, with an internal transfer relay for the load.

## In plain English

### What does Bidirectional inverter-charger mean?

An inverter-charger contains one bidirectional power stage between a battery and an AC output, together with an internal transfer relay connecting the AC input to the output when a valid source is present. With the source available it passes power through and charges the battery; without it, it opens the relay and inverts from the battery.

### A simple example

Drawings show a converter box with DC and AC marks, a bidirectional arrow, an AC input from the grid or generator and an AC output to the load. The transfer relay may be drawn inside the boundary as a changeover contact, and some units have a second output that drops during battery operation.

### What the drawings help you do

The symbol does not show the internal neutral-earth relay many units use when inverting, which matters for earthing and residual current device operation. Power assist settings, which let the inverter add battery power to a limited generator supply, are also invisible on the drawing.

### This particular reference

A battery converter that charges from an AC source and inverts back to AC, with an internal transfer relay for the load. An inverter-charger has an internal transfer relay and charger; a plain DC-to-AC inverter only converts battery power to AC.

### Terms

- DC: Direct current: electricity flowing in one direction.
- AC: Alternating current: electricity whose direction changes periodically.
- Normally open / normally closed: The contact state in the normal condition defined for the drawing.

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.

- [MultiPlus-II official product and documents](https://www.victronenergy.com/inverters-chargers/multiplus-ii)
- [Quattro official product and documents](https://www.victronenergy.com/inverters-chargers/quattro)


## What it represents

An inverter-charger contains one bidirectional power stage between a battery and an AC output, together with an internal transfer relay connecting the AC input to the output when a valid source is present. With the source available it passes power through and charges the battery; without it, it opens the relay and inverts from the battery.
Drawings show a converter box with DC and AC marks, a bidirectional arrow, an AC input from the grid or generator and an AC output to the load. The transfer relay may be drawn inside the boundary as a changeover contact, and some units have a second output that drops during battery operation.
The symbol does not show the internal neutral-earth relay many units use when inverting, which matters for earthing and residual current device operation. Power assist settings, which let the inverter add battery power to a limited generator supply, are also invisible on the drawing.

## How to read it

- Look for the internal transfer relay and any neutral-earth relay.
- Check whether a second output is shed on battery operation.

## Information to show or reference

- State inverter VA, charger current and battery voltage.
- Show AC input, outputs and earthing arrangement.
- Reference input current limit settings.

## Important distinction

An inverter-charger has an internal transfer relay and charger; a plain DC-to-AC inverter only converts battery power to AC.

## Facts

- Energy flow: Bidirectional
- Internal switching: AC transfer relay
- Earthing detail: Neutral-earth relay often fitted
- Preview: Independent educational illustration; consult the applicable standard and project legend for the exact graphic

## Public references

- [MultiPlus-II official product and documents](https://www.victronenergy.com/inverters-chargers/multiplus-ii) — Victron Energy. Public inverter-charger product and document page.
- [Quattro official product and documents](https://www.victronenergy.com/inverters-chargers/quattro) — Victron Energy. Public dual-input inverter-charger documentation.

## 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.