I have no problem using a conventional six volt battery for starting my 1915 roadster. It will start the car for months on a single charge. BUT, given the limited space in a roadster, it takes up way too much of that space. I've found several smaller six volt sealed lead batteries for sale online, ranging from 1.3 Ah to 12.0 Ah. What would be the lowest adequate Ah? The lights are MAG and the horn is mechanical. This is only to buzz the coils for starting. Electronics is one of my many incompetencies, so I need to get some guidance on this.
Steve - I would consider a 12V battery with the highest amp Hour that would fit in the space available.
Forgot to mention - My dad used a 6 volt lantern battery for the coils when starting the 19. I remember it working for a couple years before he had to replace it.
I use a child's electric car battery. Lasts forever. Purchased from Walmart. Brand is Fisher-Price. Charger is automatic.
I use a 12v motorcycle battery in my '14. I think that it is 18 Ah. I mounted it to the left of the fuel tank. I will take some pictures of the installation and post later.
One advantage of the 12v battery is that if you develop temporary mag trouble you can switch to batt and it will still run pretty well.
Steve 1.3Ah would be sufficient to buzz the coils for a long time and would even run the car for a long time if your magneto were not working. But like Fred says a small 12v Lawn and garden battery would last longer and some of them are very small. BTW since you are not using it for lighting your coils don't care if it is 12v or 6v
Actually since you are only using it to buzz the coils for starting it is just a wee bit safer to use 6V battery for that purpose since there is less heating of the coil winding in the event the car doesn't start right away and you end up buzzing the coils for awhile. The AH rating of most batteries is measured at some drain less than what is called c/10 rate. This means that an 8 AH (amp-hour) will in fact give you that 8AH rating when discharged at .8 Amp (or less) rate. Thus a good rule of thumb is to simply look at the discharge rate in amps and multiply it by 10 and you have a battery that will work fine but also will NOT be discharged very much each time you use it so it will then very likely last a long time. What gives storage batteries short life is to deeply discharge them and leave them there for any time at all. A 1.3 amp hour battery will in fact start the car OK but it won't take a lot of starts before it needs to be recharged to keep it near full charge so that it has a good service life. Coils heat up when allowed to sit and buzz and get hotter on 12V than 6V when doing that. So long as you start the car right away then it probably doesn't matter but I use 6V myself.
Like Bob on Texas Gulf Coast above, we use six volt Fisher Price Power Wheels kiddie car batteries in the '17 roadster and '17 touring. We have also used them for primary source for the ignition in the 1910 IHC roadster.
We put them under the front seat, passenger side.
The batteries have quick connects and a fuse. A simple six volt transformer is used for recharging. Charge once in the spring and install in car. Remove when touring season is over, recharge and put them on the shelf.
Got them free from my brother twenty years ago when he worked for FAO Schwartz. One died this year. The other is still going strong.
This is style we are using which is now considered obsolete. The updated version has a different style quick connect.
Does your flywheel magneto not work? I've been starting my '27 roadster on mag and handcrank for years just for the fun of it. Yes I have a starter and do use it sometimes, but I still just leave the switch on mag. If I am parking it for a indeterminate amount of time I turn off the gas and speed up the idle and just let it run the carb dry. When I want to start it, I just turn on the gas and 2 or 3 pulls it is running
Just food for thought
I use a small 12v battery that is used in small UPS units in my 15. It will last a long time between charging. If you have a Batteries Plus or similar store in your area, check there.
Les, the answer is Yes, but... The mag works fine once the car is running, and I can start on MAG when the engine is warm. But for some reason it will usually start only on BAT when cold. I don't know why.
I used a six volt lantern battery for a year and a half. Only took it out to put in a twelve volt to run a new light.
I've been using a small 12v battery from the local electronics store. It's the same size as a T coil. They last 5-10 years.
Could be a weak mag but if you haven't had your coils HCCT'd do it. My '23 started cold on mag hand cranked after I did the caps and a friend set them up on his tester.
Steve, I use a 12 volt battery in my 1913 Roadster. No problems. I also use a diode trickle charger with series 12 volt light bulb to keep the battery charged by magneto when driving. Works very well.
Good ole' Walmart lawn tractor battery recharged by a magneto charger (make it yourself $4). Never have to recharge and cheap.
The battery I'm using is also a 12v, and is the same stuff as an Optima.
I use a 12 volt lawnmower batt.in my TT wrecker it seems to
Work the starter just fine .
I would be interested in the plans for that mag. Charger Bud
Thanks in advance Jim
I picked up an 8ah gel cell on Ebay. It is about 4"X6"X2.5". I mount it right under the front seat. I use it as a hot-shot to get the coils going. Also attached to it is a John Regan magneto charger. Works well. No need to recharge and the car always starts easily.
Check your email ;o)
Another type battery is one for burglar alarm systems. They are gel cell like optimas and can be laid in any direction. The voltage is something odd like 7.something or another, but is fine for Model T use.
I built a wooden box to house two 6 volt lantern batteries. On the top, I have a 6 volt tap and 12 volt tap. 6 volts for coils and 12 volts for the LED strip light I use as a brake light. When the batteries get too weak for good spark, I move the coil box wire from the 6v to the 12v tap and know it's time to shop for new batteries. I seldom use it though, as it starts readily on mag. I most commonly use it to see if I can get a free start. At any rate, I guess the point is, like Fred said, a $5 lantern battery will work for a long time and is pretty small.