Not really an issue as long as your car has a good battery. If the battery is more than a few years old, or has run flat in the past then it might be flat when you get home. If that's a concern you might consider disconnecting it or leaving it on a battery maintainer.

If the car is in a secure location disconnect the battery as there may be a drain on it from the alarm system, especially if the battery is quite old.  Back in the old days I would take out the distributor rotor if leaving a car at an airport in UK for a few weeks but not practical with todays cars.

Nothing.

I was away for 6 weeks and left the car locked in the garage.
My battery is about 4 years old. Didnt have any issues.

duckDecoy:

 

We'll be taking a 6 week trip later in the year and so our cars will be sitting up at home.

 

Is there anything we should do with them?  Or is 6 weeks nothing for a car to sit unused.

 

My sister-in-law asked me the same question recently before her 5 week trip to England. I just told her to park the car in her garage and not to worry about it.

When we dropped her off, on her return, I waited while she tried to start her car and it fired up first time. 😄

Problems can occur if the vehicles battery is on the way out, especially during winter months. So good time to get a health check on the battery and replace if needed.

Give the car a good run the day or the day before you go away, not just around the block but a really good run, this will make sure the battery is fully charges.

On your return, do the same, take the car for a good run.

My father ( now a retired auto electrician ) said to customers to drive the long way hoem to give the battery a good charge.

Enjoy your trip.

John

Reverse the cars into the garage after a decent drive.

disconnect the battery completely 

gzt: >> drive the long way home to give the battery a good charge

Commutes getting longer these days he'd add:.. during the day with the lights off.

its actually quite difficult to fully charge batteries by driving the car, because of the time it takes. it takes a very long time to do the last little bit.  best thing is to put it on a battery charger and leave it for at least overnight, better yet a day or two (assuming modern charger).

i highly recommend NOT disconnecting the battery. 

simply charge the battery fully before you go, or leave it on a trickle charger. many good chargers can be left connected.

edit: put poison around for mice/rats. seen a few cars that have been chewed by rats while the owner was away.

tweake:

 

i highly recommend NOT disconnecting the battery. 

 

simply charge the battery fully before you go, or leave it on a trickle charger. many good chargers can be left connected.

 

edit: put poison around for mice/rats. seen a few cars that have been chewed by rats while the owner was away.

 

ok, so rat problem existed…. I wonder how the rest of the house was !

also, what’s the rationale of not disconnecting the battery?
by disconnecting, it won’t be drained by the cars clock and most Likley factory alarm system…

Goosey:

 

ok, so rat problem existed…. I wonder how the rest of the house was !

 

also, what’s the rationale of not disconnecting the battery?
by disconnecting, it won’t be drained by the cars clock and most Likley factory alarm system…

 

the house is clean enough to eat off the floor. car was parked outside. they have a bit of bush near by the rats tend to come out of. in a good season lots of food in the bush for rats during summer, not so much in winter so they go looking for food and sneak under bonnets for place to hide. also have to watch out for birds building nests under the bonnet, i've had that myself.

trouble with disconnecting battery is sometimes they loose the learning on the engine sensors. they can run like crap when you first fire them up until it relearns. i've heard of a few weird things like the fob for the alarm no longer working. also one that had engine wear the ecu compensated for, but once you loose that learning the engine won't run.

try to avoid disconnecting batteries for long periods on modern cars.

We put our vehicles on battery charger designed for this (i.e. charging and safe for continued long term connection without ruining battery) when we go away for longer than a few weeks. We use Ctek MXS 5 which was purchased after a bunch of research: https://www.cteknz.co.nz/charger/product/mxs-5-0

Eliminates the need for a bunch of other suggestions in the thread and gives piece of mind.

For 6 weeks with a fairly new battery, you can likely get away with doing nothing. If I get time, I try to make sure the cars have had a wash in the last week or so, and I top of the 12V batteries with a plug in charger in the last few days.

That said, I suspect we had a weak battery on our leaf the last time we end overseas, and got home it having a flat 12v battery (and the damage from being flat was enough that that 12v battery needed replacing soon after). It was parked in the garage, and I have a smart charger, so could have easily plugged it in, but decided wrongly it was not needed. Have some regret on that on that decision.

Ideally for long term storage you would:

• Clean the car
• Store it in a garage (with a window down so the interior can ventilate)
• Keep it on a smart charger
• Charge the battery fully before hand if that is not possible
• Pump up tyres to max sidewall to reduce the chance of flat spots forming on tyres (really overkill for 6 weeks).
• Have somebody drive the car & check the tyre pressures every three - for months
• If the above is not viable and it going to be more than say 6 months, put the car on blocks.

On disconnecting the battery, needing to break out the spanners makes this more of a chore than putting a charger on. Also many car need a bunch of stuff done by the driver when power is reconnected. My Lexus resets the seatbelt alarms, requires every widow to be cycled from the door local switch before the drivers door remotes will work, looses radio stations etc. Of course if you are willing to do that stuff it is an OK option.

On Jump pack's, I do have some lithem based ones, which are great, but they are a last resort plan. Lead acid batteries do get damaged from sitting flat for a long time. If the car is going to be in a garage with power, putting the money towards a charger would be my first pick. 

Solar trickle chargers do exist for cars stored outside, but I have never tried one.

If it is an EV, they are best stored with the pack somewhere in the middle, so it good to run the pack down to somewhere in the middle. Some EV's (i.e. Tesla's) are best stored plugged in, are best stored unplugged (like the leaf).