Leaving a car for two or three weeks: battery, tyres, frost

The battery goes flat even when nothing is happening

A parked car is never fully off. The alarm listens, control units wake on a cycle, the clock and the stored settings draw current the whole time the car sits there. Over a day that is nothing you could notice. Over three weeks it is a solid slice of the capacity.

What decides the outcome is the age of the cell, not the length of the stay. A battery five or six years old holds its charge worse than a new one, and it is the first thing to give up after a long pause. If the starter already turned over reluctantly once last winter, replace the battery before you go instead of hoping this time will be different.

Frost adds a second factor that has nothing to do with age. In low temperatures a cell delivers less current, while starting a cold engine asks for more of it than usual. Those two facts meet on the morning you come back, at six, on an open lot.

The cheapest preparation is a longer drive the day before. Half an hour out of town charges the cell properly; three five-minute hops take more out of it for each start than the alternator manages to put back.

Disconnecting a terminal on a newer car usually does more harm than good. Settings are lost, fault messages come back, and on some models the radio locks itself and needs a workshop visit. A healthy cell needs no help at all across two or three weeks.

If the car has some years on it and the trip falls in winter and runs for a month, read the lot's offer. Some parking operators list a battery check or a start-up before your landing, and that is a service worth ticking when you book.

Fuel and fluids for the season, not for tomorrow

Leave the tank with something in it rather than on the warning light. The reason is practical rather than technical: after a night landing, with suitcases and a half-asleep child in the back, hunting for an open filling station is the last thing you have energy for.

Diesel is a separate matter. Fuel bought in autumn can still be the summer blend, and in a hard frost it thickens enough that the engine will not fire. If you leave before the season and come back in the middle of it, fill up at a station that already sells the winter mix.

Check the screenwash for the temperature it is rated to, not for how much of it is in the bottle. The summer kind freezes and splits the reservoir or the lines, and that failure waits quietly and shows up on the day you return, at the first dirty windscreen.

Diesel cars have one more tank. A level close to empty means a warning and a capped rev limit when you get back, so top the additive up together with the fuel rather than on the road home.

Tyres and the handbrake

Tyres lose pressure by themselves, slowly, whether or not the car is driven. After three weeks the difference is measurable, and an autumn drop in temperature adds to it. Inflate them to the figure on the sticker in the driver's door frame before you leave home, because you will not find a compressor on a lot near the airport.

A car that stands in one position for a long time can thump or shiver through the steering wheel when it first moves. Those are flat spots where the tyre met the ground, and over two or three weeks they roll themselves out within a few kilometres. They need patience, not a reaction.

The handbrake is the one item where the habit is worth changing. After rain followed by frost, the pads can freeze to the drum or disc, and pulling away ends in a jolt or a locked wheel.

So on a flat surface leave the car in first gear, or in the parking position, and let the handbrake off. If the space slopes, the handbrake stays on and you turn the wheels towards the kerb. A car that cannot roll always matters more than a set of saved pads.

Cars with an electric parking brake rarely give you the choice, because it only releases with power. That is one more reason to sort the battery out before a long stay instead of trusting its good will.

What stays in the cabin and what travels with you

This section is not about theft. It is about what a fortnight does to the things left inside. In summer a closed cabin heats up well past the air around it; in winter it cools down to whatever the lot is doing.

Anything with a cell in it travels with you or stays at home: the power bank, the charger, the road toll box, the dash camera. Electronics work worse after two weeks in the frost, and a water bottle or a can of drink that bursts in the cabin leaves a mess you will smell for weeks.

The registration document and anything else that proves what the car is belong in your bag or in a drawer at home. The glovebox is the worst possible place for those papers precisely when the car is away from you for three weeks.

The key stays with you wherever you park and walk away on your own. You hand it over only at a lot that takes the car at the terminal, or with a key handover service you chose deliberately when booking. If the lot asks for the key because it shuffles cars around a tight site, that is ordinary practice and it says so when you book, not at the barrier.

The spare set should not travel in the same pocket as the main one, and it certainly does not stay in the cabin. With two people travelling, the sensible split is one key in each person's hand luggage.

One last small thing that is easy to miss: close the windows and the sunroof all the way. A window left ajar through three weeks of rain does more damage inside than a single night of downpour.

Coming back and the first few kilometres

You come back tired, often overnight, with bags in your hands. That is the worst possible moment for surprises, so it pays to plan the first few minutes on the lot in advance.

In winter the weather plans them for you. Clearing the roof, scraping the glass and thawing the wipers takes a genuine quarter of an hour, and wipers frozen to the screen and switched on straight away will tear a blade. Some lots carry winter care in their price list, and then the car is waiting cleared.

Once it starts, read the lights on the dashboard instead of clicking them away. The tyre pressure warning and the battery warning are the two most common ones after a long stay, and both are better settled on the lot than on the motorway slip road.

Make the first braking gentle, still inside the parking area. Discs pick up a film of rust over a few weeks; it wears off within a few stops, but the first one tends to be loud and noticeably weaker than usual.

If the engine turns over reluctantly, do not keep cranking it. A run of attempts finishes the cell off, while the staff on site usually have jump leads within reach and will help you faster than anyone you could call from town.

All of the above fits into half an hour of work the day before you leave. Three weeks of standing still are not a problem for a car in themselves; the only problem is ever the condition you send it into that stay with.