Actually those kind of solid state relays can't be used at all for DC voltage switching as the internal switching element used are thyristor based (back to back SCRs or a Triac) which can only be turned on by the trigger pulse but rely on the load AC current passing through zero (every 8.333 millisec at 60Hz power) to turn off. So if used with a DC load you could turn it on via program control but would not be able to turn a channel off without turning off the DC source power.
Solid State Relay Module
Load voltage range: 75 to 264VAC (50/60Hz); Load current: 0.1 to 2 AMP
A true relay module would be more suitable for your DC circuit switching:http://www.ebay.com/itm/Eight-8-Channel-5V-Relay-Module-Expansion-Board-For-Arduino-PIC-AVR-ARM-MCU-DSP-/220956190987?pt=LH_DefaultDomain_0&hash=item337203e90b