Starting a 6V car with a 12 Volt?

[Eric]

Hi all,
Quick question, Id like to fire up my 1952 62 after going through the carb and a few other things, however I dont have a 6 volt battery right now (Im going to keep it a 6V system).
Since its going to be quite a while before its ready for the road, I dont really want to buy a 6V battery and have it sit around for a few years before I really need it.
So my question is; can I use a 12v battery to start it?  And if so, do I need to disconnect the generator while its in the car?  I understand about not using the lights/radio and such, just wondering it it would damage the generator.
Thanks in advance.
Eric

[Fred #23106]

You dont need a 12 volt battery to start the car. I went through this for several months - first installing an 8-volt battery, but was worried about damaging the radio and clock, so left them disconnected. Then I ran out of gas, as evidently the gas gauge and other instruments run off resistance. The gauge showed 1/8 full and it ran out - luckily within 100 yards of my driveway.

They make some type of setup to start the car on 12-volts, but run on 6-volts, but this sounds complicated and probably expensive. In addition, someone told me that the 12-volts surge might damage the 6-volt starter.

My car always started on 6-volts anyhow, as my starter was rebuilt and the cables looked good. However, I just bought a pair of new cables (2/0 size for 6-volts) from J.C. Whitney and they will be installed soon.

I did something very unusual to give me more starting power. I installed two (2) 6-volt Optima batteries in parallel (voltage stays the same 6-volts), but cranking power went from about 60 cold cranking amps (with one battery) to 180 cold cranking amps with the dual Optima battery setup. I have a 1939 LaSalle and both batteries fit side-by-side in the original battery box, which is located under the front floorboards.  Since so isolated, no one will ever know the difference, unless they remove the front carpet, unscrew 4 bolts and remove the metal cover.  While undoubtedly overkill, it sure works well.

You can see this installation at my web site: http://www.fzoldcars.com TARGET=_blank>www.fzoldcars.com
When you get to the site, click on Technical Stuff link at top of page and you can see exactly how it was done, including some nice closeup photos.

Fred

[JIM CLC # 15000]

03-26-07
Eric, If I read your post correctly, you do not have a 6V battery that you can use in your car to get it started. Right?
If you can beg, borrow Or Steal a 6V battery to use to start your car, The 12V will not hurt the 6V starter,or generator,  provided, that you use jumpper-cables and have the starter engaged whem you connect the POSITIVE jumper cable to the 12V battery. ALSO, when you use 12V to jump-start or use a charger to top off the voltage in your 6V system ALWAYS connect POS. post to POS. post and NEG. to NEG. (I feel sure that you have a POSITIVE GROUND System on the 1952.(If not, someone will correct me) I havent had any experiance with the Optima bettery, but, I plan to install an Optima when my Lead-acid battery requires replacing.HTH
GOOD LUCK,JIM

[Dave Leger CLC #19256]

Cadillac switched to negative ground after the war, in 1946, as documented in the 1946 - 1947 supplement to the 1942 shop manual.  My 47 is negative ground.

Dave

[Philippe M. Ruel]

1952 circuit is NEGATIVE ground.
A 12-V battery might damage your starter, although these are quite strong and voltage will drop through poor contacts.
The use of a 12-V battery to help the 6-V one starting the engine burnt my own 52 generator, so disconnect it before you connect the battery.
Finally, the use of a 12-V battery alone when the car is running will certainly and quickly burn your 6-V ignition coil, so the car will not start twice.
As previously written, find, borrow or steal a new or second-hand 6-V battery, and help it with a 12-V one only during starting process if it is weak.

In normal, regular use, with clean, greased contacts on ground and positive straps, a good 6-V battery easily starts a 331 V-8 engine, no need for weird adaptations.

[Jim Garner CLC# 23406]

In the sixties I owned a 1952 Coupe De ville which absolutely would not start when the weather was very hot and the car had been driven for an extended distance. We lived in Florida and then in the New Mexico desert. I had to let the car cool down or the 6V battery would turn it too slowly to start the engine. I carried a spare battery in the trunk and would hook the two batteries in series to start the engine and it fired instantly. Eventually I made my own series/parallel arrangement with two batteries and ran the car for years with no adverse effect on any components. My device was very complex and no one understood how it worked except me. Later someone (maybe JC Whitney) sold a compact device to do the same thing.
Jim

[Doug Houston]

I dont know how long you will be before putting the car on the road, but you might consider getting an Optima battery for it. They cost a bit over 100 bucks. While they will self-discharge, like regular lead-acid batteries, they do it much slower, and they have a very high current output capability. They will also stay with you for many years longer.

I would definitely advise against a 6/12 Volt (Orpin relay) system. I would likewise recommend getting a vacuum cleaner instead of sweeping the dirt under your rug.

Ive preached about it for ages. A starting motor in prime condition, and cables feeding it well made, will start the car as new. Do you think that Cadillac would ever have sold car number one if they started like some of them do now?

[Dave Leger CLC #19256]

I use an Optima 6 volt battery on my 1947, and have been very pleased with the performance.  It will hold a charge a very long time. Due to our unusual amount of snow this winter, it was over 4 months that my car sat in an unheated garage.  I popped a battery tender on it briefly to top it off, and it indicated the battery was still nearly fully charged.  The car started right up.  

Dave

[Eric]

I think Ill take a look at the Optima battery, I didnt realize they had 6 volts.
Thanks again!
Eric