12v vs. 6v

[TAKerry]

Without getting overly complicated, can someone explain to me the difference between the two and how they affect the automobile. I was born in '64, and every car I have ever been involved with has been a 12v (I think?). I see so many conflicting posts where one person says they are converting and another saying its a mistake to do so. Is one any better than the other or just plain different?

[zepher]

Cars before the early 50's were mostly 6v systems.

If maintained, they were reliable and worked well.

The main difference between the two is the amount of amperage needed to perform a given job.

If you have to do the same amount of work, aka wattage, when you raise the voltage you can lower the amperage due to the formula being V x A = W.

When cars moved to 12v systems manufacturers were able to reduce the size of battery and starter cables since these cables now needed to carry less amperage to perform their duties running the starter and whatnot.

Also, higher voltages are less vulnerable to questionable connections so the condition of the wiring and connections is not as critical with 12v systems.

Having good grounds and good connections are critical to any electrical system, but it is slightly less critical with a 12v system.

Also, 12v batteries tend to have more CCA capacity than 6v systems do.

You didn't ask about positive ground vs negative ground systems but the positive ground systems do tend to eat spark plugs faster, or so I've heard.

 

Without getting into writing a dissertation on electrical theory, that is as basic as it gets.

[ABear]

A lot of misconceptions and controversy is the problem between the two..

 

Many people regard 6V as not reliable or simple to work on or 12V being superior..

 

The main issue with 6V is current draw for the same wattage load as 12V which leads to excessive voltage loss across the wiring.

 

12V on the other hand will have a lower current draw for the same wattage load leading to less voltage drop across the wiring.

 

So, 6V systems typically require substantially heavier ga wire than 12V for the same wattage load.

 

For example say you have a 6V load at 100W and a 12V load at 100W..

 

100W/6V = 16.6A

 

100W/12V = 8.3A

 

If you were to use the same wire ga for both systems the 6V system will have a much higher voltage drop than the 12V system..

 

6V worked well enough for most early engines because those engines were typically pretty low compression (5:1-6:1)..

 

But as engine compression increased, a 6V starter would require greater amounts of current than if a 12V starter was used..

 

Basically 6V became less practical as compression ratios increased.

 

Sort of the same reason 24V systems are often employed with large Diesel engines which have much greater compression ratios than gas engines.

 

Personally, I don't see anything wrong with a vehicle which was factory equipped with 6V systems but there are a lot of people that see 6V systems as inferior or not easy to work on..

 

 

[Bloo]

Well the difference is covered by Ohms Law, Volts = Amps x Ohms. To do the same work at 12 volts you need half the current (Amps). The implication is you can get by with smaller wire.

 

In the teens 6v and 12v (and some others) existed. The industry standardized on 6 volts. In the early 50s, GM changed to 12 volts on some cars. Probably they were trying to save money on wire, and they were hedging their bets about price and availability of copper during the Korean war. Nobody really expected the horsepower race to take off to the level it did. Compression ratios and displacement went sky high. There is only so much wire you can cram in a starter and, so in 1956 the rest of the industry followed, at least in the US.

 

I don't understand why anyone thinks running accessories engineered and built for a specific voltage on twice that voltage would be a good idea. You still need the same current. Granted there are some cars and some people who can't live without 12 volt accessory (maybe A/C or something), and it may make sense. It would definitely make sense on a modified car that has all 12v gauges, radio, heater, etc. The idea that every car should be converted because 12v is "better" is ludicrous. I used to believe that in the 70s. Not anymore. The laws of nature are working against you.

 

Edited July 3 by Bloo (see edit history)

[joe_padavano]

The real issue with lower voltage systems is the voltage drop caused by corroded or dirty connectors. In a 12V system, a 0.2V drop is only 1.7% loss. In a 6V system, that same 0.2V drop is a 3.3% loss. Sure, if your contacts are all shiny and clean, the 6V system works fine. If not, the higher voltage covers a multitude of sins. Is it a band-aid? Sure. Is the higher voltage more practical for the pragmatic? Yes.

