What Is Voltage Drop?

Voltage drop occurs when power is lost through cables that are too small or too long. Increased resistance reduces the voltage reaching your appliance, which can cause it to perform poorly or stop working.

For example, your battery might be supplying 12.6V, but if power is lost through long or undersized cables, the appliance may only receive 11–12V, which may not be enough for it to operate properly.

Why Voltage Drop Matters

Many 12V appliances are sensitive to voltage. If the voltage drops too much, you may experience:

• Fridges failing to start or shutting down
• Diesel heaters displaying low-voltage errors
• Lights appearing dim
• Inverters cutting out under load
• Charging systems performing poorly

Even when the battery itself is fully charged, excessive voltage drop can make it appear as though the battery is weak or flat.

Common Causes of Voltage Drop

Voltage drop is usually caused by:

• Cables that are too thin for the current being drawn
• Long cable runs between components
• Poor or loose electrical connections
• Corroded terminals or connectors

High-power equipment such as inverters, heaters, and compressors is particularly sensitive to incorrect cable sizing.

How to Reduce Voltage Drop

To minimise voltage drop in a leisure electrical system:

• Use appropriately sized cables for the current draw
• Keep cable runs as short as possible
• Ensure all connections are tight and clean
• Use quality terminals and connectors

Correct cable sizing is especially important when installing inverters, battery chargers, DC-DC chargers, and solar systems.