Porter. (and Bill) forgive me if I am jumping in at the wrong point.
Porter the transformer is for regulating shore power onto the boat. It gives one the option to use different voltage inputs on the SP cable and get 220/230v supplied to the boat's AC distribution panel. Charging the battery is a different matter.
Porter, I installed the MagnaSine 4124 inverter-charger over Christmas (2017) and have had good experience with it so far. I corresponded a lot with Bill Kinney during the installation trying to make sure I did not foul up the Amel bonding set up. I think we worked through it OK. The unit is wired between the auto transfer switch (the one that selects the generator or shore power for AC) and acts as a charger if AC is present upstream (from SP or the genset,) or as an inverter if there is no other source of AC. I set it up to be the "whole house" inverter so it supplies the main AC distribution panel. We routinely run the microwave, vacuum, food processor...etc from the battery. I paid about $1900 USD for the unit plus the remote control unit, which you will need.
As a charger it supplies 63 amps to the battery at the start and ramps down as the battery voltage comes up. It is programmable so you can set it to which ever battery type you have. We have AGMs and it does the absorb phase at 28.6V then floats at 26.5V We run in it in parallel with a 40A charger to speed things along at the start.
I installed the unit in the engine room forward port side. It has internal cooling fans, and internal temperature sensors to shut it down if it gets too hot. It seems to be happy there so far.
If you have a charger that is becoming unreliable I definitely recommend getting a new charger while you are near good shipping points. We now have three chargers, in addition to the solar, engine alternator, and shaft alternator. Can't have too much.
See you soon, John and Colleen
SV Annie SM 37
St Thomas, USVI