how do you charge a 8 volt battery.. with a 6 volt charger or a 12 volt charger.. what is the best way ted
Best is to use an 8 volt charger.
You can get these at tractor supply stores or on line. Here is one source:
Haven't any association with the above, nor worked with 8v storage batteries.
I would just replace that 8v with a 6v like Henry installed for his T's with electric starer and generator. If you need more voltage for the engine to turn over, you may have grounding issues or cable issues, or starting switch, or starter issues anyway.
A 6V charger won't usually charge an 8V battery for the simple reason that it does not put out the required 9.4 Volts or there abouts. You CAN use a 12V charger if it has a MANUAL setting or is a trickle type but ONLY if you put a voltage dropping resistor of some sort in series with its output. I have charged 8V batteries with small 12V chargers by putting a large head light bulb in series. You can put 2 of them in parallel to get more charge current. The applied voltage is not critical if your charge rate is not over 3 or 4 amps max. Usually the meter on the charger reads amps so hang a bulb in series (like an 1156) for about 1 amp of charge. Add some more bulbs in parallel with the first one to increase the charge rate. Not a clean set up but it WILL work. You then need to monitor the battery voltage and shut down once the voltage has gone over 9.4V when you can then check the cells with one of those cheapo hygrometer with the floating balls to indicate the charge level. I am NOT a big fan of 8V batteries in Model T's but my company does make an 8V voltage regulator that will allow you to keep the battery fully charged (but not overcharged) when using that battery in a T.
Model T Voltage Regulators - click here
Oops - A Hygrometer is for measuring relative humidity. I meant hydrometer with the floating balls for checking the battery. Been working on my AMPICO reproducing piano and been watching the relative humidity with a hygrometer since the moisture in the air has drastic results on player pianos and their pneumatics.
John's right regarding 8 volt systems, but I can also vouch for Dan's comments. My '26 had an 8V battery when I got it. I swapped it for a 6V battery, had a proper set of 2/0 cables built at a truck shop, cleaned up every connection with a with a wire wheel on a Dremel, and the engine cranked faster than it did with the original 8V battery. The whole deal cost me less than the 8V charger I found online.
I used John's method with two bulbs in parallel using the 12 volt charger for about 3 amps of current but I stopped it at 10.0 volts (2.5 volts/cell).
On the 6 volt setting, the charger would take a 6 volt battery to 7.5 volts and on the 12 volt setting would take a 12 volt battery to 15 volts - both 2.5 volts/cell.
My car had no generator and so 8 volt was my preference for headlight performance if I got caught out after dark. I used the magneto to charge the battery most of the time but used the bulb method with the 12 volt charger for the infrequent "topping ups".