I found this on their website:
Most DEWALT 20V batteries work with DCA1820.
However, DCA1820 should not be used with DEWALT 20V premium batteries (DCB200, DCB204, DCB204BT, DCB205) in 18-Volt compact drills DC970, DC759 (instead, use DCB201, DCB203, DCB203BT).
That should make things clear...