One ohm shouldn't make that big a difference. At least I can't imagine it doing so. I have no numbers to back up my statement. Others may have differing opinions.

 

1Ω means a voltage drop of 1V per amp. So at the observed 2A it was dropping 2V. It doesn't surprise me at all that the current dropped an order of magnitude while dropping the voltage from 14.5 to 12.5 or whatever. That's the way batteries work, they operate in a narrow voltage range.