I have a (probably dumb) question: can you retain the original 6V positive ground system on a '51 Ford, but also use a 12V battery (trunk maybe) to run a radio, A/C, other accesories (neg ground)? How would you do this if you had the time/inclination?
keep the 12 pos and neg wires in their own loop, don't ground any 12v stuff to the frame and you'll be fine , except for recharging when on the road
Yes, you can. You would need to wire two separate electrical systems. In other words, two batteries ( 1 six and one 12) and two generators/alternators. The cicuits would share nothing in common. Neither electrical system would know that the other one was there. It would be as if a car with a 6 volt positive ground system touched bumpers with another car with a 12 v negative ground system. As long as your radios/stereos/etc were truly on a separate electrical system it sould be fine.
put the 12 volt in the trunk and run an altenater to the drive shaft,and let me know how it works so i can do it,lol.
How about just installing the 12V battery in the trunk and a trickle charger too so you can charge it each night or once a week as needed? I've known many guys over the years who did this without problem for radios, CBs, etc. A lot simpler and cheaper than 2 separate electric systems and makes more sense too.
Thanks for the advice... what I'm thinking of doing is installing a bat box in the trunk, install a 12V Neg ground bat (isolated), run wiring to the A/C, radio, alarm & other accesories. I had read on another site that you could also put in an additional starter solenoid/starter button and start the car using the 12V bat, but I don't think that would work for my application seeing as I don't want to make it a 12V pos ground system.
That battery in the trunk can be grounded to the chassis )negative ground) even though the rest of the car has a positive ground system going. It is just like you had a big 18 volt battery, and you put a nail in at 12 volts. And the nail is really your chassis. One part of the battery (the 6 volt end) thinks it has a positive ground, and the other part (the 12 volt end) thinks it has a negative ground. Your stereo, etc would be mounted to the chassis/body in the normal fashion so you don't need to isolate it from the chassis. You can recharge the 12 volt batter by mounting a second alternator or by using a trickle charger, as someone else suggested.
I concur about the "boom" box system and of course a separate battery with no alternator charging would never hold up an A/C system at all, so there are simple parameters to work with. Any thought of modern ghetto-style music systems or A/C should take place with the idea of a 12V Neg. ground conversion for the vehicle.
As stated, A/Cs will take A LOT of juice, the blower will of course take a lot of juice, and even though it is easy enough to overlook, the a/c clutch takes a lot of juice also. IMO, unless a person were to carry a lot of batteries, an a/c system would probably suck a battery in less than an hour. Something to consider, when a battery gets low, an a/c clutch will start slipping and destroy itself "right now". IMO the plan will not work without an alternator/generator, or some means of charging that 12V battery. On the other side of the coin, changing my 55 Lincoln from 6 pos to 12 neg was easy-cheezzy, and dirt cheap by using an GENERATOR and regulator from a 65 Falcon.
My experience of having a mixed system, part 6v part 12v has taught me a lesson. I'll never do it again, will always go to 12v for everything.
Stop and think! Exactly what 6V parts are you needing to KEEP?? If you are talking only engine parts, that is all easy and cheap to change, far easier than building a double system. The ground means nothing except if you are running an original radio...I don't know what problems that has! A '56 generator (or easy to get alt conversion) and a '56-63 12 volt coil, plus an instrument voltage regulator from a 60's Ford and a hatful of lightbulbs, and you are done in an easy Saturday afternoon. MUCH easier than building a complex rat's nest of a double system.
I second the convert the car to 12 neg ground idea. All you have to do is put an alternator on it, and have the starter freshened up, it doesn't care about the voltage applied if it's in good nick. A cobbled up, twin system will be a headache wherever you go.
OK, OK, you've all convinced me of the inherent "good" things about converting to 12V... the starter (and generator) was rebuilt at the same time as the engine, which has less than 300 miles on it. I guess that's the way to go, seeing as I do need A/C in this heat - 108 degrees at the moment. I was thinking of getting the factory radio converted to 12V - http://www.radiosforoldcars.com/enterpwF.htm I'll tackle the car conversion in a few months, after getting all the parts I need for the restoration (new wiring, new water pumps, maybe a couple of 9 Super 7 carbs to replace the Strombergs I have - leaking gas, and any other chrome parts that are still missing).
For my radio I bought a "good" voltage step down from Ron Francis. The starter should be fine as is. As far as the gen goes, a later model 12V with reg will install painlessly. The Falcon gen I installed bolted into place with a 1" spacer for the rear mount, and by changing the Falcon pulley in favor of the Lincoln pulley. Easy-cheezzy... For the guages I used a stock Ford guage voltage drop (I think EC-1 or EC-7 from NAPA) for a late 60s early 70s Mustang, guages work great except the ammeter works backward. This can be fixed by reversing the wire through the shunt... but I have not done that yet.
Change the whole system to 12v it is relativly easy, cheap enough, takes little time and you will like driving your car a whole bunch more, I did it and I still smile everytime I turn the key and it starts right up...GM 1 wire, no Gen, no Reg. 1 reducer to gauges from a early Mustang, simple, simple, simple, unless you are running an all original car and want to leave it that way I can't think of any good reason to leave the 6v system in it... mine still looks orignal. <<<<
Everything is original in the car except for the double carb intake (Stromberg carbs) I installed - originally had a single Holley carb. It seems that as longs as I'm going to install an A/C, might as well upgrade the charging/electrical system like you've all suggested.
The Jalopy Journal
