√Should I disconnect my car’s battery if it’s not in use?

If you’re going away on holiday and aren’t sure about what to do with your car’s battery, here’s what the experts have to say.

If you’re lucky enough to be heading off on a holiday, car battery maintenance might be the last thing on your mind.

However, it could be the cause of a serious post-holiday comedown if you’re left stranded at the airport without a functioning vehicle.

So, what is the general guidance for disconnecting your car battery if you won’t be driving it for a while?

It is safe to assume that newer, mass-market cars are okay to keep their batteries connected for up to three weeks – although this is a general guideline as various factors like colder climate, age, and model variant can affect the duration of battery life when not in use.

For an extended duration of more than three weeks, it is generally recommended to attach it to a trickle charger or, if that’s not an option, have a licensed professional disconnect the battery.

Drivers should, where possible, stow their cars in safe and secure places to avoid any potential thefts and hazards because of central locking systems not working due to the battery being disconnected.

For further guidance, Drive spoke to a range of professionals to find out the guidance for disconnecting and maintaining a car battery.

Should I disconnect my petrol or diesel car’s battery when not in use?

Matt Guastella, a mechanic from Ralph Guastella Motors, told Drive: “If you’re going away for a long time, it is generally recommended to use a high-quality trickle charger that can detect the battery levels and adjust when needed.

“If it’s an older car, it should be okay to disconnect the battery, but we recommend always using a trickle charger where possible,” he added.

Alex Fisk, a senior PR Specialist for Mazda Australia, suggested Mazda drivers should not disconnect the battery themselves and use a trickle charger to prolong the life of the car battery when not in use.

It is recommended for the 12-volt battery found in Mazda’s internal combustion engined (ICE), mild-hybrid, plug-in hybrid (PHEV) and electric models to be disconnected or preferably attached to a trickle charger if the owner will be away for six weeks or more.

“For the 12-volt battery that is included in ICE, Mild Hybrid, PHEV and BEV models, the recommendation is to disconnect the 12-volt battery if the vehicle is not planned to be used for an extended period – around six weeks would be a reasonable expectation,” Mr Fisk said to Drive.

Adam Davis, a Mitsubishi Australia Product PR spokesperson, advised Mitsubishi owners to refer to licensed technicians when attempting to disconnect the battery.

“I would always recommend attention from a licensed technician,” he said.

“However, it is up to the individual’s comfort level to disconnect their battery at home, though a trickle charger is a better idea,” he added.

Mr Davis has advised Drive and its readers to only disconnect the 12-volt auxiliary battery (found in all Mitsubishi models) from the negative terminal or enable the extended storage switch when not using the car for a long period.

Should I disconnect my plug-in hybrid or full hybrid car’s battery when not in use?

No, with hybrid cars you should avoid meddling with the high-voltage battery and instead aim to drive the car at least once a month to protect battery longevity.

Adriana Saviane, the PR Manager for Subaru Australia, referred Drive and its readers to the Subaru Owner’s Manual, which outlines the required steps to ensure the longevity of Subaru’s battery in its hybrid models.

The Subaru Owner’s Manual states that “to maintain the battery in good condition, drive the vehicle at least once every month for at least 30 minutes. If you leave the vehicle for a long time, the battery may discharge or the life of the battery may be shortened”.

Ms Saviane has encouraged owners to not meddle with the car battery and to discuss any car battery maintenance and issues with their local Subaru Service Centre.

“Owners should never touch a high-voltage battery. We encourage customers to discuss the maintenance of their vehicle’s battery by contacting or visiting their local authorised Subaru Service Centre,” she said to Drive.

Meanwhile, Mr Fisk emphasised the importance of owners not disconnecting the battery in plug-in hybrid, full hybrid or all-electric Mazda models.

“For mild hybrid, PHEV, BEV models there is no mechanism that we would suggest for an owner to disconnect the battery when not in use,” he said.

Mr Guastella echoed a similar sentiment and advised drivers to look at their owner’s manual for instructions, and where possible seek advice and help from licensed professionals when dealing with modern plug-in or full hybrid cars.

For Mitsubishi plug-in hybrid models, Mitsubishi Australia generally advises that the drive battery usually found in plug-in hybrids should be charged up to no more than 90 per cent before extended storage.

Should I disconnect my all-electric car’s battery when not in use?

No, owners should not attempt to handle the battery on an electric car alone due to its high-voltage nature.

Mr Guastella emphasised the importance of leaving electric car battery maintenance to the manufacturers.

“Electric car owners should refer to what the manufacturers suggest,” he said.

For example, according to Tesla’s Model Y Owner’s Manual, it is imperative to keep the vehicle plugged in when not in use for an extended period.

Draining the Tesla battery to zero because of not charging the vehicle can result in Tesla components being damaged or requiring replacement. Owners could then be liable and responsible for the repair costs of the vehicle and/or transportation expenses.

Tesla has made it clear that discharge-related expenses are not covered by the manufacturer’s warranty or the Roadside Assistance policy.

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