Good evening to the forum, since my old charger gave up the spirit and indicated “full” for two uncharged batteries, I ordered a new one. More precisely the microprocessor charger DP 4000 from Cartrend. According to the instructions it should calculate the optimal voltage and charge current for each battery and not charge at all if the mode is wrong (12v/6v/under zero degrees outside temperature/etc.). Now I want to charge a 12v 2.3ah agm battery and connect it. e voltage from 11.5v, which corresponds to my multimeter. In selected mode the device should charge with 14.3v. At the beginning it also started to pulsate with 14.3v and I was satisfied. When I looked again after 5minutes, the display showed 15.8v however and I heard bubbling from the battery. Of course, I immediately switched off and was glad that no acid had run out. Now my questions: 1. What could be the reason for the increased charging voltage? Is my device broken? Are agm batteries special? (according to the instruction also for agm and allegedly no charging with wrong mode) 2. Is the battery once “boiled” broken? Thanks for all the answers