As GPS devices require 12 volt to recharge them, what are you gentlemen that have them using for a power supply when using them in your Model Ts?
When they are charged up they don't seem to last that long on there own power pack.
I noticed on the O to O tour several used them so to last all day they must have powered them some how unless their cars were converted to 12 volt.
I would like to use mine in the T for speed and distance as can find my way home.

I use a 12v motorcycle battery. Its small size lets you put it in several places in the cars. I actually move it from T to T, depending on my flavor of T for the tour. I have decretely added a 12v outlet to my cars and use quick disconnects on the battery end of the wiring. The battery will last many weeks. Easy to recharge when needed using a trickle charger at home. It is not wired to the T wiring in any manner.

Jack, take a look at this thread from last year:

http://www.mtfca.com/discus/messages/80257/97425.html?1246981341

Lots of people convert to 12v with alternator etc. (which I don't beleive in) and I would suspect that would be the majority of cars you see with 12v accesories.

But powering from a battery is certainly much safer if you are using a Model T's stock charging system.

Someone in our club burned out a cell phone trying to charge it I think with just a 6-12v up converter but stock T generator.

There are 6vdc to 12vdc converters available. I have one for the wife's 55 ford to run the radio/disc player. Try Googleing "6v to 12v converter". Also have seen them advertized in various collecter car publications.

Gary

If you have a 6V battery, first try that...it may just be enough to power a GPS.

I think it would be safe to say that any GPS’s that can be charged thru
the 5 volt USB port of a computer, will charge or run from 5 volts DC.
The ‘wall wart’ power supply for mine uses a mini USB cable and it’s
output is shown as 5V DC 1A.
The car cord supplied indicates 12/24V DC (800 mA) input from the
lighter socket, which is converted to 5V DC 1A Max for output thru
it’s mini USB plug.
I would not use more than 5V without the original car adapter cord,
and polarity will of course be important on any homebrew hook-up.

Constantine is absolutely right! Before taking out on various journeys, try to let the Model T 6 - 7,5V (when charging) charge via the 12-24V cord. As John Regan notes above, the battery in GPS or cellphones for that matter is often below 6V so there are potential. It all matters how much loss there is in the socalled switchmode power suply that sits in the plug.
My work Nokia 6021 charge fine on the Model T 6 - 7.5V. My private HP iPAQ 6515 cellphone with GPS I have had mixed results. The first I had was as I recall it an "original HP". That did charge it, but if the GPS was used for 6 hours the battery was empty. Then I got an unoriginal. It onlyt charged when the car was crusing. The last one I have now seems to work as a charm.

I used to run my T on a 12 V Lawn and Garden battery before I got my mag fixed. After the mag was fixed, I realized I still had the wire running from the 12V L&G battery (under the rear seat in my Touring) running up to the firewall. I ran the wire inside the cowl and mounted a 12V cigarette lighter from Radio Shack on the firewall. Now I can recharge my cell, connect my GPS, whatever, with the charger that I use in my modern vehicle.

Since it's such a low draw, I can usually make an entire tour withour a single recharge of the battery.

Doogie