What effect of 12volt batt used on electrical system


IHC in the early to mid-fifties.

Golden Jubilee
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Post Thu Jan 17, 2013 8:48 pm

Re: What effect of 12volt batt used on electrical system

I had this posted years ago on this site before it had gone thru all the software and server changes. I"ll post one more time:
Changing operating voltage of vehicle




Many questions arise about changing older trucks from 6 volt to 12.
The issues that must be addressed are the same regardless of weather the change is from 6 to 12 or 24 or the other way around.
Most starter motors will function well enough on voltages above or below their rated voltage. However, when series motors are operated on too low a voltage, the current draw will increase to the point where there will be motor damage. This is because current draw of a series wound motor are a function of speed. The slower the speed, the higher current draw. Because starters are only used for a short periods they can often absorb a little excess heat. Running a higher then rated voltage the starter will develop more torque and get up to speed faster, so there will be little damage. Once at a slightly higher speed then normal, the current draw drops to near where it would be at the rated voltage. The solenoid switch used to control most starter motors, should be of the correct voltage for the system being used. They will tolerate double the voltage but not for long. There are two kinds of solenoid switches: momentary and continuous duty. Momentary are used for starters.
Parallel wound motors, fan, wiper etc are different then series. In this case, the impedance (the resistance of the motor) doesn’t change as much with speed, so if you double the voltage, you will double the current flow through the windings. Most motors will not stand this for long, and either the windings will get hot enough to burn the insulation, or will get hot enough to throw the solder off the commentator. For this reason, it is not recommended that they be run above their rated voltage. Motors of this type don’t do so well when combined with dropping resistors because their current draw is not constant, but varies. It is high when starting and tapers once the motor gets up to speed. A resistor that provides the correct resistance at running speed would be too much to start the motor, one that would be correct to start the motor, would not be enough at running load. Wipers, whose load varies while running, low mid sweep, high at either end can be especially hard to adapt. When working with these type motors the best thing is to replace with a motor rated for the voltage being used.
Light bulbs: These are often the primary focus of the un-informed when making a change in voltage. They are the easiest to change and most function very well when combined with dropping resistors. Most common bulb types are available in 6, 12, and 24 volt types. There are a few special bulbs that are hard to find in a different voltage. These can be easily adapted with resistors in most cases. In most cases, all that is required is to replace the bulb with one of the correct voltage.

Gauges: These are often the easiest to destroy and the hardest to repair. Nothing looks worse in my opinion, then an older vehicle with modern gauges stuck somewhere on or in the dash. Older dashboards often had very nice gauges. They can be mechanical, in which case, the operating voltage doesn’t matter or electric. Nor does it matter for the ammeter, which only measures current, not voltage. The only time an ammeter can become an issue is if the new charging system will exceed the current rating of the meter or if the ground polarity is changed. All electric gauges function as mil-ammeters. They measure current flowing from the ign feed though the sender and back to the battery. If you double the voltage, the current will double. Some, like AC gauges use two coils that “buck” each other. So if you double the voltage, it doubles on both sets of coils, so the reading of the gauge will not change much but the windings will not be happy because they are being asked to handle twice the current. However, the King-Seeley gauges used in the K series and others work different. They are “thermal” type. A bi metallic strip attached to the pointer and wrapped by a winding of Ni-Chrome wire. Current flows through the wire and though the sender unit to ground and back to the battery. Too much current, and the Ni-Chrome wire will burn though. Ni- Chrome cannot be soldered or repaired other then mechanically. If you shorten the wire, you change the calibration of the gauge. If you shorten it too much, it will overheat and can burn through again. The best repair is to re-wind with the correct wire. Ni chrome is resistance wire and as current passes it heats up and warms the bi-metallic strip which moves the needle. It takes special skill and wire to repair these type gauges. They cannot withstand double their design voltage, even for a short period. For this reason, they must be protected. Because they work by the varying current, adding resistance to the circuit will change the calibration of the gauge. In later trucks, when they went to 12 volts. They added a current limiter to the power feed to the gauges. It drops the voltage but allows for the varying current. Gauges are most likely the hardest thing to adapt when making a change.


Ignition: Coil, condensers are voltage specific. The easiest way to adapt is to replace with one of the correct voltage. Coils are also polarity specific and need to be corrected if the ground was changed. 6 volt coils do not need ballast resistors, 12 volt coils might. There are two types of 12 volt coils, internally ballasted and externally ballasted. If you use an internally ballasted coil no additional resistor is required, if you use an external ballasted coil, a resistor is required. The resistor is bypassed during cranking due to the lower voltage available. Do not think that adding a ballast resistor to a 6 volt coil that you have made a 12 volt coil. It will work but will overheat the coil at sustained high speed running. Replace the coil with the correct voltage coil.


