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.

If you have a battery used in a boat they are typcially 800+ CCA which means they will need to be around the 80Ah or greater. This means you would be operating at the higher side of the maximum performance of the MXS 3.8. If you don't have large batteries the MXS 3.8 is more than capable of charging all types of vehicle batteries and includes the motorcycle mode for the smallest of batteries. All this is performed with the chargers 7 stages. The MXS 5.0 is more powerful at 5A, still with the motorcycle mode but it also includes the Recond mode which is helpful in trying to recondition the boat battery that you never charge often enough.

The Marine series have a night mode which when pressed derates the charging power of the units to 50% so that the units don't get hot and require the internal fan to run. After 8 hours the chargers return to full power. With both the MXS15 & MXS 25 chargers the Night mode is replaced with the Power Supply mode which provides 13.6 Volts so you can power electrical equipment up to the chargers rated max. current.

All chargers listed include the Recond Mode.

The M200 and M300 have a 5 year warranty, whereas the MXS chargers have a 2 year warranty.

The M200 and M300 have no alligator clips, they are fitted with M8 eyelets.

(note the M300 used to include a CTEK XS0.8 charger (bundle) also but that was removed because of the mismatch in charging requirements some years ago).

The units are manufactured in exactly the same way. The M100 gets a marine decal/label with a yacht where as the MXS 7.0 get a car icon. The M100 gets the M10 eyelets with the comfort plug where as the MXS 7.0 gets the same M6 eyelets as all the other automotive chargers. Both come with a 5 year warranty.

When the maximum current output of a charger is less than 1/20th the Ah of the total battery bank size it's trying to charge. It's effectively too small or too low a current to successfully charge a flat battery bank. The charger is now only able to maintain its state of charge. An example is the MXS 5.0 on an 70Ah battery is referred to as charging, but if you put that charger in motorcycle mode at only 0.8A it's now having a tough time maintaining the same battery.