How to Put Batteries in Correctly: AA, AAA, 9V, & More (2024)

Co-authored byMarvin Wooand Devin McSween

Last Updated: October 20, 2023Fact Checked

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1. 1

   Look for a plus symbol on your battery. The polarity of batteries is what helps them supply current to a device.^[1] The plus sign, or “+,” indicates the positive terminal. On AA, AAA, C, and D batteries, the positive end is slightly raised with a distinctive bump.^[2]

   • The negative end of the battery is completely flat. It may or may not be marked with a minus, or “-,” symbol.
2. 2

   Find the positive and negative symbols on your device. Inside most devices, you’ll see one side of the compartment has a spring, and the other side is flat. Many devices mark a plus and minus sign on each side, telling you which direction the battery needs to go.^[3] The negative end is where the spring or small metal lever is located, while the positive end is completely flat.^[4]

   • If the polarity isn’t marked on your device, you may need to consult the manufacturer's instructions.

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3. 3

   Match the polarities on the battery with those inside the device. When putting in batteries, the positive end of the battery matches up to the positive terminal in the compartment, and vice versa. It’s very important that each battery is properly aligned inside the device. If your battery faces the wrong way, it could cause your device to malfunction, or cause a leak that damages your device.^[5]

   • On devices with vertical compartments, like flashlights, see if the bottom is flat or has the spring. If the bottom has the spring, the flat, or negative side, of the battery goes in first. If the bottom is flat, the raised, or positive side of the battery goes in.^[6]
   • If there are symbols, simply match the “+” on the battery to the “+” in the compartment, and the “-” on the battery to the “-” in the compartment.
4. 4

   Slide the flat, negative end of the battery inside the compartment first. Installing the negative end first allows the battery to slide into the compartment more easily. Just push the flat end of the battery into the spring or lever, flattening it down. Then simply snap the positive, or raised, end into place against the flat side of the compartment.^[7]

   • A gentle push is all you typically need to snap the positive end of the battery into place.
5. 5

   Check the compartment’s alignment when inserting more than 1 battery. If your device’s compartment has multiple batteries side-by-side, they may alternate directions. This creates a series of currents that amplifies the energy produced by the batteries. Make sure each battery faces the direction that’s indicated in the battery compartment or the user manual.^[8]

   • On some devices, like flashlights, you’ll stack batteries directly on top of each other. In cases like these, the batteries face the same direction so the opposite polarities touch. If the negative side of the battery went in first, its positive end is facing up. So, place the next battery in with the negative side facing down.^[9]
   • Some devices that use multiple batteries may continue to function if one battery is installed incorrectly, but you can damage the device or shorten the life of the batteries by doing so.

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1. 1

   Look at the snaps on top of the 9-Volt battery. A 9V battery is small and square, with two snaps on the top. One is a male connector, and the other is female.^[10]

   • The smaller, circular snap is the male connector, while the hexagonal or octagonal snap is the female connector.
2. 2

   Line up the snaps on the battery with those inside the device. Inside the battery compartment on the device, you will see two snaps that resemble the ones on top of the battery. The male connector on the battery aligns with the female connector on the battery compartment, and vice versa.

   • It’s obvious when you put in a 9V battery incorrectly, as the connectors will bump against each other and the battery won’t snap into place.
3. 3

   Hold the battery at a 30° angle and slide the connector side in first. Once you’ve lined up the snaps, tilt the 9V battery slightly. Push the top of the battery in until the snaps are touching, then press down on the battery so that it snaps into place.^[11]

   • These types of batteries can be a little hard to install sometimes. If it doesn’t go in the first time, try again with a little more force.
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1. 1

   Examine the face of the battery for a “+” symbol. Coin and button batteries are small, flat, and round. Coin batteries are flatter, while button batteries usually have a smaller circumference. The top of the battery is usually etched with the battery size.^[12]

   • Usually only the positive side of the battery is etched. The negative side typically doesn’t have any markings at all.
   • In some button-style batteries, the positive side is slightly raised.
2. 2

   Check the device for a positive symbol. Your battery compartment may be marked with a positive symbol, especially if there is a door or a slide-out mechanism where you put the battery. However, if you had to pry off a cover, there may not be a marking indicating which direction the battery should go.^[13]

   • If you inserted the battery backwards in a device with a battery door, like a hearing aid, you’ll likely have difficulty closing the door.
3. 3

   Insert the battery with the positive side facing up. Most devices that use coin or button batteries install them with the positive side facing up, unless they state otherwise. If you don’t see any markings on your device, it’s generally safe to assume that the positive side of the battery goes in face-up.^[14]

   • If you’re installing a coin cell battery on a computer’s motherboard, for instance, there may not be any markings to indicate which way the battery should go, but the positive side should face upward.
   • If you’re still not sure how to install the battery, consult the device’s user manual.

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1. 1

   Examine the device for a small battery symbol or a plus and minus sign. Most battery compartments are on the back or bottom of the device, so check there first. Depending on the device, the compartment might be on the front, sides, or top of the device. The compartment is typically marked with either a small battery-shaped symbol or a “+” or “-” sign, indicating the polarity of the battery.^[15]

   • These markings may be on the top or just to the side of the compartment door.
2. 2

   Look for a compartment that slides off if there is no symbol. If you don’t see any markings, look for signs of the compartment on your device. On most devices, there is a piece that slides or snaps off to open the compartment. Just look for lines on the device that don’t match the other seams.

   • Some devices have a clasp or a lever that releases to open the compartment door.
   • The battery compartment may also be held shut by one or more small screws.
3. 3

   Check the user manual if you’re not sure where the compartment is. The instruction manual for your device should have a diagram showing where the batteries go. If you can’t find your manual, search for your device online. Usually, the manufacturer will provide a copy of the manual on their website.

   • When searching for the manual online, include the brand name and model number, if you know it.
4. 4

   Remove any screws holding the compartment shut. The screws in a battery compartment are typically Phillips screws, meaning they have a cross-shaped dip in the head. To remove these screws, use a Phillips-head screwdriver with a cross-shaped tip.

   • If the screw is stuck, you may be able to remove it using a screw extractor.
   • In you’re changing a watch battery, you may need to use a special tool, like a small flathead screwdriver, to remove the back of the watch.
5. 5

   Look at the compartment door to determine what size battery you need. Usually, the battery size will be printed on the outside of the compartment door. If it isn’t on your device, the information may be located inside the compartment. If it’s not listed, check the device’s manual. Or, estimate the size of the battery and try different sizes until you find the one that fits.

   • AAA, AA, C, and D batteries are all 1.5V batteries, but the different sizes produce different currents, or the amount of power that comes out of the battery at once. AAA is the smallest traditional 1.5V battery, and is usually used to power small electronics. D is the largest 1.5V battery and usually charges larger items like flashlights.
   • A 9V battery looks like a small box with snaps on top, and it's often used to power devices like smoke detectors and walkie-talkies.^[16]
   • Coin and button batteries are small and round, and they're used to power very small devices like watches, hearing aids, and computer components.^[17]

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