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How to Hook Batteries in Parallel

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For this tutorial, we will use standard 9 Volt batteries and four leads with alligator clips on both ends.  The procedure is the same regardless of the Voltage of your battery.

If you look at the top of a 9 Volt battery you first notice that the two terminals look different.  The larger one is the negative terminal (on the left), while the smaller one is positive (on the right).

Top of a 9 Volt battery.

Examine the top of the battery shown above.  Each of the terminals is marked as either negative "(-)" or positive "+".

Getting the batteries ready

Set two batteries up so that the minuses and pluses line up as depicted below.

Tops of two batteries ready to be hooked in parallel.

Linking the batteries together

Now you will need two of the four leads with alligator clips on both ends.  Like terminals are linked together to hook batteries in parallel.

Take one of the leads and clip each end to the negative terminals (shown in green).  Use the second lead to connect the two positive terminals together (shown in red).

Diagram of batteries hooked up in parallel.

Your batteries are now hooked in parallel.

Two batteries connected in parallel.

Putting the batteries into a circuit

You are now ready to put your batteries into a circuit.

Take your another lead and connect one end a negative battery terminal (shown in white).  Leave the opposite end of this lead alone for now.

Hook one end of the fourth lead onto the positive end of the same battery (shown as a second red lead).

Congratulations!  You have connected two batteries in parallel.

Batteries in parallel ready to link into a circuit.

Batteries in parallel linking to a circuit.

To hook your batteries into a circuit treat coupled batteries as a single battery. The lead from the negative terminal (in white above) is the negative of your new battery.  The lead from the positive terminal (in red) is the new battery's positive end.

Why put batteries in parallel?

A reasonable question is to ask why one wants to put batteries in parallel in the first place. After all, it is a bit of trouble.

For a circuit to work Current must be able to flow through it. The voltage determines whether the electrons have enough energy to get moving - that is, for a current to flow.

You must have enough current to make your circuit work properly. For example, a lightbulb may appear very dim if there is not enough current flowing.

By hooking two batteries in parallel, you increase the amount of time the bulb stays lit. If your batteries are identical, you effectively double that amount of time - while the Voltage difference remains the same.

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