What Size Wire from Battery to Busbar

Choosing the correct wire size from a battery to a busbar is a critical step in designing a safe and efficient power distribution system. Incorrect cable sizing can lead to overheating, voltage drop, energy loss, and even system failure.

This article explains what size wire from battery to busbar should be used, while also helping you understand what is a busbar, how an electric busbar system works, and when a Battery Busbar or custom Copper Busbar is a better solution than traditional cables.

What Is a Busbar?

Before selecting wire size, it is important to understand what is a busbar.

A busbar (electrical bus bar) is a rigid or flexible conductor—typically made of copper or aluminum—used to distribute electrical power efficiently within a system. Compared with cables, a bus bar electric solution offers lower resistance, higher current capacity, and improved reliability.

Common types include:

• Copper busbar / copper electrical busbar

• Aluminium busbar

• Battery Busbar

• Laminated busbar

• Custom busbars for specific applications

Why Wire Size Matters Between Battery and Busbar

The cable connecting the battery to the busbar system carries the full system current. If undersized, it may cause:

• Excessive heat generation

• Voltage drop, especially in low-voltage systems

• Reduced efficiency of the busbar power system

• Safety risks in electrical panels or battery packs

Correct wire sizing ensures safe current transfer until power reaches the electrical panel bus bar or Battery Bus Bar copper assembly.

Key Factors That Determine Wire Size from Battery to Busbar

1. Current (Amperage)

Current is the most important factor. Higher current requires a larger conductor cross-section.

Typical copper cable guidelines:

For very high currents, engineers often replace cables entirely with a battery busbar or copper electrical busbar.

2. System Voltage (12V / 24V / 48V)

Low-voltage systems require larger wire sizes to minimize voltage drop:

• 12V systems → very thick cables required

• 24V systems → moderate cable size

• 48V busbar systems → commonly use 35–95 mm² cables

This is why electric busbar solutions are widely used in 48V and battery energy systems.

3. Cable Length

The longer the distance between battery and busbar, the larger the cable must be.

Best practice:

• Keep battery-to-busbar distance as short as possible

• Increase wire size if length exceeds 1 meter

4. Installation Environment

Factors such as:

• High ambient temperature

• Enclosed electrical panels

• Bundled cables

all require derating or selecting a larger wire size.

When to Use a Wire vs a Busbar

For currents above 200A, a battery busbar, laminated busbar, or custom copper busbar is usually more reliable than a single cable.

Role of Busbar Connectors

When connecting a cable to a busbar, a high-quality busbar connector is essential. Proper connectors ensure:

• Low contact resistance

• Secure mechanical fastening

• Stable long-term performance

This is especially important in busbar power systems and electrical panel bus bar installations.

Copper vs Aluminium for Battery-to-Busbar Connections

• Copper busbar / Battery bus bar copper

• Lower resistance

• Smaller size for same current

• Preferred for high-current systems

• Aluminium busbar

• Lightweight and cost-effective

• Requires larger cross-section

Many copper bus bar manufacturers offer fully customized solutions to replace oversized cables.

Practical Recommendation

If your system involves:

• High current

• Low voltage

• Compact electrical panels

The best solution is often:

Short copper cable from battery → copper busbar → power distribution

This approach minimizes losses and improves system safety.

FAQ – Wire Size from Battery to Busbar

Q1: Can I connect the battery directly to a busbar without a cable?
Yes, in many designs a battery busbar is directly bolted to battery terminals using busbar connectors.

Q2: Is a laminated busbar better than a cable?
Yes. A laminated busbar reduces inductance, improves thermal performance, and is ideal for high-current or fast-switching systems.

Q3: Should I oversize the cable for safety?
Yes. Oversizing reduces heat, voltage drop, and improves system reliability.

Q4: Can wire size be reduced if I use a copper busbar?
Yes. Once current is transferred to a copper electrical busbar, cables can be shorter or eliminated entirely.