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About this tool
Checklist to park a car safely for weeks or months, with battery drain days, storage tyre pressure and a return list.
This checklist works out how long a parked car can actually be left before its 12 V battery stops it starting, and builds the preparation list around that answer. On a modern car the deciding factor is parasitic drain — the alarm, body control module and telematics keep drawing 20 to 50 mA once the car is asleep — which is added to self-discharge that roughly doubles for every 10 °C rise, giving the days to the 80 percent sulfation point and to the 50 percent point where a cold engine will not crank. The rest of the list adapts to the powertrain, the transmission, the temperature and the storage location, and includes a separate list for bringing the car back.
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Parasitic drain and self-discharge are added together, so the answer is a number of days rather than 'fit a trickle charger just in case'.
The list tells you to chock the wheels instead, because a parking brake left applied for months can bond the pads to the disc.
Diesel biocide, petrol stabiliser and the traction-battery charge band appear only for the cars they apply to.
Usually four to six weeks on a modern car. A 60 Ah battery with 30 mA of parasitic drain loses about 0.72 Ah a day to the electronics alone, reaching the 50 percent point where it will not reliably crank in roughly 40 days — and it passes the 80 percent sulfation threshold in about 16 days, which is when permanent capacity loss begins.
No. Chock the wheels and leave a manual in gear or an automatic in Park instead. A parking brake left applied for months can bond the friction material to the drum or disc, and freeing it usually means dismantling that corner of the car.
About 25 percent above the normal cold pressure, never above the maximum moulded on the sidewall — so a tyre normally at 33 psi goes to roughly 41 psi. Move the car a metre every few weeks as well, because changing the contact patch is what actually stops a flat spot becoming permanent.
Between about 40 and 60 percent. Lithium-ion cells age faster the longer they sit at a high state of charge and the warmer they are, so a middling charge is the least damaging place to leave them, and letting the pack drift to empty over a long stand risks a deep-discharge state that needs dealer recovery. Follow the manufacturer's own instructions, which sometimes differ.