6/12 Battery for 1941 Cadillac

[Jim Black #21089]

Does anyone have any experience or knowledge about the 6/12 battery offered by Restoration Battery Co., Cincinnati, Ohio? I am considering purchasing one, Thanks, Jim Black

[Doug Houston]

Dont do it.The 6/12 battery is a poor excuse for not having your electrical system (the starter, of course) in proper order. Hiting the starter wit 12 Volts is mighty tough on the starter, too.

Ive never needed it on any of my four 41s, and Im not convinced that anyone else does.

[Jack Carroll CLC#18687]

Dont do it!!!! That system was on my 39 LaSalle when I bought
and had constant problems with it. I went through 3 relays and 3
batteries in 4 years.We finialy put it back to a staight 6V system and its fine. The car was designed as a 6V system and
if all your parts and wiring is good {really good} then you will
be fine. If you still want to use the 6/12 system, Ill give
you the relay I have.I can go into more detail.call me if you want. Jack Carroll 978-433-6257

PS The only other thing I did do was to run a 2/0 ground cable
   directly from the battery the the mounting lug on the starter.
 

[Jim Black #21089]

Just read your reply to the gentleman concerning a grounding stud on the commutator plate on the starter. Could you explain a bit further and do you recommend the larger battery cables to aid in starting? Thanks, Jim

[Doug Houston]

Looks like Im the guilty party.

Back about 1985, I did an article for the Michigan Region CCCA magazine about this. Micheline Larson published it in the Self-Starter in the next issue. Its simply this: The current path to the actual ground on the starter goes through several mating surfaces which may not make good enough contact, so because of the couple hundred amperes flowing through the starter motor, you can lose a volt or two. On a warmed-up wngine, the starter cant develop enough torque to crank the engine. I found the key to all this in my 41 Oldsmobile. They have a grounding boss on the commutator end plate of the starter, and thats the place where the starter is actually grounded. Oldsmobile starters always ran fast, and that is the reason. Its a 41 98, and has essentially the same starter as on the Cadillac V8.

 I checked out a couple of Cadillac end plates (the one on the opposite end from the flywheel housing) and a hex head cap screw can be mounted in one of the little wells inside the end plate, and protrude  to the outside.  If the grounding battery cable is connected to this grounding stud, there is no resistive path through the starter to ground; its right at where the brushes connect to ground. I used a 3/8-16  or 24 thread, with a lock nut on the outside of the starter. Grounding to the engine and chassis will simply flow through the starter to the engine in the opposite direction. No further ground straps will be necessary.

The heart of this is: when new, all parts of the starter were clean and bright. All connecting points were also clean and bright, so there wasnt a grounding problem. But as years age the parts, the contact between parts of the starter and to the flywheel housing degrade, and you lose voltage. Youd be shocked at the performance of those starters. They crank like they have 12 Volt on them.  

I wonder if Steve Stewart should re-run the article. I have all of the SS mags from the beginning, and if he has trouble finding it, I have it.