[zepher]

The amperage issue and the wiring needed to carry that amperage is why even modern cars will be 24v systems, soon.

All of these infotainment systems and everything else in a modern car will necessitate the higher voltages.

[Rusty_OToole]

6v systems worked well and reliably for many years. In the mid fifties manufacturers changed to 12v mainly for cost reasons. Cars were using far more electrical accessories like windshield wipers, power seats, power windows, etc and had far more wiring. 12v cut the cost and the size of the wires in half. Batteries cost slightly more, everything else pretty much a wash. In practice the 12v systems were less prone to corrosion partly because of new vinyl coated wiring that replaced the old rubber insulated, cloth wrapped wiring. Starters spun faster and in general, the new system worked better.

 

But, the difference was not major. I have changed cars from 6 to 12 volts but today I would not bother. If you have a 6v car with weak starter, frayed wiring, dud battery etc. you are going to have to fix all that stuff anyway, why go to the extra trouble and expense of hodge podging it as well.

 

Or, if it is a big deal to you, just buy a car that came with a 12 volts system.

[edinmass]

35 minutes ago, zepher said:

The amperage issue and the wiring needed to carry that amperage is why even modern cars will be 24v systems, soon.

All of these infotainment systems and everything else in a modern car will necessitate the higher voltages.

It’s my understanding they are going to 36 volts.

[Bloo]

I've been expecting this. Time to update all those 12 Volt cars.

[arcticbuicks]

to 400-800 Volts.......like the new EVs

[ply33]

51 minutes ago, edinmass said:

It’s my understanding they are going to 36 volts.

20 or 30 years ago there was talk of switching to 48 volts. Benefits were reduced weight and lower copper wire cost as smaller diameter wire could be used.

 

However, near as I can tell, that effort died on the vine. I suspect getting all the myriad component suppliers to come up with new designs in a timely manner was a problem.

 

46 minutes ago, arcticbuicks said:

to 400-800 Volts.......like the new EVs

The main traction batteries are nominally 400 or 800 volt class. But all the "normal car" stuff like lights, power window systems, infotainment system, etc. are still 12v.

[TerryB]

Cybertruck low voltage stuff is 48v. 
 

https://www.motor1.com/features/704878/tesla-cybertruck-48-volts/

Edited July 4 by TerryB (see edit history)

[arcticbuicks]

tesla is just converting to 48 v also......to reduce wiring sizes

[Bloo]

I was expecting 48V because that is about the maximum "safe" voltage they could use without a bunch of extra engineering to prevent shock. I did not realize any manufacturers had already made the switch. 48 Volts is the voltage of copper phone lines and "phantom power" for stage equipment like microphones. It is generally regarded as safe.

 

Edited July 4 by Bloo (see edit history)

[ABear]

15 hours ago, Bloo said:

I don't understand why anyone thinks running accessories engineered and built for a specific voltage on twice that voltage would be a good idea. You still need the same current.

Actually it is same Wattage, not current to do the same amount of work.

 

It is better to use Watts Law when converting work between two different voltages.

 

See HERE for full Watts Law explanation.

 

P = Power in Watts

 

V = Volts

 

I = Current

 

You can use the pyramid in the picture below to make calculations.

 

Ohms Law and Watts Law go hand in hand with everything electrical/electronic.

 

The reason why you will use Watts Law in this example is a 6V starter and 12V starter will have different resistances. 6V starter will have a much lower resistance than a 12V starter meaning a 6V starter run on 12V will develop more HP and TQ and spin faster. It is one of the reasons why folks feel 12V is "better" but in reality you end up pushing that 6V starter past it's design limitations which may shorten the life of the starter..

 

So, if you know the rated power and the voltage you divide P (Power) by V (Volts) and result is I (current)

 

By the way, 1 HP (a measurement of work a horse can develop) is defined as 746W electrical equivalent so now we can compare physical work in electrical terms.

