Understanding the difference between wiring batteries in series and parallel is critical if you have a multiple battery system. How you connect your batteries will determine how they perform in different applications. Let’s look closer at how to wire batteries in series and parallel.

batteries in series and parallel

The difference between batteries in series and parallel

The main difference in wiring batteries in series and parallel is the impact on the output voltage and the capacity of the battery system. Batteries wired in series will have their voltages added together. Batteries wired in parallel will have their capacities added together. However, the total available energy (measured in watt-hours) in both configurations is the same.

For example, wiring two 12v 100ah battery capacities in series will output 24 volts with a 100 Ah capacity. Wiring the same two batteries in parallel will output 12 volts with a 200 Ah capacity. Thus, both systems have a total available energy of 2400 watt-hours (watt-hours = volts x amp-hours).

Additionally, batteries wired in series and parallel configurations should all have the same voltage and capacity rating. Mixing and matching voltages and capacities can lead to problems that may damage your batteries.

Wiring batteries in series

To wire multiple batteries in series, connect the positive terminal of each battery to the negative terminal of the next. Then, measure the system’s total output voltage between the negative terminal of the first battery and the positive terminal of the last battery in series.

For example, these two 6-volt batteries joined in series now produce 12 volts, but they still have a total capacity of 10 amps.

wiring 6 volt batteries in series

To connect batteries in a series, use jumper wire to connect the negative terminal of the first battery to the positive terminal of the second battery. Use another set of cables to connect the open positive and negative terminals to your application.

Guide on wiring batteries in series

  • Connect the first battery’s negative(-) wiring to the next battery positive(+) terminal.
  • Continue wiring batteries with this technique in a straight line.
  • Connect the positive(+) terminal of the first battery in the series to your application’s positive(+) terminal.
  • Connect the negative(-) terminal on your application to the negative(-) terminal on the last battery in the series.

The advantages of wiring batteries in series

  • Circuits in the series do not quickly overheat, making them useful near a potentially flammable source.
  • The series circuits are simple to understand and build. It is easy to comprehend their basic nature, ensuring repairs are easy to carry out.
  • In a series circuit, the current must pass through all of the circuit’s components. Resulting in all components carrying the same current.

The disadvantages of wiring batteries in series

  • In a series-connected battery system, you can’t acquire lower voltages from the battery bank without a converter.
  • When one point in a series circuit fails, the entire circuit will fail.
  • When the number of components in a circuit increases, the circuit’s resistance grows.

Can I connect batteries with different voltages in series?

It’s never a bad idea to connect identical batteries in series. It will help if you avoid any condition where one battery is doing more work than the other. Use similar batteries in series and parallel at all times. In concept, you can wire batteries of different voltages in series as long as their capacity ratings are the same.

However, other elements affect battery performance, like temperature.

Connecting batteries in parallel

Mixing and matching without caution are not acceptable, as it is not allowed when wiring batteries in series. The voltage of the 2 batteries should be the same (error range 0.1V).

Parallel connections will increase your current rating, but the voltage will stay the same. In the “Parallel” diagram, we’re back to 6 volts, but the amps increase to 20 AH. It’s important to note that because the amperage of the batteries increased, you may need a heavier-duty cable to keep the cables from burning out.

wiring 6 volt batteries in parallel

When connecting in Parallel you are doubling the capacity (amp hours) of the battery while maintaining the voltage of one of the individual batteries. This would be used in applications such as laptop batteries, some scooters, some ups backups, etc. Use a jumper wire between the positives of both batteries and another jumper wire between the negatives of both batteries. Connect your positive and negative wires to the same battery to run to your application. 

Guide on wiring batteries in parallel

  • Wire each battery’s negative(-) point to the negative(-) terminal of the next.
  • Proceed with the positive(+) terminals in the same way.
  • Wire the last battery’s positive (+) terminal to your application’s positive(+) terminal.
  • Proceed with the negative(-) terminals in the same way.

The advantages of batteries parallel wiring

  •  If one of the batteries fails, the other batteries can still sustain power.
  • You extend your system’s possible runtime while keeping the voltage constant. 4 units of 12v 100Ah batteries in parallel to 48v can increase your backup time. 

The disadvantages of batteries in parallel

  • The voltage level will be lower, which will result in a larger current draw. The higher the current, the thicker the wires, and the higher the voltage drop. Larger power appliances and generators are more difficult to use and less efficient when operating at lower voltages.
  • Parallel wiring needs a large number of wires.
  • Defect detection is more difficult in parallel wiring compared to series wiring.

Wiring batteries in series and parallel

Batteries equalized is to connect to the positive at one end of the battery pack, and the negative at the other end of the pack. It is also possible to connect batteries in what is called a series/parallel configuration This may sound confusing, but we will explain below. This is the way you can increase your voltage output and Amp/Hour rating. To do this successfully, you need at least 4 batteries.

You cannot wire the same batteries in series and parallel as you would short the system, but you can wire sets of batteries in series and parallel to create a larger battery bank at a higher voltage.

wiring 6 volt batteries in series and parallel

If you have two sets of batteries already connected in parallel, you can join them together to form a series. In the diagram above, we have a bank that produces 12 volts and has 20 amp hours.

Remember, electricity flows through a parallel connection just the same as it does in a single battery. It can’t tell the difference. Therefore, you can connect two parallel connections in a series as you would two batteries. Only one cable is needed; a bridge between a positive terminal from one parallel bank to a negative terminal from the other parallel bank.

Important Points to Remember while wiring batteries in series and parallel:

  • The voltage and capacity of a system wired in series will be increased.
  • Wiring batteries in series will boost voltage but not capacity.
  • Always use identical batteries when wiring them together.
  • If you’re unsure, always consult a professional.

How many batteries can you wire in series?

The limit on how many batteries you can wire in series typically depends on the battery and manufacturer. For example, GRANKIA allows up to four of their lithium batteries to be wired in series to create a 48-volt system. Always check with your battery manufacturer to ensure you do not exceed their recommended limit of batteries in series.

How many batteries can you join in parallel?

There is no limit to how many batteries you can wire in parallel. The more batteries you add in a parallel circuit, the more capacity and longer runtime you will have available. Keep in mind that the more batteries you have in parallel, the longer it will take to charge the system.

With very large parallel battery banks comes much higher current availability as well. This means the proper system fusing is critical to prevent accidental shorts that could have catastrophic consequences with so much current available.

Charging batteries in series and parallel

Besides making sure you have the correct voltage charger, batteries in series vs. parallel charge the same way. For batteries wired in series, connect the positive charger cable to the positive terminal on the first battery in series and the negative charger cable to the negative terminal on the last battery in the series. For even charge across a parallel bank, connect your charge in the same fashion: positive connect to first battery, and negative connected to last battery.

Optionally, a multi-bank battery charger may provide faster charge times for series and parallel battery banks. As always, refer to the manufacturer’s recommendation for the best way to charge your batteries.

Quick Vocabulary Reference

AMP Hour (AH) is a unit of measure for a battery’s electrical storage capacity. The standard rating is an amp rating taken for 20 Hours.

Voltage represents the pressure of electricity. Some applications require more “pressure,” meaning higher voltage.

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