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How To Connect Batteries? – Safely Make Series & Parallel Connection

If you have questions like how to connect batteries in series, parallel, or series-parallel? How to select a good cable? What should be the safety measures? Then this guide is a must-read for you.

Being an energy engineer, I have handled the huge battery bank in different Multinational firms, boats, Rv’s and households I am going to share the safest way to make battery connections without losing the voltages.

Safety Measures Should Be Taken Before Connecting The Batteries

  • Take off metallic chains or rings, metal can be easily attacked by electricity make sure to remove your bracelet, rings or even chains.
  • Wear a pair of material gloves.
  • Make sure to wear old cloths to avoid any damage, otherwise acid will destroy your new cloths.
  • Wear goggles.

How To Connect Batteries

Batteries can be connected in series, parallel, or series-parallel depending on your demands. You can make small to large battery banks with the help of those connections; even I have built a 48V and 550Ah for my heavy-duty golf cart with the help of series-parallel connections.

Below is the step by step guides to making long-lasting battery connections;

How To Connect Batteries In Series

Before starting the step-by-step guide we are going to confirm a few things, the series connection will only increase the voltages, not capacity (amp. Hours). Also, you have to connect a similar voltages battery like 2x6V, 3x12V, etc. You can connect one 6 volts and another 12 volts battery but this will potentially damage your both units.

Let’s suppose I have two 12v batteries with 100Ah and I just need 24V, I don’t want increased capacity like 200Ah then I will connect them in series.

The result will be 24V and 100Ah.

Step By Step Guide To Connect Batteries In Series:

I am going to show you how to connect two same voltage in series, you can connect 4, 6, etc. just you need to follow the below steps.

  1. Locate the positive and negative terminal of both batteries, You can determine with the volt meter or from the colors on the terminals.
  2. Connect the positive terminal of 1st battery to the negative terminal of 2nd battery with a cable.
  3. Now Put the probes of millimeter on the remaining terminals of both batteries (positive and negative). If you got 24.9V or more you have successfully connected them in series. Now you just need to connect load with the remaining two terminals.

How To Connect Batteries In Parallel

In series you will get voltage increase however in parallel you will get the amp. Hours or capacity increase, the voltage will be the same.

For e.g. I have connected two batteries of 12 V and 50Ah in parallel, as a result, I will get 12V and 100A.h

Step By Step Guide To Connect Batteries In Parallel

  1. Determine the negative and positive terminals of both batteries.
  2. Let’s take a wire and connect negative terminal of the 1st battery to the negative of the 2nd, similarly connect positive terminal of the 1st battery to the positive of the 2nd. You have done parallel connection, now just checkout the voltage and capacity.
  3. After getting accurate results connect the positive of the load to the positive of the 1st battery and the negative of the load to the negative of the 2nd battery.

How To Connect Batteries In Series-Parallel

Before starting a step-by-step guide we have to clarify why we need a series and parallel connection. Suppose I have some high voltage devices which need high capacity as well. Now I can’t increase both voltage and capacity with a single series or parallel connection so we need to connect two sets of serially connected batteries in parallel

For e.g. One set of the series system provides us 24V and 100Ah and the other provide similar capacity and voltage. If we connect both banks in parallel we will get 24V and 200Ah.

Step By Step Guide To Connect Batteries in Series-Parallel:

Take two sets of batteries connected in series; Make sure to check out the voltage and capacity of each.

Let’s connect the positive of the 1st bank to the positive of the 2nd bank, again Connect the negative of the 1st to the negative 2nd.

Now connect the positive of the load to the positive end of the 1st battery and the negative of the load to the negative end of the 4th battery.

Take readings. If you got increased capacity with a similar voltage you have done it right.


Best Practices To Connect The Batteries In Series, Parallel Or Series – Parallel.

  • Batteries should have the same voltage and amp. Hours, even I prefer to get all batteries from the same brand and I get pretty consistent efficiency for a long time.
  • The cable should be of good quality and have the same size and thickness, we have discussed in detail below make sure to give it a read.

What Should Be The Size Of The Cables?

Choosing the right size of the cables for the battery bank is really important; you have to choose the correct diameter (thickness) and the length of the wire to get the desired efficiency by reducing the resistance. The following things should be considered before purchasing a cable.

  • The cable shouldn’t be too small and thin or it shouldn’t be too long and thick. Too long cables will unnecessary loss the power.
  • Make sure to select same sized cables for connecting batteries and load, for e.g. Select 0.25m cables for connecting the batteries and 1m for the load. You can’t connect one battery with 0.25m and other with 0.30m it will increase the power loss, similarly you can’t connect 1m for +Ve load and 1.5m for –Ve load.
  • Once you have linked the batteries and load with the same sized cables you will get consistent efficiency.

Series vs. Parallel Batteries

The main difference between the series and parallel connection is you will get higher voltage in series and higher capacity in parallel. Both connections are readily used depending on the needs of different appliances. Some powerful appliances need higher voltages, so we connect them in series to increase the voltages; however, we can connect our batteries in parallel to longer the discharge time. For. eg if a 12V motor works for about 10 hours on a single 12-volt battery, we can get 18-19 hours by connecting two batteries in parallel.

FAQs – Frequently Asked Questions

How many batteries can we connect in series?

It depends on the manufacturers, some manufacturers suggest connecting 4 batteries in series while others suggest connecting 6 or more, you just need to follow the instruction of the manufacture and connect accordingly.

How many batteries can we connect in parallel?

Similarly in the parallel connection, we have to follow the manufacturer’s instructions.

As an Energy and environmental engineer, I worked in eco bottle manufacturing for the last three years. Currently, he is the leading engineer in a Lithium Iron phosphate battery manufacturing company.

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