How to Wire Batteries in Parallel- Comparison, Effect, and Quantity

Anyone with knowledge about batteries has come across the term parallel. It is mostly applicable to lithium batteries. Such terms can be pretty confusing to any new battery user. Let’s get to simplify things for you.

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Foremost to understand the mechanics of wiring batteries, you have to understand about battery bank. A battery bank is a result of joining two or more batteries for a single connection. The connected batteries must be matched to each other to avoid causing problems. We do connect batteries to increase the amperage or voltage.

Lastly, you have to know there are two primary ways to successfully connect two or more batteries in a parallel or a series.

How to Wire Batteries in Parallel vs Series

a)Wiring batteries in parallel

Parallel battery connections involve connecting two or more batteries for greater amp-hour capacity or greater current capacity. In parallel connections, your voltage is equal across all branches. 

To make a parallel connection, the positive terminals are connected via a jumper wire, and the negative terminals are connected by another jumper wire. That is a positive terminal to a positive one and a negative terminal to a negative one.

Note that a parallel battery configuration is not meant to allow your batteries to power anything above the standard voltage output. It will increase the duration for which it could power a device at such a capacity. It is crucial to note that you should not mix and match different size batteries in the same battery pack.

b)Wiring batteries in a series

series battery connections involve connecting two or more batteries for greater voltage. In this configuration, the current or amperage is equal at all points and not affected by the number of batteries. Therefore, whatever amount of current there is in any one of the series-connected batteries has to be the same for all the other batteries as well.

To wire the batteries in a series, you use a jumper wire to connect the negative terminal of the first battery to the positive terminal of a second battery. You will have to use another set of cables to connect the open positive and negative terminals to your charger or system. Negative to positive, negative, and positive to the system.

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Note that, to make a successful series connection, each battery must have the same amp-hour rating. Not having the same rating will lead to some batteries being depleted sooner than others, compromising the capacity of the whole battery bank. 

What happens when you connect batteries in parallel?

Most times, we connect batteries in a parallel connection when a single battery cannot do the job. As stated above, when two identical batteries are connected in a parallel configuration, the current capacity doubles up while the output voltage remains the same as in a single battery.

When making a parallel connection, there are no-go areas that everyone is required to understand. You can not connect batteries of different voltages in a parallel configuration. The batteries will try to balance the voltage. The battery with the higher voltage will attempt to charge the battery with the lower voltage to create a circuit balance. It will create a lot of problems. For a disposable battery, it is likely to overheat, bulge or leak, and even explode in extreme circumstances. In the case of a rechargeable battery, the results will be the same as the lower voltage battery will overheat while the higher voltage battery drains rapidly. Such a voltage difference can create an explosion or fire.

Note that such occurrences are more common when people are making a parallel battery connection. Therefore, to avoid unplanned accidents occurring, here are some guidelines you can follow;

When dealing with disposable batteries, only use batteries of the same brand, same Ah, and age (manufacturing date). To be sure, use a voltmeter to check the voltages of each battery.

With rechargeable batteries, make sure to only use batteries that are of the same brand and age. Take your time to fully charge your batteries. Charge them individually using a smart charger.

Always try to use identical or larger-sized cables than the existing ones connecting your old battery.

Always try to keep the link cables the same length and pass them through the same hole.

How many 12-volt batteries in series and parallel?

There are many ways to wire your batteries in a battery bank in a series and parallel configuration. To build up your battery voltage and capacity, you need to have more than one battery to attain the voltage and storage you need. Due to cost and space issues associated with the larger 12v batteries, people opt to use the 6volt batteries. Two series strings of 6volt batteries wired in a series-parallel configuration help you get the 12 volts and 500Ah required.

In a series-parallel configuration, you can add many batteries. But before doing so, you have to consider the number of batteries you need and your total amperage.

To know the number of batteries you need, here is a formula to use;

Number of batteries needed = Total volts needed/ volts of a single series

Examples: 24v needed / 6v per battery= 4 batteries needed per series

     2000Ah needed / 250Ah per battery= 8 batteries needed

    8 batteries for amps / 2 batteries for volts= two series strings of 4 batteries

Therefore, you can have four batteries of 6v and 250Ah each in a series-parallel configuration to give you a 12v 500Ah in total. It makes the total number of batteries required in a 12volt series-parallel configuration four.

Note that

Good battery interconnects cables are an essential part of a battery bank. It is crucial to select a proper gauge wire and correct wire length as it determines the efficiency of your system. too long cables will result in unnecessary resistance and power loss.

When determining the number of batteries needed, the total batteries for each equation should match. If not, you will need to increase the amperage of the batteries you are using.

Conclusion

Battery connections are a great way to maximize the use of your batteries and get the most out of them. The choice of a connection form depends on what you expect to get out of the batteries. It can either be higher amperage or greater correct capacity. Note that, in theory, you can connect as many batteries as you want. It might be confusing and dangerous when you end up with a tangled mess of batteries and cables. It is good to keep in mind the requirements for your application and stick to them. Always remember to be safe and keep track of your connections. A diagram may even come in handy before constructing a battery bank.