Q. Why does the MXS15 & MXS25 not have an AGM mode?

A.  Remembering the voltage during bulk mode charging is still 14.4v are indeed charging, but we are also pushing 15 or 25A which is substantial energy into a battery per hour even for the largest 12V monoblocs. This current increases heat in the plates and the plates heating can cause thermal runaway. So to be safe and sure charging at a slightly lower rate makes little difference as the float stage of the charger which is where all the finishing capacity is done at 13.6v anyway. What the higher voltage does is charge the initial bulk quicker and shake up the chemistry which is great if you were slow or self-discharging the battery but when you deep cycle your house batteries daily you’ve given the battery acid a big stir up anyway so the recharge can be at a steady rate and still achieve a full charge, albeit potentially an hour or two slower. In fact, there are benefits to charging slowly (especially for cyclic batteries if they are fast discharged). Lastly, the AGM guide is typically between 14.2-14.7v which is open to a lot of discussions as above or interpretation as to years life expectancy and operating temperatures.