Hyundai i40 - Hyundai Stop Start System - Bycro
Hi all

I am still rattling around in my i40 diesel. Four years old next spring, currently with 104,000 miles clocked. Been a good workhorse and very reliable apart from initial clutch issues.

In June the auto stop, start ceased working, so when it was colllected by the main dealer for its 100k service at the end of July I mentioned this. Anyway when the car was returned to me later that day, I was advised that it probably needed a good run !

It still isn't working now. It lives on the motorway and covers about 3000 miles a month.

Anyone know anything about the technology behind these systems or encountered the same problem

Thanks.
Hyundai i40 - Hyundai Stop Start System - RobJP

The electronics have a number of parameters, ALL of which must be satisfied before the auto start/stop will function.

The likely cause in your case will be a lack of battery charge - which indicates that the battery is losing capacity as it ages. So while the battery is fine for starting and running around, the car is reading it as (for example) 60% charged, and if that figure is below figure set by Hyundai for the stop/start, then it just won't function.

There will be a number of other parameters : outside air temperature is one, though not relevant at this time of year. But that's probably the most likely cause.

Hyundai i40 - Hyundai Stop Start System - Bycro

The electronics have a number of parameters, ALL of which must be satisfied before the auto start/stop will function.

The likely cause in your case will be a lack of battery charge - which indicates that the battery is losing capacity as it ages. So while the battery is fine for starting and running around, the car is reading it as (for example) 60% charged, and if that figure is below figure set by Hyundai for the stop/start, then it just won't function.

There will be a number of other parameters : outside air temperature is one, though not relevant at this time of year. But that's probably the most likely cause.

Thanks for the reply RobJP, it is appreciated. Shame the dealer could have bothered to explain this to me.
Hyundai i40 - Hyundai Stop Start System - FP

My Mazda stop/start (fancily called "iStop") won't function if there is any significant current demand - air-conditioning, headlights, heated screens, for example; or, it will function and then the car will re-start itself after a short time. Another consideration will be the engine temperature.

But my money would be on Rob's diagnosis - a battery on the way out, which the system thinks needs a lot of charging. If the car is four years old, that's a bit soon for a battery to fail, but still entirely possible (if, for example it has been completely discharged at some point).

With winter approaching, I suggest the battery is tested and replaced if it's not 100%; if it's even a bit down, there's only one way things can go.

Hyundai i40 - Hyundai Stop Start System - RT

My Mazda stop/start (fancily called "iStop") won't function if there is any significant current demand - air-conditioning, headlights, heated screens, for example; or, it will function and then the car will re-start itself after a short time. Another consideration will be the engine temperature.

But my money would be on Rob's diagnosis - a battery on the way out, which the system thinks needs a lot of charging. If the car is four years old, that's a bit soon for a battery to fail, but still entirely possible (if, for example it has been completely discharged at some point).

With winter approaching, I suggest the battery is tested and replaced if it's not 100%; if it's even a bit down, there's only one way things can go.

Cars with stop-start often use an AGM battery, which has a different charging regime to ordinary Lead-Acid, and many have a routine replacement recommended at 5 years old. Any car with stop-start with just a Lead-Acid battery will give the battery a harder time than without stop-start.

Hyundai i40 - Hyundai Stop Start System - elekie&a/c doctor
If the battery does prove to be suspect,then you are looking at around £200 for a replacement.!
Hyundai i40 - Hyundai Stop Start System - Bycro
If the battery does prove to be suspect,then you are looking at around £200 for a replacement.!

Thanks for all the replies everyone. It has me thinking, supposed I owned this vehicle, which I don't. It is leased as a company car. I would be a little angry if I had to fork out £200 for a new battery on a car that isn't four years old for another six months. It has a heavy duty battery, according to Hyundai. If I was buying a car privately, I think I would try to avoid buying with this feature. Seems to me to be another expensive novelty to go wrong. It can be deactivated ( when it works ) I believe, seems like a good idea.
Hyundai i40 - Hyundai Stop Start System - RT

There are very few Euro 6 cars without stop-start so you might have trouble finding one.

And remember that anything over 3 years is acceptable as conventional battery life.

Edited by RT on 09/09/2017 at 21:36

Hyundai i40 - Hyundai Stop Start System - Bycro

There are very few Euro 6 cars without stop-start so you might have trouble finding one.

And remember that anything over 3 years is acceptable as conventional battery life.

Thanks RT, madness isn't it. Less choice and more expense for the motoring masses Never had to have a new battery fitted in a car in thirty years of driving. ( call me lucky) LOL Roll on all the electric cars. Now that's a subject for another time I guess.
Hyundai i40 - Hyundai Stop Start System - RT

There are very few Euro 6 cars without stop-start so you might have trouble finding one.

And remember that anything over 3 years is acceptable as conventional battery life.

Thanks RT, madness isn't it. Less choice and more expense for the motoring masses Never had to have a new battery fitted in a car in thirty years of driving. ( call me lucky) LOL Roll on all the electric cars. Now that's a subject for another time I guess.

Surprisingly, the only battery I've ever had to replace in 50 years was a Japan-built Panasonic in a Japan-built Subaru - not a grey import but the battery couldn't cope with it's second UK winter! I could get 14 years out of Vauxhall batteries, they out lasted the cars!

 

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