Charging system: Most opt to replace with a “one wire” alternator. With this type, that alternator and voltage regulator are combined and only one heavy wire to the battery is required. If this type is feed thru the original ammeter, it should be sized so not to be too big for the ammeter. The disadvantage of this type of alternator is it senses the system voltage at the alternator output terminal, any voltage drop through the wiring and the battery can be undercharged. It also relies on the residual magnetism in the rotor to “turn on” the alternator. This can require higher speeds the then generator it replaces. To get it turning faster, smaller pulley on the alternator is required. The smaller the pulley diameter the less Hp it can handle. Older trucks had 30-40 amp generators if 6 volt and 20-30 amp if 12 volt. Remember, doubling the voltage mean you half the current for the same work. So… if going from a 30 amp 6 volt generator to a 60 amp 12 volt alternator the load on the belt will increase by 4 times but you have to use a smaller pulley. This can mean short belt life or slipping belts. A better choice would be to use a 12 volt generator and regulator set for around 20-25 amps. The generator can use the same pulley and wiring and will not overload the belt. It will also “look correct” for the year. Many 6 volt systems were positive ground, most but not all, alternators are negative ground. So often, the vehicle gets both a voltage and ground change at the same time. Generators do not care which ground is used, but alternators do. Hook an alternator up backwards and it is junk. Some alternators are “case neutral” meaning the case is not electrically connected to either terminal of the alternator, and that alternator can be used for either ground system. There are also positive ground alternators. A generator charging system consists of a generator, and regulator. The regulator turns the generator on and off and keeps the voltage AND current in safe range, an alternator charging system consists of an Alternator and voltage regulator. The alternator is “turned on or off” by the regulator via the ign feed by the stator voltage, in case of one wire alternators. A current regulator is not required because of the self-regulating design of a/c alternators. A generator voltage regulator can be used to control and alternator but not the other way around. This is because two circuits needed in the generator circuits are not needed in the alternator. 1st is the reverse current relay, this disconnects the generator from the battery if the generator is not producing current. A generator will “motor” and quickly discharge a battery if left connected while not being turned. 2nd is the current regulator. Generators will put out more current then they can handle, so must be regulated so not to damage themselves if the draw is more then the rated output. So, which is better?.... Neither is better, they are different ways of keeping the battery charged. Generator systems are very forgiving, they can except voltage spikes and reverse voltage and still work fine. It is not un-common to find 60-70-or even 80 year old generators working just fine. Alternators are common now a days and are cheap. They also can be more compact, putting out large amounts of current in a small package. They are very susceptible to voltage spikes and reverse current. They also need smaller pulleys and load the belts harder then generator systems.


Some have labeled me as anti- 12 volt… That is not true. I am against changing the voltage from the design voltage because it is very hard to do correctly. Much damage has been done by half-assed jobs. There is rarely a good reason for the change. If you look back over what I have written, you will see there is much to be changed. The 3 most common reasons I hear for changing 1st , my engine cranks slow/hard to start/ dead battery, 2nd I want good lights, 3rd I want to add a modern accessory (radio-cell phone charger etc).
1, fix your truck! If it cranks slow etc etc check the wiring, it most likely needs to be repaired. 6 volt takes twice the current to do the same work as 12 volt so needs twice the copper. Many battery cables have been replaced over the years with whatever the auto-parts store had… NO GOOD replace with 0 or 00 gauge cable both the positive and negative side. Run separate grounds to the chassis and block. 2, when 6 volt sealed beams were the norm, 35 watts was the size weather it was 6 or 12 volt. Now most headlights are at least 55 watts. 6 volt halogen 55/60 watt bulbs are available, install them and be surprised how good 6 volt headlights can be. 3, there are very small 6-12 volt converters for low amp draw accessories and they are cheap. Some can even be “cascaded” so you can go from 6 volt positive to 12 volt negative. Most will handle a normal stereo radio but not a “killer radio”. All of these “fixes put together” are far less money and time then addressing all the changes needed to change the voltage of a vehicle. If I were going to use voltage converters for modern acc, I would recommend changing to neg ground. That way you do not need to “cascade” the converters and no damage will be done to any of the original motors or gauges. Only the amp gauge needs to have the wires switched so it reads correctly. The generator need to be re-polarized (just need to jump the wires on the regulator momentarily to magnetize the field poles. You may also want to change out the regulator as they are usually marked as to polarity and while the work either way, they work best on the correct polarity. ( this is for mechanical regulators- electronic replacement regs need to e correct). Only the most picky judgeing contest will even know the ground has been changed. It will look stock.

