Yes, you should be able to build a voltage divider by putting a resistor into the filter capacitor socket (not the current loop resistor socket). Set the gain on the module to 1 and use a resistor value around 3kohm, or slightly lower, to bring your 15 VDC down to 10 VDC. Keep in mind that the amplifier input impedance will be reduced to ~4.6kohm, however, a car battery will source plenty of current as long as there are no other significant resistances in the circuit. You will need to calibrate this circuit, since the resistors on the SCXI-1100 are +/- 2%.
Best Regards,
Brent Runnels
Applications Engineer
National Instruments