[Brass is Best]

If you are selling a 6-volt car that works perfectly everybody will call and ask if it is 6-volt. When you say that it is 6-volt they will tell you it is junk and needs to be converted to 12-volt. They will tell you this will cost more than the car is worth, but they will buy the car from you at half price. If you have a car that is supposed to be 6-volt. But has been converted to 12-volt everybody will call and say that it needs to be converted back to 6-volt for them to be happy and it will cost more than the car is worth. But they will pay you half price for it. Other than that, both systems work very well. The key is to have everything working properly and have a good battery. Old batteries that live on tenders tend to cause lots of charging issues. 

[ABear]

20 minutes ago, Brass is Best said:

If you are selling a 6-volt car that works perfectly everybody will call and ask if it is 6-volt. When you say that it is 6-volt they will tell you it is junk and needs to be converted to 12-volt. They will tell you this will cost more than the car is worth, but they will buy the car from you at half price. If you have a car that is supposed to be 6-volt. But has been converted to 12-volt everybody will call and say that it needs to be converted back to 6-volt for them to be happy and it will cost more than the car is worth. But they will pay you half price for it. Other than that, both systems work very well. The key is to have everything working properly and have a good battery. Old batteries that live on tenders tend to cause lots of charging issues. 

There are two "camps" at play.

 

#1 camp is what I would call "originalists", they want every nut, bolt screw, sheet metal, engine, transmission, tires, electrical system, down to the type of paint and primer under the paint to be the exact original OEM part that came from the factory floor with no exceptions. These folks will reject any and all variations from that original design or plan..

 

THOSE are the folks who are going to nitpick the vehicle to death in order to get the vehicle for free.

 

12V back to original 6V folks LIVE in camp #1

 

I have a absolute disdain for those in that camp as it is a 100% possibility that any vehicle older than 10 yrs will have at least one part that has been replaced with wrong color, wrong fastener, wrong tire, wrong electrical system voltage..

 

#2 Camp, where everyone else in reality lives, these are ordinary more modern thinking folks who would be OK with a few changes or even massive modifications as they know that time is often not kind to old objects and sometimes ones hand is forced to find and adapt items that are not "original" to the item in order to keep that item in working order.

 

These are the folks that may be OK with original 6V systems or even 6V to 12V conversions if done well but would like to also bring along some newer modern items that do not get along with original 6V Pos or Neg systems. Not to mention many 6V items which were very common and cheap many yrs ago, are no longer common or cheap now days and some are unobtainable with no direct substitute.

 

I live in Camp #2.

 

As an owner of a 120+ yr old EV that was converted from electric to gas within it's first 3 to 7 yrs of life, I deal with the realistic fact that there is zero hope of ever putting it back to original EV, the motor is gone, the wiring is gone the controller is gone the meters are gone the steering tiller location has been moved.. But yet I still enjoy having that car despite the fact that it will never, ever, ever be capable of winning any AACA awards for originality. And I am OK with that as it is now is what it was when I was growing up and I am thankful that due to my grand father and great grand father making that conversion and making it useful that car escaped being scrapped during WW2 scrap drives.

 

As far as I am concerned folks whining about a 6V system to 12V system conversion to buy the vehicle for pennies need to be grateful that they have an opportunity to buy and own that vehicle instead of whining and dragging it into the mud. A lot of vehicles would not be here if it wasn't for folks adapting and changing things to keep it usable.

 

I would be happy with a 6V system vehicle, and even a 6V to 12V conversion if it was done well, both systems can work.

[46 woodie]

Some new cars already come with two 12 volt batteries because of the high electrical demand.

