Recently though, our E46 330Cd got left a bit too long between charges and the CTEK could not recover it - the battery was also only showing 1.4V which looked very wrong. Amazon ran a 'Lightning Deal' on the 8-stage 10A version with a 60% discount so I bought one. It completely reconditioned & recovered the battery in 24hours and has paid for itself at the first attempt.....

The extremely low voltage issue turned out to be the Alarm. I think others have found this as well. A boost of volts from the charger for under a minute, the alarm chirped, and the battery volts jumped back to 11.5. After that no issues with charging. It almost looks as if the alarm was putting a short across the battery, but that doesn't make sense. Whatever it did, it certainly dragged the supply down as measured at the front.
I don't usually like using high power chargers as they can damage batteries if they can't adjust to the battery type, and this CTEK can deal with all types - wet, gel and AGM at the press of a button.
Happy New Year :xmasgrin:
Richard