What Gauge Wire To Connect 12v Batteries?

Choosing the right battery cable size for your system is crucial, whether adding an extra battery or installing a completely new solar power system. For example, are you figuring out how big the interconnecting connections between the batteries should be? Or perhaps you’re pondering what gauge wire to connect 12v batteries?

12-volt batteries can store and deliver a wide range of power. However, if you connect batteries in series, the wire should match the maximum amperage each battery can provide. It is because voltage, not amperage, grows in series. When two or more devices are connected in parallel, the result is the polar opposite.

In a battery management system, the battery cable is one of the most significant components. High-quality battery cables can help you stay powered up and reduce battery drain—but only if they’re correctly measured, installed, and cared for. A gauge scale called American Wire Gauge is used to size copper wires (AWG). The gauge number varies depending on the overall amperage.

What is a gauge wire?

A gauge is merely a measurement of a conductor wire’s diameter or cross-sectional area. The American Wire Gauge Scale, or AWG, is the US standard for measuring wire gauges. The higher the level of the cable rating, the thinner the wire and, as a result, the less current it can carry in the AWG system. For example, a low cable-rated wire gauge can hinder correct, current distribution, whereas a high rated gauge can cause the system to short-circuit. To avoid such a situation, select a cable that is the right size for the electrical system in use. 

gauge wire

What Gauge Wire To Connect 12v Batteries?

The American Wire Gauge (AWG) system chart can identify the wire gauge to be used. Ensure that the batteries you’re connecting have the same capacity and voltage. The length of the wire may influence the wire thickness you use. For connections up to 4 feet in length, the following chart displays the number of amps and wire thickness:

Number of AmpsWire gauge
0 to 1016
10 to 2014
20 to 2512
25 to 3010
30 to 508
50 to 706
70 to 904
90 to 1202
120 to 1501/0
150 to 2002/0

You can easily find out the size of the battery cable to use from the chart if you know both the amperage and the cable length. The chart is extensively used to determine the proper wire gauge size for connecting batteries. The smaller the cables, the lower the current and the more shorted the batteries are.

If you have a battery bank capable of producing 25 amps, you should utilize 12 AWG cables to provide a secure connection. However, the chart is designed to work with 12-volt batteries. Therefore, if your batteries are 24 volts, you merely need to twice the gauge cable size listed here.

What Gauge Wire To Connect Two 12v Batteries?

To know the gauge wire to use, You must determine how many amps of current flow through the battery bank’s interconnecting cables, consisting of two 12v batteries. The flow of current or amperage and voltage is determined by whether the batteries are connected in parallel or series.

  • Batteries Connected In Series: Connecting batteries in series raises the battery bank’s voltage while maintaining the same amperage rating (amp-hour). If you connect two 6v batteries in series, the bank will output 12 volts while retaining the same 10AH rating. Connect the negative terminal jumper cable of one battery to the positive terminal of the second battery to connect 12v battery connection cables in series. also, Attach the first battery’s positive terminal to the second battery’s negative terminal 
  • Batteries Connected In parallel: When two or more batteries are connected in parallel, the overall current rating or amp-hour increases while the voltage remains constant. For example, when two 6v parallel batteries are connected, you will still get 6 volts from the bank, but the amps will increase to 20AH. To connect two batteries in parallel, use jumper wires to connect the positive and negative terminals. Keep in mind that as the amperage of the battery bank increases, you’ll need a heavier-duty wire to keep it from burning out in the parallel battery connection.

Wire Size Requirements: Determining Factors

thicker cables can carry More current over longer distances. The reason for this is that the resistance of a cable increases as its diameter or length decreases. As a result, the cable size you require is determined by the amount of current you need to transport and the length of your cable runs. The AWG sizing chart displays the various current capabilities at varying lengths. The required cable thickness rises with the cable length.

What Happens If The Battery Cable Size Is Too Small?

  • Voltage drops: The first is that there is a voltage drop. It indicates that the voltage at the wire’s end is lower than that at the battery. Your electronics will not work if the voltage drops too much. The resistance of a wire is determined by its thickness (gauge) and its overall length. If your battery cables are undersized, you may have an extreme voltage drop, which may cause your devices to stop operating.
  • The wire gets too hot: Greater resistance in the wire results in more heat being generated, similar to a voltage drop. Undersized wires can become so hot that the casing melts, resulting in a fire. Fires are far more dangerous than voltage drops and are the greatest danger of using a battery line that is too short.

What Happens If The Battery Cable Size Is Too Big?

  • Cost: The pricing is probably an essential factor to consider. Wire gauges with a larger diameter cost more. However, the additional fee will be little if you run a few feet of the battery line. Cost becomes more of a factor as cable runs become longer.


Using the proper wire gauge is essential for making good connections. For example, if you’re going to create a panel out of many 12v batteries, you’ll need to figure out what gauge wire to connect them. Otherwise, the bank may not provide the expected voltage when required, and the cable may burn out owing to extreme pressure. Using the suitable gauge wire will preserve the battery management system and the application that uses the system.

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