[arcticbuicks]

having lived through the change from 6 volt to 12 volt cars and more equipment than cars......in a cold climate.....12 volts was a welcome change in cold weather.....even a perfect serviced 6 V unit just would not have the ability to start as well as a 12 V.........the cranking reserve or whatever science explanation.....6 V battery just wasnt there to give much cranking or speed........even my brand new cummins dodge with 2 -12 V batteries cannot start past a certain normal winter temp........and upgraded bigger cranking amp batteries help greatly to have enough power to cycle grid heaters at least three times before cranking engine

Edited July 4 by arcticbuicks (see edit history)

[Bloo]

 

 

6 hours ago, ABear said:

21 hours ago, Bloo said:

I don't understand why anyone thinks running accessories engineered and built for a specific voltage on twice that voltage would be a good idea. You still need the same current.

Actually it is same Wattage, not current to do the same amount of work.

 

You're not wrong, but I might not have been clear enough about what I was saying. If you want to run most 6 volt Acessories on 12 volts, you still need the same current you did on 6 volts, because it is a 6 volt device. To drop the 12 volts to 6 volts using a resistor, the resistor will need to dissipate the same number of Watts the device does. Therefore, double the power (Watts) to run the 6 volt accessory on 12 volts. The half dissipated by the resistor is completely wasted as heat. On the other hand if you substitute a 12v accessory for the 6 volt one then then yes, the same number of watts is needed. That subtlety is way too often missed in forum threads, and especially in threads about 6v-12v conversions, where it causes endless confusion.

 

I realize you didn't miss it and were talking about how Watts Law relates to any system, but it still needs to be said.

 

A starter is a special case. I was avoiding that subject because it leads to confusion. People often do get away with running 6 volt starters directly on 12 volts, where most other devices would just draw way too much current and burn out instantly.

 

 

[Restorer32]

We restored a 1918 Rauch and Lang electric. 84 volt motor. Not uncommon but I was surprised to see the headlites were 84 volt as was the horn and even the dome lite.

[Bloo]

They probably wouldn't have wanted to waste any power (Watts) in resistors.

[ABear]

1 hour ago, Bloo said:

You're not wrong, but I might not have been clear enough about what I was saying. If you want to run most 6 volt Acessories on 12 volts, you still need the same current you did on 6 volts, because it is a 6 volt device. To drop the 12 volts to 6 volts using a resistor, the resistor will need to dissipate the same number of Watts the device does. Therefore, double the power (Watts) to run the 6 volt accessory on 12 volts. The half dissipated by the resistor is completely wasted as heat. On the other hand if you substitute a 12v accessory for the 6 volt one then then yes, the same number of watts is needed. That subtlety is way too often missed in forum threads, and especially in threads about 6v-12v conversions, where it causes endless confusion.

 

I realize you didn't miss it and were talking about how Watts Law relates to any system, but it still needs to be said.

 

A starter is a special case. I was avoiding that subject because it leads to confusion. People often do get away with running 6 volt starters directly on 12 volts, where most other devices would just draw way too much current and burn out instantly.

No, you have it backwards.

 

A 6V "accessory" run on 12V actually will require the SAME "power" but the AMPERAGE required will be HALF provided that the 6V accessory is connected via a 12V to 6V "converter" to bring the voltage down to 6V.

 

A 12V accessory run on 6V with a 6V to 12V converter will require the same amount of WATTS, but the amps on the 6V side will be twice of what the amps are for 12V..

 

Very few 6V items are able to directly be connected to 12V without letting smoke packets explode out of the device. But you can buy voltage converters which handles this problem.

 

Using WATTS is key to understanding the current draw difference between voltage changes.

 

A 6V starter not rewired for 12V however, run on 12V WILL consume more amperage (double 6V amperage) at 12V and therefore the WATTAGE and amperage drawn will increase. That 6V starter motor will develop more HP and TQ in the process. The key to "getting away with it" is not running the starter to excessively operate for long times.

 

Reason being, a 6V starter will have larger ga wire, the large wire means lower resistance field coils and armature than a 12V starter.

 

Larger heavier wire in the 6V starter does allow for some "overload" for short periods of time before it to succumbs to letting smoke packets out.

 

You can't run 6V bulbs directly from 12V, you could however use a 12V to 6V converter, but once again, 6V bulbs are pretty much obsolete, not available in retail sticks and bricks stores and only available via mail order/Internet SPECIALTY auto parts suppliers at a premium price pretty much exclusively and even that is not a given that they are available..

