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Batteries In Series Vs. Parallel – What’s The Difference & Which Is Better?

Does your boat, RV, solar setup, or other application demand more voltage or ampere capacity than one battery can muster? If so, connecting batteries in series or parallel might be the solution. But when you’re trying to decide whether to connect your batteries in series vs. parallel, which is better?

Both methods increase total available energy, measured in watt hours. But they do this in different ways–with different results. Read on to find out how to connect your batteries in series vs. parallel, and discover which method is right for you.

How to Connect Batteries in Series

batteries in series

Connecting batteries in series increases the amount of voltage. It doesn’t increase the ampere capacity. 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, make sure they have the same voltage and capacity rating. Mixing and matching is ok for your closet, but it’s 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 in this way 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. But make sure you use a charger that matches the total combined voltage of all your batteries.

Also, it’s important to know that 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

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 battery capacity. The total voltage doesn’t change.

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

Like wiring batteries in series, there’s no mixing and matching allowed. All batteries in parallel 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 on whether to put your batteries in series vs. parallel? Ultimately, the method you use depends on the needs of the applications you’re trying to power.

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

Batteries in Series: Advantages and Disadvantages

Putting batteries in series is usually the better choice for large applications that need high voltage (more than 3000 watts, for example). Higher voltage means a lower system current, allowing you to use thinner wiring. There will also be less voltage drop.

The main disadvantage of connecting batteries in series vs. parallel is that all your applications have to function at the higher voltage. For example, if you connect two 12V batteries in series, you’ll end up with 24V. You won’t be able to power any 12V appliances unless you use a converter.

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, it won’t affect the others. The working batteries will continue to power your appliances.

As far as disadvantages, placing batteries in parallel can make them take longer to charge. Also, the lower voltage means higher current draw and more voltage drop. It may be difficult to power large applications, and you’ll need thicker cables.

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

In the end, 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, solar setup, RV, or other power needs.

But there is one more choice: series-parallel. This doesn’t mean you wire your batteries in both series and parallel. That would short your system! A series-parallel connection can be achieved by wiring several batteries in series, then creating a parallel connection to another set of batteries in series. By doing this, you can increase both voltage and capacity.

Have questions about connecting batteries in series vs. parallel, or series-parallel? Contact our lithium battery experts here.

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