How quickly will a car battery run out?

stockhausen

stockhausen

stockhausen

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If a car (Mk. 5 VW Polo GTI) is parked in the street outside my house, with only the burglar alarm using the battery, how long will it take for the battery to lose power to the extent that it will no longer start the car?
 
How long can a car sit before the battery dies?
A new car battery fully charged, may last at least fourteen days without charging from the generator. It'll get discharged entirely from 2 to 3 months. You won't have the ability to start the engine of the car if you're planning to abandon it for 2.5 months on average
 
I'm no expert but usually the parked battery drain (unless you have additional accessories or a fault) should be sub 1 watt - typically more like half a watt or so. So your average car battery probably has around 30 days or so before it won't be able to start but in practise I've seen vehicles start fine after longer than that.

(On my truck I have a just over 100ah battery so it should be good for much more than 2 months even).

EDIT: As above that assumes you are starting with a fully charged battery though.
 
Days?!

I parked my car at Luton on October 31st and picked it up January 15th and it started immediately.

Also left my car on the drive for five months while I worked in China, again started with no issue.
 
A good battery that's charged should easily last 2 months+.

A lot of it depends on the car, but let's say a draw of 30mAh on the battery while the car is locked up on a charged 60Ah battery. Theoretically that would last over 80 days before the battery is completely discharged. But there are so many different factors that can alter this, the car itself, how much of a drain it has on the battery, the age and condition of the battery itself, even down to the ambient temperature.
 
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Took my 850 with a 4 year old cheap 74aH battery 3.5 weeks. That was with frequent door un-/locking and opening/closing. Its also quite a lump to start.

Will depend on your battery drain (esp if you have anything parasitic), your aH rating, its condition and how well charged it was at the time of parking. Its a question with a range of vague answers.
 
Trifid said:
Equally important question, how long does it take to recharge a battery from the engine?
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Quite a while, a good hour if it was completely flat should at least be enough to be able to start and use it again as normal. But a couple of hours at least to fully charge.
 
One of my work mates left his car while he was abroad and it started fine after a full 3 months sitting idle. It is only a 1.0 though, so your mileage may vary.
 
Zefan said:
One of my work mates left his car while he was abroad and it started fine after a full 3 months sitting idle. It is only a 1.0 though, so your mileage may vary.
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The smaller more basic cars tend to last well due to the lack of electronics, they literally just run a clock and alarm :p
 
It really depends on the car, some will drain far faster than others. My old Subaru would drain so low it couldn't be started after 2 weeks due to its aftermarket alarm, but i've had others which are fine after 2+ months like my old Toyota Yaris.
 
There are a lot of variables. It will last longer during the summer, shorter during the winter and it depends on the amperage the car draws while unused + the health of the battery. If its good battery I would say at least 3 months would be fine but I would advise against letting your car sit for that long unused.
 
stockhausen said:
True, I just wanted to get a feel for how long would be likely

Why so?
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It will have an effect on the battery health but it also things begin to seize, lubricants degrade etc. Don't get me wrong your car won't seize up in 2 or 3 months but it is definitely a good thing to give it a 20 minute run every once in a while.
 
stockhausen said:
If a car (Mk. 5 VW Polo GTI) is parked in the street outside my house, with only the burglar alarm using the battery, how long will it take for the battery to lose power to the extent that it will no longer start the car?
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Probably never because car alarm sounders don't use the car battery.... Otherwise a thief would simply have to disconnect the battery before breaking into a car.
 
Django x2 said:
Probably never because car alarm sounders don't use the car battery.... Otherwise a thief would simply have to disconnect the battery before breaking into a car.
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Power sounder has its own battery but the car battery still runs the alarm system with the sensors and such.
 
I’ve learnt the hard way with this in the past.

had to change the battery on the mondeo twice. Both leaving it stationary 3-6month at a time.

now I either run it around regular once a week at least or will trickle charge if left standing more than 2-3weeks.

Edit. Recent battery change brand new Bosch and will keep on top of it for sure.
 
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