52 replies to this topic

[Cooperman]

It does tend to make the passengers a bit nervous when a wing falls off at 30,000 ft
I remember flying back from a rally and I was with a fellow competitor who happened to be a young lady. We boarded a Trident of the then BEA. She said "You worked on these, didn't you?" I replied that I had and she said "Do they crash very often?". "No", I repled, "usually only the once!" Now here was a girl who would drive her Escort TC through the forests on gravel at well over 100 mph, but she was nervous about flying. It must have been all that aluminium alloy!

[MRA]

Ha Ha very funny Peter I would have loved to see her face after that !

Most people have a fear of falling..... I have a fear of landing :-( that is vertically from 30,000 feet

What a lot of people don't know about automotive weight saving is that it is a battle against the electrical team...

For example, 30 years ago most cars didn't have stereo systems, aircon, climate control, sat nav, ABS, etc etc.... all of which requires electrical cable to operate it, in the early 80's the average wiring harnes was a few kg, now they can be 100kg plus a Bently for instance has over 2000 circuits (individual wires possibly doubles or triples that count)

With the extra electrical units and fuse boxes etc.. 200kg extra in 30 years is quite an acheivment, now if we go onto hybrids......

[Cooperman]

I believe that with all the extra electrical demand the manufacturers are considering going to a higher voltage.
And I can remember when my first car, a 1950 Ford V8 Pilot had 6 volt electrics. That was on a 3.6 litre car.
The Escort rally cars often had two 12 volt batteries and used 24 volts for the starter to overcome the high compression when hot.

[MRA]

That is sort of right Peter.... they have been looking for at least 20 years that I know of

The higher voltage would allow for smaller gauge wiring and therefore less copper = less weight.

[tiger99]

It is going to be 36V, but the battery will have a 36V section and a 12V section, so you can imagine how expensive it will be to replace. I believe that is the deliberate intention, make more money from spares. The 12V is retained for the lights and aftermarket electronics etc, with 36V for starting and most other systems. An inverter generates 12V efficiently from the 36V system to avoid the use of a complex dual wound alternator. Apparently, if the 36V section goes flat, the inverter will also top it up from the 12V section to get the car started.

There are several things going badly wrong already. Automotive solid state switches have been in use for a long time, and are designed to cope with transients of 50V to 60V which exist in the 12V system. So, the not too bright component manufacturers have introduced some 80V rated switches for the 36V system, however very basic theory shows that the transients will in fact be up to 180V, so the electronic switches will be failing with monotonous regularity, meaning a new and horrendously expensibe "central junction box" every time.

Also the central junction box idea is plain daft,as it needs far more copper than using distributed switching. For a long time now I have been aware that the average designer of car electrical systems is a complete moron, utterly ignorant of how to to the job safely, reliably and at minimum cost. Pay peanuts, get monkeys, as they say.

They should of course have gone for an industry standard 24V system (actually 28.8V when the battery is fully charged) as used on large vehicles, aircraft, and factories amongst other things. All the bits that are needed are really well developed, safe, reliable, and usually fairly inexpensive. And, as 24V light bulbs are readily available, there is no need at all for a dual voltage system.

[Cooperman]

It is going to be 36V, but the battery will have a 36V section and a 12V section, so you can imagine how expensive it will be to replace. I believe that is the deliberate intention, make more money from spares. The 12V is retained for the lights and aftermarket electronics etc, with 36V for starting and most other systems. An inverter generates 12V efficiently from the 36V system to avoid the use of a complex dual wound alternator. Apparently, if the 36V section goes flat, the inverter will also top it up from the 12V section to get the car started.

There are several things going badly wrong already. Automotive solid state switches have been in use for a long time, and are designed to cope with transients of 50V to 60V which exist in the 12V system. So, the not too bright component manufacturers have introduced some 80V rated switches for the 36V system, however very basic theory shows that the transients will in fact be up to 180V, so the electronic switches will be failing with monotonous regularity, meaning a new and horrendously expensibe "central junction box" every time.

Also the central junction box idea is plain daft,as it needs far more copper than using distributed switching. For a long time now I have been aware that the average designer of car electrical systems is a complete moron, utterly ignorant of how to to the job safely, reliably and at minimum cost. Pay peanuts, get monkeys, as they say.

They should of course have gone for an industry standard 24V system (actually 28.8V when the battery is fully charged) as used on large vehicles, aircraft, and factories amongst other things. All the bits that are needed are really well developed, safe, reliable, and usually fairly inexpensive. And, as 24V light bulbs are readily available, there is no need at all for a dual voltage system.

But don't let common sense get in the way of the chance to make a few bucks .

[MRA]

It was going to be 42v when I was involved with EDS systems for Jaguar and Aston Martin etc... although neither of these 2 companies where that bothered by it, the work was being carried out by the main stream electrical devices and harness/connector manufacturers..

Interesting, as they could simply fit 3 x 12v batteries to do the same thing.

I did some machining for a company based in Hemel Hempstead, don't actually think they are still there now ??

Edited by mra-minis.co.uk, 02 February 2013 - 06:50 PM.

[MRA]

This makes for interesting reading.....

http://www.yazaki-eu...technology.html

Especially the bit about the supply of 600v for HEV's

Edited by mra-minis.co.uk, 02 February 2013 - 06:55 PM.