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What Happens When You Add More Batteries to a Series Circuit? 

 September 19, 2021

By  Phil Borges

There are many reasons why you might want to add more batteries to a circuit whether it is in series or parallel or series-parallel. These are the three ways of connecting batteries in any kind of circuit. In this piece, we will look at how to do it and what happens when you add more batteries.

Adding batteries to a series circuit increases the voltage of the batteries. Unlike batteries that are connected in parallel configuration, batteries that are connected in a series configuration give an increased voltage output without changing the amperage of the circuit which is measured in amp-hours.

But there is more to the process than just that. Let’s take a look.

Adding More Batteries to a Series Circuit

If you don’t know how electrical circuits work, here’s the simplest guide to it.

A circuit is basically an unbroken pathway for electric current to flow, right? This is what the simplest circuit looks like. It has a power source, two wires that are attached to both the battery terminals and on the other end of the wires is an application like a lamp.

Once you attach the wires to both the battery terminals and plug their other ends to the lamp, you will have a closed circuit that will power the application. In this case, the application is the lamp.

The moment you remove any of the wires, the circuit becomes what is called a broken circuit. Then it is called an open circuit which can no longer power the lamp. This is not always a bad thing.

Open circuits are used for devices like switches, circuit breakers and fuses for safety reasons which is why we no longer have as many short circuits as we did when we first started using circuits.

Now, batteries are connected in series, parallel or series-parallel. When you connect batteries in a series configuration, their terminals are connected in a sequence. This means that the positive terminal of the first battery is connected to the negative terminal of the second and the positive of the second battery is connected to the negative of the third battery and so on.

It is literally like a TV series where the batteries are placed one after the other. That’s where it gets its name. If you want to calculate the voltage of the circuit, you just need to add the voltage of all the batteries that are in the circuit.

For instance, if you connect three 6-volt batteries in a series configuration, the total voltage of the load will be 18 volts and the current passing through the load will be rated the current of one battery. Christmas lights are a good example of lights connected in a series configuration.

In an electrical circuit, electrons move from the negative terminal of the battery to the positive terminal. When the batteries are connected in a series, the current of all batteries must be the same so that the electrons can move at the same rate at every point in the circuit.

Now, as mentioned in the introduction, adding batteries to a series circuit increases the voltage but the total capacity of the circuit will be the same. For example, a lot of batteries in a series circuit of electronic equipment are 6 volts. When you add another, say, a 6-volt battery to a circuit that already has two 6-volt batteries, it is able to produce 18 volts but the amperage does not change.

Amperage is used to determine the electrical storage capacity of a battery and it is measured in amp-hours. The standard amp rating you see is taken for a period of 20 hours.

How to Add Batteries to a Series Circuit

Next is the step-by-step process of adding batteries to a series circuit. And luckily for you, it is a rather easy one too.

  • Step 1: Get a set of jumper cables.
  • Step 2: Plug in the positive terminal of the first battery to the negative terminal of the second one.
  • Step 3: Get another set of jumper cables.
  • Step 4: Attach the open terminals at either ends of the batteries to the application you want to power. That means, you will connect the free end of one wire with the negative terminal of the first battery and the free end of the second wire with the positive terminal of the second battery. Both these wires will then be attached to the application you are trying to power.

And there it is. You have a closed circuit with two batteries that are connected to an application with two jumper cables. This is possibly the easiest way to connect a circuit and power a simple application. You can add virtually any number of batteries depending on the output voltage you seek.

But, before you get started with the process, you must remember that the batteries that you are connecting must have the same capacity rating and voltage. Otherwise, the battery life will be drastically reduced and even before that, you will experience problems with the changing. This means that you can connect a 6-volt battery only with another 6-volt battery.

Next, you must keep in mind that during the process of connecting the circuit, the open terminals, both positive and negative, must never cross each other. If they do, there will be a short circuit and the batteries will get damaged or destroyed. It might also result in an injury.

Then you must think of ways in which you will charge these batteries. When you get to that point, you must make sure that the battery voltage must match the voltage of the charger so that there is no imbalance.

If you don’t check these specifications, you might end up damaging the batteries and might also injure yourself in the process. Short circuits and the resultant fires are nothing to play with.

Also, remember that the efficiency of any configuration of batteries depends on how good the batteries are. When a battery goes bad, the way a circuit suffers also depends on the nature of the fault.

For instance, if one of your 6-volt batteries is delivering only 5 volts, the total voltage you will get out of your circuit will be 11 volts. This is because you have one faulty battery. If this total voltage is less than the required operating threshold then the circuit could either act out or not work at all.

Frequently Asked Questions

Does Adding Batteries in Series Increase Current?

No, it does not. As mentioned in the piece, when you connect a group of batteries in a series configuration, you increase the overall voltage of the circuit but not the current.

The unit of current is called ‘amperes’ and it is measured using a device called an ammeter. The current has to be the same across all batteries in a series circuit so that there is no risk of imbalances that might cause problems like a short circuit.

How Many Batteries Can You Put in Series?

Strictly speaking, there is no actual limit on the number of batteries you can add to a series circuit. With each battery that you add, the overall output voltage of the circuit increases.

This means you can virtually create an unending power system. But remember that at some point you will need to charge these batteries and you need a power system that can do the job.

You also need to put aside a solid chunk of time to charge them all to their 100 percent. And when you increase the voltage of a circuit, you need to find a charger that can satisfy the output.

Now, since the amp-hour of the batteries in a series configuration remain unaffected, your focus when charging the batteries must be on the voltage. So, if your circuit has two 6-volt batteries, you know by now that its overall output voltage will be 12 volts. That means when you are charging the batteries, you need a charger that can satisfy the 12-volt capacity.

The only limit on the number of batteries is, theoretically, if you have connected so many of them that you start seeing sparks on one of the ends of the circuit.

About the author

Hi, I'm Phil Borges.. thanks for reading.. My wife says I can't shut up about batteries so to save my marriage I've started this blog .. where I'd be ranting about batteries! Please leave a comment if you have any questions, I'm happy to help!

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