Have to admit I don't have much experience dealing with 6 volt systems, but it seems to me the charge rate is considerably slower than 12 volt systems. My '26 is a stock 6 volt system. I have a Fun Projects regulator on the generator that seems to be working fine. But as I am driving down the road at 35-40mph it starts out producing around 8-9 amps then backs off to 4-5 amps for the duration of the drive. This seems sort of odd to me, but when I put the battery charger on the battery, I see the same thing. The charger reads 8-9 amps normally, then backs off to 4-6 amps and slowly drops from there. It usually takes 3-4 days before the green light comes on the charger to let me know the battery charging is complete. When I charge a low 12 volt battery, the whole process normally takes 7-8 hours before it "green lights" and the charge is complete. Yes, I have double checked to make sure the switch is on the correct setting.
The battery is new (in June) and I have checked all the cells are they are fine. Is this slow rate of charge characteristic of all 6 volt batteries?
A Fun Projects voltage regulator only charges the battery until it is charged. After that it maintains enough generator output to keep the battery topped off.
This is different from a cutout. A cutout simply maintains a set level of amps, which is typically overcharging the battery. The Fun Projects regulator will make your battery last longer because it is not charging except when you need it.
A 12 volt battery is no different than a 6 volt battery. If it takes longer to charge it probably means it is a higher amp - hour rating.
It sounds like you are using one of the new-fangled chargers. Consider this a fully charged 6 Volt battery should actually read 7.5 Volts But will "drain" to about 6.8 volts and maintain that charge A 12 Volt battery is considered to be fully charged at 13.5 volts (should be 15 volts if you Multiply 2.5 volts times 6 cells) but the engineers that designed the chargers didn't dial down the full charge for the 6 Volt battery like the 12 Volt battery so it is very hard to get a 6 Volt battery to "Full Charge" if they reduced full charge on 6Volt batteries by the same factor as 12 Volt it would be fully charged at 6.5 Volts and would charge much quicker!
Assuming that you are driving in the daytime, and the ignition is set on Magneto; your T is not using any of the electricity produced by the generator. The charging amperes will be low. An ammeter in an automobile shows the net electrical state of the electrical system. If the generator is producing 12 amps and the car is using nine, the gauge will show a charge of three amps. This is why the automobile industry shifted to voltmeters, which (obviously) show system voltage.
The system voltage gives a better picture of what is actually going on.
Actually, I think that your charge rate is on the high side. If you use the starter to start the car, the battery will be partially discharged and the 8-9 amperes at the on set is about normal. This charge rate should quickly (a few minutes) drop to near zero. The 4 to 5 amperes should be closer to zero after 10 minutes of driving. Your battery charger has verified that the battery acts the same on the car and when being charged off. You stated the battery is new, what is the manufactured date? It is a code on the side or may actually state it. Many times batteries will sit on the shelf a long time before being sold, especially odd ones like a 6 volt. Have you checked the specific gravity, it should be close to 1265. Have you have the battery load tested, maybe take it back to the seller and ask to have a load test done. The other item of concern may be the accuracy of the ammeter. The 26/7 ammeters are not very accurate. Maybe you should measure the current with a good meter and see what the current actually is. Mike
Think of the battery as a dam on a river. The voltage would be the water level in the dam. The current would be the flow of water needed to keep the level constant. Now think of a pipe connected to the dam drawing water out. The more water going out of the dam, the more water would need to come in to keep the water level. The amount coming in should equal the amount going out. However, if the amount of water going out of the dam increases the level of the water would drop. Therefore it would take more water flowing into the dam to bring it up to level.
The voltage regulator keeps the battery voltage topped off. When you use a starter, it draws down the voltage in the battery. Therefore right after you start the car, it takes more current flow (amps) to fill the battery. Once the battery is full, the regulator drops the currant (amps) to equal the amount being drawn by the car.
I hope this clears things up rather than muddying.
Norm, makes a good analogy. To add a little to Norm's last sentence. Once the battery is full, the regulator drops the current to equal to the amount being drawn by the car. If you are running on magneto, most Model T's will not be drawing any current and the ammeter should read zero. If you are running on battery all the time, then maybe the 4-5 amperes you are reading maybe correct. Good Luck. Mike