How to Wire Batteries in Series (or in Parallel)


Introduction: How to Wire Batteries in Series (or in Parallel)

Get the power you need from the power you have by wiring together different power sources to get the voltage or the current to drive your project.

This is a simple insructable which will graphically demonstrate how to wire multiple power sources together to get the voltage and current you need for your project.

You will see that this demo uses a couple of my Al/Air fuel cells but you should be able to use any power sources you like.

It is not required that all the power sources be the same and this can affect your output. For instance wiring 3V and 9V batteries in series will give you 12V

Step 1: Bill of Materials

Okay you're going to need some batteries to wire together and some way to wire them together.

In this example we will be wiring together two aluminum air batteries so we'll need a couple of batteries and some leads for interconnecting them.

A multimeter for measuring voltage and current also comes in handy.

Other power sources that can be used include battery packs, wall warts ( two 9V warts = 1 18V ) or just about anything else.

Step 2: Wiring Two Batteries in Series

Wiring multiple power sources in series will increase the available voltage.

First we measure the voltage from each battery. Then we wire them in series by connecting the negative lead (connected to aluminum foil) to the positive lead of the other battery.

Here we can see that two batteries, one with 850 mV and one with 774 mV produce 1.568 when wired in series. As you can see we lose a tiny bit of power in this circuit ( approximately .05 mV ) most likely due to the nature of the connections.

Now let's take a look and see what happens when we wire them in parallel...

Step 3: Wiring Two Batteries in Parallel

Now we'll take a look at what happens when we wire batteries in parallel.

Unlike wiring batteries in series when batteries are wired in parallel the voltage does not increase, the output voltage is the average voltage of all batteries in the circuit. For example if a 3V and a 9V battery were wired in parallel the output voltage would be 6V ( 9+3 divided by 2 ) however the current will be total amperage of all batteries in the circuit (minus any losses).

In this case we can see that 89.6 muA and 70.6 muA produced a collective current of 138.4 muA or about 21.6 muA below our expect 160 muA. This is accounted for by losses in the circuit.

Step 4: More Power - Series Wired in Parallel for Maximum Duration

This is how multiple power supplies can be wired together into a series that provide more voltages, these series be wired in series to provide a sustained and reliable power source. This configuration will produce the most sustained power....

Step 5: Maximum Power - Wired in Series and Parallel for Maximum Power

Absolutely the fastest way to drain your batteries in the shortest possible time.

This configuration shows the batteries wired together using both serial and parallel connections. This will maximize the voltage and the current.



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    Have you ever heard of anyone using 4 12 volt heavy truck batteries to replace 2 12 volt CAT batteries?


    i have two 12 volt batteries that i wire in series for remote wire feed welding but cant weld anything below 1/8 inch because i blow a hole every time could you give me a way to limit the voltage output between the two batteries

    i have 30 TP4056 mobile charging circuit board which require 5volt 1Amp input. i want to connect all in parallel. please help me to make a power supply for it.


    What is the way to connect 3 or more batteries with different MAH?
    IS it possible to make a powerbank out of it?

    I want to know, what will happen if we connect some batteries in series and all of them have some reasonable SOC but except one which has 0 SOC...will the 0 SOC battery will cause open circuit in battery network??

    maybe this could work with lemon batteries ?? :) thanks awesome articale

    In the series-parallel you state that it will drain your batteries fast.. as far as I'm aware it will actually increase the capacity of the batteries while also increasing the voltage at the same time.

    Wiring batteries in parallel is not dangerous, they do it in RV's all the time, as long as your voltage and CCA are the same there will be no harm

    1 reply

    I feel that is potentially misleading advice. As Mike says, very well below, it can be very dangerous to run batteries in parallel. The chances of a thermal runaway event are generally low (unless you are very silly) but the potential consequences can be severe so its always best to err on the side of caution. All batteries are unique and degrade over time. Unless you rigorously test all your batteries, which is impractical for most situations, the best way to reduce the risks are only using the same brand name cells, bought new, from a reputable source, hopefully from the same batch.

    Can I wire 3 batteries together in parallel and series? Like this photo? Or will I blow myself up?

    1 reply

    Using identical batteries, there are some interesting configs, but I don't think that your setup would work (I could be wrong, but it seems a little sketchy). There is a such thing as series-parallel, but I don't think it is what you are trying to do.

    Can you write it in series and parallel at the same time?

    1 reply

    It is called series-parallel (

    I have two 36v 8ah battery packs that consist of 3 12v 8ah batteries wired in series, can I connect the two packs together in parallel and get 36v 16ah?

    Shouldn't the total voltage of the batteries connected in parallel be 0.6 V?

    1/v = 1/v1 + 1/v2

    Putting voltage sources in parallel is potentially very dangerous, especially if there exists a difference in potential between the cells. The internal resistance will cause an over current (short) situation through one of the loads (cells) and may cause one cell to explode or catch fire. One should never put voltage sources in parallel, only current sources.

    4 replies

    I don't understand the terminology "voltage source" and "current source." Clarify please.

    voltage and current source is like a driver and bus, voltage is the ability of a battery to derive free electron, and the the movement of free electron is called current, actually voltage is the ability and current is the capacity of same

     I think this is true for ideal (ie, not real) voltage sources, but wiring up real batteries in parallel is standard practice as long as they are the same state of charge, chemistry, ah and voltage, otherwise its either slightly dangerous or useless.

    I have a riddle which I can't figure out in relation to batteries (and current sources) wiring different batteries with differing AH's in series is not a good idea, and the ckt will be limited by the one with least capacity, but how can you show this on paper ?
    Same is true of current sources (real ones, not ideal) I know series current sources isn't the norm, and ones with different values especially, how do you prove that one will be limited by the other ?
    my head hurts.

    batteries have an internal resistance which dictates what the current will be