Sorry to re-open old threads. I've since sent the panel back to the ebay seller and got a refund, then been out and got one from a reputable wholesalers but are still getting similar problems.
All seemed to be good up until I connected power for 5 PIRs. However, now the symptoms are slightly different.
I connect the battery - if I leave it at that all is good for a few minutes or so, after a few minutes the screen does turn off. Also if I try to exit engineer mode the display will turn off immediately.
It seems to be when the panel is checking for the presence of a battery (as it would periodically and when exiting engineer mode) is when it causes it to turn off.
Any ideas?