 

However, you can typically find 12V bulbs for the most part which will fit the same sockets as 12V and you can go anywhere like auto parts stores and even Walmart and find a 12V bulb..

 

6V gauges can be operated on 12V provided you use a 12V to 6V converter or have them rebuilt for 12V.

 

To be very clear, I am not in favor of converting a WORKING 6V vehicle to 12V just for the sake of making it "modern". However, 12V systems ARE overall much more electrically efficient which means the wiring can be a lighter ga size, your switches contacts do not have to be as heavy either.

 

And by the way, I do know that a 6V starter can survive for many yrs being run off of 12V, my Dad owned a oil well drilling/pulling rig that had a flat head engine which had it's original 6V starter in it. It was the ONLY 6V item we had and never made sense to buy a 6V battery for it as we used it every three months using a spare 12V battery.. My Uncle built the rig in the 1950's, we used that rig up to when my Dad sold the well in the 1990s.. The 6V generator was disconnected and even the gauges were disconnected.. and yet the starter never let out any smoke packets..

 

Is it a good idea? Nope. Better to have it rewired but that also can be problematic..

 

If one is so polarized about originality of the electrical system then better to pass on it rather than low balling the seller.

 

There are plenty more of those vehicles floating around making it not worth getting your shorts all twisted up.

 

On edit..

 

I should add that efficiency is the main reason as to why we have 120V/240V AC systems and not 6V DC or 12V DC in our homes.

 

The PoCo generates a low AC voltage at the power plant level, they run that into a transformer at the plant that boosts the voltage which lowers the current required for the transmission lines to carry, but the lines still carry the same WATTAGE. That high voltage then runs through miles of wire to a local distribution transformer which drops it to an lower voltage, that increases the amperage the local wires will need to carry but the WATTAGE stays the same. That lower voltage is distributed to the transformer at you home down to 120V/240V and once again, the current delivered increases but the WATTAGE stays the same.

 

If it wasn't for the boost to high voltage power distribution and we were still using Edison's DC system we would need wires the size of your leg to carry the voltage up to a couple of blocks from the power plant. You would basically need a power plant within a few thousand feet of your home..

Edited July 4 by ABear (see edit history)

[Bloo]

5 hours ago, ABear said:

No, you have it backwards.

Actually no. Ohms law, Kirchoff Law(s) and Watts law always hold. I think we are going to have to agree to disagree here.

 

5 hours ago, ABear said:

A 12V accessory run on 6V with a 6V to 12V converter will require the same amount of WATTS, but the amps on the 6V side will be twice of what the amps are for 12V..

And now you are bringing DC-DC converters into the conversation. This is indeed a way to accomplish it, but you are now talking about converting DC to AC and then back to DC so you can use a transformer. Of course, once you have done that of course the rules still hold, but now you are running the device on the correct voltage.

 

This is the way of the future for sure, and probably the very near future, but I don't really believe it is going to work in antique cars with any sort of reliability right now. I have a fairly good idea how dirty old automotive electrical systems were before the manufacturers cleaned them up to run engine control computers. 200V spikes are not an uncommon thing on a 12v system. Most if not all of the currently available and affordable DC-DC converters are not ready to deal with that. I'm not going to trailblaze this option. I'll leave that to you and others. 🙂

 

You are also confusing the issue by speaking to it that way. People take an extra jump.

 

It has been posted several times in this forum over the years that that doubling the voltage on a 6v device will result in less current being drawn. In other words, running a 6v accessory on 12 volts will cause it to draw half the current. Watts = Volts x Amps right? I think we both know that interpretation is completely wrong. Watts Law, like Ohms law, just means that if you have two of the values you can find the third and it will always be correct. If you raised the voltage with the resistance remaining the same, you have raised the current (Ohms law, Volts = Amps x Ohms), and that changes the numbers you plug into Watts law.....

