6 to 12 volt

[Willowbilly3]

Converting an older 6 volt vehicle to later V8. I am thinking just run two 6 volt batterys in series and tap off one of them for my gauges and stuff. Anyone else doing that? Or any obvious reasons not to, that have evaded me? thanks.

 

[PA41]

Sounds like a good idea--prolly good amps from 2 batts for the starter. The only downsides there might be is cost and room and some complicated thinking.

I have dual batts on a couple pieces of equipment, and they are both different, and I have to study them pretty hard to not make a mistake messing with them.

PA41

 

[TudorP15]

Resisters

Just get some correct rated resisters and wire them into the back of your gauges to bring the 12V down to 6V for them to work properly. That would be cheaper, and you wouldn't have to worry about space, weight, and maintenance of two batteries..

 

[Willowbilly3]

Yeah, I know that's an option but also requires to change all the bulbs, heater motor ect. Plus under dash work which my body revolts to more and more all the time. I was have room under the hood to extend the battery carrier and run 2 smaller 6 volt batterys and thought that might simplify things for now.

 

[TudorP15]

Your call..

But Im not so sure it's the best quick fix. This is what I am thinking..
If you put two batteries in series to make 12 volts, I assume for better more reliable starting? This would mean that you would be putting your start load on both batteries, but separating them to power your accessories and gauges (in paralel with your gauges and lights, etc) so they will run off only one battery? This would cause your batteries to discharge at different rates, and the state of your batteries would constantly be changing and not in the same charged state. IMO, I think this would put allot of stress on your charging system, and one battery would over charge, or one would not fully charge. It could make things worse for you.

You would have to have some sort of isolator in them, so they will charge in paralel as one large 6v, but work at a 12v for your starting system. This would have your assesories run off both (in paralel) as 6v, but the starter run off both (in series) as a 12v.

I think it can be done, but sure would complicate your electrical system..

Resistors for the gauges, and changing lamps to 12v are allot quicker and simpler solution IMHO. The fan blower will work fine on 12v. I have been running my 6v fan motor on a 12v system for over 10 years with no issues..

Just my 2 cents..

 

[Willowbilly3]

The engine would be a later model, from a 71 Econoline and be a 12 volt starter and alternator already. I had heard once that some of the old time rodders used to tap into the top of the tar top 12 volt batterys to pull off 6 volts for the rest of the vehicle, that's what got me thinking. I'm not sure if the one battery would over charge, the voltage regulator will see total voltage and charge accordingly so that might be right, that's the part I was wondering about. I was hoping to hear from someone who had actually tried it, the theory part I understand.

 

[TudorP15]

I've heard..

I've heard of people doing it on an occasion, but if memory serves, they regretted it, because it was simply a hassle to deal with the two batteries, but they were also using isolators that might have been better and safer. Old school, yeah, I bet they did just that with the battery. My dad was an old school hot rodder, and he told me stuff they used to do. Some, scared the hell out of me, hahhah... One thing I remember when I was 19 years old, driving my 49 Plymouth coupe. I was stuck on the side of the road. Dead battery, and it wouldn't start my car. An old school hot rodder saw me there, and stopped to help. He was running 12V, and I was running the original 6V. I thanked him for stopping, but he wouldn't be able to jump me because of the voltage difference. Now, this guy was old school, and was about 3 or 4 hundred years old,lol.. He replied, "Oh, ********, I can jump ya..." this old guy pulled the caps off his battery (before no maintenance batteries). He stuck a screw driver down in the 3rd cell, clipped jumper cables to the post, and to the screw driver shaft, and to my battery. He said "there ya go young fella, you got 6 volts, get in and crank that son of a bitch..".. I did just that, and it worked like a champ, and cranked my coupe.. I laughed, and said, "I love the old schoolers.. "

But anyway.. I wasn't trying to be a know it all.. I just would hate to see ya go through all that, and find out it don't work as well as you hoped. The resister, and bulb change thing, really isn't too much a pain. Less so, than dealing with the dual battery set up anyway..

 

[Outlawracer]

Used to be done on big rigs. They had a 24 volt starting system and 12 volts for accessories. You would have to run a parallel switch. They were more of a pain than good. The main reason you don't see them anymore.

 

[Willowbilly3]

I have put series/parallel on old farm trucks way back when and been around them on trucks and equipment. This isn't the same thing. Those kept the 6 volt charging system. Basically the 6 volt batterys were in parallel except the starter got 12 volts (or 12 and 24). They were complicated and problematic. This would be a lot simpler. I appreciate the advice. So far what I'm hearing as the main drawback is the hassle of 2 batterys. Although I don't see what would be a huge hassle about 2. One battery isn't any problem and multiply that x 2 still equals not much hassle.
If the gauge resistors are easy to find and install, how about some specific info on where to get them and how/where you who have done that put them. I looked into it once and the guy at the auto electric store told me I had to know the specific draw of each item to know what value of resistor to use. Is that accurate?

