6V/12V hybrid electrical system
 

Hey Yall!

My Trabant 601 is destined to arrive sometime this afternoon or tommorrow morning. For those of you not familiar with this car, it was made in East Germany up until 1990.

Trabant - Wikipedia, the free encyclopedia

Here is mine:

http://i222.photobucket.com/albums/d.../Trabant10.jpg

So why would be a Ford and Fiat enthusiast want with one these? Well I'm weird that's all I can say.

Anyway this was the last car made with a 6 volt electrical system. They did goto a 12 volt system in 1984 when the added the rear window defroster system as a standard feature (so I'm told).

Supposably the 6 volt system works OK however this means finding certain devices to run on 6 volts is a problem. Such as H4 headlamps, H3 fog lights and of course a radio and a power point for recharging cell phones.

What I was wondering was if I could install an ignition ballast resistor between a 12 volt alternator and the junction where the circuits connect which would either be the fuse box or the ignition switch.

Where the alternator connects to the ballast resistor, I could run those wires to the head and fog lights relays and the radio.

Three questions:

1) Has anyone ever done or tried this before?
2) How much would the ballast resistor drop the voltage down to? 8 volts? Would this be too harsh on 6 volt bulbs and the wiper motor?
3) Could a ballast resistor handle that much current to run headlamps?
4) Would 6 volts be enough to engage a 12 volt relay? So I'd use 6 volts from the headlamp switch to engage the electromagnetic in the relay but 12 volts would be connected to the terminal 30 (B) and complete the circuit.

I realize you can buy 6 to 12 volt inverters to run 12 volt radios but they are pricey ($160 cheapest I found) and only produce about 5 watts. Not enough to run headlamps on.

Just wondering if this is a practical solution.

I'm curious why you Wouldn't do a full 12v conversion. The current wiring would handle the 12 Volts just fine, half the amperage. You would need a resistor for instruments and for wipers/window motors. Then you would be done. A hybrid setup would to me be a pita, I don't think a ballast resistor would handle the current of an entire electrical system. If you so inclined you could mount another alternator/battery and have a completely separate 12v system I think you'll get into some issues when you try to co-mingle 6 and12v from the same battery/Charging system. If you do 2 seperate systems make sure there both negative ground, not sure but you may burn your car down if one were negative ground ad one were positive ground. The other thing to consider is that all modern electronics are negative ground.

I don't think a ballast resistor is the way to go, the voltage drop from the ballast resistor (Rb) is proportional to the system resistance (Rs). According to ohms law, I=E/R (Current equals voltage divided by resistance). If the systems resistance were fixed it would work, resulting in Ib=Eb/Rb and Is=Es/Rs (note that Ib=Is if Rb and Rs are in series). But in reality the system resistance varies with the load (switching on/off of components; lights, wipers, radio, etc); also the voltage varies (unless well regulated), and the current varies.

If you use a 12 volt battery and charging system, you could use a properly sized (current rated at ??) voltage regulator to operate the 6 volt components.
This would require some modifications to the wiring to segregate 12 volt circuits from 6 volt circuits, but properly done it would be safe and cost effective.

I don't think you'lll have a problem getting the 6v parts you need. As for cell phone recharge... leave it at home and enjoy the freedom.:welcome:

hello Smart car
 

Your not weird. You are here right?
This the precursor to the Smart Car. (The uncar).
Conversion to 12 volt is the correct way to go. Voltage reducers are common for whatever needs to remain 6 volt. Speedway Motors - Street Rod Parts, Race Parts, Ford Flathead Parts, Sprint and Midget Racing Parts, Pedal Car Parts
On the American cars that have been converted to 12 volt the 6 volt starter works ok on 12 volts.

The other option is a dual voltage system that uses (2) 6 volt batteries in series. A 12 volt alternator will be required and many common alternators can be adapted.
Also a separate fuse block will be required for the 12 volt loads.
While your at it why not drop an SBC in it?

vicrod

In my experience, a 12 volt relay will close on 6 volts.
I have an old Willys Jeep, 6 volt system. It has 6 volt relay to connect the starter to the battery, and the starter relay is wired so that GROUNDING the small terminal causes the starter relay to engage.
I wanted the Jeep to start by turning the key. The ignition switch supplies power to the start terminal on the ignition switch. This does not activate the starter relay.

I took a 12 cube "Bosch" relay, and apply power from the ignition switch to pin 86 of the relay. Pin 85 is grounded. Pin 87 goes to the Jeep starter relay, and Pin 30 is grounded.

Turning the key to "start" energizes the coil of the cube relay. The relay contacts then ground the Jeep starter relay, and the engine cranks.