Batteries in Series vs Parallel? Double Voltage vs Longer Runtime Explained

You may have come across the term batteries in series vs parallel while researching lithium batteries or a new home solar panel installation.

Perhaps you’ve gone shopping for batteries because you needed more amps (units of measure for a battery’s electrical storage capacity) or voltage than a single battery can provide?

Series, parallel or series-parallel connections can be a little confusing especially when you are new to lithium batteries or simply batteries in general.¹

But, when installing an off grid solar panel system, understanding the ways batteries in series vs parallel work can help you choose the best storage system for the power you generate.

This complete guide explains how batteries work, including double voltage and longer runtimes, so that you can choose the best (and most efficient) electrical storage option.

How Do Batteries Work: System Requirements

There are two primary ways to successfully connect two or more batteries namely: Series connection and parallel connection.

You may want to know the purpose of running batteries in series vs parallel connections, the correct configuration for off-grid systems, battery bank systems, or even solar panel installation.²

Well, all of these depend on the system requirements. It may be to increase the voltage or simply to maintain the system by connecting batteries in parallel or series-parallel connections.

Batteries in Series vs Parallel: Types of Battery Connections

Series connection and parallel connection are the two primary ways you can connect two or more batteries to increase voltage (the pressure of electricity), capacity or both.

You do not need to always buy a behemoth while you can work within the space limitations to connect two or more batteries for a single application to form a battery bank.⁹

Most batteries can handle either type of connection. Alternatively, sealed lead acid batteries have always been the best choice when it comes to increasing voltage or capacity for many years.

Batteries in Series Connection

Connecting batteries in series is when two or more batteries are connected together and the positive terminal of one cell is connected to the negative terminal of the following cell. However, connecting batteries in series does not increase the capacity, only the voltage is increased.⁹

For example, if you connect four 12-volt 26Ah batteries, then you will have a voltage of 48 volts and a battery capacity of 26Ah.

It is important to note that in a series connection, each battery should have the same voltage and capacity ratings or you may damage the batteries. You cannot connect one 6 volts 10Ah battery with one 12v 20Ah battery, but you can connect 6 volts 10Ah batteries together.⁶

To connect batteries in series, a positive terminal of one battery is connected to another negative terminal of another battery, and so on until the desired voltage is achieved. Connect a cable or link to the negative terminal of the initial battery in your application.

Connect another cable to the positive terminal of the initial battery to your application.⁵

Always make use of a charger that matches the system voltage when charging batteries in series.

To avoid battery imbalance, it is recommended to charge each battery separately with a multi-bank charger to avoid battery imbalance.^11,16

Lithium can be arranged in series but it requires to be used with PCM (Protection Circuit Module) or BMS (Battery Management System). However, sealed lead acid batteries have been the batteries of choice for high-voltage battery systems for years and for long strings of battery application.

There are no limitations on the number of batteries you need to connect in series. The voltage of the circuit is the total sum of separate batteries connected in series.

We should be able to know the insulation capacity of the system for the time we connect large numbers of batteries.

Advantages of Hooking up Batteries in Series

• The voltage will be increased while the amount of current will be maintained. This indicates less voltage in the system and thinner wiring
• Circuits do not easily overheat, therefore, useful around likely flammable sources like clothes or plants
• Voltage increases if the number of cells increases
• All components can be controlled by a single switch

Disadvantages of Hooking up Batteries in Series

• A converter is needed to achieve low voltage
• The more units there are in a series connection, the greater the resistance
• Components cannot be controlled separately
• If one part in a series connection fails then the rest system fails because the circuit has been broken

Serial Battery Connection: How To Wire 12 Volt Battery in Series

If you are to connect three 12-volt batteries in series, then you are expecting an increase of the battery voltage to be around 36 volts. Each of your three batteries has a negative and a positive terminal.

First, you need to connect the negative terminal of the first battery to the positive terminal of the second battery.

Next, connect the negative terminal of the second battery to the positive terminal of the third battery.

Lastly, connect the positive terminal of the first battery to the negative terminal of the initial battery to your application.

