Here is where quite a few of us started when we got serious about charging and desulphating our Deep Cycle flooded lead acid batteries.
MegaWatt PSUAdd in a RC watt meter...
RC watt meter, amps, voltage, total amps added, etc.and lastly, some jumper cables.
10 gauge jumper cables.Cobble together.
Adjust Voltage with batteries disconnected to 14.8V for bulk charge, on the timer. 2 or 3 hours should do it.
Attach to batteries then set timer and turn on, Intermatic spring wound timers work fine.
After it times out, disconnect and reset voltage to 13.8V, for absorption charging. this might that 12 to 24 hours.