Battery life very dependent on how it has been used, but in "normal" use I would expect at least 5 years, (I have had a battery on a car last for 12 years).

If only used for irregular short journeys you will need to keep it "topped up" using a (ideally) smart charger..

The stop start system was only introduced to help the manufactures get better figures during the "standard" tests they have to do. During these emission/mpg checks there are periods when the car is "idling", so in order to maximise the results it made sense to "stop" the engine, ie this gives periods of no emissions). All perfectly ligit as long as this is representative of production cars. I suppose if you are predominantly commuting in towns / stop start conditions it may help a little, just seems a bit OTT if you are not as it puts extra load on the battery and starter motor, (but they are designed and built with this use in mind). If I could deactivate it permanently I would.

 

A quick google on "Europarts" (just type in reg no), suggests a battery price anywhere from £65 (Lion), up to £315!! (Exide), but they all seem to come with a 3 year warranty

59 minutes ago, twoladies said:

Any idea how long a battery should last?  Or is it a piece of string?

 

My Fabia I had for 11 years was still on it on it's original battery, on my Harley Davidson I replaced it at 9 years but one motorcycle we were travelling with had a battery fail at 3 years.
I think it's mostly in the lap of the gods how long they last but will always do better if not abused or left with low charge for any period of time.

8 minutes ago, Urrell said:

 

My Fabia I had for 11 years was still on it on it's original battery, on my Harley Davidson I replaced it at 9 years but one motorcycle we were travelling with had a battery fail at 3 years.
I think it's mostly in the lap of the gods how long they last but will always do better if not abused or left with low charge for any period of time.

 

I can relate to batteries not lasting long.

My Toledo battery lasted under 5 years and I think the reason was the car has little use. So winter time it sits for a few days unused and I guess the battery gets low on power often.

My garage told me the battery was faulty although it started the car ok and everything powered up ok no problem. It's a stop/start so a higher powered battery fitted, they put a new one on as they said it showed low on power even though I thought it was fully charged.

I turn the stop start on and off as required during the journey. If say approaching a roundabout I turn it off, as I have a dsg, and the last thing I want is the pause if there is a gap to accelerate out into, yet the engine has stopped.

Similarly if creeping up to traffic lights at red and stop would only be momentary, or stop start crawling traffic it is set to off.

When pauses likely to be more than 15 seconds at lights, stationary traffic, level crossings etc I leave it on.

 

However in previous two manual Yetis, stop start is never an issue anyway as the engine does not stop whilst clutch is depressed, so the above issues don't occur. My wifes Citigo has the manaul style of stop start, and that like my former Yetis only stops the engine when put in neutral and clutch released. It instantly restarts as the clutch is touched and is running ready to go before the gear is selected.

 

Hence stop start is definately an issue with a dsg car, and I can now turn it on and off without looking down as I know where the switch is. If you have a manual car it can't really intefere at all and I used to leave it engaged and available all the time.

Had one ( older but ) new car ( come in to work ) where the battery had lasted only 6 months.

The owner drove the car from home to the doctors, to the supermarket to the post office and back to home.

This happened every Wednesday and was a total of 2 miles a week.

The battery never got driven enough to charge it up. 

They were charged to replace it at 6 months old.

 

On older ( pre stop/start ) cars the alternator always works, when the engine is running.

It only charges the battery at a slow/low rate, about 14 volts.

If the battery is very flat it charges at this slow/low rate.

If the battery is completely charged it still tries to charge the battery. 

This is wasteful and where stop/start charging is useful.

 

On newer stop/start cars there are sensors that monitor the battery.

In particular it looks at the State of Charge as well at the voltage of the battery.

There are upper and lower limits set to the State of charge of the battery that the Battery Management System monitors.

If the State of charge is at the high limit ( but this is NOT fully charged ) it turns the alternator off, to save fuel.

If the State of charge is at the low limit it will turn the alternator on and might even turn some car's electrical functions off.

This will first be noticed by the stop start system not working. This is not a fault but a design feature.

 

So on a longer journey the alternator might charge the battery just after it the car has been started.

But when the battery is at the higher State of charge the alternator will be turned off. So on a long journey this will save fuel.

The alternator will come back on, and charge at a fast/high rate, 15 - 16 volts, when you are braking.

This is called a Kinetic Energy Recovery system as fitted to the Fabia III. 

http://edu.skoda-auto.com/modelstest/fabia/technologytest#SixReasonsWhyWebPart

https://en.wikipedia.org/wiki/Kinetic_energy_recovery_system

But if the battery is already fully charged then it will not work.

This is why the battery is not fully charged by the car.

 

Some people might have noticed that there is no Battery State of Charge reading option on the MFD.