Connecting Batteries In Parallel: Parallel Battery Wiring

You can connect batteries in parallel when you want to increase the ampere-hours (Ah) or the capacity, as you maintain the voltage according to your system needs.

For example, if you have four 1.2 volts 2000 Ah wired in parallel, you will have 1.2 volts and a total capacity of 8000 Ah.

Always keep in mind that the battery discharges quickly in parallel connections compared to series battery connections.⁵

There is no rule on how many batteries you need to use to wire a parallel connection. The more batteries you add in a parallel connection, the longer runtime and the more capacity you will have.

Take note that, the more batteries you have in parallel, the longer time it will take to charge the system.¹⁰

How To Connect Batteries in Parallel To Extend Runtime

Before you connect batteries in parallel, always make sure that all the batteries are of the same voltage, or you may end up causing damage or even fire. Connecting batteries in parallel itself is a way of extending the runtime in a device.

You must ensure to connect the batteries in their proper order, that is, the positives with the positives and the negatives with the negatives.

For example, when connecting four 12-volt batteries in parallel. You will have to connect the negative terminal of the first battery to the negative terminal of the second battery and the negative terminals of the third and fourth batteries to their negative terminals respectively.

You will do the same for the positive terminals.

In case you want to create a solar supply project, then you will have to know how to connect them in parallel. It does not matter how you are going to use the battery bank.

May it be for backups or to supply power for a long time. It must be properly connected, the negative terminals to the negative terminals and positive terminals to positive terminals.

Advantages of Parallel Connections

• Each combination gets the full voltage in parallel connections, hence ensuring optimal performance for operating devices with high energy requirements such as electric bike kit with battery and electric vehicles¹⁴
• Parallel connection divides the current through appliances. Each appliance gets proper currents depending on its resistance
• It is easy to connect or disconnect new appliances without affecting others that are working
• If one appliance is switched off the others cannot be affected
• When there is any fault that has occurred in the connection, then the currents can be able to pass through the circuits in different paths

Disadvantages of Parallel Connection

• All the units have the same voltage, therefore, harder to control if the components need to have different voltage
• It is complicated to set up as more wires are involved in the connection
• Damage to the batteries can occur when there is unequal distribution of load. Especially when there is a risk of difference in voltage
• There is additional wiring and connections between the batteries, therefore, making parallel connection more expensive than series connection

Series-Parallel Battery Connection: How To Connect a Battery in Series-Parallel Connection

Series-parallel connection is when you connect a string of batteries to increase both capacity and voltage of the battery system. This is done by connecting two pairs of two batteries in series and then connecting these serial-connected batteries in parallel.⁵

Load may sometimes require more current and voltage than what an individual battery can offer. Therefore, to achieve the needed load voltage, the required number of batteries is combined in series to achieve the current needed.⁸

Electricity cannot tell the difference because it flows through a series connection like in a single battery. This setup needs only one cable to make a series of connections that will pass over the positive terminal from one parallel bank to a negative parallel on the other.

You can connect as many batteries as you want, but confusion when setting up the series-parallel connection can be very dangerous. All you need to do is to stick to the requirements for your application and use batteries of the same capacities.

Advantages of Series-Parallel Connection

• The load in a series-parallel connection is balanced in each part, therefore, preventing the excess flow of current and increasing of batteries’ lifespan
• Power and current flows are balanced by combining series and parallel connections

Disadvantages of Series and Parallel Connections

• Connecting batteries may be more confusing when connecting series-parallel connections than connecting series connection or parallel connection on their own
• There is an increase in power consumption and a decrease in efficiency when connecting batteries in series-parallel connections

Battery Wiring Series vs Parallel: Which Is the Best Battery Connection for Solar?

Even though batteries in series and parallel offer advantages, you will have to consider the one that best fits your needs. You will choose batteries in series if you do not want to worry about your high-powered devices burning out.

For example, electric vehicles or solar panel systems. Batteries in series will add each battery’s voltage to give you the desired voltage.

On the other hand, you may also choose parallel connection if you want to increase the current flow such as in a portable device or a power tool.¹²

The power of each battery will be added together to achieve the desired current.

