Starting your car's engine and idling is not enough to charge the 12V battery

Hans · Apr 28, 2020 12:14 PM

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Malaysia is now into its sixth week of the Movement Control Order (MCO) triggered by the Covid-19 pandemic. This also means that many cars have been left parked for an extended period of time.

To be clear, leaving a car parked for an extended period of time won’t damage your car. It’s not unusual for new cars to be parked at a dealer’s lot for months before it is sold. My own 36-year old classic is driven only about once a month but it starts at the first crank every single time. 

The difference is that those cars have been prepared for storage and when the car is taken out of storage, steps are being taken to prepare the car as well. Problems only occur when a car is parked for months without any preparation.

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Starting your car's engine and idling is not enough to charge the 12V battery 01

A common myth is that regularly starting the engine and leaving it to idle will charge the battery. While this is technically correct, it’s not good enough, especially on modern cars with the high electrical load.

Remember that it takes a lot of energy to crank an engine. So every time you start the engine, you are draining whatever little power that is left in the 12V battery and without driving, it takes a long time to replenish the battery.

In the end, after 15 minutes of idling, the battery’s charge is no better than before as all you’ve done was just to replenish the energy used to start the car earlier.

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The best way to charge the battery is to drive the car. Of course, this can be difficult during MCO so you have to be creative about it. You can for example, keep looping on the road around your house. No, you won’t be fined for driving your car around your house.

You can still drive the car once a week for your grocery runs and to the petrol station.

If you stay in a condominium, then drive up and down the parking area or open spaces within the property. All you need is just several hundred metres of road and keep looping that stretch for at least 30 minutes.

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But before starting your car, open the bonnet and check the engine’s fluid levels – engine oil, coolant, brake fluid etc. Refer to your owner’s manual on how to do this (please don’t ask random people on Facebook for this, always check your car’s owner’s manual)

Once done, start the engine and let it idle for a few minutes before driving (skip this for hybrids). Do not rev the car hard. Since the car has been parked for a long time, you need to gently ease it into motion. Take this time to check the floor for any oil stains. 

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If you have a manual transmission car, go through all the gear ratios (where possible), but keep it in low gear most of the time. The idea is to make sure all the mechanical parts are properly lubricated. 

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While driving, turn on all the car’s functions step by step. Windshield washers, power windows, lights, etc.

Don’t forgot to check the boot and rear seats for anything unusual. It’s not uncommon for spiders and other tiny creatures to start making your unused car their home.

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Another reason why you need to drive your car is to avoid flat spots from forming on your tyres. To avoid this, you need to regularly move the car and increase the tyre pressure slightly above the manufacturer’s recommendation.

Fill up the fuel tank to full, because a full tank will minimize air (which contains moisture) in your fuel tank.

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Wash the car regularly. Parking for extended period under the sun is very damaging to the interior so extra care needs to be taken. Make sure you have a good sunshade but nothing beats a big physical cover on the outside, over the car’s glass area so be creative about this. Just be careful to not have moisture accumulating underneath the cover.

Once you’ve done all that and it’s time to park the car again, you can decide whether you want to remove your car’s battery terminal or not.

On older cars, it’s not a big deal but on newer cars, including a basic Proton or Perodua, it will reset many of the car’s electronics, including the automatic transmission’s calibration (it adapts to a driver’s driving style).

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Some owners will choose the leave the parking/handbrake disengaged to prevent the brakes from binding. There’s nothing wrong with this if the ground is level but keep the transmission in Park and have additional safety measures like a hard, heavy object in front and behind the wheel to stop it from rolling.

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Hans

Head of Content

Over 15 years of experience in automotive, from product planning, to market research, to print and digital media. Garages a 6-cylinder manual RWD but buses to work.

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