Thank you for your advice to read the manuals. I have read the CTEX MXS 5.0 manual. The only advice that I can find on the matter is on page 3 which says: "Connect the charger to the battery". (It does have reverse polarity protection.) I have also consulted the Yeti manual and can find no advice on charging batteries. On which page in the Yeti manual should I look for this advice ? I am sorry for being out-of-date, but I have never before charged a battery with a battery monitor. I do not believe that it is mentioned in the Yeti manual. The Yeti manual has no index entry for the car's battery. only the fob's battery !From the comments made by the OP I'm beginning to wonder whether he might have cooked to voltage controller by his totally incorrect method of connecting the battery. Why don't people RTFM!!!