Question on Coleman 100W Solar Panel "open circuit" voltage

I have what looks to be a Coleman 100W Solar Panel with a 30 amp Coleman controller in the trailer. It doesn't really charge my batteries, so I checked the open circuit voltage coming off the panel and it's under 13 Volts DC (This is when I remove the leads from the panel to the controller). I can not find a spec for the solar panel open voltage, but most other panels say it should be greater than 20 volts open circuit. Is it a fair guess the panel is shot? The controller rarely shows the indicator light it's charging, but does show the voltage of the battery.