From reading the silver cell text that Steve posted, I see the thum cell runs at a suggested 3.0 volts to 4.4 volts and a current of 0.35 to 0.4 amps per square inch of anode area
For discussion lets say 3 volts and 0,35 amps and using one square inch of silver anode area.
Since Ohms law says: volts divided by amps is equal to resistance.
Then 3 volts divided by 0.35 amps equals 8.57 ohms.
So in this cell the cells resistance is 8.5 Ohms. (Electrolyte and spacing may differ)
Since Ohms law also says: watts = volts x amps.
Then 3 volts x 0.35 amps = 1.05 watts
So the cell is using about one watt (heat work) (again in this perfect cell).
Say I only have a 6-volt power supply (DC battery charger), and want to run my cell on 3 volts.
Two resistors in series, if both are the same size the voltage divides, but the current stays the same through both resistors,
so if I put two resistors, or light bulbs, or silver cells in series the voltage they receive will be half each of the supply, example two silver cells of the above resistance in series on a 6 volt supply battery would get 3 volts each, and if both cell ran at same resistance (unlikely ) the total circuit current would be 0.35 amps, and 2 watts of power used up as heat, problem here the cells resistance is variable, this may work but I want a better way and do not want to maintain two cells,
I could get a resistor from radio shack large ceramic type in a 10 ohm (close to 8.5 ohm of my cell) 10 watts so it can dissipate the heat, and wire it into series with my cell (insert it in to wire going to anode) (plus of voltage supply battery charger to one wire of resistor and jumper from other wire of resistor to my anode silver bar in the cell, now my total circuit will have 18.57 ohms and 0.32 amps, the resistor would get just a little more than three volts my cell just a little less than three volts from my six volt supply, and since the battery charger will actually put out a little more than six volts (about 7.25 volt to charge battery) my cell would be within the 3 to 4.4 volt range,
Ok now but our cells resistance changes and Kadriver said he had read 4 amp draw on his running at 6 volts, this says to me his cell resistance was 1.5 ohms when he done his readings much less than our perfect thum cell here, this is getting close to being a short circuit, (maybe a silver needle fixxin to burn his cloth?), well if our cell shorted out we still have the 10 ohm resistor in circuit, so a most we have is 6V./ 10 ohm = 0.6 amp on resistor, and 0.6amp X 6 volt = 3.6 watts of heat on resistor, our 10 watt resistor can handle that worst case scenario.
But we can use a light bulb instead of a resistor, this will give us an indication of how are cell is running, will limit current from our charger, and divide the voltage from our power supply between the light bulb and the silver cell if we put it in series with the cell as we did the resistor, I would use a 12 volt tail lamp from a vehicle like the #1157 tail light bulb(auto parts or radio shack you can solder wires to it or just get a socket for it) about 2100 milliamp (at 12 volt its hot resistance is about 5.7 ohms, now running cooler on about 3 volts in this circuit that will differ). A shorted cell the lamp will limit current, indicate the short, protect your battery charger.
Again with the light bulb take the positive from your battery charger to one wire of bulb the other wire of bulb to anode silver bar in your cell.
(Different bulbs will give different values their filament resistance varies with type of bulb), you could do experiment with a six volt tail lamp, it would be hard for me to calculate the values as we are running bulbs @different voltages and filaments will heat different, and here your cells resistance is also a variable.
All I can say is Try it you may like it, (and thank OZ for the suggestion).