The only good reason I can see for making the change is if you are putting a modern engine in an old chassis. It is hard to find a 6 volt starter for a small block Chevy. LOL even here, you must weigh out the changes needed. If you want the truck to be “all original” except for the engine, (original gauges, wipers etc) it might be worth having a 6 volt starter made, and converting the ign on the modern engine to 6 volt. As a last ditch effort, there are alternator systems for heavy trucks that have two outputs,12 and 24 volts, In the 70’s 24 volt starters were used on some big trucks. These alternators are 12 volt alternators with 2:1 step-up transformers and another set of diodes. It could be possible to reverse the windings and get a 6 and 12 volt alternator, but you would need two electrical systems, one 6 volt and 12 volt.,

Yard Art
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Post Fri Jan 18, 2013 5:25 am

Re: What effect of 12volt batt used on electrical system

Thanks a lot Cornbinder...I appreciate your time and effort and wisdom. I don't have any plans to convert to 12 volts...I was mostly just wondering if they guy did any damage by trying to start the engine with a 12 volt. I will always use 6 volt.

Thanks,

Neal

Rusty Driver
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Post Fri Jan 18, 2013 6:37 am

Re: What effect of 12volt batt used on electrical system

:roll: Recently acqiring an S line that had been coverted from 6 pos ground to 12 neg, i whole heartedly agreewith Cornbinder, you will probaby end up with a half assed rig. :| In addition, there is a good chance that your origional guages will be toast and not be able to be brought back to life.
Driving an old R line for years with a 6 volt system never caused any issues as long as appropriate maintenance was proformed. These systems worked for years and years and worked well.If yours isnt working well read his post again as it is all there. If u need to throw something in the cab that needs 12 volts there are converters out there that can be concelled ( Newport Engineering) and they work quite well.
Thanks for putting your article on here Cornbinder, it says it all. :D

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Post Sat Feb 16, 2013 3:43 pm

Re: What effect of 12volt batt used on electrical system

Idk if this will help any or not but I have a 1957 S-110, the old body style. It's all original, generator and everything and 6v as far as I know. I just put a 12v battery in it and have run it like that for almost 14 years since my grandpa gave it to me as my first vehicle. I have no problems with it, it's starts and runs and everything and have never had to replace anything on it.

Golden Jubilee
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Post Sat Feb 16, 2013 4:32 pm

Re: What effect of 12volt batt used on electrical system

IHCskilling wrote:Idk if this will help any or not but I have a 1957 S-110, the old body style. It's all original, generator and everything and 6v as far as I know. I just put a 12v battery in it and have run it like that for almost 14 years since my grandpa gave it to me as my first vehicle. I have no problems with it, it's starts and runs and everything and have never had to replace anything on it.

A '57 should be 12 volt from the factory . If it were 6 volt and you did nothing to the chargeing system it would have damaged the regulator and genny by now, not to mention the battery would never get re charged.

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Post Mon Feb 18, 2013 12:37 pm

Re: What effect of 12volt batt used on electrical system

Oh ok I guess I didn't really think about it or really even know what year they started 12v systems. I guess I was thinking that because it had a generator that it had to be 6v.

Golden Jubilee
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Post Mon Feb 18, 2013 1:57 pm

Re: What effect of 12volt batt used on electrical system

Alternators came popular in the early 60's with the advent of cheap(er) diodes although they did exest before that time. Generators were made in 6,12,24 and other voltages. The tag color on the generator will tell the voltage (on Delco's) black= 6 volt, Red= 12 volt, Orange is 24 volt or higher (32 or 36).

Rusty Driver
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Post Sat Feb 23, 2013 5:31 am

Re: What effect of 12volt batt used on electrical system

Neal, my experience with putting 12 volts to a 6 volt system was I created more problems than I solved. If you can get the truck in some place you can work on it, do that. Go through the entire system, and fix anything that might go wrong. Idea being, once you get it running, won't you want to drive it for awhile? This way you can, without too many breakdowns to contend with. Just my 2 cents worth. Bill

Golden Jubilee
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Post Sat Feb 23, 2013 7:03 pm

Re: What effect of 12volt batt used on electrical system

Use of an 8 volt battery requires re-setting the voltage regulator as well as the reverse current relay cut in voltage. Not for the electrically inept. Failure to do so can cause damage to the chargeing system and will prevent proper chargeing of the battery. Many feel that 8 volt batterys are the worsed of both worlds, others dis agree. Bottom line is 6 volt was the norm for the 1st half of the last century and it worked.
My take is: a properly maintained truck will start and work just fine with its orignal system.
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Golden Jubilee
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Post Sat Feb 23, 2013 8:39 pm

Re: What effect of 12volt batt used on electrical system

I agree with CB. As for getting things to work better with the 6 volt systems, I would make sure everything is in good working order and the battery cables have good contact AND are larger than original 0 or 00 will work quite well.
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