12 Volt Battery?

[Bill Jewell]

I recently watched a video of Jay Leno talking about his 1915 Franklin. He mentions that it was so advanced for it's time that it had a 12 volt battery. Is this accurate? Would this have had a 12 volt system originally? It's a beautiful car!!

Thanks,

Bill

[Steve Braverman]

Franklin used 12V through series 9. After that they went to a conventional 6V system.

[odyssey]

18 volt on earlier cars, as on my 1913

Tom

[Guest 1910_Anon]

There is a solid technical reason for using 18 and 12 volt on early Franklins. It was not a matter of modern, advanced engineering as Mr. Leno implies.

Up through Series 9, Franklin used a single, simple, motor-generator for starting the engine and supplying current. For Series 10, they went to a separate generator and starter motor.

The neutral-plane offset on a generator is in the opposite direction as it is on a motor. You want the brushes to ride the commutator at the neutral-plane to minimize sparking and maximize efficiency. So the brush position on a simple motor-generator cannot be ideal for both a motor and a generator therefore a compromise location must be used. As with any such system, the more current, the more sparking.

By using a high system voltage, the current, and thus the sparking, is reduced. I have not gone through the analysis of an actual M-G from a Franklin but I suspect that it is biased towards the motor position since that is the position where the most current is actually used. But then...... maybe they biased it towards the generator position since most of the time, it is a generator. In either case, the brush life is not very good on these machines.

With separate units for the starter and generator, the advantages and disadvantages of 12 or 6 volts is the same for all cars and Franklin did not stand out from the crowd.

With the wood frame requiring two conductors to each load, the savings from using the smaller wire sizes of a 12 volt system over 6 volts is even more noticeable on a Franklin than on a single wire system (where the steel frame is used as the return), yet Franklin choose 6 volts. Other considerations other than the price of copper must have swayed their decision.

Edited June 17, 2013 by 1910_Anon (see edit history)

[BillDC]

You should hear Dad tell stories about how hard it was for him with his 9B (12V) franklin in the 40's when the whole world was driving 6 volt cars. He could not buy a new battery, so had to go to a battery factory and get his old one rebuilt. Also had to run his headlights in series with 6v bulbs because he couldn't buy 12v sealed beams (sealed beams?? that is another story)...