Batteries in Series and Parallel: Which is Better?

In today’s increasingly tech-driven world, batteries are the unsung heroes in every sense of the word. From powering up devices to working as a reliable backup power source, batteries have become an integral part of the energy revolution. If you’ve worked with batteries then terms like batteries in series or batteries in parallel aren’t new terms. If you’re trying to decide whether to connect batteries in series vs parallel, you have come to the right place.

By connecting batteries in parallel or series, you can greatly increase amp-hour capacity or voltage and sometimes both. In this article, we shall look into three battery connections, outlining how they work as well as their pros and cons.

Connecting Batteries in Series

Connecting batteries in series is when you tether two or more batteries to boost the battery system’s overall voltage. It’s worth noting that connecting batteries in a series doesn’t increase ampere capacity. The batteries are tethered end-to-end by connecting the positive terminal of one battery to the negative terminal of the next one.

This way the voltage of the connected batteries is added together. For instance, if you connect two 12-volt batteries in a series combination, you will have a total voltage of 24 volts. But the current (ampere capacity) remains the same as that of one battery.

Elaborate structures such as solar systems could potentially link more than two batteries. Typically, the procedure of linking the batteries in series is the same. The remaining positive and negative terminals of the battery string are used as the positive and negative output terminals.

How to Connect Batteries in Series

To connect your batteries in series, please follow these simple steps;

• Connect the negative terminal of the first battery to the positive terminal of the next.
• You will do this until all the batteries are connected in a line or series in this case.
• After you'll then wire the positive terminal of your last battery to the positive terminal of your application.
• Then you'll connect the negative terminal of your first battery to the negative terminal of your application to complete the series. 

It's also possible to charge the batteries without disconnecting them from the series. To charge the batteries in series, find a charger with the total combined voltage of all the batteries. However, we recommend you charge each battery individually to prevent battery imbalance. Battery imbalance is when different cells within the pack exhibit different charge levels, capacities, and performances.

Most batteries in series combinations feature sealed lead acid batteries. However, most (not all) ionic lithium batteries can also be used in a series connection. It comes down to the Battery Management System or the Protection Circuit Module in question.

Connecting Batteries in Parallel

Connecting batteries in parallel is when you tether two or more batteries to increase ampere capacity (current). But the voltage of the connected batteries doesn’t increase. For instance, if two batteries with a current capacity of 2 amp each are tethered in a parallel combination. The total current capacity becomes 4 amps.

In intricate structures such as solar systems which require more than 2 batteries, the positive terminals of all batteries are linked together and the same is done for the negative terminals. The positive and negative output terminals are derived from the remaining terminals of the battery bank.

How to Wire Batteries in Parallel

To connect your batteries in parallel, please follow these simple steps:

• Connect the positive terminal of the first battery to the positive terminal of the next battery until the last one.
• Follow the same procedure for the negative terminals.
• Connect the negative terminal of the last battery to the negative terminal of your application and the positive terminal of the battery to the positive terminal of the application.

As I earlier said, batteries in parallel combination will increase the amp capacity (current) but not voltage. This will ultimately increase their duration (how long batteries can last) when powering equipment. But the increase in amp capacity also means that batteries in parallel take much longer to charge compared to those in the series combination.

You can reduce the charge time by faster charging. To get more capacity without necessarily using more batteries, find batteries with lower voltage and higher capacity. Let's say you need a 12V 300Ah battery system. You will connect three 12V 100Ah batteries in a parallel combination for a simple but robust output.

Series-Parallel Connected Batteries

In this case, you’ll connect two or more batteries in series and then connect the series in a parallel format. Confusing right? Let me break it down for you. It is a hybrid of both of the previously discussed combinations. In some sense, some components are in series format while others are in parallel.

For those eager to increase both voltage and capacity, the series-parallel combination is the one for you. For instance, if you have six 6V 100Ah and want to get 12V 300Ah. You’ll have to configure three strings of two batteries. In this configuration, you’ll have batteries linked in series and parallel combinations to ultimately get a bigger voltage and stronger capacity.

How to Connect Batteries in Series-Parallel

To connect your batteries in series-parallel, please follow these simple steps:

• If you have two sets of batteries, we suggest you put each set in a series first. To do this, connect a jumper between the inner positive and negative terminals of each set.
• Now that each set is in a series, get jumpers to parallel the two sets together. To do this, connect the jumper between the outer positive terminals of the two sets and a jumper on the outer negative terminals to complete the parallel connection.

You can do the series connection first and then the parallel one next or vice versa. Either way, it works just fine. This combination is very effective in solar installations and other complicated battery systems.

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

When trying to create the perfect battery system for your RV or boat, you’ll be faced with so many questions. One of them is whether to connect in a series or parallel format. Connecting in either format could be the solution but that all comes down to what you need most, more voltage or more amp capacity.

