Late thread reply but on the ctek there Is a red wire which needs to be connected to a 12v ignition feed like a cig lighter point or even stereo wiring.
The ctek needs to differentiate between when the alternator is charging and when it isn't.
Late thread I know but have you checked all earthing points?
I had the same issue,I did have my aux battery grounded at my chassis but still wasn't working properly so just ran an earth cable from main battery to ctek