12 volt step-down to 9 volts

[Bobby Rodd]

I’ve been told that when cars were transitioning from 6v to 12v that some people went with a 12v battery and used a “step down “ which took the voltage to 8 or 9. Has anyone heard of or tried this?  Does it work?  If it does, what’s the down side?

BobbyRodd

[Matt Harwood]

I'm sure resistors of the appropriate size exist, but there probably wasn't much need for a 12 to 8 volt resistor when manufacturers were transitioning from 6 to 12 volts in the '50s. Either your car was 6 volts or it was 12 volts. There wasn't any need for an 8 volt electrical system so there probably weren't any devices like you're describing. You can rig up a resistor of some kind, I'm sure, but that seems like a lot of work and for what end? 

 

If you are really asking how you can make your 6 volt car start and run on 12 volts yet still keep all your 6 volt devices operating, well, there are surely ways to do it and it has been discussed here at least three times in the past two weeks. The general consensus is always faster, cheaper, and easier to make your 6 volt system work properly rather than trying to use higher voltage batteries to put a band-aid on it. Most "conversions" on 6 volt cars are less than successful and you often end up with a car where it starts fine but nothing else works and the wiring is a mess that future owners will curse.

 

In the unlikely case that you simply want an 8 volt car, I think there are tractor batteries with 8 volts and you can probably crank up your original generator/regulator to put out something close to that in order to keep it charged. The lifespan of everything electrical on the car will be shortened, but you'll have a few more volts to turn it over. Again, not recommended and a properly sorted 6V system with good grounds and big cables will work just fine with no downsides.

 

Does that help? What's the end goal here? Maybe we can be more helpful with more details.

[Morgan Wright]

I'm sure they never used a step down to the starter motor. A 6V starter motor works fine with a 12 V battery. Better, actually.  Maybe the step down was for other things like the radio or the check-engine light. But the fact is, DC motors really give little f about the voltage.

[maok]

1 hour ago, Morgan Wright said:

I'm sure they never used a step down to the starter motor. A 6V starter motor works fine with a 12 V battery. Better, actually.  Maybe the step down was for other things like the radio or the check-engine light. But the fact is, DC motors really give little f about the voltage.

 

The 'liitle f' is speed of rotation, its  not torque.

A DC starter motor will turn faster as the voltage is increased, and voltage will increase with speed of rotation with a DC generator if its not regulated.

[Jack Worstell]

For our 1937 Special we changed to an eight volt alternator and an eight volt battery.   No other changes

to  the electrical system of the car.

 

 

Much faster starting.  Brighter lights.   So far no downsides but long term

I wouldn't be surprised to see some problems with 8v applied to 6V components   eg light bulbs burn

out sooner.  But so far so good.  

A little risky to make this change but we feel the pros out-weigh the cons.

 

If you should decide to go this route and have a 6V radio....I suggest you get a "buck converter"

to drop the 8V to 6V for the radio.   About $25 on Amazon. ( we haven't made this change yet

but will eventually...the radio plays OK on 8V but we don't want to risk long term damage

to a difficult to repair item ).

 

The alternator is a standard Delco Remy  10 SI unit converted to 8V.  Several vendors provide this service

 

Resistors only work well for dropping voltage when the item at issue draws a more or less constant current

This leaves out things like radios.  variable speed DC motors,   gas gauges   etc

There are  limitations to using resistors as voltage dropping devices.

 

Jack Worstell

Edited July 5, 2019 by Jack Worstell
Clarififcation (see edit history)

[Jim Nelson]

Recently,  someone talked about this.    He put two “Optma”  6 volts in parallel and ran the ground directly to the starter.   He reports it starts like a 12 volt system and you don’t have to reset your generator.    I would reset the generator to get more amperage now he has two 6 volt battery’s to keep up.    I keep my battery’s on trickle chargers when not in use.   I prefer to use the trickle chargers that electrically start with more amps and then as the battery get to the top, it changes to a ‘milliamp’ rate.  

[Frank DuVal]

Yes, big cables to the starter and ground usually makes 6 volt cars start just fine. Remember, when they were new, they started in the hottest and coldest weather, as the owners had to get to work!😉