How long does the battery last before it won't start the car?

[xplainwhy]

I recently bought a MY07 Golf GTI and I was hoping to get some of your experiences with how long the battery in the car will last if you don't start it for a long period (e.g. if you're going away on a holiday).

When i refer to how long the battery will last, i mean still have enough charge to start the car.

My previous car would start after I've been away for 3 weeks, but it had a LOT less electronics in the car that might potentially drain the battery (e.g. no car alarm motion sensors, radio central locking), not sure if all that stuff matters tho.

Hoping to get some feedback on how long people have been away from their cars and still be able to start it when they get back.

Please let me know what car it is as well.

Thanks all.

p.s. LOVE the GTI... fantastic car.

[Big Yellow]

i was interstate for 1 month, and when i came back my car started no problems

[Transporter]

It will depend how old the battery is, what stage of charge did you leave the battery in and what the outside temperature is, since the cold also slows the chemical reaction in the battery, reducing its power output.
The alternator charges only to 80% battery capacity but when the battery is aging it will not charge to this 80% capacity (capacity is reduced with age of the battery). Common lead acid battery will lose 1% capacity per day even not connected to the car's electrics, more in the car since there is small current drain from the battery to maintain ECU and other electronics memory.
From my experience if you parked your car for a month and going to start it up on cold morning when the outside temperature is 2 deg. C above 0 it probably won’t start, especially if the battery is older.
AGM (absorbed glass mat) battery loses 1% - 3% capacity per month, so when your battery is worn out and you buy a new one ask for AGM battery.

[Maverick]

As Transporter says a lot depends on the weather and the age of the battery but you should be able to get 4-6 weeks without a problem.

Assuming it's the original battery it's due to fail soon (if you get around 3 years that's about normal). It's covered under warranty so you'll get a new one if it fails before the 3 years is up.

Unless you leave it often for long periods I wouldn't buy an AGM battery due to the extra cost, they do have benefits but they're not very common in Australia so it's not unusual to end up buying a 1 to 3 year old one.

[mrcurlywhirly]

As per the guys comments above, it depends on the point in the lifecycle of the battery and the ambient temp how long it will retain charge.

Lead acid battery life can also be shortened by over discharge as much as overcharging, so it really depends on how healthy your electrical system is, and whether you drive the car regularly or inadvertantly leave lights on etc.

Its going to vary from car to car also dependant on positioning of the battery. I'm not sure about the location in the GTi but in the R32 the battery is hidden away under a panel the boot, away from the temperature fluctuations in the engine bay.
This supposedly gives it a better chance at longer life, (I have heard this can stretch it to over 5 years...though its impossible to verify) though VW probably stuffed it in there due to under bonnet space constraints.

[mrcurlywhirly]

BTW - Our Vdub started fine when we returned from an OS trip, had been sitting in the carport for around 7 weeks.

[POLARBEAR666]

If you have a manly Dekka battery that weighs only 8kg instead of 20kg then you only have 2-3 days sitting before its flat.

Just recharged mine after 1 month holiday and its hammering again! 720CCA gives such clean starts!

[xplainwhy]

Thanks all for your comments, very useful indeed. I'm more comfortable leaving my car for a few weeks now knowing that it's got a good chance of starting when i get back.

Cheers.

[spiff]

xplainwhy, in case you're worried or interested in a product such as this.
i was asking about it a short while ago, and the people on here were helpful enough to point me to this product - ctek trickle/battery charger.

the thread is here - http://www.vwwatercooled.org.au/newf...ad.php?t=30568