Recently in this forum we discussed six volt, positive ground set ups, and the problems associated with starting, particularly after running hot. I discussed this with someone the other day and he suggested hooking up two 6 volt batteries in "series" for my 51 F-3. My understanding of this was a connection of positive #1 to negative #2, and then the second positive to ground on the frame. My question is: will this work, or will it damage the electrical system? Secondly, if it can be done, will it boost the cranking power during the start up? Any other problems associated with this proposal?

 

series.......no. if you put 2 batteries in seires as you described, the voltage output would be 12 volts. 2 batteries in paralell (spelling) would give youe twice the current, but 6 volts.

 

There is a way to hook up a 12 V battery from cranking only, I dont have the web address handy, but if you do a search under "12 volt boost for 6 volt system" you will find it. When I get time, I am going to try this setup, since I have most of the parts already on hand. It is a total loss sytem, in that there is no way to charge the 12 V battery, other than occasionally hooking it up to a charger periodically. In doing research on a twin 6v set-up, or a 12 V conversion, this looked like the simplest and least costly set up to me.

Nick

 

Two six volters in series would be a way of accomplishing a 12V conversion. The generator and regulator would need to be converted to 12V. The starter would probably be okay for a time. There are many places on the web that describe the entire 12V conversion process. The benefit of using two sixes is you can leave your lights, heater and instruments all on 6V. An alternate is a 12V battery with a 6V post.

Two sixers in parallel would still be 6V but with twice the available cranking amps. I don't think the battery is usually the problem, it's the connecting cables and connections and their resulting voltage drop. Two would sure allow you to crank longer, though.

Watts 101: The turning speed of your starter is directly proportional to the voltage on its terminals. With 12V it will turn twice as fast as with 6V. As you load it up by making it turn the engine it develops torque which is directly proportional to the amps it draws. As this torque builds up and the current increases, you develop voltage drop due to the resistance of the wire and all the connections. As a result the voltage at the terminals of the starter will decrease and it will slow down. Note that horsepower is torque times RPM AND watts is amps times volts. A kilowatt is something like .75 HP. Bottom line is use big fat low resistance wire and make sure all the connections are clean and tight. (Same goes for jumper cables.) When cold the engine will need more current (torque) because it's harder to crank. When hot the resistance of all the wires and connections increases so voltage at the starter will drop. A good test is measure the voltage at the battery during starting and also measure it at the starter during starting.

Here's some more electrical math. Assume the starter resistance does not change and the torque to turn the motor does not change. If you double the voltage you will double it's speed, but the current will not significantly change. This will double the horsepower the starter delivers. This will decrease it's life somewhat. Loose connections or undersized wires will still be a concern, although not as much. A 3V drop in them is only 25% of the total, not 50%.

I hope some of this makes sense.

Good luck,
Johann

 

Thanks for the information, especially johann5, for the technical aspects of the electrical aspects of the 6 volt and 12 volt systems.
Watts 101 makes perfect sense and I appreciate the crash course. Thanks to everyone.

 

I have had the same problem with the starting or should I say not starting when the engine is warm. First I checked all my wireing and connections. 6 Volt and 12 Volt wire are of different size. The grounds need to be good. The biggest thing that worked for me was removing the battary disconect that I had installed to shut off power when the truck was stored. Also check to see if you have the bracket on the back of the starter that connects to the oil pan. I did not until I re-read my parts book. You may want to pull the starter and check for paint on the mounting flang. Good luck!!!

 

Bill F-3: My starter is located on top of the engine behind the radiator, and the bracket is mounted to the intake manifold. Should'nt be any grounding problems there. However I am going to try another ground. A positive ground from the engine block to the frame of the truck. An extension, of the one from the battery to the block, then extended to the frame. See if that helps. What year is your F-3 that the starter is down and grounded near the oil pan?
Brien:-)

 

2 6 volt batteries in series = 12 volts. A 6 volt starter will work just fine on 12 volts, and the wiring on a 6 volt system is of a heavier gauge, no problems there either. Your gauges and lights, however are another matter entirely.



Keep 'er between the ditches.

 

[updated:LAST EDITED ON 12-Aug-02 AT 03:39 PM (EST)]Brien
From Bill F3

I have a 1951 F3 Truck with the H engine 95 HP 226 Cubic inches. The M series engine also has a bottom mounted starter. I am a member of "The early Ford V8 Club of America" (Twin Cityis Regional Group)however, many of the members have 6 Cylinder vhiciles. I asked the very same question at a meeting and they all said recheck your grounds. Members have had the same problem. I did for the 3,4,and 5 time. I even put a jumper wire from the battary to the rear of the starter to gain the best ground and it did not help. Again when I removed the battary disconect I had my best results. Question in my 1949-50-51 Ford F-series Truck Shop Manual they do not show a starter on top. I also replaced my starter coil. It now starts when warm but I also carry a toe cable. I do not trust it yet. If you want to talk in person send me a phone number and I will call you. Work number is 612-333-0931 ext 8306 leave a message.

 

Did I say starter? No, I meant the generator. :-X11 Of course my starter is located along side the engine. How else could it crank the power plant? However, my ground is direct to the frame with strand type braided copper wire. Please forgive my mistake, as it was early this morning when I wrote that. It only damages my credibility. I will save you number and we can compare notes on restorations. Thanks Brien

 

I bought a 12 volt battery from Antique Auto battery. This battery has a 6 volt terminal in the middle that i run all 6 volt items off.
I also went to a welding shop and replaced all the cables. Make sure the ground cable goes from the battery to the engine, not to the frame and then to the engine.
Do not use 12 volt cables from your local parts store.

 

51frrdtrk: So do you think the ground from the starter to the frame is a bad set up? I thought it a better set up than to an oil pan. Also my Positive battery ground goes to the engine block but I was thinking about extending it to the frame from the block for better grounding. Good idea or bad idea? Brien

 

In my Ford shop manual they show the bracket on page 264 Fig 38. I know that this only helps if you have the book. If you do not here is the information

1949-50-51 ford F-series trucks Shop Manual with 1952 supplement Ford Division ford Motor Company. The book was worth every penny I spent.

 

Fact of the matter is, the frame is not a good conductor. Not when compared to a heavy welding cable. You may be drawing 250-300 amps on a hot start, thats enough to weld some heavy plate! Do yourself a favour, run a ground for your headlights, too!

Todd.

 

6 volt starter will run fast on 12 volt battery but will also have a short life. Been there done that.