24Volting a car...

[Stealer Of Souls]

Well. I was thinking the other day about this. And it seems that there could be potential benefit in converting a car to 24V. Particularly if you were building a race car or a kit car. The reduction in wire sizings could result in a weight saving, not to mention the better efficiency of 24V in terms of power delivery.
I suppose the question is. Apart from ECU, what else couldn't be run on 24V (ie part replaced with a 24V version)?

[RomanV]

Are you sure there arent hidden disadvantages to running 24v though? perhaps it creates more load on the alternator, which negates any possible advantage.

[Quint]

I'd say the coil would go through your bonnet as the induced voltage it'd induce would be so much more.

Disclaimer: I have no idea, only assumption

[NZ_AE86]

Hmm, lets see. You would have to run two batteries to make this option work so you would be adding at least 6kg for the other battery and if you can save that in 'thin' wiring your doing well!

Also when you are at the track and your dizzy/coil etc etc shits it self and you have mod'd or replaced them to be compatable with 24V then you will be unable to borrow any parts from others to keep you day of racing going!

If you must do it then it is no problem just replace:

ECU with a Motec as they are happy at 24Volt
Coil
All Bulbs
Alternator
Starter
Battery with 2 Batteries
Plus other stuff that will come to me at 4 in the morning while trying to sleep.

Still have not seen an advantage though!

[Alex B]

Factory ECU SHOULD be fine up to about 48v so my electronics lecturer tells me. A car that ran on 48v from factory would be great, thinner wires all around.

[Stealer Of Souls]

I was thinking relocating battery, and large current draw systems when I was thinking about this.
Normally you would need to run something like a 2ga (126 sqmm ??) cable to supply power from battery in the boot to the engine bay. With a 24V system you could cut this down quite a bit (a 4ga would probably do). And if you had high drain devices (headlamps, plus fogs and spots, electric heaters or demisters) you can use smaller wire and things like relays will be less stressed.
I guess there aren't huge benefits of 24V over 12V. But there are some.
Being able to relocate the battery to where ever you want is good for weight balance. 6kgs isn't a huge gain, and if you could shed 3kgs of wire weight, then you've only gained 3kgs. 24V starters and alternators can be smaller/lighter than their 12V relatives.

And yes 48V would be LOVELY to see! Then everything can be electrical based! No more mechanical loads for A/C and p/s, heating can be instantaneous!

[NZ_AE86]

Factory ECU SHOULD be fine up to about 48v so my electronics lecturer tells me. A car that ran on 48v from factory would be great, thinner wires all around.

Well how about you put 48 volt through your ecu and see what happens!

Tell you lecturer he does not know what he is talking about!

It worries me that people will tell you that shit, what if you were to do it? Do you think he would buy you a new ecu if you blew it up?


Stealer of souls.

24Volt Alternators and starters are larger and heavier then 12Volt.

When I say 6kgs for the battery that is a small Gel cell battery.

[RedMist]

Think about your sensors. Nothing will read correctly any more. The ECU wont have a clue how to scale the voltages, TPS, temp, IAT will all be screwed. The ECU, if it does run for more than 10 seconds, wont know what the heck hit it!

[Stealer Of Souls]

The ECU will most likely have a voltage control circuit in it. Which in theory will handle upto or around 48V...

Now see. Sensors that's what I would need to think about! I would think that the whole engine management will need to be run on a 12V system, which leads to a rather nasty dual voltage setup.

A 24v alternator or starter should only be heavier because you are buying a much larger item (ie meant primarily for trucks or something).
A 12V .5kW starter should be heavier than a 24V .5kW starter.

[NZ_AE86]

The ECU will most likely have a voltage control circuit in it. Which in theory will handle upto or around 48V...

Voltage control circuit eh? What the $&#$%? An ECU that is designed to run on 12V will run on 12V! When you have an overcharging fault and get above about 16V most vehicles ECU's go BANG!

If you got a custom starter and alternator built then maybe they could be smaller and lighter but starters and alternators are not that heavy anyway! Why would you spend so much money on custom stuff for no advantage?

If you are thinking of running a Voltage reducer to run some things on 12V then you are then adding weight not taking it away!

IMO all up it is a bad idea.

