Talk:42-volt electrical system

Advantages of a higher voltage
Motivation for increased voltage - higher demand by accessories such as air conditioning, power steering, adaptive suspension, electronically-controlled valves. Could need several kw electric power on a vehicle, compared to about 1 kW in a passenger car today. More power needs more current at 12 v, larger and heavier wires. A higher voltage would be useful.

All-electric drives would allow unused loads to be switched off, reducing parasitic drag on the engine. Applications in both mass-market cars and for military vehicles which could use electrically powered systems for weapons and sensors.

The reason to go to 42 V is that this is about the highest voltage that can be used without running into safety codes on insulation and contact - many codes only regulate equipment for voltages 50 v and higher. Using 42 volts allows the same wires to carry 3 x the power as a 12 volt system.

With a lead-acid battery system, 6 cells for a nominal 12-volt system needs almost 14 volts for charging the battery. Using 3 times as many cells gives 36 volt "nominal" but a 42-volt charging system. The convention seems to be use the charging voltage - a lead-acid "12 volt" battery with 12 volts on its terminals is essentially a dead battery, when charged it will show 13.6 v or more.

Discuss why not just go to 24 v (28 V charging)- which is well established in heavy trucks. maybe an sAE reference describes this?


 * Just a comment, "about 1 kW in a passenger car today". That is huge amount of power, I know this is just a talk page but cars with 42A electrics?  Surely this is an exceptionally large power drain. Headlights take about 100W and that is a major drain on many (IMHO most) car electrical systems. Mtpaley (talk) 22:43, 16 April 2010 (UTC)
 * Well, let's see. A kilowatt at 12 V would be closer to 83 A. An ignition system takes substantial power (10 A, perhaps?). Low beam is 2 x 55 watts, high beam is 2 x 65 watts on some cars anyway.  My car has various motor operated gizmos like a sun roof and power seats, and electric seat heaters. There's more than just headlamps - marker lights, turn signals, daytime running lights, brake lights, dashboard lights. The stereo takes a couple of amps.  There's a powerful blower for the heating and air conditioning. Many cars have electric radiator fans which are pretty big loads (20 or 30 A?). And that's not counting things like electric power steering, adaptive suspensions, electric power brakes, and many other toys and gadgets that the Car of the Future will have. I think it's a reasonable statement, but my best reference is packed away at the moment. --Wtshymanski (talk) 14:38, 17 April 2010 (UTC)

System components
42-volt system would need a new alternator and battery. Could use a combined starter motor and alternator, controlled by power electronics - combined with a 42 V battery bank this is used to create "mild hybrids" which use an electrical assist to add several hp for acceleration and to idle-stop engines instead of idling at standstill. To power 12-volt accessories would use either a solid-state converter or a second 12 volt battery recharged from the 42 volt system. Separating the engine cranking battery from the ignition and accessory battery would solve one big problem with automotive electrical systems.

Limitations and obstacles
It's hard to break direct current at voltages higher than 12 V because there's no natural current reversals as found in AC circuits. The same switch that is rated to interrupt 15 Amperes at 120 v AC might only be rated 1 Ampere at 120 v DC. 12-volt switches haven't needed design features to limit arcing such as spring-loaded fast break contacts, or arc containment and dispersal features as found in higher-voltage dc switching devices.

Not all the wires get smaller - very fine wire breaks easily, so devices that only draw an ampere or so at 12 V will not get smaller wires. Maybe 1/3 of the wires in a car get smaller at 42 volts.

Corrosion is a problem according to

Incandescent bulbs of the sizes used in cars work quite well at 12 v and are cheap and simple. 42 V gives no advantage for LED lamps, but might be useful for hid headlamps which have relatively high power.

A great deal of auto electronics works well at 12 v and developing semiconductors to switch and tolerate a 42 v environment is a challenging field of development. Low-power electronics doesn't benefit from 42 v (computers, navigation systems), 42 V might help high-power sound systems. Chief advantage is for electronics controlling mechanical systems such as engine valves and suspension. If 42 V devices all switched electronically, avoids the problems with snap switches.

Slow introduction
Toyota produced a low volume luxury Toyota Crown with 42 V electrical system, sold only in Japan. General Motors is incorporating 42-volt elements in vehicles like the 2005 Silverado hybrid truck.

Merge from 42V?
I have a slight preference to merge material from 42V to this article, on the grounds that "42-volt electrical system" is more descriptive than the curt "42V". I am biassed, of course -. --Wtshymanski (talk) 14:10, 25 November 2011 (UTC)


 * I agree with you on the direction of the merge. However, noone seems to have started a section on a Talk page that actually contains the merge proposal, with the rationale from the nominator.  Someone may feel free to invite me back if that ever happens.  Cheers.  N2e (talk) 15:33, 25 November 2011 (UTC)
 * Why, this is that talk page discussion. The rationale is pretty obvious - same topic, two articles, should be one article. --Wtshymanski (talk) 17:50, 25 November 2011 (UTC)


 * Merge makes sense; using this name for the merged page makes sense.--NapoliRoma (talk) 00:52, 26 November 2011 (UTC)


 * SUPPORT the merge, per rationale that the two articles cover essentially the same material. Should be merged.  Which seems to be the consensus of the commenters to date.  N2e (talk) 00:18, 9 September 2012 (UTC)


 * Looks like the merge was done on 2011-12-01. --Kvng (talk) 13:59, 10 September 2012 (UTC)

✅ Cool. That was not clear in the discussion previously, but with your note, and this one, it now is. Merge has been completed. Thanks. N2e (talk) 17:15, 10 September 2012 (UTC)

Reference?
Choice of Voltage: "because at low temperatures the charging voltage of the battery can attain 60 V" Is there any reference to this claim? — Preceding unsigned comment added by 178.78.75.150 (talk) 08:55, 1 April 2015 (UTC)

External links modified
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48-volt systems should now become the primary focus
As the (new) last paragraph of section History/Europe now states, 48-Volt systems have been announced as a future standard for several manufacturers based in Europe. This seems more important than the history of the abandoned 42V proposal. Hence 48V now deserves the primary focus of this article, or its own article, with some details about the planned applications. If the former, 42V would be limited mainly to the History section, while the Introduction would need a rewrite. Layzeeboi (talk) 05:30, 11 February 2018 (UTC)
 * It would be interesting to read more about this. What changed that 48 V was previously thought to be too high? --Wtshymanski (talk) 02:02, 13 March 2018 (UTC)
 * I concur, this wiki needs a rewrite with the widescale adoption of 48V(especially given how impactful it's been, it's opened up a lot of new tech). 42V is certainly important in the history of getting to this point, but there's no reason for it to be the primary focus now when it's been deprecated by 48Vs adoption. Ry Trapp0 (talk) 22:17, 5 September 2023 (UTC)