07-25-2014, 03:36 PM | #45 |
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Alternator design
In my younger days I was a vehicle electrician and also taught vehicle electrics at a Technical College in the UK.
Alternators were just being introduced to motor vehicles in the 1970's, and therefore I have a lot of experience with Dynamo's vs Alternators. The great advantage of the alternator is that the rotating part of the alternator, the stator, was very compact and light compared with the armature, which is the rotating part of the dynamo. This means that the rotor can be revolved at exceptionally high RPM's, in the tens of thousands. This means that the gearing of the alternator can therefore be arranged so that it rotates at thousands of revs at engine idling speeds so providing very close to maximum controlled output if required. Therefore I would expect that a correctly operating electrical charging system on any modern car should be able to meet the full electrical load at idle. Incidentally at the time we thought that an alternator producing 40amps was incredible as the standard dynamo could only produce a maximum of around 25 amps and only then when the engine was being driven at a reasonably high speed and certainly not at idling speed, and that for only a very short time due to overheating issues. This is the reason that most people needed trickle chargers in their garage and that all dealer garages had a large multi battery charging facility. Outputs of 200+ amps were not even dreamt of . Apologies for the length of this post but I thought that watchers around the world might be interested in a bit of history |
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07-26-2014, 01:49 AM | #46 |
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Just an update, BMW assist identified it as a short circuit and ordered a new battery which was installed yesterday... Seems yo be working now...
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12-18-2015, 02:45 PM | #47 |
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Had brake, DSC and type pressure warning lights come up last Saturday, turned off, restarted and all reset, asked garage to check any errors today during third service to be told they had replaced the battery under warranty!
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01-01-2016, 05:51 PM | #48 |
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Battery issue & auto stop start
Another culprit might be the auto stop-start. After a low battery issue on our 2013 X1 we were told by the dealer that a 5 mile commute, short trips & traffic w/lots of auto-restarts the battery can get damaged or worn out (he might have said "fried"). It's basically the same as not driving enough to recharge the battery but is exacerbated by the stop-start. We now try to hit the cancel button just about every time we drive. So far we've had no more issues. This is an expensive battery to replace; we really don't want to go there.
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