change a 6 volt system to a 12 volt system

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    I have a 1934 PA with a 6 volt system. The 6v battery will hardly turn the engine. How would you make the change to a 12 volt system from a 6volt system.Are there any i other options That would help to start the engine?

    Thanks Carl,PS If anyone can send me a detail How It can be done and if it works I will send them a 12 pack of Memphis famous barbecue.


    before changing to 12 volts , check battery cable size and terminals and battery size. A common problem is that the starter armature bushings are worn causing increase in the armature- pole piece clearance and thus poor starter performance and even dragging of the armature on the pole pieces. Replace the bushings. Good luck, Leo


    Hello Carl,

    Leo has given you good advice. What condition is your battery in? how many cold cranking amps, and how old is it? Have you had it load tested lately? I would add, make sure that you have a good ground off the battery and that the engine is grounded. Off-the-shelf battery cables meant for 12 volt systems may not carry the current.

    Too often, I see 6 volt cars with wimpy battery cables that cannot carry the current, and then, the grounding point on the frame is painted. Make sure that you have shiny metal where the ground lug meets the frame. I like to use dielectric paste to keep the shiny bare metal from oxidizing and adding resistance. These cars worked for many years on 6 volt systems and many still do. It can be done! But 6 volts puts an emphasis on good contacts, a good starter armature, and a good ground, and a good battery. I have an Optima 6 volt battery in my car. These are neat because they don’t outgas, they don’t get sulfuric acid on your battery box and rust it out. Optimas last a long time, if care for it. They have 900 Cold Cranking amps. If that is not enough, you can put 2 Optimas in parallel at 6 volts and have 1800 cold cranking amps and they still fit nicely in the original battery box. Also make sure that the timing is set correctly on your engine.

    Happy Motoring,

    Chris Diekman


    Hi Carl,

    I concur. Don’t change to 12 volts – solve the problem.

    I have a ’34 that had an Owen Dyneto starter, that if it didn’t start the first time, would get hotter and hotter (resistance increases with heat, and heat increases with resistance, so it’s a vicious cycle for armature, field windings, battery cables and connections). My starter finally broke, and I installed a 6v Delco 497, no more problem. (Some ’34s came off the line with Delco’s, some with Dyneto’s. If you want to check S/N’s, Delco was used for engine # 305001 to 305435, and from 310392 up on the 8-cyl.)

    Use the biggest cables you can buy, and short runs. (Besides, if you changed to 12v., the Startix, clock and horns would burn out, and all the lights would have to be changed.)

    Good luck,



    All of the other comments are great.

    Last yea, Arnold Romberg, our stupendous Editor for the Service Bulletin published a SB that walked us through hooking up two Optima 6v batteries in parallel (SB-11-2).

    I will send you a copy of the SB.

    The Optima batteries are expensive, but they will last much longer than standard led-acid batteries.

    They are also easier to find than a 6v Delco 497 starter (including rebuild costs).

    Good luck on this problem.


    PS: Don’t Convert!


    I concur with all previous advice. I use two Optimas in parallel in both my 1930 and 1934 8-cyl cars, more for the reserve than for more starting power.

    Reserve issue: A 6V Optima has 90-100 amp hrs (AH) of reserve capacity. Factors specs for a 1934 8-cyl lead-acid battery are 140 AH, and 165 AH for a 12-cyl. Reserve is necessary for running at night with a charging deficit with all lights on, given that the factory Delco generator produces only 25 amps cold, and about 18 amps when hot, even with the third brush turned all the way up. If you wish, I can send you a photo showing the hookup. Two Optimas afford 180-200 AH of reserve capacity.

    More on reserve: I use #1129 bulbs in both tail and stop lights for improved visibility, and these draw more current than the standard bulbs, resulting in more deficit at night.

    Other suggestions for better starting:

    1. For battery cables, use 00 (“double-ought”) welding cable with the battery ground cable connected to a starter mounting bolt. A local battery company here will make customers such a cable to customer specs while-u-wait.

    2. Ensure that paint is removed from the ear of the starter where the cable attaches, and from the bell housing where the starter fits. Then follow Chris’s suggestion about coating the connection with dielectric ignition grease to prevent corrosion. I also use star washers under the bolts of ground connections to improve the ground by biting into the metal.

