During research for my next car I came across a question on a forum "What is this in the boot?". Answer, a capacitor pack to assist the stop start system. Used because of its rapid charge discharge properties. I had not heard of that one before. I hope it does not preclude a spare wheel.
clubjazz.org/forum/index.php?topic=8217.0
Last edited by: Old Navy on Wed 15 Jun 16 at 10:06
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Some time ago I had wondered about the relatively small battery in the Jazz considering it has stop start. Fortunately it can be switched off. :-)
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As I'm sure you know, the stop-start will suspend its own operation if the battery doesn't have sufficient charge or demand from other consumers is too high.
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Yes, although my Ceed did not have it, the blurb was in the user manual. There were about a dozen parameters that had to be met for it to activate. Maybe a capacitor assisted system works more often because of the rapid charge.
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My guess would be there's a chance that the stop/start causes a dip on the 12V supply to the ECU (or some other bit of important electronics) and these capacitors are used to keep the supply within limits during the start of stop/start .
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Interesting: to me that doesn't look big enough to do anything useful in terms of energy storage, but presumably it does work or they wouldn't be fitting them.
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How many here are aware that some StopStart systems do not rely on the starter motor to restart. Presumably the wear and tear on the mechanicals would be too great. PSA use the alternator as a restart motor - transmitting the drive through the serpentine belt. Presumably the belt is chaeaper ( with labour) to replace? Hate to think what a replacement alternator would cost!
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ON, check the video out in this link - the car in question uses a tiny fuel cell in combination with a decent capacitor with impressive looking results.
www.car4play.com/forum/post/index.htm?f=2&t=22583
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Thanks, doc. Interesting concept. A glimpse into the future of car use? Maybe Honda are at the front of capacitor use in current cars. (Groan accepted). :-)
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>>How many here are aware that some StopStart systems do not rely on the starter motor to restart
I wasn't. How does it use the alternator?
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As a motor. There are special start-stop alternators. I didn't think they were universal though.
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If starting the car that way is seen as effective, then why do they also have the starter motor? Or is that the brutal backup for when more than a gentle nudge is required?
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>> If starting the car that way is seen as effective, then why do they also
>> have the starter motor? Or is that the brutal backup for when more than a
>> gentle nudge is required?
I don't know, but I can speculate.
The stop-start alternator will always be dealing with a warm engine, and typically the engine will have been stopped at the optimal point for restart. The battery condition will be checked before the engine is shut off. Conditions are therefore optimal.
The design of the stop-start alternator will be a compromise, and the torque and power it can deliver will be limited by the belt drive as as well as the strength of the electromagnets in the rotor and the meatiness of the stator windings. The magnetising current passes through a commutator which is usually fairly light duty (which is all it needs to be in a normal application in a normal sized alternator). I expect the normal starter can deliver significantly more torque to cope with treacly cold oil and with a much higher current, and for longer, than even a modified cost effective alternator.
The gearing will also be a factor I guess, and without the ability to "change gear" between the alternator and crank pulley that will be a compromise.
There's also the engine design to consider. Stop-start has generally been added to existing designs rather than having been part of a complete new design. Maybe we will see full-duty stop-start alternators in due course.
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>> As a motor. There are special start-stop alternators. I didn't think they were universal though.
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They used to be. As fitted to the Bullnose Morris:
www.vehicle-electrical-rewinds.co.uk/dynastart-repairs.html
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Capacitor assist. - Old Navy
