We are working on a 1922 Centerdoor. The magneto works, but it seems that the magnets are not charged as fully as they should be and that means it stalls out when the throttle is not revved up enough. We are not inclined to try to rejuice the magnets at this time.
That means we will likely run the car on battery most of the time. The car will not be driven in tours and will not likely be entered in parades. It will be a weekend toy for driving around the neighborhood or for trips of 10 miles or less.
What are the disadvantages to running the car on battery instead of magneto?
None for what you are going to do with car. 6 volt battery will be fine. Yes the car will run a little better on mag but many many people have driven 1000's of miles on battery. Have fun with it!
The disadvantage of running a Model T on 6V battery is the coils take longer to fire spark. You have to manually increase the timing advance with engine speed using the spark lever but it has a finite limit. That means ignition timing will continue to retard at higher engine speed once you reach the spark advance limit.
One solution is to operate the ignition on 12V battery. The higher voltage shortens the time the coils require to spark by approximately half. The effect of the spark lever advance is nearly doubled. You still have to manually adjust the spark advance with engine speed for optimal operation but engine performance is nearly identical to magneto operation running the coils on 12V battery.
Good luck with your car and hope you enjoy driving it locally.
The downside is that you need to charge the battery before you go unless you are driving enough to charge it with the generator. The starter takes a fair amount of electrons with each use. If the battery gets too low, your car will not run as well at higher RPM's. That is compounded with the lower voltage of the 6 volt system. An in car magnet charge is easy to do. The instruction can be found on the past forum postings with a simple search.
I ran one on 6 volt battery for about 10 years without a problem. I attended many tours. Only thing I found was my car was one of the slower cars on the tours. Later I repaired the magneto and my car became one of the faster cars.
With a centerdoor, you might be a bit slower than my roadster, because your car is heavier, however in Florida, you don't likely have many steep hills to climb, so probably no problems at all.
My cars run poorly on 6V, better on 12 best on mag.
Maybe the magneto is okay. In another post, you mentioned that the timing might not be set up correctly.
Did you test the output of the magneto?
Have the coils been properly calibrated for running on mag?
Are all the connections good?
Have you "timed the timer"?
My mag is dead, I put a small lawn mower 12 volt battery in the back and it runs good on 12 volt much better than 6 volt, I only have to charge the 12 volt batter maybe 3 times all summer
They are all different, i guess. Some say they run on 6 volts just fine. That is not the case with either of mine. Like Mike said, 12 volts is quite comparable to mag. My experience is that 6 volts results in SIGNIFICANTLY poorer performance.
The magneto in my 1925 coupe has been dead since my grandfather bought the car in 1948. Since then, our family has put over 100,000 miles on the car - all on the 6V battery system and generator. There are no significant disadvantages that will matter. So long as your generator is charging properly, you can hop in it and drive it anywhere.
I think it has been said the coil points will suffer more on dc than ac.Bud in Wheeler,Mi.
To be honest, find someone in your neighborhood with a 36 volt golf cart or 3 12 volt car battery's in series,and use a set of jumper cables and compass to recharge the magnets by instructions you should be able to find here on the site. I drove my TT for a long time thinking the mag was probably no good because it had a couple spots the cloth wrap was off the copper. But just for the heck of it 1 day I spent the few minutes with jumper cables and now it runs much better on mag than battery. Well worth the few minutes it takes to try it.
Just to answer the "riddle" as to why some cars perform on 6V and others do not - my experience is that those that have trouble with the performance on 6V but find their car runs great on magneto have coils that are very likely adjusted correctly. To make a car run pretty good on 6V alone you will generally find that the coils have been set up with substantially less operating current so that there isn't the huge delay in timing that normally happens with coils setup correctly but operated on 6V. Setting less operating current on a coil isn't as bad with modern fuels and such as it might have been back in the era of the T but a robust spark timed accurately makes a difference and those with 6V only probably have never experienced that difference. I haven't spent a lot of time looking into this but a lot of guys with early cars and no HOT SHOT battery will also set up their coils for lower current to hopefully make the car easier to start on magneto only. None of my cars are setup that way so I can't really comment further on this.
It's really honestly not that hard to re-energize weak magnets. There are descriptions how to do this, and Mack (above) alluded to how easy it really is - the hardest part is finding 3 12 volt batteries to hook up in series and knowing where to put the compass on the hogshead to make sure your magnets and coils are aligned.
Unless there is something seriously wrong (broken wiring in the field coil ring, or your ignition switch is shorted internally causing DC to hit the mag post) your car should run way better on the AC those coils were designed to run on VS 6 volts (or even 12V) DC. Add to this - if you run battery all the time (and you have a pre-starter car), you need to reverse your + and - every so often to keep your points on your coils in usable shape.
Wouldn't it make more sense to actually test the output of the magneto before doing anything else, including doing an in-car recharge?
Put a distributor on it, and your done.
I'm no T expert. My T runs fine on both mag and 6V. It definitely starts easier on battery. When driving it definitely has more power on mag. Pulls hills much easier too.
If my mag was shot, I would not hesitate to use a battery.
Have you pull the mag post, and made sure the tip is clean? My performance really dropped about 2 years after a rebuild. I decided to check for lint, and there was a good pile on the post.
Provided the ignition system is set up a certain way, I've not found any disadvantages running coils off the 6V battery. That is with 16 years experience.
Top speed is around 75kmh (47mph). The points are still the ones I installed back in 2002. The car has done about 36,000km in that time (22,500 miles).
The points erosion has been very, very minor - I've cleaned them only once. So that puts an end to the myth of "points burning up on battery". However, that is with 6V and not 12V.
The magneto turned out to be physically damaged which is why an in car recharge did not work in my situation. Because of the good performance I got with 6V, and the damage to the magneto, it was replaced with oil paddles nine years ago during an engine rebuild.
As Mike Kossor and John Regan have mentioned above, the coil firing time is the limitation with 6V operation in the normal way. The coil takes about 2 milliseconds longer to fire on 6V than on 12V.
(There was a dynamometer test some years ago which showed 12V DC operation of coils was as good as & perhaps slightly better than magneto, but the point of discussion here is 6V operation).
Therefore, for 6V operation the initial advance must be as much as possible. Not the often quoted 15 degrees ATDC, but right at the point where the piston can be just detected to leave TDC.
Next thing is the spark plugs. Certain types perform very poorly. Modern types with 14mm adaptors were by far the worst. The best are Champion X, with F11's in second place.
As for the timer, roller types are the worst choice with their contact bounce being problematic at the low voltage. The Anderson makes reliable contact but the timing changes as the contacts wear, and the loss of power caused by that eventually becomes noticeable on 6V.
I have found the best mechanical timer for 6V is the TW. Of course, the E-Timer is the ultimate and what I use now. In fact, everyone who travels in my car comments on the smoothness of operation.
And finally, the coils should be set up with equal firing time, using an instrument such as the ECCT. The important thing is that with only 6V (really 7V with the engine running), there isn't the "brute force" of 12V or magneto to mask any deficiencies.
(Message edited by 26tourer on February 24, 2018)
Thanks for all of the great input. It has new spark plugs and the mag post is free of lint.
The car really seems to run a bit more smoothly on battery than on mag, but that may be good coils that were properly set up, or it may be an indication of a problem with the mag.
I made some adjustments to the timer today and that helped it run a wee bit better on mag and on battery, but it is still not producing enough juice to keep it running on magneto when I slide the throttle to idle position. I have to keep it revved up a bit.
We are borrowing a magneto tester which should be here mid week and we will determine if the mag needs a little jolt.
Excessive crankshaft end play can cause poor magneto output. Just something to check.