Battery Symbol
Definition: The Battery symbol represents a DC voltage source composed of one or more electrochemical cells, drawn as alternating long-and-short parallel vertical lines (one cell per long-short pair) with the long line indicating the positive terminal and the short line the negative terminal, per IEC 60617-02 and ANSI Y32.2 / IEEE 315-1975, with electromotive force (EMF) measured in volts (V); it is assigned the schematic designator BT or B.
Also known as: battery symbol, cell symbol schematic, DC voltage source symbol, BT symbol circuit diagram, electrochemical cell symbol, power supply symbol.
What the Battery symbol means
The battery symbol denotes a source of direct-current (DC) electrical energy derived from a stored electrochemical reaction. Each long-line / short-line pair in the symbol represents one electrochemical cell; a single-cell battery (e.g. a 1.5 V alkaline AA cell) is drawn with one such pair, while a multi-cell battery (e.g. a 9 V block, internally six 1.5 V cells in series) is shown with multiple pairs to indicate the series-stacked cell structure. The positive terminal (pin id 'pos', marked '+') is always the long line, and the negative terminal (pin id 'neg', marked '-') is always the short line.
In a circuit schematic, the battery symbol communicates that the device is powered by a stored chemical energy source rather than a mains adapter or generator. The voltage printed beside the symbol (e.g. '9 V') specifies the nominal open-circuit electromotive force. Battery symbols are used for both primary (non-rechargeable) cells and secondary (rechargeable) cells — the symbol is identical, though component notes or a separate rechargeable-cell variant may distinguish the two.
How to identify the Battery symbol
The battery symbol is drawn as a series of alternating long and short horizontal or vertical lines, all parallel to one another and perpendicular to the lead wires. The long line (taller in vertical layout, longer in horizontal layout) is the positive terminal; the short line is the negative terminal. The connecting leads attach to the outermost positive and negative lines. A single-cell symbol has exactly one long line and one short line with leads at each end. A multi-cell symbol repeats the long-short pair, typically three to six times, with a gap between each cell pair. The + and − annotations may be added beside the corresponding terminal leads. The battery symbol is distinctive because no other common schematic symbol uses alternating long-short parallel lines in this regular pattern.
Function in a circuit
A battery converts stored chemical energy into electrical energy by sustaining a potential difference (electromotive force, EMF) between its positive and negative terminals. This EMF drives conventional current from the positive terminal, through the external circuit, and back to the negative terminal. The battery maintains this potential difference until its chemical reactants are consumed (primary cell) or until it is recharged by reversing current through it (secondary cell). The battery symbol in a schematic identifies the point from which current is sourced and establishes the supply voltage that all other circuit elements must be designed to accommodate.
Standards: IEC vs ANSI
| IEC 60617 | IEC 60617-02 defines the battery / cell symbol as one or more alternating long-line (positive) and short-line (negative) pairs; the single-cell variant uses one pair and the multi-cell variant repeats the pair. The positive terminal is the longer line as standardised in IEC 60617-02-01 (single cell) and IEC 60617-02-02 (battery of cells). |
|---|---|
| ANSI/IEEE 315 | ANSI Y32.2-1975 / IEEE 315-1975 defines the battery symbol identically — alternating long and short parallel lines, long = positive, short = negative. The single-cell and multi-cell forms follow the same convention as IEC. The designator BT (or B) is assigned by IEEE 315-1975. |
| Key difference | The battery symbol is identical in IEC 60617 and ANSI Y32.2 / IEEE 315. Both standards use alternating long (positive) and short (negative) parallel lines. The only practical difference is the designator: IEEE 315 uses BT; some IEC-aligned conventions use B or GB. |
Terminals / pins
| Pin | Name |
|---|---|
| pos | Positive (+) |
| neg | Negative (-) |
Typical values
Battery voltage is measured in volts (V). Common cell voltages: alkaline / carbon-zinc primary cell = 1.5 V; NiMH / NiCd rechargeable cell = 1.2 V; lithium-ion cell = 3.6–3.7 V nominal (4.2 V fully charged); lead-acid cell = 2.0 V per cell (12 V nominal for 6-cell automotive battery); lithium polymer (LiPo) cell = 3.7 V nominal. Capacity is measured in milliampere-hours (mAh) or ampere-hours (Ah). Common multi-cell nominal voltages: 3 V (2× alkaline), 4.5 V (3× alkaline), 6 V (4× alkaline or lead-acid), 9 V (6× 1.5 V), 12 V (8× alkaline or 6-cell lead-acid), 24 V (automotive / industrial).