Battery wired in parallel increases the capacity of the battery pack, meaning your batteries will stay longer before needing to be recharged.

There is no better or worse option between series and parallel connections. Both are essential parts of the creation of battery systems.

Yes, we all agree that parallel wiring has more challenges in discharging and charging processes. However, it is a good solution to learn how to tackle each of its attributes.

The strategy you implement will be determined by the needs of the application you are trying to power with the (LiFePo4) batteries.

Batteries in Series vs Parallel: How To Connect 8 12v Batteries to Make 24v

There are a number of ways you can connect 8 12v batteries to make 24v. You should always know at the back of your mind that when you connect batteries in series, you add voltage.

Therefore, you need two 12v batteries to make 24v.³

Connect the negative terminal of the first battery to the positive terminal of the second battery, the negative terminal of the second battery to the positive terminal of the third battery, and do the same for the rest of the batteries but the negative terminal of the last battery should be connected to the positive terminal of the first battery and this would create a circuit.

The second way you can do this is to create four pairs of two batteries in series and connect them to four pairs in parallel. This will also give you 24v.

The batteries will surely last longer, but if you want more capacity then you should use more batteries in parallel connection. Be sure to use batteries of the same type and age when connecting them in series or in parallel.

How To Hook up Solar Panel to RV Battery

RV solar power systems are becoming trendy nowadays.¹¹ The solar panels work by allowing the light particles to knock electrons free from atoms generating the flow of electricity.

If you are one of those who like to camp off the grid and would like to know how to hook up solar panel to RV battery, your RV can be powered by solar power systems giving you all the electricity that you need.¹⁰

You don’t just need batteries and solar panels to hook up solar panels to RV batteries, but also an inverter, charge controller, and a transfer switch.

• Using a tray cable, connect the battery to the charge controller¹³
  The green wire goes into the negative port whereas the red wire goes into the positive port of the charge controller. Tighten the screw and connect the other end of the tray cable to the battery
• Connect the solar panel MC4 female connector to the adapter kit’s MC4 male connector. After that, connect the solar panel’s MC4 male connector to the adapter kit’s MC4 female connector
• Connect the negative solar panel line to the negative solar terminal of the charge controller. Then connect the positive solar panel line to the positive solar terminal of the charge controller. Tighten the screws on the charge controller
• It is optional to connect the inverter by connecting the negative battery terminal to the negative port of the power inverter once everything is hooked up. Connect the positive battery terminal to the positive port of the power inverter

So, what size solar panel to charge 12v battery? You will need a minimum of 120-watt rated panel to charge your 12v battery within 10 hours. There are some factors that determine the panel’s recharge efficiency.

The greater the rated specification of your solar panel, the faster you can charge your battery.

Batteries in Series vs Parallel: Wiring Dangers and Precautions

When choosing which connection to use for solar panel system, some may wonder,⁴ “Does wiring batteries in parallel, danger-causing?”

Here are 6 wiring dangers and precautions to take.

1. You may run the risk of electrocution if a metal comes in contact with batteries. This may include your wristwatches, belts, and jewelry.
2. Do not hand-guide batteries during the moving process. You may be brought in contact with a corrosive battery acid or even worse be electrocuted.
3. Never allow yourself to make contact with both contacts simultaneously; an electrical current may pass through you.
4. Use protective equipment like gloves, hard hats, and eyewear when handling batteries. A hard hat is important especially in case a battery swings or falls whereas eye gear and gloves protect you against battery acid.
5. Practice safe lifting procedures. Use approved and only specified lifting equipment designed for this purpose otherwise, you may run the risk of damaging the lifting equipment or the batteries
6. Batteries are heavy objects that can cause damage or injury when dropped or mishandled. If batteries are not handled with proper equipment and preparation, they can result in high voltage electric shock.

However, which is better, connecting car batteries in series vs parallel? Setups that require high voltage like car batteries, require series connection compared to parallel connection which is better for devices that require more run time.

By understanding batteries in series vs parallel, you can make the best decision for your home or supplemental energy needs.

Frequently Asked Questions About Batteries in Series vs Parallel