Battery cable size (AWG and length) calculator for DC applications

Use the calculator below to easily work-out the size (gauge) of cable for your DC applications for example, when sizing  your battery bank connections for inverters and DC appliances.

Notes:

  • The information provided is a guide only. Always consult a certified professional when sizing your applications.
  • The battery cable size depends on:
    • how much current your appliances draw
    • the length of cable from the battery to the appliances and
    • what voltage drop is acceptable (usually up to 3%)

The longer the cable or larger the current drawn by the appliances, the thicker (lower gauge number) you will need to safely connect to the batteries.

Next, we are going to use the DC cable calculator in two scenarios,

  • #1 where we use it to calculated battery cable sizes for connecting to a battery bank.
  • #2 sizing battery cables to connect to a DC appliance

Worked example # 1: sizing cable connections from battery bank to inverter with the battery cable size calculator

Lets assume you have a 1,000 W/ 12V inverter that you plan to connect to a battery 10 ft. away and your maximum allowable voltage drop is 3%. You can use the calculator to work out your battery cable size (AWG).

With the above information:

  • Desired voltage drop is 3%
  • One-way cable length is 10ft
  • Supply voltage is 12V.
  • The current drawn in the conductor can be obtained using the formula: inverter power rating/DC battery voltage, i.e. 1000÷12 = 83.3 A.

The table below shows indicative battery cable sizes typically used with selected inverter capacities (W). These are worked out for up to 10ft. one-way length allowing for a 3% voltage drop.

Table: Battery cable sizes for selected inverter sizes (watts)

No

Inverter specifications (W)

Wire gauge (AWG)

1

200W/12V

10

2

1500W/24V

5

3

3000W/24V

2

Worked example # 2: sizing cable connections from battery bank to a DC appliance (fridge)

Lets assume you have a 100W/ 12V DC fridge  that you plan to connect to a battery 20 ft. away and your maximum allowable voltage drop is 3%. You can use the calculator to work out your  cable size (AWG).

With the above information:

  • Desired voltage drop is 3%
  • One-way cable length is 20ft
  • Supply voltage is 12V.
  • The current drawn in the conductor can be obtained using the formula: inverter power rating/DC battery voltage, i.e. 100÷12 = 8.3 A.

Tips for sizing battery cables

  • Always size for maximum current draw you expect for draw from the battery. Work out the total power consumption of all the appliances you expect to connect to the battery.
    This way, you will avoid damage to the cable should you connect additional appliances later.
  • Use Higher rated voltage inverters: When dealing with high power inverters e.g. 1000 W and above, when possible use higher voltage rated inverters, 24V, 48V… instead of 12V. The currents drawn are much lower and less costly wire gauges (higher AWG) can be used. 41.6 A from 1000W/24 is much safer to work with than 83.3 A from 1000W/12

Related questions

# 1. Which material to use for battery cable?

When connecting the batteries in the battery bank and the load, check to make sure that the cables are made from copper and not copper clad aluminum (CCA). Copper cable results in less wastage of power (lower voltage drop) especially for long cable runs.

# 2. How to calculate battery cable length for a set voltage drop

Occasionally, you may want to know the maximum cable length of a wire gauge that can carry a current while limiting the voltage drop to a certain threshold.

In this case, you can use the battery cable length calculator or table below to find the maximum length of cable (one-way) to carry a current for a set voltage drop.

For example, what is the maximum length of #6 cable that can carry 20 A with a voltage drop of 2%?

Using the calculator above, the estimated one-way cable length is 12 ft. If you desire to work with a longer cable, consider: increasing the cable size (lower AWG).

Table: One-way battery cable length (ft.) chart for 3% voltage drop (indicative)

AWG Cable size

25A

40A

50A

100A

200A

8

9.5

6

4.8

2.4

1.1

6

15.2

9.5

7.6

3.8

1.9

4

24.1

15

12.1

6.0

3.0

3

30

19.0

15.2

7.6

3.8

2

38.4

24

19.2

9.6

4.8

1

48.4

30.3

24.2

12.1

6.1

1/0

61.1

38.2

30.5

15.3

7.6

2/0

77

48.1

38.5

19.3

9.6

3/0

97.1

60.7

48.5

34.3

12.1

4/0

122.4

76.5

61.2

30.6

15.3

Related topics

How long batteries last with different appliances
How many amps a 2000 watt inverter draws?
How many amps a 2000 watt inverter draws?
AWG wire size chart