This was an option on some non stop start cars.

With the stop start cars the reading would appear to be low compared to a previous car they might have owned.

This was making people contact the garage unnecessarily.

 

A way to keep a battery healthy on a car with low use is by using a Smart battery Charger.

Also note the car does not know when and how far you are going to drive.

So it cannot charge the car to suit your driving.

Car batteries are lasting less than before due to all the extra electrical equipment fitted to newer cars.

They have also become bigger.

The battery on my 1985 2.0 litre petrol car is smaller/less powerful than the battery on my 2016 1.2 litre petrol car.

 

HTH.

Thanks AG Falco

13 minutes ago, AGFalco said:

It only charges the battery at a slow/low rate, about 14 volts.

 

My stop start charges at a normal 14.7 volts

Some of the Anecdotal stories and experiences of other vehicles and various people is all lovely stuff but little use to the OP who is asking in the Yeti section about her particular Yeti.

12 minutes ago, AGFalco said:

[snip]

On older ( pre stop/start ) cars the alternator always works, when the engine is running.

It only charges the battery at a slow/low rate, about 14 volts.

If the battery is very flat it charges at this slow/low rate.

If the battery is completely charged it still tries to charge the battery. 

This is wasteful and where stop/start charging is useful.

 

/[snip]

 

This paragraph is only partially true and paints traditional charging systems as inferior and much worse than they are in reality.

 

Fixed voltage charging is demand led, so only when required does the alternator produce lots of electrical energy (I.e. when the loads on the system pull down the system voltage; it increases it's field current automatically to try to maintain it's voltage setpoint). The current from the alternator continually changes up and down automatically according to need (within its rpm-related capability), whether that be for attached loads or charging of the battery itself.

 

Highly efficient at serving all the requirements and keeping the battery in a healthy, capable condition (barring extreme cases as in your first paragraph). Wasteful is not the word. Optimal would better describe it, especially if battery lifetime and user convenience are considered.

 

So called smart charging bins off all this in favour of keeping the battery at a lower, less healthy, less capable state of charge. This in exchange for 'green credentials' marketing and probable advantages in emissions type testing.  The main transference of this change to on-the-road driving seems to be shutdown of the 'emissions reduction' start-stop system and reduced battery lifetime. Go figure... 

18 minutes ago, Wino said:

This paragraph is only partially true

 

Was trying to keep it simple for the OP.

 

 

Still think the battery wants charging because of the usage stated by the OP:-

 

'Uh oh...dont want to be stranded in the winter..how do I know if it needs a new battery without waiting to be stranded!  3 years old 2.5k miles.  Thx'

 

Thanks AG Falco

46 minutes ago, Urrell said:

My stop start charges at a normal 14.7 volts

 

Higher than pre stop start cars.

 

1 hour ago, AGFalco said:

On older ( pre stop/start ) cars the alternator always works, when the engine is running.

It only charges the battery at a slow/low rate, about 14 volts.

 

Thanks AG Falco

Simple is good as long as it doesn't distort the truth.

There are other smart chargers but this is what I use

https://www.amazon.co.uk/CTEK-CTE-56263-Cigarette-Lighter-Connector/dp/B01MZZ6T5F?th=1

Shop around!

6 hours ago, twoladies said:

Any idea how long a battery should last?  Or is it a piece of string?

Piece of string but a bit dependent on the way the car has been driven. Long journeys tend to lead to longer battery life short trips tend to lead to shorter battery life. Generally if the battery is on the way out you may notice slower turn over on starting or other electrical gremlins. If you do then get the battery tested and replace it if dodgy.

2 hours ago, Urrell said:

My stop start charges at a normal 14.7 volts

 

1 hour ago, AGFalco said:

Higher than pre stop start cars.

 

I wonder why that is, Oh silly me it's because it has an AGM battery!!!

Comparing the Yeti with the alternator equipped Midget:
Yeti 14.7v
Midget 13.5v

Another factor that will prevent stop/start from working is if the engine isn't up to temperature.  Could that be the case for the OP, given the time of year that we are currently in?  It's certainly the case for my Yeti: this evening, driving through town, stop/start didn't operate until the engine temperature was up to ~70°C.  I don't think the battery voltage could have had anything to do with it: stop-start traffic, mostly in 20mph limits, is hardly going to give a massive boost to the battery.

 

The May 2017 edition of the Yeti owner's manual states:

 

The bit in red does not apply to every engine of model.

You can start a TDI or TSI with the ambient temp below freezing and move a few feet and Stop / Start work when the coolant has not started to heat and neither has the oil.

Just a nice strong battery and no demand on it and the heating knob not cranked up.