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I have a 2014 Passat and recently my battery drained just enough to not start the car. I suspected that it was a combination of short trips + that feature that leaves the lights on when locking the car that drained my battery. So I turned that feature off.

After I got a jump start I drove around for 20 minutes in the city until I got home. The next morning, the start was still rather slow but it was just enough to start the engine (yay!). That day I drove about ~100 miles on the freeway. Everything is good now and the engine starts etc.

However, since I am paying more attention to it now, I noticed that in the morning (when the engine is cold) it takes slightly longer to start the engine than after I had driven it to get it warm. I do not live in a cold climate.

Is this normal?

  • Is this VW a diesel? – CharlieRB Mar 8 '17 at 12:44
  • @CharlieRB No. It is the 1.4 TSI. – Cucumber Mar 8 '17 at 16:49
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    Thank you. In the future, try to give as much info about the vehicle as possible. – CharlieRB Mar 8 '17 at 18:49
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I don't know about longer (this is relative to the exact engine being served and the ignition type), but it is harder to start a cold engine.

There are a couple of things going on with the engine when you go to start it when it's cold. The first of which is the oil is harder to push around, so uses more juice from the battery to get the engine going. When the engine is warm, the oil will push around much easier. If the battery is at all weak, it can take its toll on it.

Next issue is the cold engine absorbs more energy from the air/fuel mixture as it explodes. This can quench the flame as combustion occurs. This doesn't take long to rectify as the particular areas will heat up rather quickly, but it doesn't happen with a warm engine.

There is probably more going on which I'm not thinking of right now, but needless to say, these two issues will cause it to take a few more revolutions before the engine will be self sustaining.

With this said, please understand that a battery's life expectancy is around three to five years. Yours is getting right in this range. While it may continue to service you for a while longer, it's probably one of those things you'll want to think about replacing in the next while because this will most likely happen again. If you replace your battery on your time, it'll save you from being stranded when you need it most. Just a thought.

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    +1 for "quenching the flame". I would also say the colder weather affects the ability for the battery to hold charge as well, as a contributing factor. Also, some batteries don't react well to being significantly drained and once this drain occurs, permanent damage is caused and you should replace the battery. – DizzyFool Mar 8 '17 at 9:35
  • I think harder describes the issue better than longer. You are right. I am considering selling the car within the next 3-4 months, so I am not sure if I want to invest in a battery right now. Maybe I should just buy one of those portable jump start things instead. Thanks! – Cucumber Mar 8 '17 at 16:53
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    @Cucumber you would still need to charge the booster, and fast charging the sealed battery in the booster while its attached to the car battery with the car alternator could cause it to explode. – Rowan Hawkins Mar 9 '17 at 3:06
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    Actually, the condition of the battery got just worse and worse over time. So I just bought a new one. Not worth the hassle now anyway. – Cucumber Mar 9 '17 at 20:07
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I would say that your main problem is the age of your battery. Your battery itself is failing less than a cold vehicle being harder to start. Over time batteries lose the ability to charge and hold a charge as well. A car battery generally lasts 3 to 5 years. Lots of short drives could make it fail after 3 if it's not receiving a full charge after starting. It should be mostly charged back up after about 20 minutes. Unless you were causing a heavy electrical load for your alternator.

The hint that tells me this is your real issue is the fact that disabling leaving the headlights on makes a difference on your ability to start your car. Leaving your headlights on has no effect on the temperature of the engine. Only the amount of energy available from the battery at the time of starting in the morning. If you hold out and it's not very cold you might get another four months out of the battery but eventually it will begin to do this same scenario when it is warm because the chemical reaction between the plates in the battery has already drained most of the electricity out of the battery.

When batteries are cold, the chemical reaction which generates the electricity would you use to start your car is limited. As a result there's less starting power available for you when you were starting.

While oil viscosity does go up when it is cold, most engines now use 5W30 and there is less of an issue with that weight of oil unless it's below 0 Fahrenheit. Of course if you are due for an oil change that may help as there is less buildup of Gunk it within the oil as well.

The temperature of a cold engine also does cause vaporized fuel to condense on the cylinder walls which limits the amount of combustible fuel within the cylinder at the time of the spark. But that effect rapidly goes away once the engine is running and the cylinder walls begin to heat up.

A third issue for very old cars is that their compression due to wear on the cylinders and compression rings within the cylinders goes down also causing low energy production from the engine. Unless you absolutely totally abused this engine by not changing the oil ever. 3 years should not be enough to cause that kind of wear. However it is something seen in vehicles over 10 years old which were not not maintained properly.

It may also be prudent to check your charging circuit for your battery. You could heavily load your electrical system by turning on your high beams turning on your windshield wipers on full and turning on your heater and air conditioning full blast. And then see if your headlights flicker a little if you're running your engine. When you take your car into a auto parts store and have them check the battery and the charging system they will have you do that while they are monitoring the amount and quality of current put out by your alternator. If the engine has been running a while it may not be as noticeable a hit on the battery because the battery has been recharged. This is why some shops will have you leave the car overnight so they can do this test while the battery is cold.

  • Thanks for your help! I went to the auto parts store and they checked the battery, but they said it's fine. However, that was after I already drove for some time. I just bought a new battery and got it replaced. Thanks! – Cucumber Mar 9 '17 at 21:24

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