 

5 hours ago, ABear said:

A 6V starter not rewired for 12V however, run on 12V WILL consume more amperage (double 6V amperage) at 12V and therefore the WATTAGE and amperage drawn will increase.

 

Umm... no. Now you have brought starters into it <sigh>. Try with some actual hardware and let us know how it goes.

 

Starters are not pure DC devices, and all sorts of factors enter into it. Factors like back EMF, and the fact that a DC brush motor makes maximum torque and draws maximum current at 0 rpm. The effective resistance changes with RPM.  It also changes with heat. I took your position for years until maok told me I was wrong and I actually tested it. My 36 Pontiac drew 170 amps cranking on 6 Volts and 174 amps on 12 volts. This is why i don't use starters when trying to explain DC circuits. 🤪

 

The winding wire is not technically overloaded because all it cares about is amps. The starter is still operating at about double the Watts. Watts is power (and mathematically convertible to horsepower as you posted earlier). That power had to go somewhere. Did it all get converted to heat? No, some of that power got converted to horsepower, because the starter is spinning the engine faster. Definitely not all of it got converted to horsepower. The starter was only so efficient in the first place, and lost some power to heat/friction when running on 6 volts. Selecting the wire size and designing an electric motor's windings for a specific voltage, RPM, and horsepower is a pretty narrow target, or so I was told years ago by someone who did that for a living. It follows that a motor running on double it's design voltage will be less efficient than it is on it's design voltage, so the wattage dissipated as waste heat at 12 volts won't simply be double what it was at 6 volts, it will be somewhat more than double due to the lower efficiency. But it will still be far less than it would be if the starter were drawing double the current. This is why running a 6 volt starter on 12 volts is less bad than it appears at first blush, and why so many people are able to get away with it. I doubt you would get away with it on something like say... a blower motor, but I am not going to try it.

 

5 hours ago, ABear said:

The key to "getting away with it" is not running the starter to excessively operate for long times.

Yep.

 

 

 

 

 

Edited July 5 by Bloo (see edit history)

[edinmass]

I’m enjoying this thread……..probably more than I should. Electricity is a fun subject because in many ways it’s very abstract……..you can’t see it. Having been taught automotive electrical theory in both automotive technical classes, and college engineering classes one comes away with both how simple and basic most of it is. Like so many things…..going back to the basics and starting from “beginning” is very important. This week Phil and I fixed a 42 Lincoln coupe that had been converted from six to twelve volts. It had been in and out of a handful of shops, and as usual it was a mess. By the time it came to us, we had to figure out the running problems as well as why it would not shift using the overdrive. Where to start? Simple. Fix the running issues first……..then deal with the rest. The 12 volt coil conversion had burnt up no less than three times without the car ever driving down the road. Long story short, we fixed it using a DVOM and a test light. No wiring diagrams were used…….we chased down EVERY wire, terminal, connection, relay, and switch. We finally found the problem, and fixed the car. It took 46 hours of labor. Everything on the car works, and it runs and drives well. My two cents…….it should have been left as a stock six volt car. The reason it was converted? Hard to start hot. It would have been much easier to fix that symptom than to do the conversion.

 

Our 1936 V-16 Caddy is bone stock. Runs and drives fine, and starts easily hot or cold. Does anyone really think a retail customer spending 10k on a car during the depression would tolerate a car that was hard to start? Or put up with a no start condition? 

Edited July 5 by edinmass (see edit history)

[Larry Schramm]

14 minutes ago, edinmass said:

The reason it was converted? Hard to start hot. It would have been much easier to fix that symptom than to do the conversion.

 

Was the starter cables undersized, corroded, or bad connections? Or did it have bad grounds?

[edinmass]

1 hour ago, Larry Schramm said:

 

Was the starter cables undersized, corroded, or bad connections? Or did it have bad grounds?

 

Never got that far. It was converted and they couldn’t make the car run or drive. It had a new 12 volt starter, and new cables when we got it.

