About 4 Gauge Battery Wire: A battery is an essential part of the car as it enables it to start and power various systems.
Further, having the right cable for your battery ensures everything runs smoothly.
However, with all the various cable options, it could be difficult to determine which cable is the perfect choice for you. Most manufacturers use the same battery cable size, the 4 AWG.
However, if the 4 gauge battery wire is the right cable size for you, read on to learn how to determine the right size cable for your project.
Table of Contents
- What is the 4 Gauge Battery Wire?
- Exact Gauge Battery Wire To Use
- What Happens if the Battery Wire Size is Too Small?
- What Happens if the Battery Cable Size is Too Big?
- Conclusion
What is the 4 Gauge Battery Wire?
A battery cable is made from flexible fine stranding designed to outperform and outlast other ordinary cables.
Normally, for the cables between your battery and starter, it’s advisable to use a 2 AWG for the negative and a 4 AWG wire for the positive.
However, the wire size you should use depends on your cable length following the distance between your battery and the starter.
Also, the amount of current your starter motor draws is a determining factor.
Exact Gauge Battery Wire To Use
Determining the right gauge for your application will require you to do some calculations to determine the cross-section area of your wire.
The formula for the cross-section area of the wire.
A=IpL/D
Where;
- A – represents the cross-sectional area in square meters.
- I – represents the max current through the wires in amps. The amount of current drawn depends on the engine’s size.
| Vehicle or Engine Type | Average Starter Draw |
| Big trucks and other higher power engines | 125 amps to 150 amps |
| V6 | 175 amps |
| V8 | 225 amps |
| SUV | 200 amps to 300 amps |
| Bigger trucks and even more powerful engines | Up to 1500 amps or higher (maximum of 2000 amps) |
Remember, whether your starter is cranking your engine or spinning freely is important.
If you’re simply testing your starter on a workbench, it would only draw 80-90 amps.
However, the same starter will draw around 250-300 amps to start your engine.
- P – represents the resistivity of the conductor. The standard PVC copper cable manufacturers use in cars has a resistivity of around 1.7 x 10-8 Ωm.
- L – represents the length of the wire in meters. This refers to the cable length from your starter to the battery. It’s important to note that the longer the cable, the more the voltage drops; therefore, you’ll need a thicker cable.
Convert the Cross-sectional Area in square millimeters to AWG.
Using the formula above, you’ll get a square-meter metric value.
- Convert the value to area in square millimeters: area in m2 X 106 (or 1 million) = area in millimeters squared.
- After using the table below to determine the equivalent value in the American Wire Gauge system (in the range of 12 – 2/0).
| Millimeters | Inches | Gauge Number |
| 2.053 | 0.080808 | 12 |
| 2.305 | 0.090742 | 11 |
| 2.588 | 0.101897 | 10 |
| 2.906 | 0.114424 | 9 |
| 3.264 | 0.128490 | 8 |
| 3.665 | 0.144285 | 7 |
| 4.115 | 0.162023 | 6 |
| 4.621 | 0.181941 | 5 |
| 5.189 | 0.204307 | 4 |
| 5.827 | 0.229423 | 3 |
| 6.544 | 0.257626 | 2 |
| 7.348 | 0.289297 | 1 |
| 8.251 | 0.324861 | 1/0 |
| 9.266 | 0.364797 | 2/0 |
Which Gauge Wire To Use- The Chart:
The table below portrays the recommended cable gauge while maintaining a 0.5% or lower voltage drop at 12 V with a certain amperage and length.
| Which Gauge Wire To Use? | Length of Wire in Feet | |||||||
| 0-4 | 4-7 | 7-10 | 10-13 | 13-16 | 16-19 | 19-22 | ||
Starter Amps | 250-300 | 4 | 2 | 2 | 1/0 | 1/0 | 1/0 | 2/0 |
| 200-250 | 4 | 4 | 2 | 2 | 1/0 | 1/0 | 2/0 | |
| 150-200 | 4 or 6 | 4 | 4 | 2 | 2 | 1/0 | 1/0 | |
| 125-150 | 8 | 4 or 6 | 4 | 4 | 2 | 2 | 2 | |
| 105-125 | 8 | 8 | 4 or 6 | 4 | 4 | 4 | 2 | |
| 85-105 | 8 | 8 | 4 or 6 | 4 | 4 | 4 | 4 | |
| 65-85 | 10 | 8 | 8 | 4 or 6 | 4 | 4 | 4 | |
| 50-65 | 10 | 10 | 8 | 8 | 4 or 6 | 4 or 6 | 4 | |
| 35-50 | 10 | 10 | 10 | 8 | 8 | 8 | 4 or 6 | |
| 20-35 | 12 | 10 | 10 | 10 | 10 | 8 | 8 | |
| 0-20 | 12 | 12 | 12 | 12 | 10 | 10 | 10 | |
The table below portrays the recommended cable gauge while maintaining a 1% or lower voltage drop at 24 V with a certain amperage and length.
| Amps | 25 – 30 ft | 20 – 25 ft | 15 – 20 ft | 10 – 15 ft | 5 – 10 ft | < 5 ft |
| 125-150 | 0 | 0 | 1 | 1 | 2 | 2 |
| 100-125 | 1 | 2 | 2 | 4 | 4 | 4 |
| 75-100 | 1 | 2 | 4 | 4 | 6 | 6 |
| 50-75 | 2 | 4 | 4 | 4 | 6 | 10 |
| 30-50 | 4 | 6 | 6 | 6 | 8 | 12 |
| 0-30 | 6 | 8 | 8 | 8 | 10 | 14 |
What Happens if the Battery Wire Size is Too Small?
A thinner cable has lower resistance, causing two key things to occur as the current passes through.
Voltage Drop:
You can calculate a wire’s voltage drop using Ohm’s law (V=I*R). V refers to the voltage drop, I refers to the current conveyed through the wire, and R refers to the resistance of the wire.
It’s important to note that an increase in resistance, current, or both results in an increase in voltage drop.
The length and thickness of the wire determine resistance.
If you use the thinner size of wire, it will result in an increased voltage drop that could prevent the electronics from functioning.
Most car manufacturers have a standard acceptable voltage drop for 12 V systems that’s about 0.5 V. For the 24 V systems, the limit is about 1 V.
Wires Get Hot.
Similar to voltage drop, an increase in resistance results in an increase in heat generation.
Therefore, if the wires are too small, they’ll overheat, causing them to melt or, in extreme scenarios, spark a fire.
Compared to a voltage drop, a fire is much more catastrophic, which is why you should always use the right size wire.
Engine Fire as a Result of Melting Wires
What Happens if the Battery Cable Size is Too Big?
On the other hand, using a wire that’s too big has its disadvantages.
Cost:
Thicker wires are more expensive. If you’re running your cable for a short distance, you won’t feel the cost as much.
However, if your cable run is long, then the cost will be a major consideration.
Weight
Just as with the cost, an increase in size results in an increase in overall weight.
If your cable run is short, the weight is pretty much insignificant. However, if the cable run is longer, you should consider this factor.
Use:
You won’t find it easy to bend and manipulate a thick wire inside the small, cramped space inside your engine.
Conclusion
From the article above, it’s safe to presume that undersizing your cable has greater risks compared to oversizing your cable.
However, with an oversized cable, there’s an increase in cost, weight, and frustration while using.
Therefore, it’s important to choose the right cable size, use the right assembly cable connectors, and adhere to proper maintenance measures to avoid future issues.
If you have any further queries or are looking for a trusted provider of battery cables, please contact Cloom Tech.