[Malcolm]

I remember reading and article once about great plans for all new cars to run on 48volt systems, the idea being that wire sizes could be reduced, in turn reducing cost of wiring, reducing total weight (apparently by a reasonably significant amount), thus improving fuel economy.
That was a good 3 or 4 years ago, since then haven't heard any developments.

[Cahuna]

I remember reading and article once about great plans for all new cars to run on 48volt systems, the idea being that wire sizes could be reduced, in turn reducing cost of wiring, reducing total weight (apparently by a reasonably significant amount), thus improving fuel economy.
That was a good 3 or 4 years ago, since then haven't heard any developments.

I believe that the main objective to doing this was to power all the electrical goodies that appear in modern cars, 12V just isn't enough. For a 48V system some people envisaged a combined starter motor/alternator built into the flywheel, which would give more efficient charging and faster spinning of the engine for startup (the extra voltage presumably required to spin it up as there would be no gearing advantage as with a normal starter motor arrangement). Faster spinning of the engine on the starter motor should mean faster starting, making motors like that on the Prius (that start and stop frequently) smoother in their start/stop operations. Also gives rise to the possibility of electro-magnetic valves (goodbye camshafts, hello infinitely variable lift, duration and timing of each individual valve) currently under development by BMW and a few other manufacturers.

One advantage for a 24V system in a race/performance car could be with the starting system. I know my FXGT tends to turn over quite slowly when warm, which may be due to the compression or dodgy wiring (I dunno, will look during the rebuild ). My father used to have plenty of starting problems with his old Escort rally car due to insufficient cranking power on the starter, he solved it by having (from memory) a system where a second battery kicked in when starting the car, which temporarily boosted everything to 24V. No ECUs or fancy electronics to worry about in that old car though...

Bear in mind with all the above that all I know about electrickery is that when I switch on a light it (usually) just works and when it doesn't I call a sparky, so basically I could be talking out of my a** for all I know...

[MrBeef]

I thought this was all about...24V-alving a car. Not bloody putting 24Volts thru the system.

[TygerTung]

This is a ridiculous idea.

I reckon insted just convert to a 6 volt system, like they used to have in old cars?

How about insted of running it on efi, just use carby's?

[Alex B]

yea i mean why dont we just go back to horse and cart.

[TygerTung]

Yeah, just do chariot racing insted of car racing

[NZ_AE86]

One advantage for a 24V system in a race/performance car could be with the starting system. I know my FXGT tends to turn over quite slowly when warm, which may be due to the compression or dodgy wiring (I dunno, will look during the rebuild ). My father used to have plenty of starting problems with his old Escort rally car due to insufficient cranking power on the starter, he solved it by having (from memory) a system where a second battery kicked in when starting the car, which temporarily boosted everything to 24V. No ECUs or fancy electronics to worry about in that old car though...

This used to be a problem with high comp engines but today you can get a reduction drive starter motor to suit anything you want and these will turn anything over!

Oh and the 40+ Volt thing is still on its way for cars. Should not be long now.

[Loudtoy]

Ok basic rule of thumb p = v over i, so by doubling your voltage you will reduce the current. However because p = v over i just by doubling your v you won't increase your p (p is a rated constant after all) - just decrease your i.
The reason the escort worked better briefly on 24 volts to start is less current needed - ever looked on a battery it will give you cold cranking amps normally.
Also think about all your switch gear - ever seen how many relays, transistors, voltage sensors are in a car - good luck to you if you want to go through and change every single one of these.
Pertaining to the ecu it will be alright for spikes, and dips but try running it at a constant double voltage it won't last long at all - think of it as similar to running your pc at 400 volts instead of 230 - the transformer would simply be fried in a matter of milli seconds the bang would be worth watching though.
Thats enough from me now anyhow i'l sit back and watch what you make of it!

[DeeCee]

there has been talk about cars moving up to 36v.. but that has been talked about for a couple of years now.. too many demands on the current 12v electrical systems..

[skoty]

OMG, I wont bother going into it but if your got a reasonable understanding of electricity and its number of laws and principles you will understand why you wouldn't convert to 24v I really cant be bothered going into it but for starters the average ECU operates on 5volts, why? Because during starting etc voltage drops below 12 and 5v is a safe voltage to work with in an ECU say car manufactures.