Just to add to this, I have a little more info. Having just installed a CTEK 250SE B2B and AGM battery I am having the same issue. (I will fit a voltage stabiliser, so that I can use it on the move). I have spoken to Propex and they have NOT cured the issue on the unit itself and themselves recommend a stabiliser/rectifier or a switch for a simpler solution, but confirm that the unit should be okay to 14.5v without showing an error which would tie in with an earlier post.
With the CTEK you can "set" the input voltage by not connecting the black wire which is the AGM setting which allows the charger to charge at 14.9v, whereas omitting this forces the unit to charge at the bog standard 14.5v which won't (shouldn't!) activate the over voltage protection.
For anyone wanting to reset the error codes, it is simple but not widely publicised- switch the unit (either analogue or digital) off and on 3 times and the codes are cleared, thereby enabling it's use.
With the CTEK you can "set" the input voltage by not connecting the black wire which is the AGM setting which allows the charger to charge at 14.9v, whereas omitting this forces the unit to charge at the bog standard 14.5v which won't (shouldn't!) activate the over voltage protection.
For anyone wanting to reset the error codes, it is simple but not widely publicised- switch the unit (either analogue or digital) off and on 3 times and the codes are cleared, thereby enabling it's use.