22-03-2020, 12:54 PM
From what I've been reading, most - perhaps all - vehicles these days with auto start stop come with smart charging. If nothing else, before stopping the engine, it's useful to know the SoC of the battery so it knows if it will actually start again.
This reminds me of a colleague who bought a new Jaguar XF back in 2013. He got to work one morning and couldn't stop the engine - it didn't respond to the stop/start button. It finally let him out after after about half an hour. Turns out the smart charging algorithm had decided there wasn't enough charge in the battery to restart the engine later. Admittedly he did have a short journey to work (but a bit longer than mine), but had never had this problem with other cars. Jaguar issued a software update shortly after to alter the smart-charge strategy, and he's had no problems since.
I remember some VWs tried this in the '80s. Their system was called "SSA" (stop-start automatic), and was very simple - based on nothing more clever than a handful of BC548s IIRC. There was a later iteration available for the mk3 Golf, which could turn off the engine when you lifted off the gas, which most people really didn't like at the time. I'm sure that most people who owned cars with these systems would have left them switched off for the vast majority of the time. Apart from a beefier battery, I'm not sure what other measures were made to ensure reliability. Given that my standard mk3 Golf required a new starter motor at only 4 years old, I wouldn't have had much faith in such a system. Modern systems are hopefully better, but I still worry about long-term wear on the starter and battery, and tend to switch them off (I manually switch the engine off if it's obvious I'll be stationary for more than a couple of minutes). There's rumours that stop-start defeat switches will be banned at some point in the future, and while I understand the environmental impetus, it's really not good for people who want to keep their cars for longer than the warranty period. I haven't done the calculations to see if more frequent battery and starter motor replacements are better than the emissions from idling engines, but that wouldn't take into account air quality in towns - as a cyclist I don't ignore or belittle that, but it means it's hard to make sense of the raw data.
I do remember a difficult journey crawling through Birmingham in rush-hour. We were in our pool car (a 2013 diesel Focus) and the driver had stop-start enabled, so this thing was on and off every 5 seconds or so. Being diesel, the noise and vibration at startup/shutdown was really quite uncomfortable, and I did ask my colleague to disable the system - he did a lot of his own car maintenance, so I appealed on grounds of mechanical sympathy, but to no end. Anyway, at one point, when it restarted, the engine went berserk! I've no idea what went wrong, but it was vibrating wildly (presumably misfiring) and running at a very high speed, and was unresponsive to any controls (including the engine start-stop button). It was really very scary, and we'd all undone our seat belts and were ready to take our chances before the thing blew up (in 3 lanes of queuing traffic!). Eventually he put it in 6th and stalled it. When restarted, it did run normally. And he finally relented and switched off the auto start-stop system. Obviously a software glitch, but potentially really quite nasty. To be fair, we didn't see that again, but it shakes your confidence!
This reminds me of a colleague who bought a new Jaguar XF back in 2013. He got to work one morning and couldn't stop the engine - it didn't respond to the stop/start button. It finally let him out after after about half an hour. Turns out the smart charging algorithm had decided there wasn't enough charge in the battery to restart the engine later. Admittedly he did have a short journey to work (but a bit longer than mine), but had never had this problem with other cars. Jaguar issued a software update shortly after to alter the smart-charge strategy, and he's had no problems since.
I remember some VWs tried this in the '80s. Their system was called "SSA" (stop-start automatic), and was very simple - based on nothing more clever than a handful of BC548s IIRC. There was a later iteration available for the mk3 Golf, which could turn off the engine when you lifted off the gas, which most people really didn't like at the time. I'm sure that most people who owned cars with these systems would have left them switched off for the vast majority of the time. Apart from a beefier battery, I'm not sure what other measures were made to ensure reliability. Given that my standard mk3 Golf required a new starter motor at only 4 years old, I wouldn't have had much faith in such a system. Modern systems are hopefully better, but I still worry about long-term wear on the starter and battery, and tend to switch them off (I manually switch the engine off if it's obvious I'll be stationary for more than a couple of minutes). There's rumours that stop-start defeat switches will be banned at some point in the future, and while I understand the environmental impetus, it's really not good for people who want to keep their cars for longer than the warranty period. I haven't done the calculations to see if more frequent battery and starter motor replacements are better than the emissions from idling engines, but that wouldn't take into account air quality in towns - as a cyclist I don't ignore or belittle that, but it means it's hard to make sense of the raw data.
I do remember a difficult journey crawling through Birmingham in rush-hour. We were in our pool car (a 2013 diesel Focus) and the driver had stop-start enabled, so this thing was on and off every 5 seconds or so. Being diesel, the noise and vibration at startup/shutdown was really quite uncomfortable, and I did ask my colleague to disable the system - he did a lot of his own car maintenance, so I appealed on grounds of mechanical sympathy, but to no end. Anyway, at one point, when it restarted, the engine went berserk! I've no idea what went wrong, but it was vibrating wildly (presumably misfiring) and running at a very high speed, and was unresponsive to any controls (including the engine start-stop button). It was really very scary, and we'd all undone our seat belts and were ready to take our chances before the thing blew up (in 3 lanes of queuing traffic!). Eventually he put it in 6th and stalled it. When restarted, it did run normally. And he finally relented and switched off the auto start-stop system. Obviously a software glitch, but potentially really quite nasty. To be fair, we didn't see that again, but it shakes your confidence!