Where the Battery symbol is used
- Portable consumer electronics (smartphones, laptops, torches) powered by lithium-ion or NiMH multi-cell packs, shown as a battery symbol with BT1 designator and voltage annotation
- Automotive wiring diagrams where the 12 V lead-acid battery symbol appears as the primary power source for all vehicle electrical systems
- Embedded and IoT circuit schematics where a coin-cell (CR2032, 3 V) battery symbol provides backup power for real-time clock (RTC) circuits
- Uninterruptible power supplies (UPS) where a battery bank symbol represents the sealed lead-acid or lithium backup source
- Laboratory and test equipment schematics where a battery symbol indicates a self-contained portable power source
- Emergency lighting circuits where a battery provides maintained power during mains failure
Example
In a simple LED torch schematic, a 4.5 V battery symbol (BT1, three long-short cell pairs) has its positive terminal (pin 'pos') connected through a 100 Ω current-limiting resistor (R1) to the anode of a white LED (D1). The LED cathode connects back to the battery's negative terminal (pin 'neg'). The battery symbol immediately communicates to the reader that the circuit runs from three alkaline cells in series, producing 4.5 V, with no mains connection required.
Key facts
- The battery symbol uses alternating long (positive) and short (negative) parallel lines; one long-short pair represents a single electrochemical cell, and multiple pairs represent a multi-cell battery.
- The positive terminal is always the longer line and the negative terminal is always the shorter line in both IEC 60617-02 and ANSI Y32.2 / IEEE 315-1975 — this convention is universal.
- The schematic designator for a battery is BT (sometimes B), as assigned in IEEE 315-1975; individual batteries are labelled BT1, BT2, etc.
- Battery voltage (electromotive force) is measured in volts (V); common nominal voltages are 1.5 V (single alkaline cell), 3.7 V (single Li-ion cell), 9 V (6-cell alkaline), and 12 V (automotive lead-acid).
- The battery symbol has two terminals: positive (pin id 'pos', marked '+') connecting to the outermost long line, and negative (pin id 'neg', marked '-') connecting to the outermost short line.
- The battery symbol represents both primary (non-rechargeable) and secondary (rechargeable) cells; the schematic symbol is identical for both types unless a specific rechargeable-cell variant symbol is used.
- Battery capacity is rated in ampere-hours (Ah) or milliampere-hours (mAh) and represents how much charge the battery can deliver; this value is annotated in the component notes, not encoded in the standard symbol.
- The battery symbol is identical in IEC 60617 and ANSI Y32.2 / IEEE 315 — one of the few schematic symbols that is truly standardised identically across both major conventions.
Diagrams that use this symbol
- electrical connection diagram
- ignition diagram
- series and parallel circuit diagram
- series circuit diagram
- series connection diagram
- electrical circuit diagram
- electric circuit diagram
- relay diagram
Frequently asked questions
What does the battery symbol look like in a circuit diagram?
The battery symbol looks like a series of alternating long and short parallel lines between two connecting leads. The long line represents the positive terminal and the short line represents the negative terminal. A single-cell battery has one long and one short line; a multi-cell battery (like a 9 V block) has several long-short pairs stacked together. A '+' sign may be added next to the long line and a '−' next to the short line for clarity.
What does the battery symbol mean in a schematic?
The battery symbol means that the circuit is powered by a stored electrochemical energy source providing a direct-current (DC) voltage. The voltage value beside the symbol (e.g. '9 V') gives the nominal supply voltage. The symbol shows which terminal is positive (long line) and which is negative (short line), establishing the polarity of the supply throughout the circuit.
Which line in the battery symbol is positive and which is negative?
In the battery symbol, the longer line is always the positive terminal and the shorter line is always the negative terminal — in both IEC 60617-02 and ANSI Y32.2 / IEEE 315-1975. This convention is universal: if you see '+' marked, it will always be next to the long line. The positive terminal (pin 'pos') connects to the longer line; the negative terminal (pin 'neg') connects to the shorter line.
What is the designator letter for a battery on a schematic?
The designator letter for a battery is BT (or B in some conventions), as defined in IEEE 315-1975. Individual batteries are labelled BT1, BT2, etc. The designator appears adjacent to the battery symbol on the schematic and in the bill of materials.
What is the difference between the IEC and ANSI battery symbols?
The battery symbol is identical in IEC 60617-02 and ANSI Y32.2 / IEEE 315-1975 — alternating long (positive) and short (negative) parallel lines. This is one of the few electrical symbols that is the same in both standards. The only minor difference is the designator: IEEE 315 uses BT; some IEC-aligned references use B or GB.
What unit is battery voltage measured in?
Battery voltage (electromotive force, EMF) is measured in volts (V), an SI unit. Common values are 1.5 V for a single alkaline cell, 3.7 V for a lithium-ion cell, 9 V for a 6-cell alkaline battery, and 12 V for an automotive lead-acid battery. Capacity (how long the battery lasts) is measured in milliampere-hours (mAh) or ampere-hours (Ah).
What is the difference between a battery symbol and a cell symbol?
A single-cell symbol shows exactly one long line and one short line, representing a single electrochemical cell (e.g. one 1.5 V alkaline cell). A battery symbol shows multiple long-short pairs, representing several cells connected in series. In common usage, 'battery' often refers to either a single cell or a multi-cell pack, so the terms are used interchangeably on schematics — the number of line pairs indicates the actual cell count.
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