[ply33]

2 hours ago, edinmass said:

Our 1936 V-16 Caddy is bone stock. Runs and drives fine, and starts easily hot or cold. Does anyone really think a retail customer spending 10k on a car during the depression would tolerate a car that was hard to start? Or put up with a no start condition? 

I don’t think a retail customer spending only $500 to $700 for a new car during the Great Depression would tolerate a car that was hard to start either. By the 1930s that was pretty much figured out by all automobile manufacturers.

[maok]

8 hours ago, Bloo said:

Actually no. Ohms law, Kirchoff Law(s) and Watts law always hold. I think we are going to have to agree to disagree here.

 

And now you are bringing DC-DC converters into the conversation. This is indeed a way to accomplish it, but you are now talking about converting DC to AC and then back to DC so you can use a transformer. Of course, once you have done that of course the rules still hold, but now you are running the device on the correct voltage.

 

This is the way of the future for sure, and probably the very near future, but I don't really believe it is going to work in antique cars with any sort of reliability right now. I have a fairly good idea how dirty old automotive electrical systems were before the manufacturers cleaned them up to run engine control computers. 200V spikes are not an uncommon thing on a 12v system. Most if not all of the currently available and affordable DC-DC converters are not ready to deal with that. I'm not going to trailblaze this option. I'll leave that to you and others. 🙂

 

You are also confusing the issue by speaking to it that way. People take an extra jump.

 

It has been posted several times in this forum over the years that that doubling the voltage on a 6v device will result in less current being drawn. In other words, running a 6v accessory on 12 volts will cause it to draw half the current. Watts = Volts x Amps right? I think we both know that interpretation is completely wrong. Watts Law, like Ohms law, just means that if you have two of the values you can find the third and it will always be correct. If you raised the voltage with the resistance remaining the same, you have raised the current (Ohms law, Volts = Amps x Ohms), and that changes the numbers you plug into Watts law.....

 

 

Umm... no. Now you have brought starters into it <sigh>. Try with some actual hardware and let us know how it goes.

 

Starters are not pure DC devices, and all sorts of factors enter into it. Factors like back EMF, and the fact that a DC brush motor makes maximum torque and draws maximum current at 0 rpm. The effective resistance changes with RPM.  It also changes with heat. I took your position for years until maok told me I was wrong and I actually tested it. My 36 Pontiac drew 170 amps cranking on 6 Volts and 174 amps on 12 volts. This is why i don't use starters when trying to explain DC circuits. 🤪

 

The winding wire is not technically overloaded because all it cares about is amps. The starter is still operating at about double the Watts. Watts is power (and mathematically convertible to horsepower as you posted earlier). That power had to go somewhere. Did it all get converted to heat? No, some of that power got converted to horsepower, because the starter is spinning the engine faster. Definitely not all of it got converted to horsepower. The starter was only so efficient in the first place, and lost some power to heat/friction when running on 6 volts. Selecting the wire size and designing an electric motor's windings for a specific voltage, RPM, and horsepower is a pretty narrow target, or so I was told years ago by someone who did that for a living. It follows that a motor running on double it's design voltage will be less efficient than it is on it's design voltage, so the wattage dissipated as waste heat at 12 volts won't simply be double what it was at 6 volts, it will be somewhat more than double due to the lower efficiency. But it will still be far less than it would be if the starter were drawing double the current. This is why running a 6 volt starter on 12 volts is less bad than it appears at first blush, and why so many people are able to get away with it. I doubt you would get away with it on something like say... a blower motor, but I am not going to try it.

 

Yep.

 

 

 

 

 

The general rule of thumb with electric motors, voltage = speed and amps = torque.

 

The current draw of a starter motor is purely reliant on the mechanical resistance of turning the engine.

[edinmass]

Electricity is one of the most studied and researched fields in the world, and yet still its seems the most misunderstood by 99 percent of the people who use it countless times every day.

