My car has not been on any long runs over the past two weeks - my wife has been the main daily user and always on short trips of less than 5 miles in the town.
When I drove it yesterday the ISG did not work. So I put the battery on charge overnight. This morning when I used the car - the ISG started working OK within the first mile. This proved that low battery charge was the culprit.
I guess the problem originates from the fact that some cars with ISG - and mine is one of them - only charge the battery on engine over-run when you are slowing down. This is to harvest energy that would otherwise be wasted by braking or rolling/wind resistance. Short urban journeys don't give the battery enough charge to recover - particularly if the iSG is being invoked often. One of my neighbours has a VW Polo with similar behaviour and this morning said that he did a 60 mile round trip by motorway which had failed to recharge the battery enough last month. I speculated that if he was on a clear motorway and never had cause to lift off the accelerator - the fact he was cruising on a long journey may well not provide enough engine over-run events to get much charge into the battery.
This quest for low carbon emissions - be it DPF or ISG sure has its drawbacks.
So those with ISG take note - if it stops activating and you have recently only done short trips - give your battery a charge. But use the appropriate charger because your car has a special battery for stop and go usage.
