[euromodder]

Originally Posted by BPHannes

We've done user research to figure out why these systems aren't as widely spread as they could be and the result so far is that

I think your analysis is pretty much complete.

A main factor in why it's introduced is the time spent at idle during NEDC.
These test cycles are hardly realistic at best, and when fuel is cut off during the idle periods, the test only becomes less realistic.

1) Fuel savings are not high enough to make a difference for the average driver

It's most effective in situations that typically increase fuel consumption, i.e. repeated stops and accelerations.
So it'd be hard to see the relatively small positive effect of stopping the engine, as it gets drowned in the increased consumption due to these situations.

With many diesels using around 0.5L/h at idle, shutting down for a minute only saves 0.0083 liters.
In order to save 1 liter, you'd need to be stopped for a full 2 hours.
On a 1000km tank, in a car averaging 5L/100km without start/stop, that'd mean an improvement of just 0.1 L/100km, to 4.9L/100km - and that's well within the variation noise from tank-to-tank.

2) The functionality is limited by the battery

Hence a second battery is sometimes used to provide power for the accessories - adding more weight and complexity.

4) The usability is limited

Because it shuts down the engine only when the car is stopped.

If it also shut down during periods when the engine is not required - i.e. gliding or coasting periods - its usability would improve dramatically for people who coast.
But in today's power-hungry cars, that'd require even more extra battery capacity during extended glides.

But coasting isn't on the NEDC.
It'll make one fail the driving tests to get a licence, and it's regarded as weird by most motorists - myself included until not too long ago.

What people fail to realise is that coasting is how an electric engine operates.
It shuts off when no power is demanded.

Failure to coast, and falling into the regeneration trap, is what prevents many people from getting the full range out of electric cars.
They'll drive them like they drive their ICE cars.

5) Drivers are concerned about faster deterioration of car parts

The starters are improved to make them handle the many more starts, but their durability will only be truly proven in real life.

e.g. increased wear doesn’t seem to be a problem for the Toyota Prius

Because it uses the very powerful electric engine and massive battery to start the ICE.

All these concerns are of a technical nature

Solving the technical side of it, will likely be the easiest part.
I see user acceptance - or lack thereof - as the main issue.

Most folks I know with a car that has a stop/start function, have shut it off.