We have a system that will not power up with the DC supply disconnected. Fully charged batteries are in the system and tries to boot however the green power on light remains on for about 10 seconds then switches off. If the dc supply is connected the system boots up. Additionally the system will stay on after boot up once the dc supply has been removed. So the batteries are connected. The batteries also last for around 90 mins so I really don't think the batteries are an issue. Any help would be appreciated.