Car Advice

Myth-Busting: Going for a drive will charge your flat battery

We’ve all heard the one about idling your car or driving it around the block to recharge a flat battery…shame that it’s nonsense then.

It used to motoring law that if you came out to your car and turned the key in the ignition and nothing happened that you’d wheel up another car, connect a set of jumper leads and start the car that way. The flat battery would get enough spark, via, the other car to start your car at which time the alternator would take over running the car’s electrics. Most would leave the car idling or go for a drive around the block and think that was that, the battery was recharged.

But almost everyone thought, and plenty still do, think that idling your car after the battery has been jump-started or driving around the block is all you need to do. It’s exactly what my neighbour did just this week. He went out to his car and it wouldn’t start, so, he did what most people would do and called a breakdown service.

The breakdown service arrived and jump-started the car. It fired into life. Great. But then my neighbour left his car to idle for ages. I noticed it because his driveway is right next to my office window and the smell of diesel exhaust fumes wafting through my office window was becoming a little too much to take.

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Sure, I could have closed the window and got back to my day, but after having witnessed the flat-battery scenario and the long idle afterwards I felt it my civic duty to intervene. My neighbour explained he was charging his battery by letting it idle. Um, no, he wasn’t. All he was doing was gassing me and wasting fuel.

See, your car battery is there to power the starter motor which kick-starts the engine. Once that’s done, the alternator (think of it as a generator) which is powered via the motor and produces electricity, takes over powering your cars electrics and ‘topping’ up the battery or surface charging and this will ultimately cause more damage to your already sick battery. Your alternator can’t recharge your flat battery, not even if you let the thing idle all day or drove around the block 10 times. Not even if you drove on the highway at 100km/h.

See, if your car’s battery is flat, it’s flat. The only way to charge it is with a suitable multi-stage battery charger which will restore your battery to good health. So, if your battery is sick and you can’t start your engine then a battery charger is the best way to go…they’re cheaper than a new battery.

And if you do replace your battery then remember to use a memory minder to ensure the sensitive electrics in modern cars aren’t damaged by the disconnection. See, even when your car is not running there are bits and bobs that still need power and they draw from the battery.

Isaac Bober

Isaac Bober

Isaac Bober was born in the shadow of Mount Panorama in Bathurst and, so, it was inevitable he’d fall into work as a motoring writer. He began his motoring career in 2000 reviewing commercial vehicles, before becoming editor of Caravan & Motorhome magazine. He then moved to MOTOR Magazine before going freelance and contributing to Overlander 4WD, 4×4 Australia, TopGear Australia, Men’s Health, Men’s Fitness, The Australian, CARSguide, and many more.