In practical terms, the positive side of a battery is the terminal marked with a plus sign (+) and often color-coded red, while the negative side carries a minus sign (-) and is commonly black. For the most common formats you’ll encounter, the positive end is typically the top or a raised terminal, and the negative end is the bottom or a flat contact.
How to identify polarity on common battery types
Here are quick guidelines for the most common battery formats you’ll encounter. Use the indicators below to determine which side is positive and which is negative.
- Disposable cylindrical cells (AA, AAA, C, D, and similar): The positive terminal is the small, raised nub at the top; the negative terminal is the flat bottom. Devices often contact the spring (negative) at the bottom and the top contact (positive).
- Coin or button cells (CR2032, LR41, etc.): The positive side is usually the flat, top surface and is often marked with a plus sign on the top; the negative side is the opposite side (the outer edge or can).
- Lead-acid car batteries: The positive terminal is typically red and marked with a plus sign (+); the negative terminal is typically black and marked with a minus sign (-).
- Rechargeable lithium-ion or NiMH packs: Polarity is indicated on the label with a + and −; the positive contact is the one marked “+” and is often connected to a red lead in chargers.
- Battery packs inside devices: Many packs are labeled with + and − near each terminal; follow those markings when inserting or replacing batteries.
Understanding these indicators helps you avoid reverse polarity that can damage devices or pose safety risks.
Verifying polarity with a multimeter
If you want to confirm polarity using a multimeter, follow these steps:
- Set the multimeter to DC voltage (appropriate range for the battery you’re testing).
- Connect the red probe to the terminal you suspect is positive and the black probe to the suspected negative terminal.
- Read the voltage: a positive reading indicates the red probe is on the positive terminal; a negative reading indicates the opposite. Confirm with the device or battery documentation if needed.
Following these steps will help you verify which terminal is positive and which is negative in a safe, non-destructive way.
Safety considerations
Handle batteries with care to avoid short circuits, leaks, or exposure to high current. Keep terminals away from metal objects, never bridge terminals with tools, and follow manufacturer guidelines for high-drain or high-current packs. If you notice damage, leakage, or swelling, discontinue use and dispose of the battery properly.
Summary
In short, the side labeled with a plus sign (+) is the positive terminal, and the side labeled with a minus sign (-) is the negative terminal. For common formats: the positive end of cylindrical cells (AA/AAA, etc.) is the top nub; car batteries use red for positive and black for negative; coin cells typically have the positive on the top surface. When in doubt, check markings on the battery or test with a multimeter to confirm polarity.