How to Set Up a Dual Battery System

The best way to add another battery to your car

Co-authored by Duston Maynes

Last Updated: December 20, 2024 Fact Checked

It makes sense if you think about it: more batteries means more power! Running dual batteries can give you more capacity or more volts, depending on how you hook it up. Fortunately, it’s actually really simple to connect 2 batteries together. You just need to do it correctly and safely. To make it easier, we’ve answered some of the most common questions that people have about what it takes to run dual batteries.

How to Install a Second Car Battery

The best way to install or set up a second car battery is to connect the negative of the first batter to the negative of the second battery with a battery cable. Then, use another cable to connect the 2 positives.

Question 1 of 5:

Can I run 2 batteries in my car?

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Most cars use a 12-volt system and you can give your electrical system a boost by running 2 batteries at once. You’ll have literally twice the battery capacity if you wire them for 12 volts or twice the output if you wire them for 24 volts.^{[1]
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Question 2 of 5:

How do you hook up dual batteries?

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Use a battery cable to connect the negative of one battery to the negative of the other battery. Then, use another cable to connect the 2 positives together. This will double your total battery capacity without increasing your amps or volts.^{[2]
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You can also hook them up together in series for 24 volts. To connect 2 batteries in a series, connect the 2 negatives of each battery to the positive of the other batteries with a battery cable. This will double your volts from 12 to 24.^{[3]
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- Alternatively, if you want to jump start your car battery, look at the owner's manual.
- Touch the positive cable on your car and the positive point on the car providing the jump.^{[4]
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- Then touch the ground on the terminal of your car and the car providing the jump. Find a separate ground that is not on the battery. The top of the strut tower nut is a good spot and works well.^{[5]
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Question 3 of 5:

Can you run two batteries one alternator?

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Your alternator actually recharges your batteries while your engine is running. If you have 2 batteries connected, and they’re the exact same type, then your alternator will charge both of them.^{[6]
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Question 4 of 5:

What is a dual battery isolator?

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A dual battery isolator is a device that you can use to connect 2 batteries together without causing 1 battery to drain the power of the other battery. It essentially keeps the batteries isolated from each other.^{[7]
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Research source} To install one, connect the positive terminals of each battery to the isolator and connect a ground wire to a safe grounding location such as the frame of the car.^{[8]
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Question 5 of 5:

Is a dual battery system worth it?

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If you have a bunch of extra devices hooked up to your vehicle, such as lights and a sound system, they’re likely a major drain on your battery. By having 2 batteries hooked up to your vehicle, you have double the capacity to handle all of your devices.^{[9]
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