Jumper lead buying guide

A jumper lead only works as well as its cable and its joints. Thick cable, the right metal and well-made clamps decide whether a lead starts your vehicle or just gets warm. Here is what to check before you buy.

Cable size: mm² and AWG

Cable size is the cross-section of the metal inside the cable. In Australia it is usually written in square millimetres (mm²). Some cable is sized in the older AWG system (American Wire Gauge, also called B&S in Australia), where a smaller number means thicker cable. A bigger cross-section has less resistance, so the cable stays cooler and more of the battery’s power reaches the starter.

Our leads range from 16mm² for light commercial use, through 35mm² heavy duty, to 70mm² on the 1000A leads. The 70mm² lead is the same size as 2/0 AWG.

AWG and metric sizes don’t line up exactly, so a lead sold as 35mm² is close to 2 AWG, not identical to it. Always compare the mm² figure on the product page.

Copper or CCA?

Copper cable is solid copper wire throughout. CCA is copper-clad aluminium: an aluminium core with a thin coating of copper. Copper conducts better than aluminium, so a copper lead carries more current than a CCA lead of the same size and runs cooler. CCA is lighter and costs less, so it is common in budget leads.

The amount of copper in CCA varies between makers, so two CCA leads of the same size can perform differently. This is why we state the conductor on every product, and why the size and the metal need to be read together. A thick CCA lead can carry as much as a thinner copper lead, but it will be heavier and bulkier to do it.

We sell both. Copper suits frequent, heavy use. A well-sized CCA lead can suit occasional use where cost and weight matter.

Length

Current loses a little along every metre of cable, and the loss rises with length. A 3.5 metre lead delivers more of the battery’s power to the starter than a 6 metre lead of the same size. Choose the shortest lead that reaches from one battery or jump starter to the other without strain. Pick a longer one only when the vehicles can’t be parked close, such as a truck or machine that can’t be moved.

Clamps and joints

A thick cable is wasted if the clamp or the joint can’t carry the same current. Check three things:

• Clamp rating. The clamp should be rated for at least the current of the lead.
• How the cable joins the clamp. The joint is where many cheap leads fail. Look for a solid, well-made connection, not a thin wrap or a loose crimp.
• Grip. A clamp that grips firmly on the terminal gives better contact and less heat.

Anderson and CAT connectors

Many jump starters and machines connect through a plug rather than clamps. Match the lead to the socket you have. Anderson connectors come in different current ratings, such as 175A and 350A. A 350A to 175A adapter lets the two sizes connect, but the lower-rated connector limits the whole connection. Some machinery uses a CAT receptacle, which needs a lead or adapter made for it.

Our leads at a glance