Cars with 36 volt batteries - Peter D
I recently read an article in Professional Motor Mechanic written by Keith Rudd of Exide Technologies that the cars of the future will require 36 volt batteries and 42 volt electrical systems. He talks of cars requiring between 12 and 14 kW, electrically powered oil and water pumps, electrically assisted cat converters and starter alternators. Instantaneous engine start times of 220 to 300 milliseconds and reduced fuel consumption of 10% to 15%. All very interesting but I assume that this is going to be a very expensive car with more electrical systems than an aeroplane. I personally can not imaging a car that requires 12 to 14 kW to run it that is a huge load that takes 20 HP out of the engine. Mat this guy meant 14kw to start it. Apparently the battery manufacturers and vehicle makers have been working closely to develop 42V systems. Have any of you read of this and any time scales envisaged Regards Peter
Cars with 36 volt batteries - Gen
Is this the electric/petrol hybrid cars?
Cars with 36 volt batteries - Peter D
The article did ellude to power boosting using the starter/alternator to set off but it was mainly hung around the 36 /42 volt electrical system. Regards Peter
Cars with 36 volt batteries - SteveH42
They have been talking about 42V auto electrical systems for a while now. The main problem with 12V is that to get any decent power from it, you need to draw a lot of current. (P=VI) Tripling the voltage means you only need a third of the current, and semiconductor systems are better suited to a higher voltage (within limits) than a higher current.

There are a number of existing and proposed systems that need more power - ECUs and the like are getting more and more power hungry (auto electronic designers obviously haven't heard of low power design..) but I think the main proposed system is electromagnetic brakes. Not sure of the pros / cons of these - I assume the main one is that you aren't using brake pads so it will be less wearing and potentially safer.
Cars with 36 volt batteries - Tomo.
"the main proposed system is electromagnetic brakes. Not sure of the pros / cons of these - I assume the main one is that you aren't using brake pads so it will be less wearing and potentially safer."

Very sorry, blew a fuse, could not stop!

Tomo
Cars with 36 volt batteries - SteveH42
Presumably backed up with some sort of fail-safe system. I'd imagine the park brake would be something applied by a spring and held off during normal operation. Any failure detected in the braking system and this will be applied.
Cars with 36 volt batteries - Flat in Fifth
42 volt systems:

This was discussed back on this forum in 2001.

Basically it is because vehicles are becoming so power hungry it is easier to generate the required at a higher volts.

The alternator and starter would be combined in a unit, sort of attached to the flywheel, and one of the features is the stop-start device to reduce emissions in urban driving. ie engine stops at lights and auto starts.

But if idle-stop is the main thrust of 42 systems it begs to question how all the other systems will be powered, eg aircon , heaters, lights which will all have to be powered continuously.

However 42 volts is not the ideal voltage for other applications eg logic circuits, lights so its likely that 14 v systems (ie what we call 12v) would continue in parallel. Of course that opens up all sorts of other issues like what happens if a 14v circuit is exposed to 42v and other cans of worms.

electric brakes (Brake by wire):
BBW are another so far experimental device being developed by amongst others Renault, who must be the wrong geezers to develop such complicated safety critical devices in my opinion.

However 42v/14v electrical systems greatly simplify the design of BBW so in a way when 42v systems come then so will BBW.


Cars with 36 volt batteries - Deryck Tintagel
FYI

There are generally two forms of electric park brake: the first uses what is called a "cable puller" which uses the same shoes as would a conventional handbrake lever but has an electric motor to pull on the yoke wire between each caliper; the second uses an electric motor mounted on the brake caliper. Both use a switch on the dash to replace the handbrake lever and cable.

Each system uses information from the engine management, ABS speed sensors and an accelerometer to verify if the vehicle is on a slope to determine how and when to apply the brakes, ie. you can't apply the handbrake at 60MPH!
Cars with 36 volt batteries - Peter D
The cost of the control units and safety critical itmes is going to be horrendous lets face it a Multi Timer Falser unit for a Clio is £130 and you have to reprogram the Ignition inhibitor £25 plus vat. And BBW sounds dangerous to me at least if you pop a seal in a hydralic system you can pump it again and use the daul circuit. Blow/crack a fuse and your gone, and what no hand brake at 60 miles per hour, so you can't use that either. Scarey Peter
Cars with 36 volt batteries - SteveH42
I'd imagine BBW will be implemented in a safety-critical way. After all, trains have had brakes that you release rather than apply for years, so it's about time cars had a similarly safe system.

As for the costs, hopefully someone will wise-up to the fact motorists are being ripped off over electronic component replacement and insist the charges are more representative. The worst I've seen is an ECU for a Gallant which Mitsubishi wanted nearly £1k for that contained about a tenners worth of components at today's prices.
Cars with 36 volt batteries - Deryck Tintagel
I work in automotive electronics and 42V seems to be the way most things are going at the moment but is still some time away -obvious advantage of reduced size motors and wiring harness.

There are proposals to link the BBW with adaptive cruise control, lane guidance and elecric power steering. The components are available but we haven't put them all together - yet! Think about that when it all goes pear-shaped.
Cars with 36 volt batteries - smokie
ECUs joyriding on their own ya mean?

They probably have more intelligence than today's batch of joyriders.

Remember to add satnav to the linked components so it can find it's way home.
Cars with 36 volt batteries - SteveH42
Just wondering here, are you talking of BBW as just a variant of the existing braking systems? I've read about a number of proposals in various electronics trade journals, but the most interesting ones are electromagnetic braking systems - i.e. ones that don't feature friction material at all. (Other than as a backup and park brake) However, there are also systems (such as on the Ford Tonka Truck - yes, it is honestly called this!) that store the energy from braking rather than dissipating it. (Can't remember if they are hydrokinetic or what....) This would make a lot of sense as well as saving a lot of fuel, but whether it is suitable for smaller cars I'm not sure.


Isn't there a car that actually features a steer-by-wire system? I'm sure I've read about it somewhere but whether it was a prototype, racer or what I can't remember. Makes a lot of sense but would need plenty of fail-safes.
Cars with 36 volt batteries - Deryck Tintagel
BBW is currently using existing calipers with electrically operated pistons. I've not heard of electromagnetic brakes as yet.

I think that Jaguar are looking at steer-by-wire - not sure how this works if the electronics packs up.
Cars with 36 volt batteries - SteveH42
I've not heard of electromagnetic brakes as yet.


I think they were mentioned in New Electronics a while back - if you don't get it, I'll see if I've still got the old copies at work and post some more details. They do quite a few interested car-related articles for anyone in to electronics - www.neon.co.uk gived details of how to get copies.
Brake by wire simple explanation - Flat in Fifth
The best and simplest explanations are on Teves' site. There are other projects/companies working on this but its a clear explanation.

tinyurl.com/8klw

When you go to that page what we are really talking about are EMB electro mechanical brakes which is one of the links on that page. The EMB are the only ones that do away with hydraulic circuits by using electrical motors to actuate the brakes.

The others are hybrids eg electro-hydraulic brakes etc.

Sometimes wonder if we really need or want all this complication.
Cars with 36 volt batteries - Dave_TD
After all, trains have had brakes that you release rather than apply
for years


As indeed have lorries!


Doesn't the current (boom boom) BMW 7-series have 42v electrics?
 

Value my car