Batteries In Series Vs. Parallel - Which Is Better?

How to Connect Batteries in Series

Connecting batteries in series increases the amount of voltage. It doesn't increase the ampere capacity. But two batteries connected in series means their positive and negative terminals will work together. For example, if you connect two 12V 30Ah batteries in series, you get a combined voltage of 24V. The capacity, 30 amp hours (Ah), stays the same.

Before you connect batteries in series, ensure they have the same voltage and capacity rating. Mixing and matching is ok for your closet, but it is a no-go when creating your battery setup! Doing so can be dangerous and may damage your batteries.

Here’s how to wire batteries in series, step by step:

1. Connect the negative terminal of one battery to the positive terminal of the next.
2. Continue to connect them until all the batteries are connected in a line (your “series”).
3. Now, wire the positive terminal of the first battery in the series to the positive terminal on your application.
4. Connect the negative terminal of the last battery in the series to the negative terminal on your application.

Things to note: You can also charge several batteries in series. Just make sure you use a charger that matches the total combined voltage of all your batteries.

This is also important to know. Most but not all Ionic lithium batteries are capable of series connections. See your battery’s user manual for more information.

How to Connect Batteries in Parallel

So what’s the main difference between putting your batteries in series vs. parallel? Connecting in series increases voltage, but wiring in parallel increases your battery bank capacity. That is, amp-hour capacity. The total voltage does not change.

That means that two 12V 30Ah batteries in parallel would give you a total capacity of 60 amp hours. Voltage stays at 12 volts. Two 12V 50Ah batteries in parallel would give you a total capacity of 100 amp hours. Voltage again stays at 12 volts.

Like wiring batteries in series, there's no mixing and matching allowed. All parallel-connected batteries must have the same voltage and capacity.

Here’s how to wire batteries in parallel:

1. Connect the negative terminal of each battery to the negative terminal of the battery next to it.
2. Do the same with the positive terminals.
3. Connect the positive terminal of the last battery to the positive terminal on your application. Do the same with the negative terminals.

Things to note: You can minimize the amount of parallel wires by using batteries with lower voltage and higher capacity.

Batteries in Series vs. Parallel: Which is Right for Me?

Stumped about putting your batteries in series vs. parallel? Ultimately, the best method depends on the needs of the applications you’re powering.

Let’s take a look at the advantages and disadvantages of each method.

Batteries in Parallel: Advantages and Disadvantages

What's the principal advantage of wiring batteries in parallel vs. series? Voltage stays the same, but you can run your applications longer because you've increased the capacity. Also, if there's a problem with one battery pack, it won't affect the others. The working batteries will continue to power your appliances.

But there are disadvantages. Placing batteries in parallel can make them take longer to charge. Also, the lower voltage means a higher current draw and more voltage drop. It may be difficult to power large applications, and you will need thicker cables.

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Batteries in Series vs. Parallel... or Series-Parallel?

Ultimately, neither connection method is better than the other. Choosing to wire your batteries in series vs. parallel ultimately depends on what works best for your boat, your solar setup hooked up to your solar panels, RV, or other power and battery systems. But there is one more choice. Series-parallel. That's not wiring your batteries in both series and parallel. That would short your battery system!

A series-parallel connection is when you wire several batteries in series. Then, you create a parallel connection to another set of batteries in series. By doing this, you can increase both voltage and capacity.

Questions about connecting batteries in series vs parallel or series-parallel? See if you can find the answers below, or contact our lithium battery experts here.

Series vs. Parallel Quick Answers

Does connecting batteries in parallel increase amp hours?

Yes. When you connect your batteries in parallel, you increase the amp-hour capacity of your batteries. The voltage stays the same.

For example, say you connect two 12v 100ah batteries in parallel. It’ll stay a 12 volt system, but the amps will double to 200ah. And the batteries will last a lot longer, of course.

What happens when you put two 12 volt batteries in series?

When you have two or more 12 volt batteries hooked up in series, you develop 24 volts, but your amps don’t change. On the other hand, if you have those 12 volt batteries wired in parallel, it’s still a 12 volt system, but the amps will increase. (See example in the section below.)

Do batteries last longer in series or parallel?

Batteries last longer in parallel, because the voltage remains the same, but the amps increase. If you connect two 12v 50ah batteries in parallel, it will still be a 12 volt system, but the amps will double to 100ah, so the batteries will last longer. On the other hand, when you connect batteries in series, voltage is increased while capacity (ah) stays the same.

Can you put Lifepo4 batteries in series?

It depends on the batteries - if you have Ionic batteries, chances are you can (double check). Many Lifepo4 batteries can’t be hooked up in series, because they’ll get damaged. But most Ionic lithium batteries are capable of series connections. Not all of them are, so please check your battery’s user manual.

Is series or parallel more powerful?

A parallel circuit consumes more power. Compared to series (both having the same voltage), parallel causes much more power dissipation by each resistor.

Which is safer, series or parallel?

Generally speaking, neither is safer than the other. They’re more or less equally safe. The supply voltage is the main thing that matters there.

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