6V & 12 V together

[janan5243]

I posted on this topic previously & got some good ideas & opinions & options. I'm going to use to Optima 6V's in series. One will be tapped off for original 6V equipment. Will use second tap for 12V equipment. I'm going to switch to Neg. Grd. so I don't have to worry about isolating grds. Going to convert to alternator. Trying to find out if a 12V alternator would pose any problems with the 6V stuff. Anybody with any experience in this out there?

[desoto1939]

With the cost of two Optima batteries would it be cheaper just to conver the entire car over to 12v and then only chnage what need to be change with a volt reducer.  Now you could then use a 12 v alternator and then run 12 v headlights for all of your night driving?

 

Rich HArtung

[TodFitch]

What is your reason for wanting 12v? If the current draw is not too high (a couple of amps or less at 12v) then a +6v to -12v inverter/converter is probably the cheapest way to go. No replacing lights, batteries, generator/alternators, etc.

[48mirage]

I did exactly as you did several years ago, but found it a little troublesome.  You will find that the alternator will have a small continuous draw on the batteries.  I solved this by installing a latching relay that would open the battery circuit.  You will also want to build a buss for the 2 separate voltages.  Look at Blue Sea dual buss bars.  They are built for the marine market but I found a simple one that worked for me.  As time went on I found my 12 volt load continued to grow.  Heater blower, starter, brake lights, headlights, modern radio.  I still run a dual voltage system but I have gone to a 12 volt battery with a GM 10SI single wire alternator and I step down the voltage for the ignition and the remaining 6 volt system with a voltage reducer from www.koolcars.us./catalog.html .  Even this system has it's limits at 20 amps.  I put in a fuse ahead of the voltage reducer to keep from burning it up.  I found that running the 6 volt defroster and the 6 volt wipers at the same time would overload the voltage reducer and burn it up.  The fuse protects the voltage reducer now, I just have to make a decision which I need more, wipers or defroster.  I don't think the operating loads are that high but both motors have a starting spike that creates the problem. 

Edited August 1, 2014 by 48mirage

[greg g]

are 35/45 watt 12 volt head lights brighter than the 35/45 watt 6 Volt ones they are replacing???  If light output is a problem why not just mount some auxiliary lamps with either fog lenses or driving lenses, depending upon where you think more lumens would be helpful.  And remember the National Safety Council reminds you to drive slower at night and increase your following distance.

[Plymouthy Adams]

watts is the expressed value of current times voltage in operation ie power consumed....lumens is the measure of intensity/brilliance...candle power if you will by the old term..

 

this chart will come close to expressing lumens in watts....but you cannot use this as a guide for headlights as the parabolic shape of the reflector concentrates the beam and projects it forward..so watts is again just a measure of consumed power

 

http://www.clarkhoward.com/watt-to-lumen-lightbulb-conversion/

Edited August 2, 2014 by Plymouthy Adams

[greg g]

Oh drat your foot candles, Adams.  Never said I was the brightest bulb in the drawer.  Perhaps the reason that people think 12v bulbs are brighter other power in power out factors being equal, has more to do with this, bulbs that produce light closer to the color of daylight (color temperatures above 3000K) may appear brighter because the color of the light is less yellow, rather than an actual difference in actual illuminal (how's that for a word) power.  Plus we all know it has nothing to do with the fact that as we age we see less well.....................

Edited August 2, 2014 by greg g

[Plymouthy Adams]

Greg again you bring up a point that I did not want to really get into and that is the very color of the light being projected...that also has a very big impact on visibility...but I think the very question here is watts in general 6 volt/12 volts...the voltage and amperage is different but the very consumption of power is equal thus the use of wattage to compare and in the back of my mind it boils down to the question of what guage wire to run for their circuits when upgrading..that is a very easy to find chart on the internet and posted here in the past by myself..it will be listed by amperage, length of run and these values ARE different on 6 verses 12 so be sure to download the correct chart...the industry has not moved to higher voltage as like the aircraft industry and other military applications where higher voltage is less power and smaller wires...but we have moved into the realms of shared buss and making retrofit of stuff almost totally impractical..

[janan5243]

Thanks for the input. I am considering this change because of MODERN CONVENIENCES. My lights are actually quite bright at night, even with my 70 year old eyes. Only problem I had was with starting & after cleaning battery clamps, terminals & posts, problem was gone. As far as wiring goes, 6V uses twice the amperage of 12V, so wires are heavier gauge. When rewiring or adding electronics or electrical parts, it is important to know necessary wire & fuse sizes. I have to research voltage reducers. I've seen posts about them, Don mentioned them & 48Mirage mentions his system which is what I am considering. He has problems with overloading the reducer. Do they make larger ones or do you have to use more than one? As parts fail I would probably convert each one to 12V. My wife & I opened a hardware store in the village of Schoharie after Irene flood in 2011. I'm here 6 days a week till it starts to make money(soon I hope) so I don't even have time to install 6V to 12V convertor I bought week after buying car to have tunes in car. Using I-pod with Bluetooth speaker for now.

Edited August 4, 2014 by janan5243

[wayfarer]

One subject that I have not seen addressed is the condition of the existing wire...how good is the insulation after 65 years?

Although not a Saturday morning job, I would rewire the car and use a 'kit' that allowed for what ever potential additions I might contemplate.

This would make the 12v part easy and then individual volt drops/resistors could be used where needed.