MTFCA Forum

If I was to run a T motor using the 4 coils and a 12 volt battery, no generator and no mag, about how long would the battery last before needing recharging ? Then throw in LED headlights and tail-stop light and charge life would be reduced but reduced less if ran in daylight hours without headlights. Would it last 6-7 hours without using a starter?

Best way to determine how long the battery will last is to measure the load of each electrical thing one at a time on your ammeter: coil; lights; etc. Batteries are rated for so many amp hours, divide the battery amp hours by the total load in amps, and you will get how many hours...that is on a healthy fully charged battery. You might figure a 5-8% reduction in amp hours for every year the battery is old.

Also depends on whether you use a starter or hand crank. And whether you drive with lights on. If only ignition, it will last very likely all day or at least until you can use a charger. If using the starter, you might drain it very fast.
Norm

If you are running a fully charged automotive style battery, the answer to your last question is: Yes

Back in the day, a fellow club member ran his 13 all day on a makita 9.6V battery. Carried a spare in case.

You'd probably be in the ball park if you allowed 1.5 amps for the ignition with a stock system in good adjustment, then multipy the battery amp hours rating by .7. Battery capacity is reduced in cold weather, and a battery more than a year old will have reduced capacity. It's best not to run batteries down beyond about 1/2 to 2/3 of their capacity.

You can always carry a pair of the square 6V lantern batteries under the seat. When needed, for ignition only, wire them together (+ of one to - of the other) and they will run the car very well for quite awhile. Unlike a storage battery, you don't have to worry about spilling acid under the seat. And, of course, if you don't happen to have a set handy, you can pick them up at any Sprawl Mart, Home Desperate, or hardware store.

I have a mountain of Dewalt battery chargers for my power tools which have the capacity to charge 9.6, 12, or 18 volt batteries which I also have a good supply of. I separated the case of one of the chargers and soldered in a pair of wires which I routed through the case when I glued it back on. They terminate in a polarized plug which mates to another wire connected to my coil box. It is a simple matter to attach the charger to the car, insert a battery (choice of voltage) and drive away. Not sure how long the car would run on one battery powering the coils full time but it is really easy to carry multiple batteries under the seat and the charger will still work if unplugged from the car and plugged into a wall socket.

Dennis_Brown wrote: ↑

Mon Sep 27, 2021 8:44 pm

If I was to run a T motor using the 4 coils and a 12 volt battery, no generator and no mag, about how long would the battery last before needing recharging ? Then throw in LED headlights and tail-stop light and charge life would be reduced but reduced less if ran in daylight hours without headlights. Would it last 6-7 hours without using a starter?

Not all vehicle batteries are designed the same. Some are for starting )Modern Cars (CCA spec) other s recharging over and over (golf carts , boats, casual use Reserve Capacity or Ah). A battery's ability to provide power to operate lights, coils etc depends on its Ah, amp hour, specification. NOT to be confused with Cold Crank Amps or Reserve Capacity, which is are measures for an entirely different context and calculation method. AND the load placed upon it as well as ambient temperature. https://www.mkbattery.com/blog/what-do- ... ut-battery. There are many different "ratings" to help sell car batteries designed for modern vehicles
Not all batteries have the same Ah rating so.... some averages
-12 volt motor cycle battery about 12 Ah.
-Optima 6v Red Top about 50 Ah.
- 6 volt lantern battery 5Ah
-6 volt Group 1 car battery 210Ah
So how long can you run on a battery. Ah / load in amps = Time in hours
OR approximately on a fully charged battery not being recharged
car battery 50Ah / 4 amps =12.5 hours
Lantern battery 5Ah / 1 amp = 5 hours

What does a Model T ignition system actually draw in average amps running on a battery at 6, 8, 12 volts? I'd guess about 1 amp. Does engine speed matter much?

I have run my 1912 Chocolate van with a True fire on 12 volt for some 20 years now. I use a motor cycle battery in a pocket next to the fuel tank, under the seat. I can do a day and a half of city driving on one charge. I found out about the half day when I forgot to put it on the charger after one day!
This runs indicator lights and brake lights but no driving lights.

Allan from down under.

In your case, carrying a second, LI type cycle battery as a reserve would probably get you through 3 days. They seem to hold a charge very well over time.