6/12 volt battery question

[jmiller_2308]

My 36 still has the original 6 volt system and I would like to keep it that way. However, after seeing the 6/12 volt batter from Antique Auto Battery it got me wondering if I could use two 6 volt batteries to run the car on but also use to genearate 12 volts for starting and to run misc modern accessories.

Would it be possible to connect two batteries in parrallel for 6 volt charging and to run the rest of the car (lights, guages, etc) and at the same time connect them in series to supply 12 volts for the starter and accessories? See my attached schematic for an idea of what I am thinking.

I know that if one battery is lower then the other it will drag that battery down but what other concerns might there be? Or is this something that in the immortal words of ghostbusters "would be bad"?

Jeff

[Bob]

This may or may not apply to what your doing, but this is my experience with heavy equipment 24 volt multi battery systems.

The best practise is to replace all the batteries at the same time.

On a 24 volt system it is possible to take 12 volts off it to run 12 volt accessories like radios. Unfortunatly it often seems to creat problems and the best practise is to tie into the 24 volt system with a 12 volt converter for trouble free installations.

[njlimbaugh]

Long ago, during my youth (and the days of kerosene-powered TV) somebody manufactured a device to do exactly what you have in mind. It was a relay that switched automatically between 6 and 12 volts, using 2 batteries, and (if my failing memory serves) kept both charged! Now. the question is, are there any still around? I'm not enough of an electrical guy to begin to design something like this, but if anyone out there knows an electical engineer or even a service man, I wouldn't think they would be that hard to build. The units I'm talking about were sold by Warshawsky in Chicago which is the same company as J.C. Whitney! Maybe they have some left on a shelf ?

[R/T]

Jeff,
I guess you've probably got this figured out by now but I'll post up anyway. If you follow the diagram you posted you could burn out your generator or cause your battery to explode. You have a direct short across both batteries in the 6 volt charging system.
I will be converting to a 12v system but using a voltage reducer I'll be able to keep my original 6v am radio and all gauges working properly. From my figures I should be able to convert for less than it would cost to have the 6v generator rebuilt.

[njlimbaugh]

I installed a 6 volt alternator on my '40 which works great. PMX Custom Alternators & Starters supplied the alternator, pulley for the wide belt and an adjustable universal bracket for just over $150. I had to get a slightly longer belt and tinker with the adjusting bracket but I've been very happy with the unit. Call Bill Jungck at 503-777-7172. He can supply 6 or 12 volt, pos or neg ground with single wire hook-up.

[bobc455]

One other option for your modern accessories is to keep your car completley 6V as it is now, but add a 12V deep-cycle battery and just run wires to the devices you want (i.e. stereo, GPS, cell phone, etc.). Then when you get home, throw a battery charger on the 12V battery. The deep-cycle battery can take the extended drain period, and as long as you don't go TOO crazy with accessories then it will last several hours between charges.

-Bob C.