As I earlier told you, connecting your batteries in series will boost the voltage of the battery system. However, the capacity will remain entirely the same as that of one battery. To help ease your decision-making, here are the advantages and disadvantages of the batteries in series format.

Advantages of Batteries in Series

• Connecting your batteries in series increases the overall voltage output of the battery system which can be invaluable when you want to power a device of a higher voltage.
• Connecting your batteries in series increases the system's ability to store energy. This format can be a lifesaver when you need to power devices for extended periods while in remote areas.
• Lastly, connecting your batteries in series can help reduce stress on individual batteries which in turn improves the system's overall efficiency.

Disadvantages of Batteries in Series

• If one battery in the series fails, the entire system crumbles. This can be frustrating especially when you need a reliable power supply.
• If one battery is weaker than the rest in the series, it will become overcharged or undercharged which will ultimately affect its lifespan and the performance of the entire system.
• With batteries in series format, you'll need an external device like a battery equalizer to help balance the charge and discharge. This ultimately increases the complexity of the entire system and also makes installation and maintenance more difficult.
• When charging batteries in series, battery imbalance is common. This causes some batteries to discharge more quickly than others which ultimately leads to shorter battery lifespans.

In contrast to batteries in series, batteries in parallel only increase the amp capacity rather than voltage. This means you can power your devices for much longer. Here are the advantages and disadvantages of connecting your batteries in parallel.

Advantages of Batteries in Parallel

• Connecting batteries in parallel will increase the overall power output of the system which can prove helpful when powering devices with high power demands.
• If one battery in parallel fails or stops working, the others will continue working ensuring system continuity.
• Batteries in parallel all receive the same voltage which ultimately reduces the risk of any battery becoming overcharged or undercharged.

Disadvantages of Batteries in Parallel

• If one battery in the parallel heats up it can cause others to also heat up. This could lead to a potential thermal runaway situation which will damage the system in the long run.
• Connecting batteries in parallel doesn’t increase storage capacity like connecting them in series.
• When you connect batteries in parallel, you’ll reduce the overall system efficiency. This is due to differences in voltage and current output in the individual batteries.

When Do I Need to Choose Series-Parallel?

There are times when the load might require more voltage and current than one battery cell can offer. In such scenarios, you will connect your batteries in series and then the series in parallel to get the required load voltage.

Let’s say you have six batteries, each of 12V 200Ah and you want to increase voltage to 24V and capacity to 600Ah. To achieve this, you will connect two sets of three batteries in series and then connect the two series in parallel. You can increase load voltage and capacity using any number of batteries depending on the voltage and capacity of the batteries in question.

Conclusion

In today’s increasingly battery-reliant world, knowing how to make the most of your battery system could be the difference between a fun time and a nightmare. And knowing which format gives you what is a great start to making the most of your batteries and ultimately getting an efficient system. Hopefully, our elaborate guide has helped you differentiate batteries in series vs parallel.

But to recap, connecting your batteries in series will give you a bigger voltage output but the capacity will stay the same. In contrast, connecting your batteries in parallel will increase the amp capacity but the voltage output will remain the same. However, if you want to increase both the voltage and capacity then you will connect your batteries in a series-parallel format.

Frequently Asked Questions

1. How many batteries can you wire in parallel?

The number of batteries that can be connected ultimately depends on several factors such as the type, capacity, and application requirements. Typically, you can wire up to eight batteries regardless of whether they are lithium or lead acid.

It’s also worth noting that wiring too many batteries could result in several problems. These include; unequal charging and discharging, higher risks of overloading, and shorter lifespan of the battery bank. So, it’s better to connect larger batteries (in terms of amp capacity) to ensure you achieve your required current. Yes, larger batteries are more expensive in terms of maintenance and upfront cost but they will offer better efficiency in the long run.

2. Do batteries last longer in series or parallel?

In either configuration, the lifespan comes down to a couple of factors. These include; the type and quality of batteries, the depth of discharge, and lastly, the charging and discharging rates. But typically, batteries in parallel last longer. That’s because the amp is enhanced as the charge and discharge cycles a battery can release also shoot up.

3. Does series or parallel give more power?

Connecting your batteries in series or parallel doesn’t necessarily provide more power. These configurations only affect the battery bank’s voltage and current. Connecting batteries in series will boost voltage output while connecting batteries in parallel will increase ampere hours. The overall power output of either configuration will depend on both the voltage and ampere hour ratings.

In some scenarios, the series-parallel combination is used to achieve the required voltage load and ampere hour requirements. It’s worth noting that batteries have a limited power output. This is usually determined by their chemistry make-up (lead acid or ionic lithium), size, and other factors.