 

[TudorP15]

Yeah, pretty much. But, most of that is pretty much common. Hang out at a classic car place, or club, and you will see that it is very common, and most those guys will tell ya exactly what values of resisters you will need, and where to get them. I used to be able to break it down and value it but it has been so long since I got into that, I would have to really dust some brain cell cobwebs off, lol.. As far as installing them, I just soldered them on the back of the gage itself.

The biggest thing, is not as much the draw of the gage, altho it does play a part. But, basically it really doesn't matter. All you want to do is take a resistor that will burn off half the voltage (connect 12VDC to it, and it brings it down to 6VDC). The current, just as long as there is enough current available, the gage will only use what it needs. So, what he said is true to an extent, but it sounds more like he was trying to make it sound more complicated than it really is. You just need a value resistor that will give ya a voltage drop of 12v to 6v. You can probably look up the value on the internet in some vintage auto sites, etc.

I still think your biggest problem with dual battery set up for use of the two separate voltages would be keeping them at the same charge state. Also, doing it without an isolator could end up being a fire hazzard. I would hate to see a cool car burned down. I have seen that happen on squirly battery systems more than a couple times. Can ruin an otherwise fun weekend..

I have put series/parallel on old farm trucks way back when and been around them on trucks and equipment. This isn't the same thing. Those kept the 6 volt charging system. Basically the 6 volt batterys were in parallel except the starter got 12 volts (or 12 and 24). They were complicated and problematic. This would be a lot simpler. I appreciate the advice. So far what I'm hearing as the main drawback is the hassle of 2 batterys. Although I don't see what would be a huge hassle about 2. One battery isn't any problem and multiply that x 2 still equals not much hassle.
If the gauge resistors are easy to find and install, how about some specific info on where to get them and how/where you who have done that put them. I looked into it once and the guy at the auto electric store told me I had to know the specific draw of each item to know what value of resistor to use. Is that accurate?

 

[Willowbilly3]

Thanks. I will probably research this more and see what I can come up with. Maybe the resistor from a 70s Ford pickup instrument cluster, I think they cut it down to 5 volts. I would probably take the amp gauge out of service as I usually like to install a voltmeter somewhere in my vehicles.

 

[cherokee_64]

Here you go:

http://www.how-to-build-hotrods.com/6v-to-12v.html

 

[Blue Eyed Devil]

You don't need to know specific draw. Early gauges aren't that picky. All you need is a simple voltage reducer. You can buy a "Runtz" resistor from Speedway for $17.99. Here's a link - http://www.speedwaymotors.com/12-Volt-to-6-Volt-Reducer,2374.html

OR... If you are electronically inclined you can build your own for much cheaper. Here's a link for that - http://www.jalopyjournal.com/forum/showthread.php?t=448038

There ya go...

 

[TudorP15]

Thats the ticket...

You don't need to know specific draw. Early gauges aren't that picky. All you need is a simple voltage reducer. You can buy a "Runtz" resistor from Speedway for $17.99. Here's a link - http://www.speedwaymotors.com/12-Volt-to-6-Volt-Reducer,2374.html

OR... If you are electronically inclined you can build your own for much cheaper. Here's a link for that - http://www.jalopyjournal.com/forum/showthread.php?t=448038

There ya go...

....................

 

[Willowbilly3]

You don't need to know specific draw. Early gauges aren't that picky. All you need is a simple voltage reducer. You can buy a "Runtz" resistor from Speedway for $17.99. Here's a link - http://www.speedwaymotors.com/12-Volt-to-6-Volt-Reducer,2374.html

OR... If you are electronically inclined you can build your own for much cheaper. Here's a link for that - http://www.jalopyjournal.com/forum/showthread.php?t=448038

There ya go...

COOL!! Thanks, that is just what I was hoping for, something solid. Funny thing I go through the speedway catalog from cover to cover and never saw those.

 

[R Pope]

I have run two 6v's like you describe with no bad effects. Ground the negative post on one battery, hook a short cable from the positive post to the negative on the other battery and the 12v positive draw is the other post. The 6v draw goes to the jumper between the batteries.
It would seem that one battery will discharge more than the other, but in the real world it seems to work fine. The only problem you might encounter is if the 6v system was positive ground. Then you have to swap the wires on the ammeter so it works the right way.
With this setup, the ammeter doesn't work exactly right, only reading what is going on in the 6v system, but it works well enough, especially if you use a voltmeter too.

 

[Willowbilly3]

Thanks R Pope, It's good to hear from someone who has actually done it. I don't have plans to use the existing ammeter. I will install a voltmeter.