    3. Check your secondary grounds: you should have one ground strap from the engine to the frame (this counters the insulation provided by the rubber motor mounts), and another from the body to the frame. On general principles, I refresh those ground connections about every three years.

    One benefit of the Optimas that offsets their acquisition cost is their longevity: The pair of Optimas in my 1930 are now **twelve** years old and they have not slowed a bit. Another is that, generally, Optimas need not be on a maintenance charger over the winter or other periods of non-use. That is, they hold a charge much better and far longer than lead-acid batteries.

    However, Optimas are not good at tolerating a major depletion (running dead).

    Remember that Pierces, Cadillacs and Packards (and lesser cars) got along very well on 6 volt systems when new. Do you think that buyers who spent so much money on these cars would have tolerated poor starting performance?

    The downside to 6V systems is that the ground connections need to be refreshed more often than on 12V systems. Given the cost and aggravation of conversion, periodic refreshing of ground connections is a very small price to pay.

    Good luck–and please keep it 6-volt!



    The previous advice is very good. I would add one more item. To determine where a bad connection(s) or cable(s) is turn the engine over with the starter with the ignition disconnected for about fifteen seconds. After that, use a Mini-Temp or your hand and look for connections or cables that are hot. When a hot area is found, there is a problem at that location.


    More advice: Google—William C. “Bill” Anderson, P.E. click on Starter

    This a very good review of starter problems of the classic era. Should answer most of your problems.Two Optimas are fine but not really needed .I have one Optima on my Series 5, works well.


    Here we go with more info.

    If you buy the Optima 6v red tops on Amazon, there is a seller offering them at about $115 each, free shipping.

    That is a LOT less than the cost of finding a better starter plus the rebuild cost.

    Do what the other guys suggested and you will be cruising.


    I had Optima red tops in both Pierce-Arrows (the 1931 has been sold). One battery with good starters and cables spun both cars over on the hottest days, with a hot engine. As near as I can tell the 12V Optima in my 58 Cadillac has been installed for 15 years. At this point, I have to be playing Russian roulette.


    After all of the comments from you guys, I have decided to keep it a 6v system. I did some of the thing you guys recommended and have the engine running for the first time.Thank you guys very much, it saved me a lot of time and money to try to make it a 12v system.

    DR.Leo Parmagian, Chris and Delphine Diekman,Peter Williams,Bob Jacobsen, George Teebay, Paul Johnson Jr, and Tony Zappone. Thank all of you for your advice


    As Society members, we are here to help each other.


    George Teebay, please send me a photo of the double Optima connections




    I attach the article that Leo mentioned above.

    It sounds like you are having good luck without making a nice 6-volt into an unnecessary 12-volt.



    The photo is the wiring arrangement on my 1703. Just out of the pic is the disconnect switch which is accessed under the front of the driver’s seat. Hope this helps.


    I added a disconnect switch to each positve line to allow each battery to be charged or discharged independantly, or both together.


    2 of those 6 volt gel cell batteries will fit in that compartment perfect.but wire em 6 volt.thats what i did & mine starts fine now


    I have only one 6 volt Optima battery on my 1929 133 & it turns it over a treat!! Better than the 12 volt Lucas starter on my 1964 Austin Healey Sprite!! The only drawback it that the battery looks a bit lonely in that great big box on it’s own!!


    For my two Pierce-Arrows, I built wooden boxes the outside dimensions of which are the size of the inside of each car’s battery carrier with inside dimensions the size of the Optima battery.


    I’m late at adding to this discussion: years ago in my ’33 836, I was having very slow cranking speed, the engine would barely turn over. Even when jumped with a 12v source..

    So I assumed I had a starter problem. I changed to my spare, known-good starter, and there was no change in cranking speed..

    A new 6v battery was installed, and still no change… what was left to ‘fix’ or change? Yep, the cables..

    The positive ground cable was an old-stock flat braided copper cable, I added a new cable from the nut/bolt on the positive post of the battery to one of the starter-to-engine mounting bolts.. I made sure that the connections were clean and bright. The new cable was made from OO copper welding cable and with copper ends soldered on..

    The difference is astounding, the engine cranking speed is almost like a 12v car, and the lead-acid 6v battery is working fine.. I installed an Optima to try it, and noticed zero difference, so I went back to the lead-acid black battery. It has been working fine for several years.

    So extra cranking amps are of no use without good cables to conduct the amperage to the starter..

    Glad you have your situation repaired..

    Greg Long

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