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How long can a car battery sit?

Hey all!

I am currently on vacation, and will be here for another 2 weeks (3 total). I live in the midwest, and my car is currently parked at O’Hare Airport. I have a 2012 Subaru Legacy 2.5i with 42k miles, full synthetic oil, and a 3 year old battery. Will I have any issues when I go to start it upon my return home?

The car always seems to fire right up, and with these warmer temps, I am thinking I’ll be ok, but thought I would ask. I just kind of want to know if I should be looking for someone to jump me when I get back to my car, LOL.

Last, in warmer temps, in the garage, with a good battery, how long can a car usually sit for without being started? Also, if I start the car and just let it idle for 5-10 minutes, will that recharge the battery, or do I need to actually drive the car and get my speeds above 60mph?

Thanks so much, guys!

Probably no problem. Left my truck for 6 months in storage for a europe backpack tour, but different cars have different draws. Worst case a jump and new battery. Not quite the same battery but my deep cell boat battery is 12 years old, trickle charge in spring and still doing well.

It should be fine for a few weeks. As to how long a battery can last while sitting idle that depends.
Sitting idle is not good for any battery so the effect could be cumulative. Five minutes is not much of a charge and if the car is sitting a lot in the garage for a week here and a week there I would probably recommend getting a Battery Tender to keep the battery from sulfating.

Three weeks should be fine as long as everything is off.
You’re on vacation. Stop fretting about your car. Worst case, you’ll need an auto club jump. It ain’t worth fretting over.

I regularly go 4-6 weeks or longer without starting one of my cars with no problems. Letting it idle though isn’t going to do much and you really need to drive it some or put a charger on it.

“It ain’t worth fretting over.”

Well said mountainbike.

3 weeks is fine. Any longer than that and I’d put a trickle charger on it.

The electronics in cars go into sleep mode and only draw about 50 mA, but that varies from model to model. Plus the battery itself has internal leakage current, which increases with age.

Idling for 5-10 minutes and then shutting down will not charge the battery. The net charge may well be negative, depending on how fast it started.

Up to 3 months, I would do nothing and just take a jumper battery with me just in case. When you get it home, put a charger on it. Longer then 3 months, long before I put a trickle charger on, I would disconnect the negative terminal…and reconnect and continue as it first situation. If the battery is disconnected, they will last quite a few months to a year depending on the temp…the cooler the better. Even if you have a jumper to get you started, always bring it up to full charge on a charger ASAP.

I parked my spare vehicle in a storage lot while my wife and I went on an extended trip to Alaska. The trip was going to last 3 months but we extended that to 15 months because we loved it up there. When I got back…our car (1986 Cadillac…FWD) started with very little cranking. The engine did sputter somewhat but still ran pretty good. How long a battery…or gas, for that matter, will last is just a toss of the coin. I did not have a battery tender or a gas stabilizer in the tank.

Somehow my luck would never be that good. I disconnect batteries when a vehicle will be resting for more than a week.

Will I have any issues when I go to start it upon my return home?

Probably not.

Last, in warmer temps, in the garage, with a good battery, how long can a car usually sit for without being started?

Usually months, but it can cause other issues.

Also, if I start the car and just let it idle for 5-10 minutes, will that recharge the battery, or do I need to actually drive the car and get my speeds above 60mph?

If you’re just trying to recharge the battery, you can leave it in Park and throttle it to about 2000 RPM or so for maybe 10 minutes. Moving the car is irrelevant to the alternator.

“Somehow my luck would never be that good.”

Mine isn’t always that good. I left my truck at the Atlanta airport for a week and the battery was dead when I got back. I did have some luck though…the guy in front of me had a dead battery and had called a tow truck. I split the bill with him and we both got back on the road.

Told the story before but years ago my wife had the Olds at the airport for about four days. The one she was with failed to close the trunk completely and the light was on the whole time (before automatic power cut-offs). The airport ramp had a truck and tried starting the thing but it was so dead, it didn’t take. So she called the Amoco motor club (after several calls to me 45 miles away and at my cousins golden wedding reception). When she was talking to the dispatcher (I assume India) she said she was having trouble finding her. My wife said you mean the airport, no the voice said, she couldn’t find Minneapolis! Pretty easy to miss about three million people and an international airport I guess. Motor club finally came through though and saved me a trip. I thought it wise to replace the battery. Ya wanna double check though everything is off and the doors are shut.

I’ve kinda had the same thing talking to a guy with an Indian accent, sitting on I-35 and reading him the mile marker and the over-pass road number while he was having trouble finding it. I was about 5 miles from the towing outfit so I finally said just call them and they’ll know where I am. Can’t miss me, just south of McDonalds. I could walk there if it wasn’t raining.

I agree with @RodKnox in general, not because a week requires you disconnect the battery, but sometimes a week can turn into a month or so due to unforeseen circumstances. When people around here leave their cars for the winter at the lake, they prep them for up to two years even though they could be back in a few months. You just don’t need the aggravation of two year old gas and a dead battery and flat tires if they don’t get back.

A lead- acid battery will self-discharge at about 5% a month at 60 degrees temperature. The colder it is the slower the self discharge…That’s if there is no load on the battery, as in battery disconnected from the car…Today, all cars have a SLIGHT draw on the battery because some circuits are always on…Each car is different so answering your question is difficult…Most cars can still start after sitting for 3 months…After that, luck starts playing more of a role…

Just had this happen to me with 2009 Forester. Battery less than 4 mos old. I probably drive my car 20 minutes per day (to and from commuter lot) on most days. But this last week da spouse was my chaffeur. So my car not was not used for 7 days. Tried to start on day 8 and it did nothing. Took battery for charging at local parts store & nothing going. Battery would not charge

Since this was a fairly new battery and under warranty, da spouse called up Subaru to see if we could get a new one but no they wanted to test it in car. Uhhh the car is dead but we by a new battery and take car in where they charge it to 60% rendering it in “good shape.”

It seems either Subie batteries are crap or I’m missing something.

Can anyone enlighten me as to why a seemingly new battery did that. This is Chicago in March but it’s been a fairly warm one. 2009 2.5XT Forester no major bells & whistles.

Subaru doesn’t make batteries so yes you are missing something.

This can happen with any brand of battery. It can even depend upon how long the battery sat between the time it was manufactured and the time the car became a daily driver.

As Volvo_V70 correctly states; Subaru does not manufacture their batteries so they should not get the blame.

Some years ago I bought a Sears Die-Hard for one of my motorcycles. The next day at quitting time; dead as a door nail.
Pushed it into the shop for testing and found it would not even take a charge. That’s the fastest I’ve ever had a new battery go south but have had others fail within 4 to 6 months. It happens with every brand.

You bought the battery from the dealer but took it to a parts store where it wouldn’t take a charge?

Then you bought a new battery, took the dealer battery back with car and they could charge it to 60%? And you accepted that from the dealer? Why couldn’t they charge it full? Why didn’t you insist on that as expected from a 4 month old battery?

Probably just a defective replacement battery on your Forester from the get-go. The way to test a battery btw is a “load test”. Batteries which are good but already fully charged won’t take a charge. So whether it takes a charge or not isn’t the best way to test the health of a battery. A perfectly healthy fully charged battery might not crank the engine either, due to a problem with the battery connections or starter motor.

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