Ehm I left the battery in the iPaq and left it plugged into the charger but no joy
Sooooo (a week later) I think hmmm maybe the iPaq performs some logic checks before charging and can't. Also I am thinking that batterys don't die in that manner!
So today I plugged the battery into the auc-battery slot on the desktop charger and got a constant amber light. I searched this forum and others are read that amber flashing=charging and thought hmm no flashing so posted here. But Lo! After a while the amber light turned green and I thought, this looks promising! So I backed up my iPaq and switched batteries and switched it on and Eureka! It worked
So the lesson is even if the iPaq wont charge it the Aux Battery charger on the desktop charger might!