Truck and Fleet Electrics in Adelaide’s North and Port

This guide is for owner-drivers, transport operators and fleet managers based around Adelaide's northern and port industrial areas. It explains how 24V truck electrical systems work, the faults that keep trucks off the road, how to add 12V accessories safely, and how to plan electrical maintenance so it doesn't cost you a day's work.

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Adelaide's freight belt

A large share of Adelaide's freight, logistics and industrial work happens across a belt from the Port to the northern suburbs. Wingfield and Regency Park are home to transport yards, distribution centres, recycling operations and workshops. Port Adelaide and the surrounding port land handle shipping and bulk freight. Further north, Edinburgh and the industrial land around it have grown into a major base for manufacturing, defence and warehousing.

These areas are linked by big freight roads. The Port River Expressway connects the port to the north, and the Northern Connector links it and South Road with the Northern Expressway, giving trucks a route north without travelling through local streets. A fleet in this area might do short, stop-start delivery runs across the city, then long hauls north to Port Augusta and beyond, often in the same week.

How a 24V truck system works

Most heavy trucks, and many buses and larger machines, use 24V electrical systems. Usually that's two 12V batteries wired in series, so their voltages add up to 24V. The higher voltage means a big diesel's starter motor and other heavy loads can work with less current, which allows thinner cables and less voltage drop over the length of a truck.

The catch is that the two batteries must stay matched. If one battery is weaker, older or a different type, it gets overcharged or undercharged compared with its partner, and both fail sooner. When one battery in a 24V pair fails, it's usually best to replace both together with identical batteries. Our guide to testing a battery explains the basics, but test each battery in the pair separately.

Running 12V accessories on a 24V truck

Plenty of useful gear is built for 12V: radios, phone chargers, fridges, some cameras and GPS units. The tempting shortcut is to take 12V from the first battery in the series pair. Don't do this. Pulling current from only one battery drains it more than the other, unbalances the pair and shortens the life of both.

The right options are a 24V-to-12V converter (a step-down or DC-DC converter) sized for the load, or, where the load is big, a battery equaliser that keeps both batteries balanced while supplying 12V. Better still, choose 24V versions of accessories where they're available. Whatever you fit, use properly sized cable and a fuse close to the supply. See our guide on where to put the fuse.

The faults that stop trucks

Summer adds load as well as heat. A truck idling in a yard or queuing at the port with the air conditioning running asks a lot of the alternator at low engine speed, while cab electronics, fridges and telematics draw current around the clock. A charging system that copes in winter can fall behind in January, and the first sign is often a truck that cranks slowly on Monday morning after sitting over the weekend.

In fleet work, the faults that cost the most are the ones that stop a truck at the start of a shift. The common culprits:

• Batteries that are worn out or unbalanced, especially after a hot summer. Heat shortens battery life, and the north gets very hot: on 24 January 2019 the Bureau of Meteorology recorded 47.5°C at Edinburgh RAAF.
• Corroded or loose battery terminals and main cables, made worse by vibration and dust around industrial yards.
• Poor earth connections between the chassis, engine and cab.
• Alternators that have lost output, which slowly flattens the batteries over a week of short runs. See how to tell if an alternator needs replacing.
• Parasitic drain from aftermarket gear such as telematics units, fridges or cameras left connected to the batteries without a cut-off.
• Trailer connection faults, where plugs and sockets get damaged, dirty or corroded from constant coupling and uncoupling.

Jump-starting and charging 24V vehicles

Never jump-start a 24V truck from a 12V vehicle or a 12V jump pack, and never connect a 24V source to a 12V vehicle. Mismatched voltages can damage electronics, batteries and starters. Use a jump pack or charger rated for 24V, or charge the batteries individually at 12V with a suitable charger if the system allows it.

If a truck in your fleet needs jump-starting more than once, treat that as a fault to find, not a habit. Modern trucks have many control modules, and repeated deep discharges and voltage spikes are hard on them. Reading the truck's fault codes can help narrow the cause; see reading fault codes with an OBD2 scanner, though heavy vehicles often need specific diagnostic equipment.

Planning electrical maintenance for a fleet

Electrical faults in a fleet are far cheaper to fix in the yard than on the side of the road. A simple routine catches most of them:

• Test every truck's batteries and charging system at the end of summer, and again before winter.
• Clean and tighten battery terminals and main earth points at each scheduled service.
• Keep a record of battery fit dates, and replace 24V pairs together.
• Check trailer plugs, sockets and suzie coils for damage and corrosion.
• Make sure drivers report slow cranking, flickering lights or warning lights straight away, rather than at the end of the week.

Booking work around your schedule

Many auto electricians in the north and the port areas work on trucks and fleets, and some can come to your depot, which saves a truck's downtime. Ask whether they handle 24V systems and your brand of truck before you book. Look through our pages for the Inner West and Port and the Northern Suburbs to find help close to your yard.

Parts for this job

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Get it done: get a quoteDo it yourself: shop 24V to 12V converters

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Get it done: get a quoteDo it yourself: shop truck batteries

Questions Adelaide drivers ask

Can I take 12V from one battery on my 24V truck?

It's not a good idea. Drawing 12V from only one battery in a series pair drains it more than the other, so the pair goes out of balance and both batteries wear out sooner. Use a 24V-to-12V converter sized for the load, a battery equaliser for bigger loads, or 24V versions of the accessory.

Should I replace both batteries in a 24V system at once?

Usually, yes. The two batteries share the work and need to be matched in type, capacity and age. Fitting one new battery next to an old one means the new battery is undercharged or overcharged relative to the old one, and the pair wears out unevenly. Replacing both together with identical batteries gives the best life.

Why do our trucks' batteries keep failing after summer?

Heat speeds up plate corrosion and water loss in lead-acid batteries, so capacity drops over the hot months. The damage shows up when cooler mornings arrive and the engine needs more cranking power. Unbalanced 24V pairs, weak alternators and parasitic drains from added accessories make it worse. Test batteries and charging systems at the end of each summer.

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