Edited July 5 by edinmass (see edit history)

[Frank DuVal]

16 hours ago, ABear said:

A 6V "accessory" run on 12V actually will require the SAME "power" but the AMPERAGE required will be HALF provided that the 6V accessory is connected via a 12V to 6V "converter" to bring the voltage down to 6V.

Nope, well, right if talking about a 12 to 6 volt converter from Amazon today, but Bloo was discussing a RESISTOR as the conversion device, a common automotive accessory in the 50s and 60s when converting a car from 6 volts to 12 volts. These 12 to 6 converters available today were not available back then. 😉🏎️🚒🚗

 

Don't forget there are conversion losses from these modern converters, so the watts used for the converter plus the 6 volt accessory are greater than when running the 6 volt accessory from a 6 volt system.😉🚋🚓

[Frank DuVal]

17 hours ago, ABear said:

However, 12V systems ARE overall much more electrically efficient

If the watts used by the accessory are the same, how is 12 volts more efficient? By the slight I²R losses of the wire? Not that much, so not "much more".

 

Yes. going from 6 volts to 120 volts does mean very very smaller wire! So mining less copper to make wire makes higher voltage more efficient? Guess so. Just ask any Brit! Europe does not use much in the 120 VAC range for residences, mostly 230 VAC.😉

Edited July 5 by Frank DuVal (see edit history)

[zepher]

Since high tension electric wires were sort of brought into this discussion, here is an interesting tidbit about them.

The voltage they carry is so high that the electricity travels on the outside of the wire only, this is called the 'skin effect'.

For that reason the high tension wires you see going from one massive tower to the next are actually using hollow conductors with an inner piece, such as steel, for strength but not for conduction of electricity.

 

[ABear]

22 minutes ago, zepher said:

Since high tension electric wires were sort of brought into this discussion, here is an interesting tidbit about them.

The voltage they carry is so high that the electricity travels on the outside of the wire only, this is called the 'skin effect'.

For that reason the high tension wires you see going from one massive tower to the next are actually using hollow conductors with an inner piece, such as steel, for strength but not for conduction of electricity.

 

I was wondering when someone would mention "skin effect"..

 

To clarify.

 

Skin effect does not happen in DC circuits, it is strictly a AC circuit thing.

 

Skin Effect is more related to AC circuits.

 

Skin effect is very little at low frequencies but as the frequency increases the more pronounce the effect will be.

 

Skin effect at AC grid frequency 50/60HZ is so small it is basically a non issue and it is also compensated for in large diameter wires by using smaller strands.

 

Skin effect at RF frequencies does become a problem.

 

So, since skin effect does not happen with DC, you might wish to be careful with adding more confusion to the 6V VS 12V thing..

[edinmass]

Ok boys……..simple question. What color is electricity? 🤔

[John348]

9 minutes ago, edinmass said:

Ok boys……..simple question. What color is electricity? 🤔

Electricity knows no colors, 

[joe_padavano]

[John348]

51 minutes ago, edinmass said:

Ok boys……..simple question. What color is electricity? 🤔

Actually, thinking about it some more electricity was and still is the color of green in my household considering the income I earned, pension and benefit's I still collect from have worked with it 

Edited July 5 by John348 (see edit history)

[Bloo]

1 hour ago, edinmass said:

Ok boys……..simple question. What color is electricity? 🤔

Purple. 🤪

 

 

[rocketraider]

4 hours ago, edinmass said:

Ok boys……..simple question. What color is electricity? 🤔

It's all according to how your boogaloo situation stands... or so saith the Wolfman.

 

I've seen white, electric green or blue, orange, pink and purple depending on what the surrounding atmosphere being ionized contained and what the relative humidity was at the time.

 

Static from breaking a 230kV or 500kV buss bar disconnect can create some fancy light shows especially in dry air.

 

But, electricity itself is like oxygen. Colorless, odorless and, in modern circumstances, essential to life. The colors and smells associated with it are from materials in whatever application it's being used for.

 

Back to original question: if components are sized correctly and connections are clean and tight, a 6v system will work fine on vehicles designed for it.