20,000Ω is way too high a resistance.i have this coming from ebay
20k Wirewound Rheostat Variable Resistor
That will limit the current to a fraction of an amp.
Do you not know Ohm's law, which states that Current = Volts divided by Resistance?
This 50W resistor selected with 0.5Ω should work.
It should limit the maximum current to <10A with the battery attached (less than 5V across the resistance).